Which databases does pubmed search

What is the difference between Pubmed and Medline? Will I get the same results if I look in one or the other? Toggle menu visibility. Ask Another Question. Answered By: Reference Librarian.

Last Updated: Mar 29, Views: Toggle action bar FAQ Actions. A question mark can be used to search for a single character. It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.

Expert Searching. What Should I Document? Why Document the Search? When to Use PubMed 2. PubMed Cool Tools 3. How to Use Keywords 5. PubMed Pro Tips 6. Combining Search Terms and Concepts 7. Saving Your Searches 8. PDF Printable Handout 9. PubMed Practice When to Use Embase 2. Embase Cool Tools 3. How to Use Emtree Controlled Vocabulary 4. Embase Pro Tips 6. When to Use the Cochrane Library 2.

Cochrane Library Cool Tools 3. Cochrane Library Pro Tips 6. Printable PDF Handout 9. Literature Searching Services. How Can the Library Help? A literature search consultation might include one or more of the following: Refining the research topic to an answerable question Recommending information sources or databases for the search topic Identifying relevant search terms Creating and executing search strategies Suggesting reference management software and strategies An informationist can also provide you with an expert search, which may include: Refinement of the search question Search term identification Identification of sources and databases to be searched Search strategy formulation and documentation Execution of searches Are you interested in performing a systematic review?

Do you want to meet with an informationist? Browse this document to prepare for electronic submission of the literature review request form linked above. Before You Meet With Your Informationist A meeting with an informationist will be most beneficial for you if you first do a little bit of planning and searching on your own. Prior to meeting with an informationist, we recommend that you: Have a clear and concise understanding of your research question Be prepared to discuss the scope of your project, including limits on the body of literature Brainstorm search terms associated with your topics acronyms, synonyms, and variations on spelling Note any relevant literature you have found so far.

Literature Review Process. The Literature Review Process There are eight distinct steps that will assist you in moving through a literature search. Write down your topic in a way to identify the key concepts and issues that you want to address. Although it is not necessary to use all elements of the PICO in the search strategy, this will help you frame the topic into a translatable framework.

Do some background research to see what's already been written about the topic. You may find it helpful to search books and journals through the library catalog, as well as databases that may be relevant to your topic. Narrow down the topic, if necessary.

You may find that the original question is too broad. After you have done the background research, you will have a better idea of what specifically you are interested in. Decide on the scope and nature of your review. What types of research are you interested in? Are you prepared to do title and abstract screening? What are you hoping to address with your research? Create and execute your database searches. Searching is an iterative process, so you may need to test and refine before setting on your final search strategy.

Your search strategy should use a combination of keywords and controlled vocabulary terms to represent each concept of your research topic. Examine and evaluate your results to make sure that they could potentially answer your research question. This is the point to make changes before proceeding. Export and screen your results. Using a citation manager will allow you to remove duplicates when you screen.

Your informationist can also recommend screening software and strategies. For more information on using a citation manager, see our citation management guide. Extrapolate the data and evidence to draw conclusions about your research topic. Clinical Search Building Worksheets.

This worksheet bundle consists of step-by-step forms you can use to build and document your search using the PICO Research Question Framework. Putting the Search Together For more on combining search terms and concepts, see our page on Combining Search Concepts. Formulating Your Research Question. Work with an informationist to search relevant sources to see what's been written about your topic so far. Consider your audience.

Who might be interested in this issue? Pro Tips Identify a framework that works for your topic and stick with it. Aim for clarity. Start documentation to keep all your ideas in one place. Get input from collaborators, peers, and mentors. Consult with an informationist so that you can complete a thorough search of existing research.

Selected Bibliography Farrugia, P. Practical tips for surgical research: Research questions, hypotheses and objectives. Canadian Journal of Surgery, 53 4 , — Hanson B. Designing, conducting and reporting clinical research. A step by step approach. Injury, 37 7 , — Which Databases to Use. Which Databases to Use? Database vs. Platform Database A database indexes individual records with metadata.

Platform A platform is a search interface. Note Be sure to keep sufficient records of your database searches so that you can appropriately report your search methodology. Subject Databases Different databases cover different content areas.

Choosing Search Terms. Controlled Vocabulary Controlled vocabularies are a set of predetermined terms that describe specific concepts. Embase's Emtree: 'chronic kidney failure'. Keywords Keywords are the words used in an article title, abstract, or other text field in a database. Here are a few reasons: Not every database uses a controlled vocabulary Scopus and Web of Science are two examples Each database has its own controlled vocabulary terms If an article is too new , it may not be indexed with controlled vocabulary yet, and you would only find it with keywords In PubMed, if an article is out of scope of MEDLINE , a component of PubMed, it may not ever be indexed with MeSH PubMed's controlled vocabulary , and you would only find it with keywords If an article lacks an abstract or additional author-supplied keywords , you may only find it with controlled vocabulary If you want to be as comprehensive as possible, search with both controlled vocabulary and keywords.

Alternative Method for Finding Controlled Vocabulary Terms Do a basic keyword search and choose a few citations that are relevant to your research question Make a note of any keywords used in the article title or citation you may wish to add to your current list of keywords Examine the full citation information for each article to find the controlled vocabulary terms assigned and write them down Redo your search using both the controlled vocabulary and keyword terms Avoid Stopwords In bibliographic databases, stop words are words that the database has been programmed to ignore in a search string or query.

Combining Search Terms. Boolean Operators: Combining Your Search Terms Boolean operators form the basis of mathematical sets and database logic. Example: "children" AND "poverty" OR Use OR between similar keywords, like synonyms, acronyms, and variations in spelling within the same idea or concept.

The area in blue on the diagram highlights the recall of the search when OR is used to combine words or concepts.

As you can see, OR broadens the search. The area in blue on the diagram shows the search results that you will get when you combine two concepts using NOT.

As you can see, NOT is used to make broad exclusions. In our example, any article that discusses both "pediatrics" as well as "adults" will be excluded.

Example: "pediatrics" NOT "adults". Proximity and Adjacency Proximity and adjacency operators allow you to search for words next to or near each other. Finding Spelling Variations. Truncation Truncation allows you to find multiple spelling variations of a keyword in your search. Wildcards Using a wildcard in a search term allows you to substitute a symbol for a letter in a word. Examples: wom! Search by Parts of a Citation.

What are Database Fields? Examples of citation fields:. Searching With Field Tags An alternative way to search for terms in a specific field of a citation is to add a "Field Tag" to your search terms. Limiting a Search with Filters. Limiting a Search with Filters Many databases allow you to apply filters to limit to your search. Below, you will find just a few examples of filters and limits in frequently-used databases.

Saving Your Search. Documenting and saving your search will save you time. There are two ways to save your work. Each database will allow you to register for an account. After you create and run a search, look for the option to save or "create alert. After you create and run a search, copy and paste the search string into a document.

Save the document with the date and title of your project. It's a best practice to document the databases searched; the date searched any filters applied, such as language or date; the number of results; and any evidence identified through other methods, such as handsearching. Keep this in your existing search document, which can be either a text or spreadsheet format. Finding Related Articles. Reference Lists If you find an article that is very relevant, search the reference list to identify other literature that may be pertinent to your research.

In PubMed, these articles are listed in the article record under the heading "Cited By. Systematic Reviews. Searching with Google. Describes the material presented in the article e. Citations may include multiple Publication Types. Use the search tag [pt] with any PubMed Publication Type , e. Publication Types are arranged hierarchically with more specific terms arranged beneath broader terms, and publication types automatically include the more specific publication types in a search.

To turn off this automatic feature, use the search syntax [pt:noexp], e. The SI field identifies secondary source databanks and accession numbers, e. The field is composed of the source followed by a slash followed by an accession number and can be searched with one or both components, e. To retrieve all citations with an SI value, search hasdatabanklist.

The subset field is a method of restricting retrieval by subject, citation status and journal category, with the search tag [SB]. See also filters and Find related resources using LinkOut. Includes chemical, protocol, disease or organism terms. Synonyms to the supplementary concepts will automatically map when tagged with [nm]. This field was implemented in mid; however, many chemical names are searchable as MeSH terms before that date.

Words and numbers included in the title of a citation, as well as the collection title for book citations. Words and numbers included in a citation's title, collection title, abstract, other abstract and keywords. English language abstracts are taken directly from the published article. If an article does not have a published abstract, NLM does not create one.

Words and numbers in title originally published in a non-English language, in that language. Non-Roman alphabet language titles are transliterated. Transliterated title is not included in Text Word [TW] retrieval.

Untagged terms that are entered in the search box are matched in this order against a Subject translation table including MeSH Medical Subject Headings , a Journals translation table, the Author index, and an Investigator Collaborator index.

When a match is found for a term or phrase in a translation table the mapping process is complete and does not continue on to the next translation table. To see how your terms were translated, check the Search Details available on the Advanced Search page for each query under History.

If you want to report a translation that does not seem accurate for your search topic, please e-mail the information to the NLM Help Desk. If a match is found in this translation table, the term will be searched as MeSH that includes the MeSH term and any specific terms indented under that term in the MeSH hierarchy , and in all fields.

If you enter an entry term for a MeSH term the translation will also include an all fields search for the MeSH term associated with the entry term. Substance name mappings do not include a mapping for individual terms in a phrase, e. MeSH term mappings that include a standalone number or single character do not include a mapping for individual terms in a phrase, e.

These will automatically map to the journal abbreviation that is used to search journals in PubMed and in all fields. If the term is not found in the above tables, and is not a single term, PubMed checks the author index for a match. The author index includes author names and initials, as well as full author names for articles published from forward, if available. If the term is not found in the above tables, except for Author, and is not a single term, the investigator index is consulted for a match.

The investigator collaborator index includes full names, if available. Enter a full investigator name in natural or inverted order, e. PubMed breaks apart the phrase and repeats the above automatic term mapping process until a match is found. PubMed ignores stopwords in searches. If there is no match, the individual terms will be combined ANDed together and searched in all fields.

When a search includes terms that were tagged with a search field during the automatic term mapping process and retrieves zero results, the system triggers a subsequent search using "Schema: all. The learned ranking algorithm combines over signals that are helpful for finding best matching results. Most of these signals are computed from the query-document term pairs e. The new ranking model was built on relevance data extracted from the anonymous and aggregated PubMed search logs over an extended period of time.

The PubMed database contains citations and abstracts to biomedical literature, facilitating searching across several NLM literature resources:. PubMed Central PMC is a full text archive that includes articles from journals reviewed and selected by NLM for archiving current and historical , as well as individual articles and preprints collected for archiving in compliance with funder policies.

Citations to these preprints are deposited in PubMed. Bookshelf is a full text archive of books, reports, databases, and other documents related to biomedical, health, and life sciences. PubMed includes citations for books and some individual chapters available on Bookshelf. The tags are presented in alphabetical order. Some of the tags e. Other tags e. You can download records in PubMed format as a text file. Note: Not all fields are searchable in PubMed.

See: Search Field Descriptions and Tags. Antivirus software may affect page caching which can result in unexpected page expired messages.

Also, nlm. You may have to delete your browser's cache temporary files before trying to access PubMed again. Please contact the journal publisher directly to report an error and initiate a correction to PubMed citations for content other than MeSH. NLM provides data to vendors around the world. Other products and services will not necessarily immediately reflect corrections made to PubMed records.

If you search through a vendor's system, please contact your vendor about their maintenance schedules. A "cookie" is information stored by a web site server on your computer. In the case of PubMed, cookies store information about your interactions that may be needed later to perform a function.

To use these interactive features you need to enable cookies on your computer. Consult your browser's help for information on enabling cookies. If you have problems using cookie-dependent features of PubMed, even after enabling cookies, possible reasons may include:.

Some characters have special meaning in MeSH fields:. Publication types found in PubMed are listed below. Most article type filters use the article type name with the publication type [pt] search field tag; for example, "multicenter study"[pt]. The Systematic Review filter uses a search strategy in addition to the publication type [pt]. The language filters use the language name with the language [la] search field tag; for example, esperanto[la]. The COVID article filters limit retrieval to citations about the novel coronavirus; these filters may evolve over time.

The Clinical Queries search strategies have been updated based on new evidence from Haynes et al. The current strategies have better performance than their predecessors. Details of methods appear in the references below. The neighbors of a document are those documents in the database that are the most similar to it.

The similarity between documents is measured by the words they have in common, with some adjustment for document lengths. To carry out such a program, one must first define what a word is. For us, a word is basically an unbroken string of letters and numerals with at least one letter of the alphabet in it. Words end at hyphens, spaces, new lines, and punctuation.

The common, but uninformative, words also known as stopwords are eliminated from processing at this stage. Next, a limited amount of stemming of words is done, but no thesaurus is used in processing.

Words from the abstract of a document are classified as text words. Words from titles are also classified as text words, but words from titles are added in a second time to give them a small advantage in the local weighting scheme.

MeSH terms are placed in a third category, and a MeSH term with a subheading qualifier is entered twice, once without the qualifier and once with it. If a MeSH term is starred indicating a major concept in a document , the star is ignored.

These three categories of words or phrases in the case of MeSH comprise the representation of a document. No other fields, such as Author or Journal, enter into the calculations. Having obtained the set of terms that represent each document, the next step is to recognize that not all words are of equal value.

Each time a word is used, it is assigned a numerical weight. This numerical weight is based on information that the computer can obtain by automatic processing.

Automatic processing is important because the number of different terms that have to be assigned weights is close to two million for this system. The weight or value of a term is dependent on three types of information: 1 the number of different documents in the database that contain the term; 2 the number of times the term occurs in a particular document; and 3 the number of term occurrences in the document.

The first of these pieces of information is used to produce a number called the global weight of the term. The global weight is used in weighting the term throughout the database.

The second and third pieces of information pertain only to a particular document and are used to produce a number called the local weight of the term in that specific document. When a word occurs in two documents, its weight is computed as the product of the global weight times the two local weights one pertaining to each of the documents. The global weight of a term is greater for the less frequent terms. This is reasonable because the presence of a term that occurred in most of the documents would really tell one very little about a document.

On the other hand, a term that occurred in only documents of one million would be very helpful in limiting the set of documents of interest.

A word that occurred in only 10 documents is likely to be even more informative and will receive an even higher weight. The local weight of a term is the measure of its importance in a particular document. Generally, the more frequent a term is within a document, the more important it is in representing the content of that document. However, this relationship is saturating, i.

In addition, we do not want a longer document to be considered more important just because it is longer; therefore, a length correction is applied. If you want review articles, you can add the word "review" to your Google Scholar search, but as a keyword. This means you may or may not get real review articles.

Content words are no tagged, so you must search for all possible variations of the words from your topic. Inaccurate retrieval and variable content means that search results are not necessarily reproducible and therefore not reportable.

Google Scholar would not be appropriate to use for systematic reviews. Web of Science and Google Scholar track the most citations. PubMed tracks citations only for PubMed Central articles. Both Google Scholar and Web of Science track citations--how many times that an article has been cited by other articles, books, or sources. Both Google Scholar and Web of Science allow you to sort your results by times cited Google Scholar includes this in its "relevancy ranking".

Be aware that times cited will differ greatly between Web of Science and Google Scholar. Neither one is complete, although Web of Science citation data is considered more accurate and reproducible and is used by official organizations as the standard. Google Scholar citations include books, theses, other reports, but may not include a lot of older citations because of lack of tagging of older files. PubMed has started tracking some citations, but it is only able to track citations by articles in PubMed Central, which is an open access repository of articles.

It is useful for discovery of articles, but not recommended for any kind of counting or statistics of citations. Google Scholar searches full text of articles but PubMed and Web of Science search only the citation, abstract, and tagging information.

Because Google Scholar searches the full text of articles, you can find information that is not necessarily in the citation or abstract of an article, for instance, a detail buried in the Methods section of a journal article.