If you are a biomedical researcher, clinician, teacher, or student you probably have used or will use MEDLINE® for most of your literature searching. The NIH Library provides access to MEDLINE in three ways: via the Entrez PubMed® search system from the National Library of Medicine, via the Ovid® platform, and via the Web of KnowledgeSM platform. Which one you use is mostly a matter of personal preference, though each has its advantages.
PubMed is an expanded version of MEDLINE, with not only the core medical database but also articles that haven't been fully processed into MEDLINE yet and other articles that, for various reasons, are searchable but will never be fully processed as MEDLINE records. All told, PubMed contains more than 17 million citations and can be searched for free from anywhere in the world. The system is very powerful but not always fully intuitive. We recognize that you may have specific search strategies that you want to learn how to do in PubMed. While you are always welcome to attend a class or get a one-on-one tutorial (see our Resource Training page), you may want to use the following ten tips for self-study or as a reference:
1: The basics - simple searching and viewing results
It is very important that you enter PubMed via the links on either our homepage or our databases page. Doing so ensures you have access to added features of PubMed that are only available to NIH staff, including full-text access to some of our electronic journals.
The standard PubMed screen has a blue vertical navigation bar on the left side that contains links to help pages, PubMed services (several of which are discussed in this guide), and related resources for searching biomedical information. Across the top of the screen you will see the name of the database in which you are searching (in our case, PubMed), a black bar with links to the different NCBI/NLM databases, a row of tabs, and a gray bar that contains the main search box and links to search options. Clicking on the tabs will take you to different features of PubMed: Limits ( Tip #2 ), Preview/Index, History ( Tip #3 ), Clipboard ( Tip #5 ), and Details.
To begin searching, simply type your keyword(s) into the search box. Don't worry about MeSH® (Medical Subject Heading®) terms, unless you already know them; PubMed will attempt to match (or "map") your keyword(s) to appropriate MeSH terms. If you type in more than one keyword or phrase, connect them with the Boolean connectors AND, OR, or NOT. Make sure your connectors are in ALL CAPS! Click Go to run the search.
Your initial results will be displayed below the gray bar. The database defaults to showing a "Summary" view (citation only) of articles in reverse chronological order.
The Display options indicate the amount and format of information for each article. Highlight AbstractPlus from the pull-down menu to see the citation, abstract, and related records information. PubMed will automatically switch to the newly selected display type.
Other options include:
- Brief - Abbreviated author and title, PMID
- Citation - Citation, abstract, and MeSH terms
- Abstract - Citation and abstract, as in AbstractPlus, but no related records
- MEDLINE - All information available, marked in tagged format (use for reference formatting software such as EndNote® and Reference Manager®)
In addition, you can change the number of articles shown on a screen and/or the order in which they are shown (by date, author, or journal) by selecting an option from the appropriate pull-down menus.
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2: Setting limits
You may limit the results of a search in several ways. Click the Limits tab under the main search box to see the limits screen:
Choose appropriate limits from the pull-down menus. For example, if you are interested in early-onset cancers in women, you could choose Adult 19-44 from the Ages menu, Human from the Human or Animal menu, and Female from the Gender menu. Likewise you can select from a variety of article types (e.g., clinical trial, review, editorial, etc.), languages, subsets (subject-based journal collections), date, and in what field your keyword(s) should appear.
Once you have selected your limits, make sure your keywords are visible in the search box, and click Go. PubMed automatically applies your limits to everything else you search in this session unless you take the limits off. After a few minutes, it's easy to forget that you had set limits and you may end up getting strange search results. Check to see if there is a little checkmark next to the the word Limits. Either un-check the box next to the word Limits or go back into the Limits menu to release/modify your limits from search to search.
NOTE: Setting limits in a search will remove non-MEDLINE citations from your search (e.g.., articles that are too new to have been processed), because these articles have not yet been indexed with the terms and codes that make the limit feature work.
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3: Combining searches using History
You can combine different searches in PubMed by viewing your History. Select this option from the gray bar under the main search box. Any searches you have run in PubMed this session will be displayed. The number on the left is the search number. The hyperlinked number on the right takes you to the results of the search.
To combine searches, type # (number of one search) in the search box, followed by AND, OR, or NOT (depending on how you want the terms to relate to each other), then # (second search number), such as #1 AND #4. You can add new terms if needed. Click Go to run the new search, or Preview to see how many articles are found with the search (this will keep you in the history screen rather than showing you articles).
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4: Viewing full-text documents
When you look at an article listed in in the Abstract, AbstractPlus, and Citation displays, you will see one or more colorful buttons. If you used one of our links to PubMed (see Tip #1 ), every article will show at least one button:
Simply click the NIH Library Full-Text Plus! button to go to the article. A new window will open and you will be given a link to the article itself if we have an electronic subscription covering that issue. (If the link doesn't work, please call 301.496.1080.) If the article isn't available online, you will be provided a link to our Order a Document form. Please keep in mind that you will have to be on the NIH Campus or using a VPN connection to NIH to access most of our subscription journals and databases.
Some articles will show an icon for PubMed Central®:
The National Library of Medicine has created a database of free, full-text medical articles. PubMedCentral contains a number of well-known journals, including the BMJ: British Medical Journal and the Canadian Medical Association Journal , and specialized journals such as Critical Care and Nucleic Acids Research . The journals have varying dates of coverage; some go back to 1997, and some include the most recent issues. However, many start with issues published in 2000 and end with issues published a year to six months ago. It is also a repository for manuscripts of publicly-funded research, per NIH's Public Access policy.
For many articles, you will also see another button for the publisher. Often this button will take you directly to the article, so feel free to try it, but if it doesn't work, try the NIH Library Full-Text Plus! button. For more information, you may want to read the NLM brochure Full Text and PubMed . 
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5: Saving, emailing, and printing items
As you search PubMed MEDLINE you may find it useful to temporarily store articles of interest on your Clipboard. This feature allows you to keep track of which articles you have already found useful in a previous search in one session with the database. To add an article to your clipboard, check the box next to the article, and select Clipboard from the Send To pull-down menu. You will get a message stating that your article has been posted to the clipboard, and the word Clipboard in the tabs under the main search box will have a star (*). To view items on your clipboard, click the Clipboard tab. Articles already posted to the clipboard are marked with green numbers rather than black in the summary list.
NOTE: Items on your Clipboard will be lost after 8 hours of inactivity. To save items indefinitely, use MyNCBI (Tip #6).
If you make a habit of putting articles of interest on your clipboard you will find it easier to save, print, and email all of the articles in which you are interested at once:
- Go to the Clipboard.
- Confirm that all of the articles in the clipboard are of interest to you. To remove an item from the clipboard, check the box next to it, then select Clip Remove from the Send To box.
- Decide in what format you need the articles. If you only want the citation information, choose Summary from the Display pull-down menu. The Abstract and AbstractPlus options will give you the citation and abstract; the Citation option will give you the citation, abstract, and MeSH terms.
- Once the articles are in the format you need, decide what you want to do with them. From the Send To menu, choose File if you want to save the citations, Email if you want to email them to yourself or someone else, or Print if you wish to print them out.
- NOTE: Another option in the Send To menu is Order. The National Library of Medicine will send you articles via their Loansome Doc® service. If you are on the NIH staff and would like to sign up to use this service, go here .
If you would like to import your results into one of the reference formatting programs such as EndNote you will need to do a few extra steps to make the results fit the format needed by these programs. If you aren't sure how to do this, please contact a librarian or register for one of our classes for EndNote or Reference Manager.
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6: MyNCBI: Saving Searches
You can save a complicated search for repeated use via the MyNCBI system. This will allow you to either manually update the results of your search or to have new citations automatically emailed to you on a regular basis (an "alert" service). After you have run a search in PubMed, click the "Save Search" link located to the right of the search box.
You will be prompted to sign in to My NCBI or create a new account. Once you do so, you will be able to select options for storing and retrieving your search, including whether you would like to have the search be run automatically on a daily, weekly, or monthly basis.
The National Library of Medicine has prepared a brochure for those interested in using the MyNCBI system.
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7: Using MeSH subject headings
There are three ways of discovering the indexing (MeSH) terms in PubMed MEDLINE. The first is to change the display option for an article of interest to Citation (see Tip #1 ). The second is to look at the details of your search. PubMed automatically attempts to map keywords to MeSH terms. You can see what terms PubMed is using in your search by clicking the "Details" tab below the main search box.
The third option is to search for terms using PubMed's MeSH Database. The MeSH Database is listed under PubMed Services in the blue column at the left of your screen. Once in the MeSH Database, enter your keyword into the search box and click Go. Select terms by checking the boxes next to the term name.
Clicking the hyperlinked MeSH term will give you a more complete description of the term, including subheadings, options to limit your search, history of the term, and the placement of the term in the MeSH tree hierarchy. Check the boxes next to subheadings and/or limits you desire. To search, click Send to Search Box with AND then Search PubMed.
One nice feature of searching with MeSH terms PubMed is that PubMed automatically explodes terms. That is, the database assumes you want to see articles coded not only with the term given but also with any term more specific than it in the tree hierarchy. This means that a MeSH search for "Extremities" in PubMed will include articles indexed under "Foot", "Ankle", and "Toes" that would otherwise have been excluded in a non-exploded search.
For more information, see the National Library of Medicine brochure Searching PubMed with MeSH .
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8: EBM/Clinical Queries
The Clinical Queries service (also in the blue panel on the left, under PubMed Services) offers three modes of searching for articles to support evidence-based medicine. First, you may wish to search for evidence by clinical study category (etiology, diagnosis, therapy, or prognosis) using a broad (sensitive) or narrow (specific) focus. Second, you can find systematic reviews on a topic. Third, you may look for information on the genetics of a disease, including genetic diagnosis, clinical description, management, counseling, molecular genetics, and genetic testing. All three of these modes use preset filters and search terms that have been designed by researchers at the National Library of Medicine.
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9: The Single Citation Matcher
Often times you may be looking for a specific article, either because it was recommended to you or because you need to verify the citation for a bibliography. The Single Citation Matcher is a helpful option in the PubMed Services menu in the blue column at the left of your screen. The Single Citation Matcher simplifies your search by offering you a form with spaces for the relevant parts of the citation. You need only fill out one of the boxes, but it is usually a good idea to enter information in at least two:
The above example finds all articles published in Oncogene in 2003 that have the word "BRCA1" in the title. In this case, several articles are found.
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10: Getting More Help
If you would like more training on using PubMed, you may wish to meet with a librarian to search on a particular topic of interest. We are happy to meet with you at your office or ours, generally during business hours. Please let us know who you are and how we can help you, on our Ask A Librarian or our Tutorials request form.
Finally, the National Library of Medicine has created a number of useful online training tools for PubMed, including their interactive tutorial and a series of animated "quick tours."
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Special thanks to the Health Science Library, UNC-Chapel Hill, for granting permission to use their idea and adapt their content for this page.