Friedsam Memorial Library: Medline Instructions

FRIEDSAM MEMORIAL LIBRARY

Medline Instructions

Using PubMed to Search for Research Articles in Medline

A remarkable resource is available to everyone in the world now, that you can use to locate source materials for papers and research projects. It is a searchable database called Medline, which contains information on all articles published in over 3500 biological and medical journals since 1966. This database can be searched by title, author, subject, journal name, etc., and searches can be restricted to a range of years, certain types of article, language, etc.

Medline is very simple to use for the beginner, and the advanced user can also use special instructions to tailor their search to their particular needs. As with all search engines, there is an art to selecting search terms to narrow down a search to a reasonable number of articles on precisely the subject you are looking for. PubMed has extensive online help that will guide you through all of the features of this search engine. This document is intended as a quick guide to get you started, and it also gives you some tips on how to perform the most powerful and effective searches.

To use PubMed, click on the Medline link below or use the Medline or PubMed links throughout the page. It will take you to the "Search Medline" page at the National Library of Medicine.

Medline via PubMed

From the "Search Medline" page, click on PubMed. You are now on the PubMed Query page. The default database is Medline, which is what you want. To perform a search, you just type your search terms into the box near the top of the page and click "search". Detailed help on every aspect of searching can be found by clicking "Help" in the left column.

If you don’t have the time to read the entire (long) help document, here are the main things you should know when searching.

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The Simplest Search

When you simply enter words in the search box, Medline will show you citations to any articles containing those words in the title, abstract, list of authors, journal title, or subject headings. This is the easiest and most general form of search. Often, it is better to specify terms as subject headings, as described below.

If not otherwise specified, Medline treats multiple words as though they were separated by ‘AND’. This means that only those articles containing all of the words you enter will be shown. For example, if you search

osteoporosis calcium

You will get any articles containing BOTH ‘osteoporosis’ AND ‘calcium’ in the title, abstract, subject headings, journal title, or list of authors (that’s "Dr. Osteoporosis" to you). If you were to search

osteoporosis AND calcium

you would get the same results (note that Boolean operators like AND and OR always need to be entered in CAPITAL LETTERS.

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Searching By Subject

All Medline citations are assigned to certain subject categories in the extensive categorized list of Medical Subject Headings. To limit your search to only those articles which have been assigned a particular subject heading, you just type ‘[mh]’ after your search term(s):

osteoporosis [mh] calcium [mh]

osteoporosis [mh] AND calcium [mh]

When using qualifiers, be sure to type them after every search term you want to qualify. If instead you wanted to search for ‘osteoporosis’ anywhere in the title, abstract, etc., but limit ‘calcium’ to the subject headings, you would search

osteoporosis AND calcium [mh]

The ‘AND’ distinguished ‘osteoporosis’ and ‘calcium’ as two different types of search terms, and since no qualifier (such as [mh]) is specified for ‘osteoporosis’ the search engine treats it as a general search term.

If you retrieve too many citations, even with an [mh] search, you might want to try using the [majr] qualifier. This limits the search only to those articles which have been assigned a Medical Subject Heading containing your search term as a major subject. These articles are more likely to focus primarily on the issue you are interested in. As an example of how this can restrict your search, consider the number of citations retrieved by the following two searches:

osteoporosis [mh] calcium [mh] (2718 citations)

osteoporosis [majr] calcium [majr] (631 citations)

631 citations is still a lot. You could reduce this number further using the additional qualifiers described below.

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Searching For Phrases

If you want to search for a phrase, surround it by double quotes, as follows:

"breast cancer"

If you don’t use the quotes, Medline assumes you mean

breast AND cancer

and you might get articles in which the words ‘breast’ and ‘cancer’ appear in no particular relation to each other.

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Searching For Authors

Occasionally, you may wish to search for articles by a particular author. PubMed allows you to do this, using the [au] qualifier. To search for articles by Francis Crick, type:

Crick F [au]

Note that the last name comes before the initial(s), that there is no comma before the initials, and that you can enter just one initial. John Watson could be searched for as

Watson J [au]

Watson JD [au]

The second is more specific. Note also that there are no periods after the initials.

Author searches can be combined with other types of search as well. For example:

Crick F [au] AND DNA

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Tips For More Powerful Searches

Here are some other tips that will make your searches more powerful.

The default setting displays 20 citations per page. It is often quicker to display 100 or 200 citations per page, especially with the fast internet connections we have on campus. You can select this by clicking on the arrow next to the "Number of documents to display per page" box and choosing the number you want.
The default setting retrieves all articles from 1966 to the present. Often, you will be most interested in article from the past 2 years or 5 years. You can choose to limit your searches by ‘entrez date’ (the date citations were added to the database) by clicking on the arrow next to this box and choosing the date range you want.
In addition to the Boolean operators described here, you can also use the OR and NOT operators. Detailed explanations for how to use these operators can be found in the online help on PubMed.
When you are exploring the literature in a subject that is new to you, it is usually most helpful to start with review articles. These are reviews and interpretations of a body of literature. They are more demanding and jargon-laden than most textbooks but they are still much more accessible than the ‘primary research articles’ that they are reviews of. To limit your search to review articles, add ‘review [pt]’ to your search terms. Note that you must separate this term from your other terms by an AND, or the search engine will assume all search terms are ‘[pt]’ (publication type):

osteoporosis [majr] calcium [majr] AND review [pt]
If you would like to exclude articles that are not in English, add ‘English [la]’ to your search terms:

osteoporosis [majr] calcium [majr] AND review [pt] AND English [la]

This is a powerful search! Consider the number of citations yielded by each of these searches:

osteoporosis [mh] calcium [mh] (2718)

osteoporosis [majr] calcium [majr] (631)

osteoporosis [majr] calcium [majr] AND review [pt] (73)
osteoporosis [majr] calcium [majr] AND review [pt] AND English [la] (52)

Now 52 citations is a manageable number. If we limit the search to just the past five years, we get it down to 23 citations; just the last two years gives us 11 citations.

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Viewing Your Search Results

After you press the ‘search’ button, PubMed displays a list of citations, each of which includes the title of the article, the authors, the journal name, volume number, page numbers, and year of publication. When you request an interlibrary loan, you will need all of this information.

To view the abstracts of articles that look interesting, click on the box to the left of the citation so a check appears there, and once you have selected all articles you are interested in on a page, go to the top of that page and click ‘display (abstract report)’. Note that your selections do not carry over from one page to the next, so you will need to display all interesting citations on one page before going to the next page of citations. This is one reason why it is best to display citations 100 or 200 per page.

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Finding the Most Useful Subject Headings

To search by subject, you need to enter the right subject terms, from the organized list of Medical Subject Headings. There are two ways to refine your selection of subject terms. First, you can do a more general search, select articles that look like what you want, and then click on the arrow next to ‘display’ at the top of the list of citations, and select ‘MEDLINE report’. This display format will show you all of the subject headings assigned to this article. By selectioning subject terms associated with one good article, you can often narrow down your search to other articles like it.

Another way to find the best subject terms is to browse the Medical Subject Headings themselves. To do so, click on ‘MeSH Browser’ in the left column of the PubMed main page. In the search box on the browser page, enter words that you think might be MeSH terms. The browser will show you the entire tree structure(s) in which your terms can be found, or if your term is not an actual MeSH term it will offer you a list of similar terms to choose from. You can also browse the entire MeSH tree, starting with the list of the most general headings, by clicking ‘Start at the top of the tree’.

Once you have found the best subject heading terms, you can return to the PubMed main page and perform an [mh] search.

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Requesting an Article by Interlibrary Loan

Some of the articles you retrieve will be available in journals in our library, but given that you are retrieving articles from over 3500 journals, you may need to request a photocopy of an article by interlibrary loan. To do so, make sure you have the entire citation (title, authors, journal, volume, pages, and year) and speak with the faculty member who is advising you on your research project or the instructor of the class for which you are writing a paper. They will be able to advise you as to which articles look best, and they can then submit a request for you to the ILL department of the library. Interlibrary loan articles usually arrive within 1-2 weeks of the request, so be sure to start your searching in plenty of time before the assignment is due.

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For further research on the Internet, you may wish to select a Search Engine.

Return to Pathfinders and Internet Resources page.