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Health Sciences Research Guide: Find the Primary Literature

A guide to library research for students in Health Sciences programs

View PubMed Tutorials

Each of these 2 to 3 minute tutorials gives you an understanding about the various apsects of searching PubMed efficiently and effectively.

Why Primary Literature?

The Council of Biology Editors has defined primary literature is the "first disclosure" of new research. Its purpose is to present information about researchers' experiments and studies so that the reader can make their own evaluation by:

  • assessing the researchers' observations,
  • repeating their experiments, and
  • evaluating the researchers' intellectual processes. (1)

When you are preparing to write a paper you must do your own search and analysis of the primary literature. Below are some resources to guide you through this process.

Research Databases

Medline is the preeminent abstracting & indexing service in the biomedical literature. It comprises 22 million citations from basic and clinical research published in peer-reviewed journals internationally. PubMed is the free tool to search Medline. Depending on your topic you may wish to supplement your search by using additional databases. Below is a selection of relevant secondary sources.


Perform a test search.

Select the secondary literature sources (databases) you will search. Be sure to include PubMed on this list. 

Not all databases work the same way. You may need to alter your search strategy slightly from database to database. If you have questions, please ask a librarian using the chat box on the right.

Test your search strategy in each database. Are you getting relevant results?


Alter your search strategy, if needed, according to the following scenarios:

I see some articles that look relevant to my research question, but many that do not:

Refer to your original search strategy and test the narrower keywords you identified. Consider combining multiple search terms with the Boolean operator AND if you have not already done so. Select any appropriate limiters that your database offers. Relevant limiters may include age, sex, human or animal, publication type, and publication date. Be sure to record any employed limiters in your search strategy documentation.

I don't see any relevant results:

Re-examine your keywords. Test any related words or synonyms that you identified. If these don't work return to the tertiary literature to see if you find any others.

My search is returning 70,000 results:

Try employing any appropriate search limits. Publication date is a great place to start. The scope of your research may call on you to use only articles published in the last 5 years, for example.

If you are researching the conjunction of two concepts consider narrowing your search by combining keywords with AND. If this does not help, your research question may be too broad. Consider refining your question into something more specific.

My search is returning 2 results:

Refer to your original search strategy and test the broader keywords you identified.

Consider combining synonyms or closely related keywords with the Boolean operator OR (i.e., "pleural tuberculosis OR latent tuberculosis").

If you still don't retrieve satisfactory results, it may be necessary to change your research question. Sometimes there simply aren't enough studies published in the primary literature to support a paper.


At the end of this section you should have:

  • Selected the secondary literature (databases) you will use
  • Tested your search strategy in each and made necessary adjustments



Council of Biology Editors. Proposed definition of a primary publication. Newsletter, Council of Biology Editors. 1969 (Nov); 1-2, as cited by: Day RA. How to write and publish a scientific paper. Phoenix (AZ) : Oryx Press; 1994: p. 9.

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