PubMed

If your search returns too many results, you can make it more exact by using advanced filters. The advanced search function can also help you build more complex searches, such as those used for systematic and literature reviews.

For example, if you want to see articles about heart attacks and aspirin use, you can use the query builder in advanced search. Enter terms one at a time, clicking the "AND" button after each word. (You can also change AND to OR, which will show you either result. AND will only show results that contain both terms.)

Once you click "Search" you will see a list of results. To learn more about how PubMed ran that search, go back to the advanced search page and expand the query:

The advanced search feature automatically looked for Medical Subject Headings, also known as MeSH terms.

Subject headings are helpful when you're searching, because some concepts have multiple words related to them.

Example:
        Concept:
            An abnormal growth of tissues
        Terms:
            Neoplasm
            Neoplasia
            Tumor
            Tumors
            Cancer
            Cancers

Different authors may each use different terms for this concept in their articles. Using a subject heading lets you search all of these terms at once.

Subject headings group multiple words under a concept. By entering the word "neoplasm" as a subject heading, you are telling the database to search for articles with the subjects neoplasm, neoplasia, tumor, tumors, cancer, or cancers. The results in your list should be more relevant to your needs.