The ability to conduct searches to locate relevant sources for a research paper is an acquired skill. It takes practice. Below are some search strategies that you can employ in your own research process. If your initial approach doesn't work, don't worry. Try a different combination of words and concepts until you get the results you want. Research is a process and sometimes it takes several attempts to get the search results you want.
The approach you take when entering your search terms in a library database will affect the results you get. Before building a search, think about how you want to combine your search terms.
Putting words in quotation marks - if you want a group of words to appear exactly as written, place the words in quotation marks. You might use quotation marks so those terms appear as a phrase and not isolated from one another. Example: "cognitive neuroscience"
Using AND to combine search terms - when you combine terms using AND, you will retrieve results in which these terms appear somewhere in the fields searched. Example: Cognitive AND Neuroscience - Cognitive could appear in the first sentence of the abstract and Neuroscience could appear in the subject fields.
Using OR to combine search terms - combining terms with OR will increase the number of results that you get. You would use OR when you have multiple terms that describe your topic. This will broaden your search results. Example: attitude OR behavior
Using an asterisk (*) at the end of a word will bring back variations of the word.
Example: cogn* will retrieve results with the words cognate, cognition, cognitive etc.
Warning: Be careful to not place the asterisk to early in the word because it may retrieve irrelevant results.
Example: mem* will retrieve memory, memories, memorize, but it will also retrieve results with words like member, memorial, etc. which are not likely on point.
Sometimes when searching a database you might enter terms that yield no results. If this happens, you might want to search the subject or thesaurus to ensure that the terms you are using are appropriate. The subject headings can also help you expand your search terms by suggesting, broader, narrower and related terms.
Example: In PsycINFO you can select Thesaurus. Enter progestins. In PsychInfo, the term Progestational Hormones should be used in place of progrestins.