In the sciences primary and secondary sources refer to how close an article is to the research that is being describe. For example, if the author completed the research study herself, than an article is a Primary source. However, if the author is writing about research done by others, then it is a secondary source.
Popular articles (those written for the general public) are most often secondary sources. Scholarly and Peer-reviewed articles can be both primary and secondary.
Look for clues in the databases, such as the article type of "review article" (for a secondary article), or "original research" or "research article" for primary sources.
Once you find a database, here are some tips for searching it as efficiently as possible
Look for ways to limit your results