Use these databases to find scholarly journal articles.
There's no perfect way to find primary research articles.
Most primary research articles will describe a study that has been done, so you're best bet is to use the word "study" as one of your search words.
Some databases (e.g. PsycInfo, PubMed) have a special limit for different types of articles, but use with caution.
Also look at the bibliographies of review articles; the authors likely used one or more primary research articles to write the review.
