What is a primary source research article?
A research article (primary source article) reports new or original data
In the sciences, this can be experimental results, new analysis of existing data, or a meta-analysis that combines data from several different studies. Research can be quantitative (based on numbers) or qualitative (nonnumeric; e.g., narrative, personal experience, and interviews).
To identify a research article/primary source article, read the abstract. If the abstract describes specific methodology or results, then the article is most likely a primary source or research article. On the other hand, if the abstract summarizes information about a subject, the article is probably a review article or secondary source.
Some databases (like CINAHL) have limiters that allow you to search for only research articles. This video will show you where the research article limiter is in CINAHL: http://screencast.com/t/2CLtOoH2mR.