In the CINAHL database, there is a limiter for “research article.” When applied, your search is limited to articles that are about a research study or examination of subject matter that uses investigational or experimental techniques.
A research study includes data collection, subject selection, methodology, discussion of results, and application, if any. For materials about or how to conduct a research study see the specific CINAHL subject headings such as Nursing Research or Research, Medical.
"Peer-reviewed" or "refereed" journals are those that subject content to a critical review by other experts in the field prior to accepting a manuscript for publication. Limiting your literature search to the peer-reviewed journals ensures a higher level of scholarship and research methodology.
Magazines, trade journals, and newspapers tend to be "non-peer-reviewed," meaning perhaps just the editor or someone who is not an expert in the field has reviewed the content before publishing.
Some article databases (not all) will have a filter (or "Limit") available for "peer-reviewed." Look for this feature in Proquest Central and CINAHL.