To find peer-reviewed journal articles: look for a checkbox or filter to select "peer-reviewed journals". Why filter your search? The databases linked below often also include letters to the editor, personal essays, newspaper and magazine articles, reports, working papers, dissertations and conference proceedings.
Supplement peer-reviewed articles: those other resources can complement peer-reviewed articles and help broaden your perspective on your topic:
Digital library of academic journals, books, and primary sources.
PubMed Central (PMC) is the U.S. National Institutes of Health (NIH) free digital archive of biomedical and life sciences journal literature. It provides access to over 12 million MEDLINE citations back to the mid-1960s.
These journals are: currently publishing, freely available online, and charge no fees to authors to publish in open access (meaning there are no Article Processing Charges).