Entries include information about whether the journal or magazine is a scholarly journal, consumer magazine, etc.
Additional strategies
Search the internet for the web site of the journal, which frequently includes instruction for authors. Often the instructions will use the phrase "peer reviewed" or say that manuscripts are sent for blind review, reviewed by a committee, or anonymously reviewed.
As you search for articles in the library's research databases, look for an option to limit your search to scholarly journals or peer-reviewed journals. These kinds of filters aren't perfect. It is still important to double-check the journal's web site if you have any doubts.