Most library databases include a scholarly or peer-reviewed filter. Look for the peer reviewed or scholarly filter in the advanced search page.

The peer-reviewed or scholarly filter can often be found in the filter, limiter or refine results panel, as well.

Once clicked, this feature limits search results to content from scholarly, peer-reviewed journals.
Not every article published in a scholarly, peer-reviewed journal is a peer-reviewed article. Book reviews, editorials, and opinion pieces are often not peer reviewed, but may still appear in your search results.