PubMed - Articles in PubMed are considered peer reviewed and there isn't a limiter to use in the database.
EBSCOhost (includes Cochrane, SPORTDiscus, Food Science Source, AMED) - Click on Advanced Search under the search box and select Peer Reviewed.
Google Scholar - There isn't a limiter in Google Scholar. You will have to look at the publisher page and "about this journal" or similar to find out if a journal is peer reviewed.
Index to Chiropractic Literature - Click on "Switch to Advanced Search" and then select "Peer Reviewed Citations" under "Peer Review".
See also How do I know if an article is considered peer reviewed? and Tutorials.