Some of the library's online databases, such as Proquest and Academic Search Complete, have a feature that allows you to click in a checkmark box to find articles from peer-reviewed journals. This should weed out articles from magazines, newspapers, and non-peer-reviewed journals.
When you use a database, look for this option on the search screen (usually it's somewhere below the search box), or look for it in the filtering options after you've done your search. For example:
NOTE: Not everything published in a peer reviewed journal is a peer reviewed article. Peer reviewed journals typically include letters to the editor, commentaries or book reviews. These are not considered peer reviewed articles. Look carefully at the articles in your list of results to make sure they have the criteria for a scholarly article. Some criteria are listed in the section, "Making Sure: Is This Article Scholarly/Peer Reviewed?"