Identifying scholarly materials can be tricky, but peer-reviewed articles are going to have at least two out of three basic characteristics:
1) Peer-reviewed articles cite their sources.
2) Peer-reviewed articles are going to be long. (There is no set length for how long a peer-reviewed article has to be, but scholarly articles are usually more than five pages long.)
3) The article has clearly marked sections, i.e. Introduction, Methods, etc.
A complaint I often hear about the databases is: I put in my search terms,checked the box for full-text and peer-reviewed articles, hit search, then selected my articles from the list and my instructor is saying it is not peer-reviewed. This is because not all of those articles in the results are peer-reviewed. When you check the peer-reviewed limiter, you are asking the database to retrieve articles found in peer-reviewed journals. The catch is that peer-reviewed journals often (usually) contain news stories, opinion articles, book reviews, etc. In other words, not all the articles in a peer-reviewed journal are peer-reviewed.
See the Finding Peer Reviewed Information page under My eLibrary and please feel free to ask any questions you may have finding peer-reviewed articles for your writing assignments!