Peer review is the evaluation of work by one or more people of similar competence to the producers of the work (peers). It constitutes a form of self-regulation by qualified members of a profession within the relevant field. Peer review methods are employed to maintain standards of quality, improve performance, and provide credibility. In academia peer review is often used to determine an academic paper's suitability for publication.
Scholarly peer review (also known as refereeing) is the process of subjecting an author's scholarly work, research, or ideas to the scrutiny of others who are experts in the same field, before a paper describing this work is published in a journal or as a book. The peer review helps the publisher deciding whether the work should be accepted, considered acceptable with revisions, or rejected. Peer review requires a community of experts in a given (and often narrowly defined) field, who are qualified and able to perform reasonably impartial review. Peer review is generally considered necessary to academic quality and is used in most major scientific journals, but does by no means prevent publication of all invalid research.
Some databases (for example, Academic Search Complete) enable gathering peer reviewed publications by offering a Peer Reviewed filter the search options. This way all of the search results will already be filtered to show only publications that are peer reviewed.
Another approach is to search scholarly databases which do not index popular journals but contain mostly peer reviewed articles. Examples are PubMed, and Web of Science. Though many articles in these databases are peer reviewed, there is no way to use Web of Science to make this distinction for you.
Here are two options for determining if a journal is peer reviewed.
Find the journal home page and look for specific wording regarding this. This can be found on various pages of the journal website such as the About page.
Use a periodicals (another term for journals) directory such as Ulrich's International Periodicals Directory. Note: Ulrich's uses the term 'refereed' instead of 'peer reviewed.'
Use one of the methods described above to determine whether or not these three articles are peer-reviewed.
Loprinzi PD, Lee IM, Andersen RE, Crespo CJ, Smit E. Association of Concurrent Healthy Eating and Regular Physical Activity With Cardiovascular Disease Risk Factors in U.S. Youth. Am J Health Promot. 2015 Sep-Oct;30(1):2-8.
Loprinzi PD, Mahoney S. Concurrent occurrence of multiple positive lifestyle behaviors and depression among adults in the United States. J Affect Disord. 2014 Aug;165:126-30.
Winston S, Winther T, Smitnh C. Building integrated treatment for dually diagnosed youth. Behav Healthc. 2012 Nov-Dec;32(6):12, 14-5.