In most of our indexes (EBSCOhost & ProQuest) you can limit your search to scholarly/peer reviewed. Peer review is the process by which qualified members of the same profession or field as the author(s) or subject of the work evaluate the piece in question. This seeks to maintain standards of quality, check research methods, and provide credibility. As opposed to articles in popular or professional journals, these scholarly articles are lengthy, original research or in-depth analysis of a topic, written in the specialized language of the discipline, contain extensive documentation through footnotes and bibliographies, and written by authors who provide their credentials indicating their expertise.
Ulrich's Web, available at http://ulrichsweb.serialssolutions.com/ is a resource about journals. Type in a journal's name and it will have information about that journal's peer review status. Also, the journal's homepage will describe how it is edited. Note that peer-reviewed journals are sometimes called "refereed" journals.
