The literature of nursing is primarily indexed in MEDLINE (via PubMed), and CINAHL1, linked in the box below. Questions related to medicine and health more broadly may also be well served by other databases like EMBASE, Web of Science, and PsycINFO.
1. Allen, M. P., Jacobs, S. K., & Levy, J. R. (2006). Mapping the literature of nursing: 1996-2000. Journal of the Medical Library Association : JMLA, 94(2), 206–220.
"Peer-reviewed" or "refereed" journals are those that subject content to a critical review by other experts in the field prior to accepting a manuscript for publication. Limiting your literature search to the peer-reviewed journals ensures a higher level of scholarship and research methodology.
Magazines, trade journals, and newspapers tend to be "non-peer-reviewed," meaning perhaps just the editor or someone who is not an expert in the field has reviewed the content before publishing.
Some article databases (not all) will have a filter (or "Limit") available for "peer-reviewed." Look for this feature in Proquest Central and CINAHL.
See this tutorial for more information about Peer Review in the Health Sciences.