There are many databases available that collect together published research papers on selected disciplines (e.g. education; engineering; chemistry; nursing; medicine; etc.).
When answering clinical questions, the 3 main databases used for general medical queries are Medline, Embase and the Cochrane Library. However, there are other databases which may also be appropriate to search, depending on the exact nature of your query, so resources such as PsychInfo (for mental health/psychology); CINAHL (for nursing), etc., may be useful too. To find out which databases are available for use in your institution, consult your Library or Information Services staff, who should be able to advise and provide details on how to gain access and undertake a search.