Cochrane Reviews section of this database contains systematic iterature reviews in health care. The Cochrane Central Register of Controlled Trials reports randomised and quasi-randomised controlled trials.
UpToDate is an evidence-based clinical decision support resource intended to help healthcare practitioners make the best decisions at the point of care. It also contains patient education information.
There are several major indexes to doctoral dissertations. Not all Universities are covered by any one of these sources. To be thorough, all of them should be searched.
Doctoral disserations and masteres theses from over 1,000 colleges and universities. Full text available for most doctoral dissertations starts with 1997.
NDLTD - The Networked Digital Library of Theses and DIssertations is an International organization promoting the adoption, creation, use, dissemination, and preservation of electronic theses and dissertations. The Global ETD search engine is where you can search these resources.