Cochrane is a specialty database that publishes systematic reviews, attempting to identify, appraise, and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question. Far smaller in size than CINAHL or Medline, the Cochrane Library is an excellent resource for finding systematic reviews.
This specialty database from the Joanna Briggs Institute spans a range of medical, nursing, and healthcare specialties and includes evidence summaries, systematic reviews, best practice guidelines, and more. JBI does not draw their contents from published journals like many of our database resources; they publish their own research. It is a vastly smaller database than CINAHL or Medline, but a great source of high-quality systematic reviews.