"Only 63% of results from abstracts describing randomized or controlled clinical trials are published in full. ’Positive’ results were more frequently published than not ’positive’ results."¹
Many of the resources on this page list clinical trials that are still in process. Having as much information as you can find about the positive and negative results of a trial will help you avoid bias in your research.
¹From the Plain Language Summary of: Scherer RW, Langenberg P, von Elm E. Full publication of results initially presented in abstracts. Cochrane Database of Systematic Reviews 2007, Issue 2. Art. No.: MR000005. DOI: 10.1002/14651858.MR000005.pub3.