For medical research, I would suggest https://www.medrxiv.org/. It is maintained by various organisations, including Yale University.

However, you need to be careful as all articles on medRxiv are not peer-reviewed, edited, or typeset before being posted online. The submitted manuscripts undergo a basic screening process for basic check such as offensive and/or non-scientific content and for material that might pose a health risk and are checked for plagiarism. 

However, no endorsement of a manuscript’s methods, assumptions, conclusions, or scientific quality by CSHL, Yale University, or BMJ is implied by its appearance in medRxiv.