Dear IHH -
You've probable seen this before, but from where I am the best single source of free full-text studies is the collection of peer reviewed medical studies at the RSDSA Medical Articles Archive page, which you can link to here:
http://www.rsds.org/2/library/articl...ive/index.html (free Adobe Reader required). It's really a very impressive collection and I would urge you to check it out if you haven't done do already.
Mike