Many research projects are never formally published because they lack mass appeal, fail to show significant results, or are not held to the same rigorous standards that these journals require.

Lemouth is Correct

and a significant number of studies are not published because the author couldn't afford entry fees to the "Publishing Machine" which rules the science world. There are a significant number of studies which are excellent, which were done by financially poor scientists.

Fortunately, there are systems being created now which allow scientists to publish their works without having to pay substantial fees. :)