The following web sites (and search engines) are a place to start, though they offer just a hint of what's out there.
Find websites that are more relevant to your needs by using the advanced search features in Google
You are researching how stem cells from human embryos might help cure neurological diseases, especially Parkinson's disease
As outlined in the example search in the image below, you can use the following advanced search limiters are used and why:
(click on image to enlarge)