The highest impact factor of the nutrition journals doesn't necessarily mean the best journal, but this site is pretty well-organised, if somewhat sparse.
Abstracts are available as normal web pages.
It has on-line issues back to 1997. Again, full articles are in PDF format. The site is very well designed. You can even get any JPEN article after 1992 faxed to you, for a fee. It's official journal is Clinical Nutrition , which doesn't yet appear on the web.