From the JURN blog:
What’s not in the mix? The closed “paid-for” ejournals (on Muse, Sage, Blackwell, Intellect, etc) are not indexed. The “buffet style” article-banks, such as findarticles.com and similar, are not indexed. Flash-heavy websites have a hard time being indexed by Google even if they’re in the mix. Some journals are not yet indexed by Google, and some URLs “hide” the actual articles in various ways (e.g. hard image scans of journal pages). Journals in languages other than English are not heavily indexed, and JURN aims to cover only English-language journals. Full-text conference proceedings are not indexed, but may be added at some future date. About six sites were removed during my scrutiny of test searches, since they were of poor quality (dubious art sales sites, fashion mags, etc).
JURN is not accepting submissions, but will track and add new URLs from Intute, DOAJ, and other trusted sources.