http://www.digizeitschriften.de/index.php?id=239&L=2 has many papers with free access (e.g. Inventiones Mathematicae) but when you search with scholar.google.com it does not index this site!
Are there any other archives like this?
Just in case let me list other archives (they are indexed by google as far as I understand).
e.g. I cannot find:
Koszul, J (1981), "Les algebres de Lie graduées de type sl (n, 1) et l'opérateur de A. Capelli", C.R. Acad. Sci. Paris (292): 139-141
Does it mean search skills are poor or it is really not available electronically?