From Heather Morrison, some useful links:
The Bielefeld Academic Search Engine searches over 30 million documents (most are free to download):
If you don’t find a free copy, consider asking the author to make their work openly available through an open access archive. In my experience, authors appreciate hearing about this interest in their work.
There are more than 2,000 open access archives available – you can find a list here:
A large percentage of academic authors will have an institutional repository available. There are also a number of subject repositories, including PubMedCentral, arXiv (physics), RePEC (economics), the Social Sciences Research Network, and E-LIS for library and information science.
If the author has no other repository available, there is a free service called My Open Archive:
To find out if the author has rights to self archive, look up the Sherpa RoMEO Publisher Copyright Policies and Self-Archiving:
Most publishers allow authors to self-archive their own work, whether as preprint (before refereeing) or postprint (author’s own copy, after peer review).
There is also a growing body of born open access materials. I cover the growth of OA in a quarterly series which I call the Dramatic Growth of Open Access: