'Searcher' has an overview of the linking (fulltext retrieval) services offered by SFX, LinkFinderPlus, and 1Cate. I don't know how PubMed's linking system is powered, but it seems to work better than any of these individually. Nice to have them there as a backup though. CrossRef and the DOI Handle Resolver seem to work well too, but only if the article has a DOI (Digital Object Identifier). [via Library Techlog]