No, it is not really a hidden feature – but keep your mouse on “links” at the right part of the citation, wait for the drop-down, select “Link-out” and there is a good chance to jump directly to the publisher site, yea, yea.
Addendum
The nodalpoint blog” writes about MEDIE, a new PUBMED parser:
…is an “intelligent†semantic search engine that retrieves biomedical correlations from over 14 million articles in MEDLINE. You can find abstracts and sentences in MEDLINE by specifying the semantics of correlations; for example, What activates tumour suppressor protein p53? So just how useful is MEDIE and is it at the cutting edge?