Searches with Google Scholar

An Advanced Scholar Search, using the key words "cancer stem cell", for articles published in 2008, yielded a list of articles. At the top of the list was: Identification and expansion of the tumorigenic lung cancer stem cell population, by A Eramo and 9 co-authors, Cell Death Differ 2008(Mar); 15(3): 504-14. Unfortunately, at the time this search was done (2008-09-14), only the Abstract was freely accessible.

An analogous advanced search was done (also on 2008-09-14) , again using the key words "cancer stem cell", for articles published in 2007 and 2008. At the top of the list was: Identification of a subpopulation of cells with cancer stem cell properties in head and neck squamous cell carcinoma, by M E Prince and 8 co-authors, Proc Natl Acad Sci U S A 2007 (Jan 16); 104(3): 973-8. This time, the article is freely accessible. As is evident from the PubMed citation, this article has also been archived in the PubMed Central repository.

At the time when this particular search was done, among the first 20 articles listed in the results, 15 were marked with green triangles.

Search results marked in this way are a novel feature. See: Google Scholar starts to flag gratis OA content, by Peter Suber, Open Access News, September 11, 2008.

Peter Suber uses the term "gratis OA" to identify the most basic kind of free online access to the peer-reviewed literature. Price barriers are removed, but permission barriers may still remain. Permission barriers may prevent a range of uses of the freely accessible articles. For example, libraries may be prevented, by licensing terms, from using electronic journals in the same free and full way that they may now use print journals.

At present, as Peter Suber has noted in his post, not all of the search results are correctly marked. However. it's a useful beginning, for those who seek freely accessible versions of articles of interest.