Scopus‘ new free service TopCited was mentioned by Gavin Baker, the new „adlatus“ (or „famulus“ like Wagner …) of Peter Suber’s Open Access News.
Here are links to the free (OA i.e. free of cost access) versions if there are such versions (and I found them with Google):
(10) http://cbs.dtu.dk/services/SignalP/paper-3.0.pdf (Preprint)
(15) http://www.cs.ubc.ca/~lowe/papers/ijcv04.pdf (Preprint)
(18) http://www.ama-med.org.ar/obesidad/Interheart-LANCET-2004.pdf (Postprint?)
In summa: Open Access works. All 20 Top articles are available OA! I would like to suggest that they are top-cited because they are OA …