Most online versions of scientific journals are not freely available but since JCB is published by a non-profit, they actually provide free content and an archive that goes all the way back to 1955. Click on the search button to look for your topic related to cell biology. Also Stanford University's HighWire is the best free index to scientific journal literature. Use the search engine on the opening page to locate journal articles on your topic. HighWire results are clearly marked, so you will quickly know whether an article is available for free or not.
A noble project, "The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource." PLoS publishes its own peer-reviewed journals, beginning with PLoS Biology on October 13, 2003 and PLoS Medicine on October 19, 2004, and now has a suite of 7 titles.