Keep up with the newest literature on a subject of interest by using this strategy: locate the most important previously published papers and then track where those papers are being cited, i.e. included in the references of other papers. SciFinder-n has made this even more simple to accomplish through their "Citation map" feature. 

You may also do this by using the citation searching capability in Scopus, Google Scholar, and PubMed. Most databases allow you to create alerts for your searches or for citations, which will result in emails sent to you when new articles fitting your search or referencing a particular citation are added to their databases.