Scirus, Elsevier's science-specific web database that offers access to content from a targeted crawl of the open web along with material from many science focused specialized/deep web databases (including full text articles some free, some fee-based) has enhanced their service today.
Scirus now provides searchable access and direct links to more than 13,000 million "scientific" patents from the United States Patent and Trademark Office (USPTO), the European Patent Office (EPO), the Japanese Patent Office (JPO) and the Patent Cooperation Treaty (PCT) of the World Intellectual Property Organization (WIPO).
As for how patents are chosen for inclusion in Scirus, Elsevier said in a news release that the patents are, "selected on the criteria of being either scientific in nature or relevant to the scientific community based upon categorization used by patent offices."
I was unable to find any documentation about how often new patents will be added to the Scirus collection. It would also be useful if Scirus allowed you to refine your search to only patents from a serp.