From the middle of 1998 onwards, espacenet users have been able to access the bibliographic data of all patents published in the preceding two years by any member state of the European Patent Organisation, as well as by the European Patent Office and the World Intellectual Property Organization (WIPO). In addition, full-page facsimile images of documents are also retrievable to facilitate more detailed analysis of these documents. The data for this particular service is stored at the relevant national office. Access is also being provided to a comprehensive collection of patents published worldwide since 1920. For documents published since 1970, each patent family in the collection has a representative document with a searchable English-language title and abstract.
More Info: http://www.library.wisc.edu/Q/patentchart2004.pdf