Several catalogs. Of particular interest is Ariadne, a Women's Studies database, listed under "Research" ("Forschung").
A major resource. The main OPAC covers 1501 – 1840, 1953– present. New: an "image catalog" based on the old card catalog now covers the years 1841-1952.
Helveticat is the Swiss National Library catalog. Additional catalogs and databases are listed on the library website.