The library portal Primo is the central search interface for searching and accessing local and outside resources such as books, e-books, journal articles etc.; the Primo mega-index contains nearly one billion datasets.
The mega-index covers mainly English-language sources. A total of about 55,000 journals from more than 50 providers are indexed (see: List of activated e-resources in Primo).
Depending on subject area and language, a comprehensive literature and information search should comprise (subject) databases (via DBIS in German) in addition to Primo, in order to find sources beyond the contents of the Primo mega-index. You can also use the databases search scope in Primo.