KVK: The Karlsruher Virtuelle Katalog (Karlsruhe Virtual Catalog) allows for parallel searches in several catalogs at once, for example in bookstore directories as well. Currently, it can direct you to approximately 100 million books and journal titles worldwide. 

HBZ: the Hochschulbibliothekszentrum (University Library Center) for the state of North Rhine-Westphalia gives you access to the state’s collaborative catalog. Here, you can also access DigiBib. 

Universitäts- und Stadtbibliothek Köln: The Cologne University and State Library is a special collection library that focuses on business studies and social sciences. Like the ZBW, the USB-Köln links to journal articles in its OPAC 

EconBiz : (Virtual Specialist Library for Economic Sciences): EconBiz originated as a collaborative project between the ZBW, and the Cologne university and state libraries. EconBiz contains full texts, a specialist information guide that refers to websites that focus on economics-related topics and library catalogs belonging to the cooperation partners.

ViFa-Math:  the Virtuelle Fachbibliothek Mathematik (Virtual Specialist Library for Mathematics) aims to facilitate research for information related to mathematics. Here, you can search for conventional media and electronic resources.

EZB: Access to more than 47,000 academic publications and e-journals, half of which are freely available in their entirety. It also contains online publications for which the Hochschule Kaiserslautern’s University Library is licensed, so they are available across the whole campus. You can search for publications alphabetically or by subject. 

Springer-Link: allows for online viewing of around 2,000 Springer journals. Springer primarily deals with the topics of technology, medicine, and life sciences.

Wiley Online Library: offers research possibilities under various aspects including access to abstracts and full texts of open access journals. If licenses are purchased, additional full texts can be accessed.

Directory of Open Access Journals (DOAJ): this is a directory of electronic journals which are free to access, based on the principle of open access online. Unlike with the EZB, you can search for individual articles here. 

bookboon.com: The resources for students currently include over 1,000 textbooks. The collection is curated exclusively by professors with teaching duties at a recognized university. 

Openbooks des Rheinwerks Verlags : a selection of approximately 30 up-to-date specialist IT books in German published by Rheinwerk Verlag, which can be viewed and downloaded free of charge.

O'Reilly OpenBooks: a selection of approximately 40 up-to-date specialist IT books in English published by O’Reilly, which can be viewed and downloaded free of charge.

DBIS: A cooperative project to allow use of academic online and CD-ROM databases. There is free, campus-wide access to all of the subject-specific databases for which the University Library is licensed and around 4,500 databases available for free online. 

Beck-online: Extensive database of full texts on legal studies (containslegislative texts, commentaries, handbooks, journals). Additionally, Beck-online also has current judicial rulings as well as some collections of forms.

Wiso-net: offers access to approx. 8.7 million economic references as well as more than 4,300 eBooks on topics ranging from agricultural sciences, general business administration, controlling, leadership and organization, international economics, human resources, sociology to time management and much more. Plus over 500 business-oriented journals.

Ebsco Business Source Premier : EBSCOhost's Business Source Premier database is a major research database on business and provides full text of more than 2,300 journals, including over 1,100 peer-reviewed titles. In addition, it includes searchable, cited source information back to 1998.

Google Scholar: on Google Scholar, you can search for academic texts. 

BASE (Bielefeld Academic Search Engine): Is one of the world's largest search engines for online academic documents. The index spans over 100 million documents from over 4,000 sources. Some 60% of the documents included in the BASE directory are full texts available to access for free (open access). The BASE search engine is operated by the Bielefeld University Library.

Handbuch Internet-Recherche: the focus of this German-language online guide for internet research is on searching for academic information. 

Suchdienste-Kompass: the Suchdienste-Kompass (Search Services Finder) of the Bielefeld University Library explains in a user-friendly way how to achieve your internet search goals quickly.

Online-Fernleihe: the portal for online inter-library loans, officially known in German as “Deutscher Leihverkehr”, is a cooperative establishment by libraries in the Federal Republic of Germany for sharing and providing media. It is based on the principle of reciprocity, i.e. every library contributes to and makes use of the shared stocks.