The DOAJ service lists toll-free, quality controlled, scientific and scholarly journals. It generally aims at covering all subjects and languages. The DOAJ Articles Search is restricted to those journals the publisher has supplied article metadata for.

The EZB is a huge directory of electronic journals which mirrors the central Max Planck Society subscriptions as well as the local licensing situation of the institutes. Access rights to the contents of the individual journals are indicated with "traffic lights". Entries are searchable on journal level.

Throughout Europe, national patent offices and the European Patent Office (EPO) offer free patent information on the Internet Patents reveal solutions to technical problems, and they represent an inexhaustable source of information: more than 80 percent of man's technical knowledge is described in patent literature. From the middle of 1998 onwards, esp@cenet 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.

The Max Planck Journal Index provides holdings of a great range of printed journals available within the Max Planck Society. Besides, it contains metadata of electronic journals as loaded from the EZB. The database is updated regularly from the ZDB (twice a year) and the EZB (monthly).

MPG.PuRe is the publication repository of the Max Planck Society. It contains bibliographic data and numerous fulltexts of the publications of its researchers. The repository is based on PubMan, a publication repository software developed by the Max Planck Digital Library. PuRe was introduced in the MPG in May 2009 and replaced the former institutional repository eDoc.

The ZDB is the world’s largest specialized database for serial titles (journals, annuals, newspapers etc., incl. e-journals). The ZDB contains more than 1 million bibliographic records of serials from the 16th century onwards, from all countries, in all languages, held in 4000 German (and some foreign) libraries, with holdings information. It does not index individual journal articles.