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.
Journal Collection • MPG Library Catalog
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).
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.