Google scholar is an excellent service for looking at basic metadata about publications (e.g. authors, title, abstract, and papers it cites). But they do not offer an official API (free or otherwise).
Is there also a non-commercial database of such publications? I'm wondering because this is something that perhaps libraries in universities would require to organize information about publications across disciplines.
Since there are non-profit systems like doi.org and cross-ref which let publications get an identification numbers, I'm wondering if all disciplines use them. Or is it the case that universities get this metadata from a variety of publishers (like Springer, Elsevier, etc) and there is no single central index?
To avoid bikeshedding on what a "major discipline" is, we could limit ourselves to what's already found on google scholar, or perhaps to what top 100 (or choose your number) university libraries in the world might index.