I am pretty sure the metadata from dx.doi.org doesn't contain any abstract information, so there is not a way to put anything useful in it. The abstract is often covered by copyright. You can add your own abstract with bibtex-make-field (C-c C-f) in a bibtex entry, or you can copy the bibtex entries from publisher sites which usually do contain the abstract if you ask for it.
Julien Cubizolles writes: > I'm starting to use org-ref to manage bibtex file, and it's impressively > useful! However I couldn't find a variable to have the > *-add-bibtex-entry create an abstract field in the bibtex entry. Is it > possible? If not, I think it would be a useful addition. > > J. Cubizolles -- Professor John Kitchin Doherty Hall A207F Department of Chemical Engineering Carnegie Mellon University Pittsburgh, PA 15213 412-268-7803 @johnkitchin http://kitchingroup.cheme.cmu.edu