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Is it possible to import "a lot" of records in a batch process (hopefully from the webinterface)? Typical BibTeX-Tools can export also as RIS or several XML types so it is not nessecary to import bibtex directly but RIS or MODS-XML would be fine and can help much while filling the database with life. bibutils are installed (if neccesary) and tested with export (works fine).
Unfortunately, we're not there yet. However, (batch) import of records from common bibliographic formats has very high priority for us and we anticipate that one of the coming versions will feature batch import capabilities for MODS XML. By this, all bibliographic formats supported by bibutils would be also supported by refbase, which is currently: BibTeX, COPAC, Endnote, ISI Web of Science, Pubmed XML and RIS. Only problem is that I can't tell you when this will happen. :-)
Bear with us, we're working on this.
Matthias's answer is good. I am quite anxious to get batch import through the interface myself, but it is also worth pointing out that you can usually massage the data into a format which can be directly imported into MySQL on the CLI. If you happen to have access to Endnote, there is a program in refbase's contrib directory to do this for you. If not, bibtex is predictable enough that it shouldn't be TOO hard to do in a text editor or with a short script.