Here is the export in AMA format with missing publication:

1. Adler DS, Bar-Yosef O, Belfer-Cohen A, u. a. Dating the demise: Neandertal extinction and the establishment of modern humans in the southern Caucasus. 2008.

And here is the corresponding excerpt of the BibTeX file, I imported:

@Article{Adler232,
author = {Adler, D. S. and Bar-Yosef, O. and Belfer-Cohen, A. and Tushabramishvili, N. and Boaretto, E. and Mercier, N. and Valladas, H. and Rink, W. J.},
title = {Dating the demise: Neandertal extinction and the establishment of modern humans in the southern Caucasus.
},
keywords = { Einzeldownload ahaedofprint Aussterben},
journal = {J Hum Evol},
booktitle = {},
editor = {},
address = {},
publisher = {},
edition = {},
volume = {},
number = {},
year = {2008},
pages = {},
signature = {},
abstract = {This paper considers the recent radiometric dating ((14)C-AMS, TL, ESR) of 76 late Middle and early Upper Paleolithic samples from Ortvale Klde Rockshelter, located in the Republic of Georgia. We present a critical evaluation of each date based on its stratigraphic and archaeological context, its pretreatment and contamination history, and its resulting accuracy and precision, the goal being to establish a sound chronology for the site. Only by systematically identifying aberrant dates within a data set and isolating them from further analysis can we hope to understand cultural and biological phenomena on an accurate temporal scale. Based on the strict discard protocol outlined here, we omit 25% of the dated samples from the analysis. The remaining data speak to the lengthy tenure of Neandertals in the region, but also to their relatively rapid demise and the establishment of modern human populations approximately 38-34ka (14)C BP (42-39kacalBP(Hulu)). We compare these chronometric data with those from the neighboring sites of Bronze and Dzudzuana caves, as well as Mezmaiskaya Cave, located in the northern Caucasus. While the lack of key contextual information limit our ability to subject these other data sets to the same critical evaluation procedure, they provide the first interregional temporal assessment of the Middle to Upper Paleolithic "transition," the results of which suggest an initial expansion of modern humans into the southern Caucasus followed by expansion along the Black Sea coast and into the northern Caucasus.},
notes = {},
key = {Adler232}
}

I don't find the journal's title in any other field. Could it be, that the German translation simply does not map 'journal' to 'publication'?
Thank you very much for your assistance

I'll double check, but if that's what's happening, I'll fix it. We can safely discard any empty values; no BibTeX should be depending on such an override.

Some words to the background. bibliograhix3, which does not work on 64bit Windows, does not offer options for the export to BibTeX. But I could replace the emty brackets in a text editor, if you really think, this would solve the problem. Since the other fields worked fine, I had not thought of this...

Please go to http://github.com/ajlyon/zotero-bits/raw/master/BibTeX.js and save the file to the translators directory of your Zotero data directory (http://www.zotero.org/support/zotero_data).

It should work, but it should be tested carefully -- there's a risk that this might break some BibTeX. If this works for you, please post here so that I can submit this change to be pushed to all users.

I searched and replaced all empty brackets - but the publication fields remain empty!
My import file looks like this now:

@Article{Adler232,
author = {Adler, D. S. and Bar-Yosef, O. and Belfer-Cohen, A. and Tushabramishvili, N. and Boaretto, E. and Mercier, N. and Valladas, H. and Rink, W. J.},
title = {Dating the demise: Neandertal extinction and the establishment of modern humans in the southern Caucasus.
},
keywords = { Einzeldownload ahaedofprint Aussterben},
journal = {J Hum Evol},
booktitle = ,
editor = ,
address = ,
publisher = ,
edition = ,
volume = ,
number = ,
year = {2008},
pages = ,
signature = ,
abstract = {...}...

I think it would be easiest to import tab seperated txt-files, but zotero doesn't seem to support this feature. All other export formats from bibliographix don't work at all, giving me only error messages, if I try to import them into zotero.

In fact it did! The new filter seems to fix my problem. Thank you very much, ajlyon!