There are two good resources to find abbreviations for science journals:

1. Chemical Abstracts source index

CASSI (CAS Source Index) Search Tool
http://cassi.cas.org/
CAS Core Journal Abbreviations
http://www.cas.org/content/references/corejournals

2. Web of Science journal abbreviations index

Journal Abbreviations Index (ISI)
http://library.caltech.edu/reference/abbreviations/
http://images.webofknowledge.com/WOK46/help/WOS/A_abrvjt.html