National Nuclear Data Centre

The National Nuclear Data Centre (NNDC) is a comprehensive, web-based nuclear data resource. It collects, evaluates and disseminates nuclear physics data for basic nuclear research and for applied nuclear technologies. The information available to the users of NNDC services is the product of the combined efforts of the NNDC and cooperating data centers and other interested groups in the United States and worldwide.

The NNDC specializes in nuclear structure and low-energy nuclear reactions, nuclear databases and information technology and nuclear data compilation and evaluation. 

http://www.nndc.bnl.gov/