Encyclopedia Dictionary of the Chinese Language (中文大辭典) - It contains more than 80 million words.
Han yu da ci dian - The comprehensive dictionary of Chinese. 
Oxford Bibliographies (Chinese Studies) - provides accurate and reliable resources for various topics in Chinese Studies. Each entry contains original commentary and annotated bibliographies. A good place to start a research project. [Index] [English]
Quan guo tu shu shu mu zi xun wang: National Bibliographic Information Network (NBINet) - The network includes three bibliographic databases: NBINet Union Catalog (Taiwan), Chinese Publications in China and Chinese rare books. [Index] [Chinese] 
