基金Supported by the National Natural Science Foundation of China under Grant Nos.60233010,60403014,60603034(国家自然科学基金)the National High-Tech Research and Development Plan of China under Grant Nos.2004AA112090,2005AA113160,2006AA01Z159,2006AA01Z177(国家高技术研究发展计划(863))the National Basic Research Program of China under Grant No.2002CB312002(国家重点基础研究发展计划(973))