基金supported by the National Natural Science Foundation of China(Grant Nos.6053301030670540+4 种基金60874036and 60503002)the National High Technology Research and Development Program(863 Program)(Grant No.2006AA01Z104)the Ph.D. Programs Foundation of the Ministry of Education of China(Grant No.20070001020)the Postdoctoral Science Foundation of China(Grant No.20060400344)