基金This work was supported by the National Science Foundation of China (No. 30470564)the Foreign Expert Bureau of the State Council of China (No. 2002-30211120641, T010360056)
基金This work was supported by the National Natural Science Foundation of China (No. 30470564) the Natural Science Foundation of Hubei Province (No. 2004ABA180)Construction Fund for "211" Project of the Ministry of Education of China.