基金This work was supported by the National Natural Science Foundation of China (10471151)National 863 Project(2003AA148040)the Educational Science Foundation of Chongqing,Chongqing of China(041302).
基金This research is supported by the National Natural Science Foundation of China(69903012, 60216263) National 863 Project 2003AA148040the Educational Science Foundation of Chongqing, Chongqing of China (KJ051307)