TY - Journal of Peking University (Health Sciences) A1 - T1 - Y1 - 2006-06-18 JF - Journal of Peking University(Health Sciences) JO - Journal of Peking University (Health Sciences) SP - 271 EP - 275 VL - 38 IS - 3 UR - http://xuebao.bjmu.edu.cn N1 - ER -