The Cytotoxic Effect of Topotecan on Topocisomerase(Ⅰ or Ⅱ) in SUD4 and DOHH2Topotecan对癌细胞系SUD4和DOHH2的拓扑异构酶(Ⅰ,Ⅱ)的毒性作用(英文)