另两个为胸腺嘧啶和胞嘧啶, 即称为嘧啶的单环结构.The other two, thymine and cytosine, are single ring structures called pyrimidines.嘌呤为嘧啶取代或嘧啶为嘌呤所取代,叫做颠换.The substitution of a purine for a pyrimidine, or vice versa is a transversion.本文研究氟脲嘧啶(5—...
Suddenly he heard a rustle in the peony pavilion and someone sighing deeply.他忽闻有人在牡丹亭畔长吁短叹.What are you sighing about?你为什么唉声叹气?What are you sighing about? Is something wrong?你叹息什么? 出什么事了?Sighing for sorrow can be harmful...