以下对头孢菌素的结构改造,哪个不能延长作用时间或提高活性()
A.3位引入甲基
B.5位用N取代
C.2位羧基成酯
D.7位引入氨基噻唑
E.5位用S替代
参考答案:B
根据首字母和汉语提示完成单词。
1. In the USA,when you get a present,you must open it i______.?
2. In China,when someone gives you a present, you must w______ and open it later.?
3. When you ______(接受)a present,you must use both hands.?
4. You mustn't do any c______ on the first day of the Chinese New Year.?
5. In China, people eat lots of d______ at Spring Festival.?
不属于毛茛科的是()。
A.牡丹
B.昙花
C.飞燕草
D.芍药