毛花洋地黄苷丙碱水解去除乙酰基,为什么用氢氧化钙而不用氢氧化钠?
在强心苷色谱检识中,展开剂常加人少量水或甲酰胺,起什么作用
I was speaking to Jane on the phone when suddenly we were .
A. cut off
B. cut down
C. cut back
D. cut out
Peter complained to the owner of the book store that there were some pages in the dictionary.
A. losing
B. missing
C. dropping
D. falling