【单选题】This past spring, my wife and I ______ enough to be able to spend 10 days in Italy.
【简答题】B On the last day of his life, my dog Otto spent that morning of spring napping in the garden. This was always one of his favorite things to do, even before the days when he was too old and too weak t...
【判断题】斜度在图样上通常以1:n的形式标注,并在前面加上斜度符号,加∠1:5.
【简答题】用二甲酚橙作指示剂以EDTA直接滴定Bi3+ ,Th4+ ,Pb2+ ,Zn2+ 等离子时.终点由( )变为( ).
【单选题】关于氨基酸的等电点,下列说法正确的是()
【单选题】合成嘌呤核苷酸与嘧啶核苷酸所需的 5- 磷酸核糖来自
【简答题】二极管是由 PN 结构成,故二极管也具备 。
【单选题】关于氨基酸等电点,下列叙述错误的是( )
A.
pH > pI 时,氨基酸在电场中向阴极方向移动
B.
pH < pI 时,氨基酸主要以阳离子形式存在
C.
pH=pI 时,氨基酸溶解度最小,在电场中不向任何一极移动