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【单选题】
关于X线对比剂，以下叙述错误的是A.
可分为阳性对比剂和阴性对比剂
B.
阳性对比剂原子序数髙,密度大
C.
阴性对比剂原子序数低,密度小
D.
对比剂都不能人血
E.
阴性对比剂和阳性对比剂可混合使用
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【简答题】Parents with skilled maths,______.
【简答题】设计一个带复位端且对输入时钟clk进行二分频模块,并画出仿真波形。 设计要求:复位信号为同步、高电平有效,时钟的下降沿触发
【单选题】Skilled negotiators may
A.
suggest different forms of a potential settlement that are worth about the same to them.
B.
recognize that not all issues are worth the same amount to both parties.
C.
frequently save a final small concession for near the end of the negotiation to "sweeten" the deal.
D.
make the last concession substantial to indicate that "this is the last offer".
E.
Skilled negotiators may take all of the above actions.
【单选题】Skilled negotiators may
A.
suggest different forms of a potential settlement that are worth about the same to them.
B.
Skilled negotiators may take all of the above actions.
C.
recognize that not all issues are worth the same amount to both parties.
D.
frequently save a final small concession for near the end of the negotiation to "sweeten" the deal.
【多选题】过长转录物的产生在很大程度上会影响外源基因的表达,原因有()
A.
转录产物越长，RNA聚合酶转录一分子mRNA所需的时间就相应增加，外源基因的转录效率下降
B.
如果外源基因下游紧接有载体上的其它重要基因或DNA功能区域，则RNA聚合酶在此处的转录可能干扰质粒的复制及其它生物功能，甚至导致重组质粒的不稳定性；
C.
往往会产生大量无用的蛋白质，增加工程菌无谓的能量消耗
D.
过长的转录物往往不能形成理想的二级结构，从而大大降低外源基因编码产物的翻译效率
【单选题】下列有关基因工程的相关叙述,错误的是( )
A.
基因工程可以克服不同物种之间的生殖隔离,实现生物的定向变异
B.
在同一DNA分子中,限制酶的识别序列越长,酶切点出现的概率越大
C.
基因载体上有一个或多个限制酶的切割位点,供外源DNA插入
D.
以大肠杆菌为受体细胞时,先要用Ca 2 + 处理细胞以使其处于感受态
【简答题】America’s skilled white-collar work force has overtaken the ranks of skilled blue-collar workers for the first time.(翻译)
【单选题】Just as the veteran worker is skilled in the handling of machine, ______ the experienced writer is skilled in the handling of his words.
A.
as
B.
so
C.
thus
D.
like
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