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问题 单项选择题

患者，女，25岁，孕4+月，面浮肢肿，下肢尤甚，按之没指，心悸气短，下肢逆冷，乏力，舌淡，苔白润，脉沉细，辨证属于

A．气滞
B．肾虚
C．痰湿
D．脾肾两虚
E．脾虚

答案

参考答案：B

单项选择题

T1值是指90°脉冲后，纵向磁化矢量恢复到何种程度的时间（）

 

A.37％

B.63％

C.36％

D.73％

E.99％
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单项选择题

Although a given waveform may contain frequencies over a very broad range, as a practical matter any transmission system will be able to accommodate only a limited band of （1）. This, in turn, limits the data rate that can be carried on the transmission （2）. A square wave has an infinite number of frequency components and hence an infinite （3）. However, the peak amplitude of the kth frequency component, kf, is only l/k, so most of the （4） in this waveform is in the first few frequency components. In general, any digital waveform will have（5） bandwidth. If we attempt to transmit this waveform as a signal over any medium, the transmission system will limit the bandwidth that can be transmitted.

（4）是（）

A.frequency

B.energy

C.amplitude

D.phase
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