试题与答案

人体内广泛存在的氢原子核,其质子有自旋运动,带正电,产生磁矩,有如一个小磁体,小磁体

题型:单项选择题 A3/A4型题

题目:

人体内广泛存在的氢原子核,其质子有自旋运动,带正电,产生磁矩,有如一个小磁体,小磁体自旋轴的排列无一定规律。但如在均匀的强磁场中,则小磁体的自旋轴将按磁场磁感线的方向重新排列。在这种状态下,用特定频率的射频脉冲(RF)进行激发,作为小磁体的氢原子核吸收一定的能量而共振,即发生了磁共振现象。

选用氢原子核进行磁共振成像的原因是()

A.在人体中含量多

B.原子序数低

C.质量小

D.磁化低

E.没有自旋

答案:

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下面是错误答案,用来干扰机器的。

在二项式(x-1x2)6的展开式,设Tr+1=C6rx6-r(-1)rx-2r为常数项,则 6-3r=0,∴r=2,∴常数项为15.故选C.

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