第23题: [单项选择]What is the most appropriate title for this passage a. Two Types of Stocks b. A New Strategy of Investment c. Distinctions between Trading and Investment d. Conflicting Perspectives on Stock Investment 参考答案:D 答案解析:[解析]Stocks can be divided into two categories: those for trading and those for investing. Within tra
第34题: [单项选择]关于共振频率的叙述哪一种是错误的() A. 是产生磁共振现象的必要条件 B. 当射频脉冲频率与质子进动频率相同称共振频率 C. 共振频率的脉冲可以使纵向磁场发生偏转 D. 共振频率随磁场强度变化而变化 E. 共振频率与成像质子的种类无关 参考答案:E 答案解析:当向静磁场中的人体发射与质子进动频率相同的RF脉冲时,就能将RF脉冲能量传递给质子而出现磁共振现象,这个频率称为共振频率。