下列感受器中，对刺激变化十分灵敏、有利于探索新异事物的是（）

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问题单项选择题

A.皮肤麦斯纳小体

B.关节囊感受器

C.脑渗透压感受器

D.心房容量感受器

E.颈动脉体化学感受器

答案

参考答案：A

单项选择题

某药口服吸收良好，但经过肝脏之后只有30%的药物到达体循环，其原因是该药

A．与血浆蛋白结合率高

B．效价低

C．存在首过效应

D．治疗指数低

E．排泄快

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单项选择题

Networks can be interconnected by different devices．In the physical layer，networks can be connected by (64) or Hubs, which just move the bits from one network to an identical net-work. One layer up we find bridgas and swiehes, which operate at data link layer. They can accept (65) , examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two netwoks. If two networks have (66) network layer, the router may be able to translate between the packet formats. In the transport layer we find transport gateway, which can interface between the two transport connections. Finally, in the application layer, application gateways translate message

(67) . As an example, gateways between Internet e-mail and X.400 e-mail must (68) the e-mail message and change various header fields.

64（）

A．reapers

B．relays

C．connects

D．modems

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