关于潜伏性感染的概念,下列哪项不正确()A.病原体潜伏于机体某些部位而不出现症状 B

题型:单项选择题

问题:

关于潜伏性感染的概念,下列哪项不正确()

A.病原体潜伏于机体某些部位而不出现症状

B.机体免疫力下降时可引起显性感染

C.潜伏性感染是重要而危险的传染源

D.潜伏性感染期间,病原体一般不排出体外

E.疟疾、结核、单纯疱疹可有潜伏性感染

考点:传染病学(医学高级)一、总论一、总论题库
题型:单项选择题

阅读回答问题。

     People believe that climbing can do good to health. Where can you learn the skill of climbing then? If you

think that you have to go to the mountains to learn how to climb, you're wrong. Many Americans are learning

to climb in city gyms. Here, people are learning on special climbing walls. The climbing wall goes straight up

and has small holding places for hands and feet.

     How do people climb the wall? To climb, you need special shoes and a harness (保护带) around your chest

to hold you. There are ropes (绳索) tied to your harness. The ropes hold you in place so that you don't fall.

A beginner's wall is usually about 15 feet high, and you climb straight up. There are small pieces of metal that

stick out for you to stand on and hold on to. Sometimes it' s easy to see the new piece of metal. Sometimes,

it's not. The most difficult part is to control your fear. It's normal (正常的) for humans to be afraid of falling,

so it's difficult not to feel fear. But when you move away from the wall, the harness and the ropes hold you,

and you begin to feel safe. You move slowly until you reach the top. 

     Climbing attracts people because-it's good exercise for almost everyone. You use your whole body,

especially your arms and legs. This sport gives your body a complete workout. When you climb, both your

mind and your body can become stronger.

1. Do people have to go to the mountains to learn how to climb?

    ___________________________________________________________________________

2. Where are many Americans learning to climb?

    ___________________________________________________________________________

3. How can ropes help people in climbing? 

    ___________________________________________________________________________

4. What is the most difficult part for climbers in climbing?

    ___________________________________________________________________________

5. What is a good climber like?

    ___________________________________________________________________________

题型:单项选择题

(8分)某同学通过实验测量一种合金的电阻率。

(1)用螺旋测微器测量合金丝的直径。为防止读数时测微螺杆发生转动,读数前应先旋紧题图所示的部件     (选填“A”、“B”、“C”或“D”)。从图中的示数可读出合金丝的直径为       mm。

(2)题图所示是测量合金丝电阻的电路,相关器材的规格已在图中标出。合上开关,将滑动变阻器的滑片移到最左端的过程中,发现电压表和电流表的指针只在图示位置发生很小的变化。由此可以推断:电路中   (选填图中表示接线柱的数字)之间出现了       (选填“短路”或“断路”)。

(3)在电路故障被排除后,调节滑动变阻器,读出电压表和电流表的示数分别为2.23V和38mA,由此,该同学算出接入电路部分的合金丝的阻值为58.7Ω。为了更准确地测出合金丝的阻值,在不更换实验器材的条件下,对实验应作怎样的改进? 请写出两条建议。

                                                                                        

                                                                                        

题型:单项选择题

测定大气中的微量有机化合物(M大于400)首选的仪器分析方法是()

A、GC

B、ISE

C、AAS

D、UV

题型:单项选择题

霍乱的发病机制中,起主要作用的是

A.侵袭力
B.肠毒素
C.神经节苷脂
D.内毒素
E.cAMP

题型:单项选择题

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