【单选题】
Death rates declined in many places, partly because of the ___ in hunger.
A. decrease
B. myth
C. obstacle
D. burden
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【单选题】
In deciding whether or not a situation is safe, pilots must be taught to assume that the worst will happen, and then to ___ whether there is a risk or not.
A. absorb
B. apply
C. assess
D. occupy
【单选题】
The worker was not worried as he knew that if he gave up the job, there would be ___ opportunities for him to work somewhere else.
A. formative
B. marginal
C. vigorous
D. numerous
【单选题】
The research shows the region might ___ overheating (经济过热), but the policymakers so far appear to be relatively relaxed about the future of the economy.
A. catch a glimpse of
B. be at risk of
C. take a toll on
D. be free from
【单选题】
Measures have been taken to ensure that no student will have to ___ of college for economic reasons.
A. lay out
B. cancel out
C. drop out
D. stand out
【单选题】
Stress that is not treated can lead to significant medical illnesses, which ___ can lead to greater stress and even depression (抑郁症).
A. after all
B. in turn
C. on the contrary
D. at least
【单选题】
Narcissism (自恋) has its benefits in terms of self-belief and confidence, but it also tends to be ___ risky decision-making.
A. associated with
B. contrasted with
C. reserved for
D. relieved of
【单选题】
When Tom saw his doctor again, she suggested that maybe a more substantial lunch, like a sandwich, might ___ his desire to have snacks in the afternoon.
A. count on
B. cut back on
C. hold on to
D. contribute to
【单选题】
You shouldn’t ___ – let your children make their own decisions.
A. interact
B. abuse
C. startle
D. interfere
【单选题】
This is a huge and difficult project and if you take it up, you ___ many difficulties.
A. like to encounter
B. like encountering
C. are likely to encounter
D. are like to encounter
【单选题】
The ability to live for a long time without water is characteristic ___ the camel.
A. of
B. for
C. about
D. in
【单选题】
Rising sales is a good ___ that this product is well received in the market.
A. response
B. convention
C. indication
D. Influence
【单选题】
When tourists travel abroad, they are sometimes ___ by the local people because the tourists don’t know the real value of products.
A. turned in
B. given chase
C. wrapped up
D. ripped off
【单选题】
The professor’s lecture ___ the capacity of his young audience. They all looked puzzled at him.
A. pointed out
B. went beyond
C. contributed to
D. kept off
【单选题】
We must ___ on the amount of time we use on this project.
A. cut both ways
B. cut in line
C. cut off
D. cut down
【单选题】
We have to be very patient with this experiment. It will take time for some effects to ___ clearly.
A. build up
B. break up
C. clear up
D. show up
【单选题】
Perhaps there is a(n) ___ of truth in both theories, but few of us would ever have the opportunity to find out.
A. lump
B. substance
C. section
D. element
【单选题】
Be careful when you get along with her because she is known for her short ___.
A. temper
B. emotion
C. mood
D. feeling
【单选题】
It seems that wearing less formal clothing to school and work is becoming a(n) ___.
A. trend
B. campaign
C. goal
D. occurrence
【单选题】
You cannot correct children’s bad behavior simply with a (n) ___ or two on the hand or face.
A. slap
B. smash
C. slam
D. strike
【单选题】
Our investigations (调查) ___ something very surprising – many of the employees are underpaid and work overtime all the time.
A. reveal
B. bump
C. rip
D. frustrate
【单选题】
She was James’s faithful assistant, in whom he could have ___ confidence.
A. essential
B. automatic
C. ultimate
D. absolute
【单选题】
If you visit this website, you can ___ the categories to find information about all the universities in that area.
A. observe
B. browse
C. glance
D. look
【单选题】
Making New Year’s resolutions (计划) is a custom that still ___ in this country.
A. prevails
B. attaches
C. descends
D. launches
【单选题】
The military officers were more ___ about their own victory and therefore more willing to predict their enemy’s defeat.
A. appropriate
B. ignorant
C. negative
D. optimistic
【单选题】
___ is no doubt that overwork and much worry caused his illness.
A. It
B. There
C. Here
D. This
【单选题】
___ a day goes by that I don’t receive dozens of junk mails in my email box.
A. None
B. Usually
C. Nearly
D. Hardly
【单选题】
Please trust me. Try this new method ___.
A. you feel very relaxed
B. and you feel very relaxed
C. you will feel very relaxed
D. and you will feel very relaxed
【单选题】
John said Mom was coming back tomorrow, not next week. If this is the ___, we’ll all have to clean the house thoroughly.
A. point
B. norm
C. question
D. case
【单选题】
It is far too late for you to go out and play football, ___ the fact that it’s raining.
A. no doubt
B. despite
C. given
D. not to mention
【单选题】
However, under no circumstances should we ___ our achievements, nor should we regard our accomplishments as unimportant.
A. present
B. perceive
C. exemplify
D. exaggerate
【单选题】
Jane picked up a magazine from the bookshelf and started reading here and there ___.
A. accurately
B. randomly
C. emotionally
D. continually
【单选题】
In many Middle Eastern cultures a deadline is taken as a(n) ___, and such terms should not appear in a purchase contract with businessmen from these countries.
A. target
B. favor
C. honor
D. insult
【单选题】
He is by no means a(n) ___ man. On the contrary, he always departs from customs.
A. disgraceful
B. sophisticated
C. traditional
D. intelligent
【单选题】
Although the nuclear radiation problems remain unsolved, the government’s emphasis has been ___ from coal to nuclear.
A. intended
B. defined
C. attached
D. switched
【单选题】
The psychologist doesn’t say directly, but seems to ___ that emotional maturity and self-stimulation are the key elements for success.
A. inquire
B. imply
C. refer
D. confront
【单选题】
The top floors of a building collapsed, trapping a construction worker in the rubble (瓦砾), but he was ___ and could talk to rescuers.
A. reasonable
B. rational
C. innocent
D. conscious
【单选题】
After ___ research by the local government, officials confidently stated that this area of the sea was much safer than before.
A. extensive
B. durable
C. partial
D. extreme
【单选题】
As the world is becoming global, it is increasingly important that countries work together to ___ international trade.
A. soar
B. rise
C. facilitate
D. prompt
【单选题】
As the technology develops, it is probable that electronic books will start to ___ paper books in the near future.
A. ban
B. exchange
C. employ
D. replace
【单选题】
The man was sentenced to 10 years in prison after he was accused of ___ a senior bank official.
A. bribing
B. frustrating
C. chasing
D. eliminating
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【单选题】
9一个平衡PN结,用导线将P区和N区连起来,而导线中___。
A. 有微弱电流
B. 无电流
C. 有瞬间微弱电流
【单选题】
10二极管两端正向电压大于___电压时,二极管才导通。
A. 击穿电压;
B. 死区;
C. 饱和。
【单选题】
11当温度升高时,二极管的反向饱和电流 ___ 。
A. 增大;
B. 减小;
C. 不变;
D. 无法判定。
【单选题】
12硅二极管的正向导通压降比锗二极管的___ 。
A. 大
B. 小
C. 相等
【单选题】
13三端集成稳压器 CW7906的输出电压是___
A. -12v
B. -9v
C. -6V
【单选题】
14稳压管的工作是利用伏安特性中的___。
A. 正向特性
B. 反向特性
C. 反向击穿特性
【单选题】
15二极管具有___
A. 正向特性
B. 反向特性
C. 单向导电特性
D. 反向击穿特性
【单选题】
16图中D1-D3为理想二极管,A,B,C灯都相同,试问___灯最亮。
A. A灯
B. B灯
C. C灯
【单选题】
18在单相桥式整流电容滤波电路中,设U2为其输入电压,输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
19在单相桥式整流电路中,设U2为其输入电压,输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
20在半波整流电容滤波电路中,设U2为其输入电压,输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
21在半波整流电路中,设U2为其输入电压,输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
22温度影响了放大电路中的___,从而使静态工作点不稳定。
A. 电阻;
B. 电容;
C. 三极管;
D. 电源。
【单选题】
23用直流电压表测得放大电路中某三极管各极电位分别是2V、6V、2.7V,则三个电极分别是___。
A. [B、C、E]
B. [C、B、E]
C. [E、C、B]
【单选题】
24共射极放大电路的交流输出波形上半周失真时为___
A. 饱和失真
B. 截止失真
C. 交越失真
【单选题】
25三极管的反向电流ICBO是由___组成的。
A. 多数载流子
B. 少数载流子
C. 多数载流子和少数载流子
【单选题】
27如果在NPN型三极管放大电路中测得发射结为正向偏置,集电结也为正向偏置,则此管的工作状态为___
A. 放大状态;
B. 截止状态;
C. 饱和状态;
D. 不能确定。
【单选题】
28在以下三种电路中输入电阻最大的电路是___。
A. 共基放大电路
B. 共集放大电路
C. 共射放大电路
【单选题】
29在以下三种电路中既能放大电流,又能放大电压的电路是___。
A. 共基放大电路
B. 共集放大电路
C. 共射放大电路
【单选题】
30在以下三种电路中输出电阻最小的电路是___;
A. 共基放大电路
B. 共集放大电路
C. 共射放大电路
【单选题】
当PNP型晶体管工作在放大区时,各极电位关系为uC ___uB。
A. >
B. <
C. =
D. ≤
【单选题】
32当PNP型晶体管工作在放大区时,各极电位关系为uB___uE 。
A. >
B. <
C. =
D. ≤
【单选题】
33测得NPN型三极管上各电极对地电位分别为,,,说明此三极管处在___。
A. 放大区
B. 饱和区
C. 截止区
D. 反向击穿区
【单选题】
34若使三极管具有电流放大能力,必须满足的外部条件是___。
A. 发射结正偏、集电结正偏
B. 发射结反偏、集电结反偏
C. 发射结正偏、集电结反偏
D. 发射结反偏、集电结正偏
【单选题】
35在由PNP晶体管组成的基本共射放大电路中,当输入信号为1KHz、5mV的正弦电压时,输出电压波形出现了顶部削平的失真。这种失真是___ 。
A. 饱和失真
B. 截止失真
C. 交越失真
D. 频率失真
【单选题】
36在由PNP晶体管组成的基本共射放大电路中,当输入信号为1KHz、5mV的正弦电压时,输出电压波形出现了底部削平的失真。这种失真是___ 。
A. 饱和失真
B. 截止失真
C. 交越失真
D. 频率失真
【单选题】
37共集电极放大电路中Re的负反馈组态是___。
A. 电压串联负反馈
B. 电流串联负反馈
C. 电压并联负反馈
【单选题】
38为了使放大器带负载能力强,一般引入___负反馈。
A. 电压
B. 电流
C. 串联
【单选题】
41为了提高三极管放大电路的输入电阻,采用___负反馈 i=i1+i2
A. 电流
B. 电压
C. 并联
D. 串联
【单选题】
42为了稳定输出电流,采用___负反馈。
A. 电流
B. 电压
C. 并联
D. 串联
【单选题】
43为了改善放大器的动态性能,应该引入___电路。
A. 直流负反馈
B. 交流负反馈
C. 电压负反馈
D. 电流负反馈
【单选题】
44为了稳定放大器的静态工作点,应该引入___电路。
A. 直流负反馈
B. 交流负反馈
C. 电压负反馈
D. 电流负反馈
【单选题】
45共模抑制比是差分放大电路的一个主要技术指标,它反映放大电路___能力。
A. 放大差模抑制共模
B. 输入电阻高
C. 输出电阻低
【单选题】
46差分放大电路是为了___而设置的。
A. 稳定Au
B. 放大信号
C. 抑制零点漂移
【单选题】
47分析运放的“虚短”是指是___。
A. U-≈U+
B. I-≈I+≈0
C. U0=Ui
D. U-≈U+≈0
【单选题】
48分析运放的“虚断”是指是___。
A. U-≈U+
B. I-≈I+≈0
C. I-≈I+
D. U-≈U+≈0
【单选题】
51两级放大电路,Au1=-40,Au2=-50,若输入电压U1=5mv,则输出电压Uo为 ___
A. -200mv;
B. -250mV;
C. 10V;
D. 100V
【单选题】
52通用型集成运放的输入级多采用___。
A. 共基接法
B. 共集接法
C. 共射接法
D. 差分接法
【单选题】
53理想运放的两个重要性质是___。
A. 虚短与虚地
B. 虚断与虚短
C. 断路与短路
【单选题】
54振荡器的输出信号最初由___而来的。
A. 基本放大器
B. 选频网络
C. 干扰或噪声信号