将一瓶水倒去一半,则留下的一半( ) A.密度不变,质量和比热容都变为原来的一半

题型:选择题

问题:

将一瓶水倒去一半,则留下的一半(  )

A.密度不变,质量和比热容都变为原来的一半

B.质量、比热容、密度都变为原来的一半

C.比热容不变,质量和密度都变为原来的一半

D.比热容和密度都不变,质量变为原来的一半

考点:比热容的概念密度及其特性
题型:选择题

  【甲】①那是力争上游的一种树,笔直的干,笔直的枝。②它的干通常是丈把高,像是加过人工似的,一丈以内绝无旁枝。③它所有的丫枝一律向上,而且紧紧靠拢,也像是加过人工似的,成为一束,绝不旁逸斜出。④它的宽大的叶子也是片片向上,几乎没有斜生的,更不用说倒垂了。⑤它的皮光滑而有银色的晕圈,微微泛出淡青色。⑥这是虽在北方风雪的压迫下却保持着倔强挺立的一种树。⑦哪怕只有碗口那样的粗细,它却努力向上发展,高到丈许,两丈,参天耸立,不折不挠,对抗着西北风。

  【乙】街上的柳树像病了似的,叶子挂着层灰土在枝上打着卷;枝条一动也懒得动,无精打采地低垂着,马路上一个水点也没有,干巴巴地发着白光。便道上尘土飞扬飞起多高,跟天上的灰气连接起来,结成一片毒恶的沙阵,烫着行人的脸。处处干燥,处处烫手,处处憋闷,整个老城像烧透了的砖窑,使人喘不过气来。

  【丙】这里的树,以古老苍劲见长。有两棵老树:一颗是周柏,另一棵是唐槐。那周柏,树干劲直,树皮皴裂,顶上____着几根青的疏枝,偃卧在石阶旁。那唐槐,老干粗大,虬枝盘曲,一簇簇柔条,绿叶如盖。还有水边殿外的松柏槐柳,无不显出苍劲的风骨。以造型奇特见长的,有的____如老妪负水,有的____如壮士托天,不一而足,圣母殿前的左扭柏,拔地而起,直冲云霄,它的树皮上的纹理一齐向左边____去,一圈一圈,丝纹不乱,像地下旋起了一股烟,又似天上垂下了一根绳。晋祠在古木的荫护下,显得分外幽静、典雅。

1.甲段中最能体现白杨树精神特点的两个词语是:____、____。丙段中最能突出晋祠树的特点的两个词语是:____、____。

2.丙段横线处应依次填入的词,最恰当的一项是(    )

A.挑 偃 挺 拧

B.横 偃 劲 扭

C.排 犹 劲 扭

D.横 犹 挺 拧

3.《白杨礼赞》运用____的表现手法,借白杨树来赞美抗日军民;

乙段运用____的修辞手法,生动地写出了烈日下柳树的“病态”;丙段在介绍左扭柏时,运用了____的说明方法,形象地写出了它高而“扭”的特点。

4.从表达方式看,甲段主要是描写与____相结合,丙段是描写与____相结合,而乙段则是比较单一的自然环境描写。

5.对三段文字描写的目的与作用理解正确的一项是(    )

A.甲、乙两段是为了体现树的精神,丙段是为了突出树的形态特征。

B.甲、乙两段是为了突出树的形态特征,丙段是为了体现树的精神。

C.甲段突出树的神态,丙段体现树的精神,乙段突出“烈日”之酷。

D.甲段体现树的精神,丙段突出树的神态,乙段突出“烈日”之酷。

题型:选择题

There is a lot of misunderstanding about studying. Most students have not been taught the principles behind really effective working. Imagine a graph showing the amount a person learns against the number of hours he works in a day. If he doesn’t do any work, he learns nothing (point 0). If he does an hour’s work he learns a certain amount (point 1). If he does two hours’ work he learns about twice as much (point 2). If he does more work he’ll learn still more (point 3). However, if he tries to do twenty-three and a half hours’ work in a day, he will be so tired that he’ll hardly remember anything: what he learns will be very little (point 4). If he did less work he’d learn more (point 5).

Now whatever the exact shape of the graph’s curve(曲线), made by joining these points, it must have a high point. Point “X” is the very maximum anyone can learn in the day. And this represents the optimum(最适度), the best, amount of work to do. It is the best possible compromise between adequate time at the books and fatigue(劳累). Fatigue is an absolutely real thing; one can’t escape it or ignore it. If you try to ignore it and press yourself to work past the optimum, you will only get on this downward slope and achieve less than the best – and then become very tired and lose your power of concentration.

The skill in being a student consists of getting one’s daily study as near the optimum point as possible. I cannot tell you what the optimum is. It differs with the type of work, it differs from person to person, and even in the same person it varies from week to week. You must try to find your own. Every day you study, bear this principle of the optimum in mind. When you feel yourself getting fatigued, if you find yourself reading the same paragraph over and over again and not taking it in, that’s a pretty good sign you’ve reached your highest point for the day and should stop. Most ordinary students find their optimum at five hours a day. Yours may be a little more or a little less – but if you get in five hours’ good work a day, you will be doing well.

Now, what are you doing with yourself when you aren’t working? Before examinations some students do nothing at all except sit in a chair and worry. Here is another misunderstanding. People often think that the mind works like the body; it does not. If one wanted to save one’s physical energy in order to cut the maximum amount of firewood, one would lie flat on a bed and rest when one wasn’t chopping. But the mind cannot rest. Even in sleep you dream, even if you forget your dreams. The mind is always turning. It gets its relaxation only by variety. That is what makes the mind rest.

When you’ve finished your optimum number of hours you must stop. You must not then sit around in the chair thinking about the work – that only tires without any learning. You must get out and do something. It doesn’t matter what – anything so long as you are actively doing something else but work.

小题1:According to the passage, _______.

A.the longer you study every day, the more you will learn

B.you’ll achieve better learning results if you work three hours every day

C.the less work you do, the better you will learn

D.your work efficiency will decrease once you exceed a certain point of work小题2:Fatigue can result in ________.

A.loss of memory

B.a need for relaxation

C.a lot of anxiety

D.loss of concentration小题3:The passage tells us that a person’s optimum number of working hours _______.

A.follows a regular pattern with each individual

B.changes regularly from week to week

C.can be partly determined by the sort of work he is doing

D.should be determined before he gets too tired小题4:The only way the mind can relax is by ________.

A.doing a variety of things in turn

B.not thinking about anything

C.turning continuously

D.getting oneself in a state of fatigue小题5:After you have reached the optimum point of study in a day, you should ________.

A.lie in bed and rest

B.do something else actively

C.do some physical labor

D.stop thinking about your studies

题型:选择题

用燃气灶烧水,使50kg的水从20℃升高到90℃,燃气灶烧水的效率是40%,已知煤气的热值为4.2×107J/kg.求:

(1)水吸收的热量.

(2)煤气完全燃烧放出的热量.

(3)需要消耗多少燃气.

题型:选择题

为了提高数据流图的易理解性,应注意()

A. 简化加工间联系和数据守恒

B. 均匀分解和数据守恒

C. 简化加工间联系和均匀分解

D. 均匀分解和文件操作的正确性

题型:选择题

儿童小脑星形细胞瘤的特点为()

A.多起源于小脑半球

B.多起源于小脑蚓部

C.多是单房或多房的囊样结构

D.水肿程度比大脑半球者重

E.水肿程度比大脑半球者轻

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