题干

下列说法不正确的是                                       (      )

A:经典力学只适用于宏观物体和低速运动的问题

B:20世纪初,爱因斯坦提出了狭义相对论,引起人们对时空认识的革命

C:当普朗克常量不能忽略不计时,量子力学和经典力学的结论没有区别

D:爱因斯坦建立了狭义相对论,把物理学推到高速领域

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答案(点此获取答案解析)

C

同类题1

阅读短文,完成练习。

仙人掌

    ①烈日炙烤着大地,沙漠上粒粒沙石反射出灼目的光晕,到处是恼人的炙热,到处是难耐的干渴,然而就在这60℃的灼热的沙漠上,满身是刺的仙人掌却傲然存活。

    ②这顽强的生命力是怎样赢得的呢?原来为了适应干旱艰苦的环境,仙人掌有自身的结构和生活方式。

    ③干旱地带的植物都有发达的根系,仙人掌也不例外。它的根有很强的吸水能力,这有利于它们从炎热干燥的沙漠环境中吸收更多的水分,维持生命活动的需要。

    ④仙人掌的茎叶起了很大变化。它的茎秆又大又粗,而且肉质化,很像水果的果肉,这有利于它贮藏更多的水分。仙人掌在水分供应充足时,积极吸水,把水贮存在自己像果肉一样的茎中,一旦水分缺乏,贮水的茎就把水供给周围的组织,满足整个植株的生存需要,在沙漠上往来的行人口渴时,往往劈开仙人掌的茎,取它里面的积水来解渴。

    ⑤为了减少水分的蒸发,仙人掌的叶子严重退化,有人做过实验,连续6年不给仙人掌供水,它仍然能够活下去。由于叶子无法进行光合作用,它的茎秆就承担了这个重任,进行光合作用,供给整个植株营养。

⑥仙人掌具有顽强的生命力,它不像温室里的花朵那样娇气,它不需要人们特别的照料便能茁壮成长,而且它的用途还非常广泛。

    ⑦仙人掌的果实是紫红色的,呈椭圆形,大一点的果实有鹅蛋那么大,汁多味甜,除了可以当作美味的水果食用外,还可用来练糖和酿酒。

    ⑧有的仙人掌茎片,经过发酵加工,可以做成饲料;仙人掌树上经常会有一种叫胭脂虫的小虫子,能用来提炼名贵的红色染料;在农村,干枯的仙人掌还可以当燃料用;仙人掌高大的片状茎像板子一样,可以做建筑材料,建造农舍。

    ⑨世界上已知的仙人掌有一千多个品种;高的、矮的,圆的、扁的,绿的、紫的,开花的、不开花的,结果的、不结果的,这一千多个品种有一半生长在墨西哥。墨西哥境内多山缺水,仙人掌耐旱,根须又长又发达,当地农民利用它来防止水土流失、固定流沙,保护农田。小一点的仙人掌还可以种到花盆里,放在桌角窗台当作观赏植物。

    ⑩仙人掌凭着顽强旺盛的生命力在最酷热干旱的艰苦环境中生长着,而且给人们贡献出许多有价值的东西。它虽然浑身是刺,貌不惊人,外表比不过高大挺拔的乔木、摇曳多姿的奇花异草,但仙人掌适应艰苦环境而生存的坚忍顽强和它那种默默奉献的精神,却是一种独特的美丽。可以说,仙人掌是个只讲奉献不讲索取的典范!

同类题5

完形填空
    When I spent the summer with my grandmother, she sent me down to the 1with a list, I walked up to the counter.Behind it was an old lady named Miss Bee.
    “Excuse me,”I said. She 2“I need to get these,”I continued, 3up my list.
    “So? Go get them,”Miss Bee said.“4is here except you and me, and I'm not your servant. I suggest you get yourself a basket over there and start5.”It was not 6for a 7­ year ­old child, there were so many different kinds of things. I spent over an hour in the store.
I visited Miss Bee twice a week that summer. She 7short­changed me. Other times she overcharged. Going to the store was like going into a war. But by the end of that summer, I could finish my shopping trip8around 15 minutes. The morning I was to return home, I stopped in the store again to buy something.
    “All right,”Miss Bee said. “What did you 9this summer?”
    “That you're mean!”I replied.
    Miss Bee just laughed,“ I know 10you think of me,”she said. “Well, I don't care! My job is to teach every child I meet some life 11. When you get older you'll be glad that you met me!”Glad I met Miss Bee? Ha!How could it be?
    It sounded funny until one day my son came to me with his homework. “It's too 12 . ”he said. “Could you finish the math problem for me?”
    “13I do it for you, how will you ever learn to do it  yourself?”I said. Suddenly, I was back in that store where I had learned to add up my bill by myself. Had I ever been overcharged since?
    Life is full of all kinds of 14. We may be 15 a hand once or twice, but luck may not find us every time. So we should work them out by ourselves.