题干

氢气在氧气中燃烧的实验说明,水是由 ____组成的;请写出氢气在氧气中燃烧的化学方程式 ____

上一题 下一题 0.0难度 选择题 更新时间:2012-07-17 08:42:51

答案(点此获取答案解析)

氢元素和氧元素,2H2+O2​2H2O

同类题3

阅读下面的短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。

    I lost my sight when I was four years old by falling off a box car in a freight(货运) yard in Atlantic City and landing on my head. Now I am thirty-two. I can slightly 1 the brightness of sunshine and what color red is. It would be wonderful to see again, but 2 can do strange things to people.

    It 3 to me the other day that I might not have come to love life as I do if I hadn't been 4. I believe in life now. I am not so sure that I would have believed in it so 5, otherwise. I don't mean that I would prefer to go without my 6. I simply mean that the loss of them made me 7 the more what I had left.

    Life, I believe, asks a continuous series of 8 to reality. The more readily a person is able to make these adjustments, the more 9 his own private world becomes. The adjustment is never easy. The hardest 10 I had to learn was to believe in myself. That was 11, If I hadn't been able to do that, I would have 12 and become a chair rocker on the front porch(门廊) for the rest of my life.

    It took me years to discover and 13 this believe. It had to start with the most elementary things. Once a man gave me an indoor baseball. I thought he was 14 at me and I was hurt. "I can't use this," I said. "15 it with you," he urged me, "and roll it around." The words stuck in my head. "Roll it around!" By rolling the ball I could hear 16 it went. This gave me an idea how to achieve a goal I had thought 17: playing baseball. At Philadelphia's Overbrook School for the Blind I invented a successful variation of 18. We called it ground ball.

    All my life I have set ahead of me a series of goals and then tried to reach them, one at a time. I had to learn my 19. It was no good to try for something I knew at the start was wildly out of reach because that only invited the bitterness of 20. I would fail sometimes anyway but on average I made progress.

同类题5

阅读下文,回答问题

信息时代的“无价之宝”

张唯诚

       ①在古代,炼金术士声称他们能将铅之类的金属变成贵重的黄金,当然这是不可能的。现在,数据科学家正在将大量数据变成信息,这些信息虽然不是黄金,但价值胜似黄金。数据科学家可以说是现代的“炼金术士”。

       ②英国数据科学家维克托·迈尔·舍恩伯格在他的著作《大数据》中指出,今天全世界存储的信息中,书和磁带只占不到两成,多数信息都以数据形式存储在电脑硬盘、通信设备和其他数字设备中。全世界产生的数据正在以惊人的速度增长,最近两年的数据产生量就占到总数据量的90%。一家互联网研究公司预测,人类产生的数据还将以每三年翻一番的速度增长。

       ③互联网并不是产生大量信息的唯一地方,另有大量信息是由科学家们“制造”出来的,这些信息来自于他们对大量事实的研究,而对这些事实的记录就是数据。例如,生物学家测量了成千上万个细胞,从而收集到大量数据;天文学家观测了恒星、星系和太空中的各种能量活动,从而收集到大量数据;地球科学家收集到世界各地的有关水、风和气流的资料,从而也形成了大量数据。

       ④数据经过分析和归纳会形成有用的信息,于是人们发明了各种各样用于处理数据的计算机软件,人们利用数据做各种各样的事。在美国,人们通过分析数据了解到,每当飓风来袭前,超市中的草莓糖霜果塔饼干便特别抢手,这时的销售量会比平时增加7倍,而在暴风雨天气来临前,啤酒的销售也特别好,于是超市便知道在这种时候及时补充货源,从而令销量大增。数据还给警察们的工作带来了方便。在那些犯罪率高的城市,以前积累下来的犯罪数据可以派上用场,警察们使用这些数据预测犯罪的高发时间和地区,从而合理地调配警力,提高工作效率和防范效果。

       ⑤数据之所以能发挥上述作用,很重要的一个原因是它帮助我们预测了未来有可能发生的事,然而在有些领域,知道为什么会有某种事情发生显得更加重要。例如在医学领域,来自人体或者人体细胞的数据就有可能告诉医生们,某种疾病为什么会发生,从而帮助医生治疗这些疾病。

       ⑥科学家们还期待有一天数据能使各行各业变得更加高效和更具“个性化”。例如,当一个病人向医生提供了详细的数据,医生便可以将这些数据和其他病人的数据进行比较,从而依据这个病人的生活方式制定特定的治疗方案。同样在一个班级里,学生们利用平板电脑或者阅读器进行阅读练习。数据传到老师那里,如阅读用了多长时间,某个词语被学生标注了多少次等。分析这些数据 ,老师便可以发现读物的难点和学生们的兴趣点,从而有针对性地进行讲解,还可以对个别学生提供有针对性的辅导。数据同样可以运用到其他行业。

       ⑦因此,在我们这样一个信息时代,假若你成了一个数据科学家,你便拥有了神奇的魔力,就好像中世纪的炼金术士们所声称的那样。

(选自《百科知识》,2016年02期,略有删改)