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人造太阳
何 平
①前不久，一条新闻引起全世界关注：中国科学院等离子体物理研究所研制的“人造太阳”调试成功，年内即可试发电。
②“人造太阳”？难道真要在地球上造一个太阳？当然不是！“人造太阳”是指科学家利用太阳核反应原理，为人类制造一种能提供能源的机器——人工可控核聚变装置，科学家称它为“全超导托克马克试验装置”。
③太阳的光和热，来源于氢的两个同胞兄弟——氘和氚（物理学叫氢的同位素）在聚变成一个氦原子的过程中释放出的能量。“人造太阳”就是模仿这一过程。
④氢弹是人们最早制造出的“人造太阳”。但氢弹的聚变过程是不可控的，它瞬间释放出的巨大能量足以毁灭一切。而“全超导托克马克试验装置”却能够稳定控制核聚变，使聚变产生的能量缓缓输出，转化为人们可持续使用的电能。
⑤核聚变反应，首要条件是高温高压。太阳中心的温度高达1500万摄氏度，压强达到3000多亿个大气压。在这样的高温高压下，太阳的聚变反应非常容易。但在地球上可不容易，因为用任何一种材料制作的容器都无法耐受这样的高温高压。
⑥怎么办？科学家们想到了用磁场做容器。从氢弹爆炸至今，科学界用了60年的努力，目前已成功地在磁场容器中将温度提高到4亿至5亿摄氏度，然后投入氘氚产生聚变反应。但由于很难把这种高温长时间维持下去，所以全世界30多个国家上百个实验装置的聚变放电时间都很短！少则几秒，长的也不过数百秒。我国从1965年研究“人造太阳”开始，如今已能使放电时间持续千秒以上。
⑦所以，科学家说，建设核聚变电站投入民用，至少要再等上50年时间。但等待是值得的！现在地球上的石油、煤炭等化石能源至多可用200年时间，其中石油不足50年。即使目前核裂变电站使用的铀燃料，全世界也只能再开采60年。用这些材料做能源还有个致命弱点——环境污染！
⑧相反，氘和氚却是清洁能源，如空气中平时就有氘和氚。所以不用担心聚变反应会产生废气、废渣和放射性污染等问题。有人担心电站爆炸，但科学家说，聚变在磁场中进行，维持温度已很不易，只要稍微马虎，温度就会降下来，聚变就停止了，因此爆炸的可能性是零。
⑨氘和氚是取之不尽用之不竭的能源。世界海洋中大概蕴藏了40万亿吨氘。如果全部用于聚变反应，释放的能量足够人类使用几百亿年，这比太阳的寿命还要长了。
【小题1】选文的说明对象是什么？它的总体特征是什么？（3分）
【小题2】选文第③段的目的在于说明什么？（2分）
【小题3】第⑥自然段与第⑦自然段能不能互换？为什么？（3分）
【小题4】氘和氚是清洁的能源，这样说的根据是什么？在自然界中，你认为还能开发哪些目前还未利用的清洁的能源？简要说说能开发的理由。（4分） 查看习题详情和答案>>
先阅读短文，再在答题卡上相应的空白处写出各单词的正确形式。单词的第一个字母已给出。
I worked at a Care Center where most of the people are elderly. About a year and a half ago a 59-year-old lady came to us who had cancer. She had to have her right leg cut off and she didn’t have a family to take care of her after the o_1._.
This lady was a quiet lady who mostly stayed a_2._. But in the afternoons, when she was feeling w_3._, she would go to help the other people in the home. She would v_4._ a lady who was blind and read to her. She would go into the room of a young girl with severe cerebral palsy(脑瘫) and sing to her.
She p_5._ away last Wednesday and after her death, stories are coming forward of her quiet acts of k_6._ in her own hour of sadness.
We n_7._ know what we have upon others. She had every r_8._ to be bitter, to be angry, or to be sorry for her own fortune. But she wasn’t. She didn’t have a family and probably felt forgotten, but her small and quiet acts of service had a great influence upon the whole Care Center.
Each of us feels b_9._ than before for having know her. We have decided to be more aware(意识) of the service that we can o_10._ to others.
查看习题详情和答案>>
"Look at all these umbrellas," Harvey's wife said to him. "There are eight and they all b 1 ."
"I'll take them all to the umbrella shop and have them repaired," Harvey said. "They are too good to t 2
away."
Harvey took the eight umbrellas to the shop and l 3 them there. The shopkeeper said, "They'll be
r 4 tomorrow."
That evening Harvey went home from the office by bus as he u 5 did. He sat next to an old woman.
She had an umbrella on the floor between the s 6 . When the bus reached his stop, he picked up her
umbrella and stood up.
"Hey!" the woman said, "That umbrella b 7 to me."
"I'm so sorry." Harvey said, giving it to her. "Please excuse me for taking your umbrella by m 8 ."
The next day he collected the umbrellas from the umbrella shop and got on the bus. As he sat down, a
v 9 behind said, "You have certainly had a s 10 day!" He turned around and saw the woman whose
umbrella he had almost taken the day before.
6. 7. 8. 9. 10. 查看习题详情和答案>>
请把下列的单词中的第一个字母变成别的字母，使它成为一个另外的单词，并将其汉语意思写在后面的横线上。 注意：只能变第一个字母，后面的读音要相同。
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