问题 单项选择题

正常人心率超过180次/分时,引起心输出量减少的主要原因是()

A.心室充盈时间明显缩短,充盈量减少

B.心室舒张期过长,心室充盈早已接近限度

C.快速射血期缩短

D.慢速射血期缩短

E.迷走神经活动加强

答案

参考答案:A

解析:心率增快,心输出量增加,但有一定限度。如果心率过快,超过170~180次/分,心室充盈时间明显缩短,充盈量减少,搏出量可减少一半左右,心输出量亦开始下降

阅读理解

Reading comprehension.

     When I was leaving to meet Lynne, my friend Tony told me that I'd better take some money. But I didn't

listen to him. I thought Lynne would pay because she had invited me. I arrived at the restaurant on time. I

know Americans expect you to be on time. Lynne and I sat at a table and a waiter brought us some delicious

food.

     The dinner was a great success. We talked a lot while eating. After two hours, the waiter finally came and

asked if we wanted one check (账单) or two, Lynne said two. We went to the cashier and Lynne paid her

check. I was embarrassed when the cashier gave me my bill. I had no money to pay for my meal. Then I had

an idea. I said, "Oh! I forgot my wallet! Can I call my friend, please?" The cashier showed me where the phone

was and I quickly called Tony. In a few minutes, he arrived with some money, and paid my check. He laughed

at me all the way home. Now, I think it's funny too, but at that time I was very embarrassed. I thought an

invitation to have dinner in America meant the same thing as that in China. Now I think you have to understand

that your customs are only your customs. When you visit a foreign country, you have to learn about their

customs, too. They can be quite different.

Fill in the blanks according to the passage. Only one word for each blank.

     One day I got an invitation to dinner from Lynne. Before I left, my friend Tony told me to take some

money, but I didn't take his 1______. I reached the restaurant on time because I know being late is thought

to be 2______ . Lynne and I enjoyed the dinner very much. But two hours 3______, I got into trouble

4______ my check. I thought Lyrme would pay 5______ of the checks. In fact I was wrong. I had to call

Tony for help. After the problem was solved, I realized the importance of learning about different customs.

阅读理解与欣赏

阅读《微晶玻璃》一文,完成问题。

  ①微晶玻璃是一种我国刚刚开发的新型的建筑材料,它的学名叫做玻璃陶瓷。微晶玻璃和我们常见的玻璃看起来大不相同。它具有玻璃和陶瓷的双重特性,普通玻璃内部的原子排列是没有规则的,这也是玻璃易碎的原因之一。而微晶玻璃象陶瓷一样,由晶体组成,也就是说,它的原子排列是有规律的。所以,微晶玻璃比陶瓷的亮度高,比玻璃韧性强。

  ②现在,我们做一个微晶玻璃与天然石材的对比实验。我们把墨水分别倒在大理石和微晶玻璃上,稍等片刻,微晶玻璃上的墨汁可以轻易的擦掉,而大理石上的墨迹却留了下来。这是为什么呢?大理石、花岗岩等天然石材表面粗糙,可以藏污纳垢,微晶玻璃就没有这种问题。大家都知道,大理石的主要成分是碳酸钙,用它做成建筑物,很容易与空气中的水和二氧化碳发生化学反应,这就是大理石建筑物日久变色的原因,而微晶玻璃几乎不与空气发生反应,所以可以历久长新。

  ③专家介绍说,这项发明的突破点主要有两个,分别是原料的配比和工艺的设计。其中,工艺的设计是技术的关键。置备微晶玻璃首先要把原材料按照比例配好,放到窑炉里烧熔,等全部融化之后,把熔液倒在冰冷的铁板上,这叫做淬火,淬火之后,原料已经变成了一块晶莹的玻璃,这一步是烧结的过程。现在,我们把玻璃捣碎,装入模具,抹平,再次放入窑炉,这次煅烧使它的原子排列规则化,是从普通玻璃到微晶玻琉的过程。

  ④一般的废渣土中都含有制作微晶玻璃的大多数成分,我们通过电脑检测,确定现有原料的化学组成,添加所缺部分,大大降低了成本。微晶玻璃利用废渣、废土做原材料,有利于环境治理,可以变废为宝,与各地环保工作同步进行。

1.微晶玻璃与普通玻璃、陶瓷相比有哪些特性?

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2.微晶玻璃比普通玻璃韧性强的根本原因是什么?

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3.通过微晶玻璃与天然石材的对比实验,得出了怎样的结论?

____________________________________________

4.文中划线的“大多数”一词能否删去?为什么?

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5.从文中看,微晶玻璃的工艺设计是制作技术的关键,概括地说,它包括两步,一是_____________,二是____________。

6.阅读下面的两则链接材料,写出你的发现。(至少写两点)

  材料一最新研制开发的矿渣微晶玻璃,受到了人们的重视及青睐,它是第四代替代天然石材理想的装饰建筑材料。在我国有取之不尽、用之不竭的丰富原料(如各种工业尾矿、灰渣、炉渣等),目前已有研制开发成功的矿渣微晶玻璃问世,它们都同样具有机械强度高,表面硬度大及优良的化学稳定性,适于用作高档次的地铁、大楼、机场、车站、宾馆、大饭店等建筑物的装饰材料。

  材料二随着人民生活水平的不断提高,对建筑装饰的追求也会愈来愈高。我国年装饰消费达800亿元,建筑装饰石材年消费已超过8000万平方米。巨大的市场迫切要求生产企业制造出更多更好的产品,适应和满足规模大型化,色彩多样化,施工便捷化,用途异型化的市场需求趋势。

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