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扫描电镜与透射电镜相比有哪些特点？

答案

参考答案：

①能够与直接观察样品表面的结构，样品尺寸可大至120mm*80mm*50mm；

②样品制备过程简单，不用切成薄片；

③样品可以在样品室作三度空间的平移和旋转，因此，可以从各种角度对样品进行观察；

④景深，图像富有立体感。扫描电镜的景深较光学显微镜大几百倍，比透射电镜大十几倍；

⑤图像的放大范围广，分辨率也比较高。可放大十几倍到几十万倍，它基本上包括了从放大镜、光学显微镜直到透射电镜的放大范围。分辨率介于光学显微镜与透射显微镜之间，可达3nm；

⑥电子束对样品的损伤与污染程度较小；

⑦在观察形貌的同时，还可利用从样品发出的其他信号作成分分析。

单项选择题

对已婚的女性客人应称呼（）。

A.小姐

B.同志

C.太太

D.先生
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单项选择题

Americans have a great love for informality and nowhere is this better expressed than in their love for nicknames (昵称，绰号). Upon greeting strangers for the first time they will quickly introduce themselves by their nickname. These are shortened forms of their given name at birth and reflect the casual relationships which exist among friends and coworkers. Family names are hardly ever used in daily situations and the use of one’s father’s last name is saved only for rare and formal occasions.
In many traditional cultures the use of the family name is seen as a sign of respect. For Americans, however, it’s the nickname which creates an immediate intimacy between two people upon which to build a relationship. By speaking to another on a first name basis and using his nickname, walls are immediately torn down and equality between two people is established.
At work bosses will refer to their employees by their nicknames. Should an employer use a worker’s family name, you can be sure that some kind of correction or serious business will follow.
This love for nicknames can create a sense of closeness between people who are otherwise not related. Even the presidents of the United States have borne nicknames. Abraham Lincoln was known as Honest Abe. John F. Kennedy was known as Jack or JFK and William Clinton has no reservations in letting people know he prefers to be called Bill, but those who look upon him with disfavor may call him Slick Willy.
Not only people but cities often carry their own nicknames. Chicago is called the "Windy City" because of the p winds which come down from Canada throughout the year. New York City is considered the "Big Apple" for reasons which are still obscure to most people including many New Yorkers.
Not every nickname, however, is positive and some can be rather rude and insulting. If someone should demonstrate a certain negative characteristic, a label will soon be attached to describe that person in an unpleasant way.
Likewise a person’s physical traits which are very dominant may lead to nicknames but not necessarily to one’s liking or choice. A nickname, therefore, is a way of identifying or describing someone or something for better or worse.

Americans tend to use others’ family names ______.

A. on formal occasions
B. when writing letters
C. in the work place
D. when making phone calls
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