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问题 单项选择题

氯霉素的抗菌作用原理是（）。

A.干扰叶酸合成

B.抑制蛋白质合成

C.抑制分枝菌酸的生物合成

D.抑制DNA回旋酶

E.抑制依赖于DNA的RNA多聚酶

答案

参考答案：B

解析：针对"抗结核病药"知识点进行考核。对氨基水杨酸钠抗菌谱极窄，仅对细胞外的结核分枝杆菌有抑制作用，存在干酪组织及脓液时能降低其抑菌作用。一般认为其作用机制是：对氨基水杨酸的化学结构与对氨基苯甲酸相似，对氨基水杨酸可竞争性抑制二氢蝶酸合成酶，使二氢叶酸合成障碍而抑制结核分枝杆菌的生长。利福平的抗菌作用机制是特异性抑制敏感微生物的DNA依赖性RNA多聚酶，阻碍其mRNA的合成，而对人细胞的此酶则无影响。异烟肼的抗菌作用机制是抑制分枝菌酸的合成，从而使细胞丧失耐酸性、疏水性和增殖力而死亡。分枝菌酸为结核分枝杆菌细胞壁的重要成分，为分枝杆菌的专有成分。氯霉素为酰胺醇类抗生素，酰胺醇类药主要为抑菌剂，作用机制为抑制细菌蛋白质的合成。

单项选择题

妊娠期阑尾位置随孕周增长总的变化特点是

A．向上、内、后移位

B．向上、外、后移位

C．向上、内、前移位

D．向上、外、前移位

E．向上、后移位
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填空题

(41)

Conflicts:


If you do get a place in the student dormitory, it is likely that you will have to share your living space with one other student. While having an American roommate will help you to learn more about American ways, there will probably be many times that discomfort or conflict will arise due to cultural differences.
(42)

Sex:


With regard to sex in general, American behavior is quite different from the norms found in China.
(43)

Relationship Between Teachers & Students:


On the campus, particularly where classes are small, I found a strange informality that characterized the relationship between students and their professors.
(44)

Gifts:


In my interaction with American friends, I noticed that the concept of a gift is quite different here. Many things we give to each other in China are not called "gifts" but are considered to be a reflection of ordinary duties and mutual obligations. Accustomed as we are to using the word "gift" to refer to something valuable given on special occasions, it comes as a surprise to see how often the word is used in America. In the United States, "gifts", given on many different occasions, are only services.
(45)

Social Intercourse.


When you do enter American homes, you will have an opportunity to observe different ways of greeting people. On the whole, Americans tend to be far more physical than we in their greetings.
[A] I was astonished, for example, when a friend told me that he was offering to care for his younger brother and sister so that his father could take a vacation for his birthday--this was a gift to him. For us, this would be considered duty rather than a gift. Even between friends gestures of this sort might be considered "gifts" here.
[B] While many students do call their professors, "Professor" so and so or "Dr. " so and so, some professors prefer to be called familiarly by their first names. And in the spirit of informality, many professors may invite students to their homes or can be seen chatting with students over a meal or a cup of coffee in the school cafeteria. A good number of instructors even request that students fill out class evaluation forms which assess the content and presentation of the course.
[C] My roommate was very sociable and had many boyfriends who came to visit often very late. One night, after midnight, I had to stay in the bathroom for an extra 40 minutes because I had heard a man’s voice in my room. My roommate did not realize how awkward I would feel meeting a man while I was in my nightgown. You see, American students tend to be much more casual about these matters.
[D] On many occasions, for instance, close friends or sometimes even casual acquaintances embrace or kiss each other on the cheeks in greeting or bidding farewell. It may even happen that where couples are close friends, the two husbands will kiss the other man’s wife!
[E] In the United States, for example, if a student wants to invite his teacher to a dinner party, the invitation should be sent a week or so before the party date. If the invitation is extended only three or four days before the party date, the teacher will feel he is not highly regarded.
[F] For example, many American students seem to like to listen to popular and sometimes loud music while studying in their rooms. Sometimes they will even leave the music on when they leave the room. For some reason, many will tell you, music helps them to relax and concentrate, an idea which other foreign students and I found very strange and disturbing. We’d like to study quietly without any disturbance.
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