计算:(1)12-(-2009)0+(12)-2+|1-3|;(2)(2-1)2

题型:解答题

问题:

计算:
(1)
12
-(-2009)0+(
1
2
-2+|1-
3
|;
(2)(
2
-1)2-(3+2
2
).
考点:零指数幂(负指数幂和指数为1)二次根式的加减乘除混合运算,二次根式的化简
题型:解答题
解不等式组
3x-1>2
2x<x+2.
题型:解答题

非水滴定法测定维生素B1原料药的含量,应选

A.淀粉指示剂
B.喹哪啶红—亚甲蓝混合指示剂
C.二苯胺指示剂
D.邻二氮菲指示剂
E.酚酞指示剂

题型:解答题

The first people who gave names to hurricanes were those who knew them best — the people of Puerto Rico. The small island of Puerto Rico is in the West Indies, off the coast of Florida. This is where all the hurricanes begin that strike the east coast of the United States. Often they pass near Puerto Rico or cross it on their way north. The people of Puerto Rico expect some of these unwelcome visitors every year. Each one is named after the Saint’s Day on which it arrives. Two of the most destructive storms were the Santo Ana in 1840 and the San Ciriaco in 1899.

Giving girls’ names to hurricanes is a fairly new idea. It all began with a story called “Storm”, written by George Stewart in 1941. In it a weatherman amused himself by naming storms after girls he knew. He named one Maria. The story describes how she Maria grew and developed, and how she changed the lives of people when she struck the United States.

Weathermen of the U.S. Army and Navy used the same system during World WarⅡ. They were studying weather conditions over the Pacific Ocean. One of their duties was to warn American ships and planes when a storm was coming. Whenever they spotted one, they gave it a girl’s name. The first one of the year was given a name beginning with [A]. The second one got a name beginning with [B]. They used all the letters from A to W, and still the storms kept coming. They had to use three lists from A to W to have enough names to go around. This was the first list of hurricane names that followed the alphabet. It served as a model for the system the Weather Bureau (局) introduced in 1942.

Before 1950 the Weather Bureau had no special system for naming hurricanes. When a hurricane was born down in the West Indies, the Weather Bureau simply collected information about it. It reported how fast the storm was moving and where it would go next. Weather reports warned people in the path of the hurricane, so that they could do whatever was necessary to protect themselves.

This system worked out fine as long as weather reports talked about only one hurricane at a time. But one week in September 1950 there were three hurricanes at the same time. The things began to get confused. Some people got the hurricanes mixed up and didn’t know which was which. This convinced the Weather Bureau that it needed a code for naming the storms in order to avoid confusion in the future.

1.Hurricanes were first named after the _________.

A. date on which they occurred                         

B. place where they began

C. amount of destruction they did                     

D. particular feature they have

2.The practice of giving girls’ names to hurricanes was started by _________.

A. a radio operator        B. an author                  C. a sailor                     D. local people

3.The purpose for which weathermen of the army and navy began using girls’ names for hurricanes was _________.

A. to keep information from the enemy

B. to follow the standard method of the United States

C. not given in the article

D. to remember a certain girl

4.The Weather Bureau began naming hurricanes because it would help them _________.

A. collect information more rapidly                  

B. warn people more efficiently

C. make use of military (军事的) records          

D. remember them

题型:解答题

用弧形视野计检查时,应用蓝、红、绿色视标检测的正常周边视野范围较白色视标依次递减()

A.5°

B.10°

C.15°

D.20°

E.25°

题型:解答题

一般不需热处理即可直接使用的钢材是()。

A.普通碳素结构钢

B.优质碳素结构钢

C.碳素工具钢

D.轴承钢

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