Although he thought of the key idea in 1951, the first maser was not completed until a couple of years later.
2. account for 解释
Variations of clay composition and the temperatures at which they are fired account for the differences in texture and appearance.
3. adapt to 使适应于
They have been able to adapt to ecological changes.
4, adorn with sth 用…装饰
Some pots were adorned with incised or stamped decorations.
5.appeal to 吸引
Publishing literature consisting of exciting stories that would appeal to both children and adults
6.apply to 适用于
Ethological theory began to be applied to research on children in the 1960’s.
7.at best 充其量，最多
Hunting is at best a precarious way of procuring food, even when the diet is supplemented with seeds and fruits.
8.at intervals 相隔一定距离
However, at intervals of 10 to 100 years, these glaciers move forward up to 100 times faster than usual.
9.at the expense of sth 在损害…的情况下
A multitude of microorganisms make their livings directly at the expense of other creatures.
10.at the height of sth 在…最鼎盛时期
The violin had reached the height of its popularity by the middle of the eighteenth century.
11.back and forth 来回地
They then spiral back and forth between the Earth’s magnetic poles very rapidly.
12.be absent from 缺席，不在
Lacking the right to vote and absent from the seats of power, women line were not considered an important force in history.
13.be capable of 能…的
Many animals are capable of using objects in the natural environment as rudimentary tools.
14. be characterized by 以…为特征
The nervous system of vertebrates is characterized by a hollow, dorsal nerve cord that ends in the head region as an enlargement, the brain.
15.be composed of 由…组成
Ocean life is primarily composed of plants.
16.be concerned with 与某事物有关
Ethnology is concerned with the study of adaptive, or survival, value of behavior and its Evolutionary history.
17.be distinct from 与…不同
Jupiter and the other giant planets are of a low-density type quite distinct from the terrestrial planets
18.be essential to 对…不可缺少
Public performance is essential to verbal art.
19.be exposed to 使接触，使遭受
Body contact reduces the surface area exposed to the cold air.
20.be far from 离…很远，根本不是
But far from being random, molt is controlled by strong evolutionary forces that have established an optimal time and duration.
21. be hostile to 极不友好的，极厌恶的
Ocean bottom is a hostile environment to humans
22.be regarded as 被认为是
Humanity’s primal efforts to systematize the concepts of size, shapes, and number are usually regarded as the earliest mathematics.
23.be related to 与…有关的，相联系的
Why is dancing closely related to popular music in the United States?
24. be responsible for 对…负责
In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce.
25. be sensitive to 对…敏感的
Ants can be extremely sensitive to these signals.
26.be subjected to 经历，遭受
Oil is formed when organic material trapped in sediments is slowly buried and subjected to increased temperatures and pressures, transforming it into petroleum.
27. be superior to 优越于
Natural vitamins are superior to synthetic ones
28 .be traced to 找出根源
The ancestry of the piano can be traced to the early keyboard instruments of the fifteenth and sixteenth centuries.
29. be/become aware of 意识到，认识到
People became aware of the new service by word of mouth or newspaper advertisements.
30. be/become/get accustomed to 习惯于
In the harsh environment of northern Europe, Scandinavian women had been accustomed to practicing forms of shifting cultivation, and they immediately understood Native American horticulture.
31. be/become/get involved in 与…有关联的
Two distinct processes are involved in molting.
32.benefit from 从…中受益
Students benefit from schools, which require long hours and homework.
33.break down 分解
All of these forces slowly break down the Earth’s exposed rocky crust into smaller and smaller pieces that eventually become clay.
34.by far 到目前为止
Marine sediment is by far the most important environment for the preservation of fossils.
35.by means of 通过，凭借
The topic of the passage is developed primarily by means of Adividing the discussion into two major areas.
36.by virtue of 由于
Many are uninhabitable, by virtue of their small size and particular characteristics
37.confine to 限制在一定范围之内
The delivery service was at first confined to cities.
38.conform to 符合
Parks should be designed to conform to the topography of the area
39.contribute to 有贡献，有助于
Transportation contributed to the development and maintenance of trade.
40.cope with 对付
Under certain circumstance the human body must cope with gases at greater-than-normal atmospheric pressure.
41.date back to 始于
In the United States, rent controls date back to at least World War II.
42. depend on 依靠
The gulls depend on the falcons for protection.
43. deprive sb/sth of sth 剥夺..某事物
Plant stems die when deprived of water.
44.derive from 获得，起源于
Babies obviously derive pleasure from sound input.
45.due to 由于，因为
Due to their dense structure, iron meteorites have the best chance of surviving an impact, and most are found by farmers plowing their fields.
46. evolve from/out of 从...进化来，从…发展来
The one most widely accepted today is based on the assumption that drama evolved from ritual.
47.extract from 提取
It turns out that some fossils can be extracted from these sediments by putting the rocks in an acid bath.
48.feed on 以…为食物
Predators are animals that capture and feed on other animals.
49.focus on 集中(注意力)于
They focus on the meaning of their parents’ words.
50. get rid of 处理掉
Atoms or molecules get rid of excess energy by themselves, without any outside intervention.