发表于2025-01-22
新东方·新托福考试专项进阶:高级阅读 pdf epub mobi txt 电子书 下载
Timothy Hall,毕业于美国哥伦比亚大学,英语语言学专业硕士。
Arthur H. Milch,美国新泽西学院TESOL专业教育学硕士。
Denise McCormack,美国新泽西学院TESOL专业教育学硕士。
The principles making radio possible were developed throughout the nineteenth century. The first breakthrough was by the British physicist Michael Faraday in 1831. He discovered that when an electric current passes through one wire, it produces a current in another wire even though the wires do not touch each other. In 1864, James Maxwell showed that this current——composed of electromagnetic waves——travels at the speed of light. Heinrich Hertz proved that the waves pass through solid objects. With these discoveries in place, the race was on to develop a system of wireless radio.
Among the contenders was Reginald Fessenden, a Canadian inventor. Fessenden began experimenting with radio detectors in order to explore the possibility of voice transmission. In 1900, he was the first person to transmit his voice, but the sound was unrecognizable because the waves were not continuous. He invented a barreter detector, taking its name from the French word exchanger, to receive AM (amplitude modulated) signals, but it was not sensitive enough. One day in 1901, he accidentally left a filament of wire in acid for too long until only a tip of the wire was in contact with the acid. Fessenden noticed that, with the wire in the acid, the barreter was very sensitive to nearby continuous radio waves.
Fessenden called his invention a liquid barreter, but it became known as an electrolytic detector. The detector consisted of several connected parts forming an electric circuit. A silver-coated platinum wire was dipped into a small platinum cup filled with nitric or sulfuric acid and connected to the ground. A battery was connected between the wire and the acid, prompting a current to flow in the detector. Someone wearing headphones that were hooked up to the detector could hear a hissing noise, which could be adjusted by turning a dial until the hissing noise stopped. At that point, the detector was highly sensitive to incoming radio waves.
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还行吧,质量还不错,手感也不错
评分 评分托福考试的一本好书
评分美国的大学在录取工作中越来越看重托福成绩,尤其在2012年不少美国大学提高了对国际生的托福录取标准,托福录取分数线上调幅度大概在10分左右,比如凯斯西储大学(Top38)由2011年的80分上调至2012年的90分。俄亥俄州立大学由2011年的71分上调至2012年的79分。这一现象在高端名校中更为严重,综合排名Top20的埃默里大学甚至建议学生考取托福100分以上。中国大学生去纽约、伦敦、香港的大学留学,托福成绩都是被申请学校认可的。因此到纽伦港留学考托福成绩的占绝大部分。[2]
评分给学生买的书,很实用
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评分书很不错,还在看初级,等着最后用高级提高自己了
评分书很不错,还在看初级,等着最后用高级提高自己了
新东方·新托福考试专项进阶:高级阅读 pdf epub mobi txt 电子书 下载