题目内容
Text 3 Thousands of years ago man used handy rocks for his surgical operations. Later he used sharp bone or horn, metal knives and more recently, rubber and plastic and that was where we stuck, in surgical instrument terms, for many years. In the 1960s a new tool was developed, one which was, first of all, to be of great practical use to the armed forces and industry, but which was also, in time, to revolutionize the art and science of surgery. The tool is the laser and it is being used by more and more surgeons all over the world, for a very large number of different complaints. The word "laser" means: light amplification by stimulated emission of radiation. As we all know, light is hot, any source of light -- from the sun itself down to a humble match burning -- will give warmth. But light is usually spread out over a wide area. The light in a laser beam, however, is concentrated. This means that a light with no more power than that produced by an ordinary electric light bulb becomes intensely strong as it is concentrated to a pinpoint-sized beam. Experiments with these pinpoint beams showed researchers that different energy sources produce beams that have a particular effect on certain living cells. It is now possible for eye surgeons to operate on the back of the human eye without harming the front of the eye, simply by passing a laser beam right through the eyeball. No knives, no stitches, no unwanted damage -- a true surgical wonder. Operations which once left patients exhausted and in need of long period of recovery time now leave them feeling relaxed and comfortable. So much more difficult operations can now be tried. The rapid development of laser techniques in the past ten years has made it clear that the future is likely to be very exciting. Perhaps some cancers will be treated with laser in a way that makes surgery not only safer but also more effective. Altogether, tomorrow may see more and more information coming to light on the diseases which can be treated medically. Which of the following would be appropriate to describe the instruments for surgical operations up until 1960s
查看答案
搜索结果不匹配？点我反馈
更多问题
Is the woman going to take the bus
“病人手足厥冷，脉乍紧者，邪结在胸中，心下满而烦，饥不能食者，病在胸中，______，______。
听下面5段对话。每段对话后有一个小题，从题中所给的A、B、C三个选项中选出最佳选项，并标在试卷的相应位置。听完每段对话后，你都有10秒钟的时间来回答有关小题和阅读下一小题。每段对话仅读一遍。 Which T-shirt would the woman like to buy
Text 1 Americans are getting ready for the biggest soccer event in the world. For the first time the world cup soccer competition will be held in the United States. While millions play the game around the world, soccer or football has only recently become popular here. It is only in the last 30 years that large numbers of young Americans became interested in soccer. Now it is the fastest growing sport in the country. A recent study found that almost 18 million young boys and girls play soccer in the United States. The study also found that soccer is beginning to replace more traditional games like American football as the most popular sport among students. And so, when the world cup begins next week, more than one million Americans are expected to go and see the teams play. Organizers say this year’s world cup will be the biggest ever. All the seats at most of the 52 games have already been sold. Soccer has been played in the United States for a little more than one hundred years. But how did the sport come to this country And how long has it existed in other parts of the world No one knows exactly where the idea for soccer came from, or when people began playing the game. Some scientists say there is evidence that ball games using the feet were played thousands of years ago. There is evidence that ancient Greeks and Romans and native American Indians all played games similar to soccer. Most experts agree that Britain is the birthplace of modem soccer. They also agree that the British spread the game around the world. Unlike the game today, which uses balls of man-made material or leather, early soccer balls were often made of animal stomachs. The rules of early soccer games also differed from those we have today. What is the author going to state in the next paragraph
微信支付 
支付宝支付