题目内容
It is hard to track the blue whale, the ocean’’s largest creature, which has almost been killed off by commercial whaling and is now listed as an endangered species. Attaching radio devices to it is difficult, and visual sightings are too unreliable to give real insight into its behavior. So biologists were delighted early this year when, with the help of the Navy, they were able to track a particular blue whale for 43 days, monitoring its sounds. This was possible because of the Navy’’s formerly top-secret system of underwater listening devices spanning the oceans. Tracking whales is but one example of an exciting new world just opening to civilian scientists after the cold war as the Navy starts to share and partly uncover its global network of underwater listening system built over the decades to track the ships of potential enemies. Earth scientists announced at a news conference recently that they had used the system for closely monitoring a deep-sea volcanic eruption (爆发) for the first time and that they plan similar studies. Other scientists have proposed to use the network for tracking ocean currents and measuring changes in ocean and global temperatures. The speed of sound in water is roughly one mile a second -- slower than through land but faster than through air. What is most important, different layers of ocean water can act as channels for sounds, focusing them in the same way a stethoscope (听诊器) does when it carries faint noises from a patient’’s chest to a doctor’’s ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles. The passage is chiefly about ________.
查看答案
搜索结果不匹配？点我反馈
更多问题
供体菌裂解游离的DNA片段被受体菌直接摄取，使受体菌获得新的性状
在下列药物中，既可祛风湿，止痹痛，又可清虚热的药物是
It is easier to negotiate initial salary requirement because once you are inside, the organizational constraints influence wage increases. One thing, however, is certain: your chances of getting the raise you feel you deserve are less if you don’t at least ask for it. Men tend to ask for more, and they get more, and this holds true with other resources, not just pay increases. Consider Beth’s story:I did not get what I wanted when I did not ask for it. We had cubicle (小隔间 ) offices and window offices. I sat in the cubicles with several male colleagues. One by one they were moved into window offices, while I remained in the cubicles. Several males who were hired after me also went to offices. One in particular told me he was next in line for an office and that it had been part of his negotiations for the job. I guess they thought me content to stay in the cubicles since I did not voice my opinion either way.It would be nice if we all received automatic pay increases equal to our merit, but "nice" isn’t a quality attributed to most organizations. If you feel you deserve a significant raise in pay, you’ll probably have to ask for it.Performance is your best bargaining chip when you are seeking a raise. You must be able to demonstrate that you deserve a raise. Timing is also a good bargaining chip. If you can give your boss something he or she needs (a new client or a sizable contract, for example) just before merit pay decisions are being made, you are more likely to get the raise you want.Use information as a bargaining chip too. Find out what you are worth on the open market. What will someone else pay for your servicesGo into the negotiations prepared to place your chips on the table at the appropriate time and prepared to use communication style to guide the direction of the interaction. What can be inferred from Beth’s story().
The percentage of immigrants (including those unlawfully present) in the United States has been creeping upward for years. At 12.6 percent, it is now higher than at any point since the mid-1920s.We are not about to go back to the days when Congress openly worried about inferior races polluting America’s bloodstream. But once again we are wondering whether we have too many of the wrong sort of newcomers. Their loudest critics argue that the new wave of immigrants cannot, and indeed do not want to, fit in as previous generations did.We now know that these racist views were wrong. In time, Italians, Romanians and members of other so-called inferior races became exemplary Americans and contributed greatly, in ways too numerous to detail, to the building of this magnificent nation. There is no reason why these new immigrants should not have the same success.Although children of Mexican immigrants do better, in terms of educational and professional attainment, than their parents, UCLA sociologist Edward Telles has found that the gains don’t continue. Indeed, the fourth generation is marginally worse off than the third. James Jackson, of the University of Michigan, has found a similar trend among black Caribbean immigrants, Telles fears that Mexican-Americans may be fated to follow in the footsteps of American blacks—that large parts of the community may become mired (陷入) in a seemingly permanent state of poverty and underachievement. Like African-Americans, Mexican-Americans are increasingly relegated to(降入) segregated(隔离), substandard schools, and their dropout rate is the highest for any ethnic group in the country.We have learned much about the foolish idea of excluding people on the presumption of the ethnic/racial inferiority. But what we have not yet learned is how to make the process of Americanization work for all. I am not talking about requiring people to learn English or to adopt American ways; those things happen pretty much on their own. But as arguments about immigration heat up the campaign trail, we also ought to ask some broader questions about assimilation (同化), about how to ensure that people, once outsiders, don’t forever remain marginalized within these shores.That is a much larger question than what should happen with undocumented workers, or how best to secure the border, and it is one that affects not only newcomers but groups that have been here for generations. It will have more impact on our future than where we decide to set the admissions bar for the latest wave of would-be Americans. And it would be nice if we finally got the answer right. According to the author, the burning issue concerning immigration is().
微信支付 
支付宝支付