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By Michael Bowman Washington 29 June 2006 The Bush administration says it is taking effective steps to stem illegal immigration to the United States, but Congress must act to overhaul America's immigration system. Homeland Security Secretary Michael
By Carol Pearson Washington 26 September 2009 As the H1N1 swine flu virus spreads rapidly through the Northern Hemisphere, doctors and other health care professionals face a heavier-than-usual workload. Even without a flu pandemic, studies show, up
You see, you can take out one or two hub trees, 你们看,我们可以拿走一两颗中心树, but there comes a tipping point, 但这样就会达到森林承受极限了, because hub trees are not unlike rivets in an airplane. 因为森林里的
科学家估计,如果不减少二氧化碳排放,2100年地球平均气温将至少上升4摄氏度,到2200年会上升8摄氏度,无疑是地球灾难性的噩梦。 此前有科学家用气候模型分析称,全球气温将受二氧化碳排
Altogether there is about twenty thousand times as much carbon locked away in the Earth's rocks as in the atmosphere. 总的来说,被关在地球岩石里的碳,大约相当于大气里的2000倍。 Eventually much of that limestone will end up