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两个非零向量 ab 不共线.
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同类题1

近代以来,中国人民为了实现“中国梦”,中华民族在屈辱和抗争中不断走向觉醒和团结。阅读下列材料,回答问题。

材料一:唤起吾国四千年之大梦,实自甲午一役始也。吾国之大患,由国家视其民为奴隶,积之既久,民之自视亦如奴隶焉。……吾国之人视国事若于己无与焉,虽经国耻、历国难,而漠然不以动其心者,非其性然也,势使然也。且其地太辽阔,而道路不通,彼此隔绝,异省之民,罕有交通之事,其相视若异国焉。……故非受巨创负深痛,固不足以震动之

——梁启超《戊戌政变记》(1898年)

材料二:五四运动……成为每个中国人自我认同、民族意识崛起的契机。五四运动后不久,梁启超也改变了自己过去的看法,将“中华民族”的概念扩大为所有民族的共同体。

——摘编自《近代中华民族意识的觉醒》

材料三:日本军国主义者发动对华全面侵略,最致命的错误是大大低估了中国民众内部深深蕴藏着的那种无穷无尽的力量,特别是当中华民族处于生死关头时那种万众一心的民族凝聚力。日本侵略者眼中看到的只有武器而看不到人……抗日战争的胜利,……它成为中华民族从衰败走向复兴的重要枢纽。中国是世界反法西斯主要战场之一,中国抗日战争受到了国际社会的肯定和尊重。中国的国际地位有了很大的提高。……不管是国内的居民还是海外的华侨,都同样难以抑制地热血沸腾,聚结成一个整体去抵抗外来的侵略者

——摘编自金冲及《二十世纪中国史纲》

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同类题4

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B

    Researchers say they have created a new super-tough material in the laboratory. It is stronger, lighter and costs less than steel. But the new material is not a product of high technology. It is wood. Researcher Liangbing Hu says that it can compete with some of the world's strongest materials or even replace steel.

    The product is called Super Wood. It doesn't require any special raw, unprocessed material. That means the cost of the product will be relatively low.Hu said, “We can start with very cheap wood, and also very fancy, expensive wood. But in the end, we get very similar performance.”

    Super Wood is made by partially removing a natural polymer called lignin(木质素). Hu explained, “Lignin is like glue to hold all the parts together in natural wood. To be able to densify(增密)the wood completely, some of the lignin has to be removed. “Strong chemicals are put on the wood to remove about half of its lignin. Then, after being left in extreme heat and pressurized for a day, the treated wood is ready.

    The wood is strong enough to build automobiles, airplanes, wind turbines and more. Researchers are finding many new ways to use wood, including creating batteries and see-through wood and paper.Hu said, “Wood has been existing on Earth for more than a million years. And human beings have been using wood for furniture, construction for more than 10 thousand years. And the more we worked on this material, we realized, we have never fully exhausted the potential of this amazing material.”