什么是自行车
bicycle
Lightweight, two-wheeled, steerable machine that is propelled by the rider. The wheels are mounted in a metal frame, and the front wheel is held in a movable fork. The rider sits on a saddle and steers by handlebars attached to the fork, propelling the bicycle by two pedals attached to cranks that turn a driving sprocket. An endless chain transmits power from the driving sprocket to a back-wheel sprocket. A heavy pedalless form built in 1818 was propelled simply by the rider paddling his feet against the ground. In 1839 the Scottish blacksmith Kirkpatrick Macmillan (1813-1878) built a bicycle propelled by pedals, cranks, and drive rods; he is widely credited with inventing the bicycle. Important innovations were introduced by Pierre and Ernest Michaux in France in 1861, and by 1865 their company was manufacturing 400 vélocipèdes a year. A lighter version produced in England in 1870 (nicknamed the “penny-farthing”) featured a large front wheel and small back wheel. By the 1890s the standard bicycle design was established, and with the smooth ride enabled by the new pneumatic tires its popularity exploded. 20th-century improvements included lighter frames and improved gears and brakes. Widely used throughout the world, it is a basic means of transportation in many countries. See also bicycle industry.
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择地而蹈是什么意思?
意思是:选择地方行走。形容做事小心谨慎。成语名字:择地而蹈成语发音:zédìérdǎo成语解释:选择地方行走。形容做事小心谨慎。成语出处:《史记·伯夷列传》:“或择地而蹈之,时然后出言,行不由径,非公正不发愤。”成语繁体:擇地而蹈感情色彩:中性成语成语用法:作谓语、定...
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一掷百万是什么意思?
意思是:指用钱满不在乎,一花就是一大笔。成语名字:一掷百万成语发音:yīzhìbǎiwàn成语解释:指用钱满不在乎,一花就是一大笔。成语出处:《晋书·何无忌传》:“刘毅家无儋石之储,樗蒱一掷百万。”成语繁体:一擲百萬常用程度:常用成语感情色彩:中性成语成语用法:作谓语、定...
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透骨酸心是什么意思?
意思是:形容极度伤心。成语名字:透骨酸心成语发音:tòugǔsuānxīn成语解释:形容极度伤心。成语出处:《儿女英雄传》第五回:“她自己心中,以有一腔的弥天恨事,透骨酸心。感情色彩:中性成语成语用法:作谓语、定语;指十分伤心成语结构:偏正式成语产生年代:近代成语老妈离世的...
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遗迹谈虚是什么意思?
意思是:谓舍弃根据而空谈玄虚。成语名字:遗迹谈虚成语发音:yíjìtánxū成语解释:谓舍弃根据而空谈玄虚。成语出处:宋·程大昌《〈演繁露〉序》:“然有退之(韩愈)之学则可,无退之之学而遗迹谈虚,恐援据所及,金根金银或相贸易,并可赧矣。”成语繁体:遺跡談虚感情色彩:中性成...