共查询到20条相似文献，搜索用时 31 毫秒
1.
《Journal of The Franklin Institute》1987,323(2):233-252
A general matching theory between an arbitrary passive impedance and an active load impedance is presented. It extends the broadband matching theory to include both lossless reciprocal and nonreciprocal networks. Application of the result to the design of nonreciprocal negative-resistance amplifier is given. The significance of the present approach is that the realization of the equalizer is accomplished by means of the driving-point synthesis based on the Darlington theory. The result enlarges the domain of realizable broadband matching networks.An illustrative example is presented to show the design procedure and the conditions under which a lossless nonreciprocal network is realized for an active load. 相似文献
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Brock WH 《Endeavour》2002,26(3):87-91
Forging a scientific career in 19th-century Britain was difficult for most middle-class scientists. Despite his discovery of thallium in 1861 and later distinction as an experimental physicist that led him to the Presidency of the Royal Society (1913-1915), William Crookes (1832-1919) never obtained one of the limited number of academic or official positions. Scientific journalism and commercial activities were eventually to bring him financial security, but before that he was an opportunist willing to try his hand at anything that would win him national publicity. This is illustrated by his intervention in the great cattle plague epidemic that swept the UK between 1865 and 1866. 相似文献
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P H Smith 《Isis; an international review devoted to the history of science and its cultural influences》1999,90(3):420-461
This article argues that the art collection owned by Franciscus dele Bo?, Sylvius, a professor of practical medicine at the University of Leiden from 1658 to 1672, gives insight into some aspects of the character and significance of the new philosophy in the midseventeenth century. Through his teaching, his advocacy, and his practice of the new experimental philosophy, Sylvius played a role in shaping and institutionalizing the practices of the new philosophy that spread throughout Europe in the late seventeenth and eighteenth centuries. Sylvius's house design and large painting collection also exemplified the consumption and taste of the northern Netherlands in the seventeenth century. An examination of both Sylvius's science and his taste can help us understand what was at stake for Sylvius and his contemporaries in their practice of the new philosophy. This article finds that Sylvius's taste and his science both involved practices of social distinction, demarcation, and control. Moreover, both were enmeshed in controversy about the epistemological status of knowledge gained through the senses and about the practices by which that knowledge was gathered. 相似文献
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史铁生．一个在人生最狂妄的年龄残废了双腿的人．苦难命运的突然降临使他原本光鲜亮丽的人生霎时显得苍白无力．“原本能使他活下去、走下去的东西骤然间消失干净。就像一根不能拉紧的琴弦．再难弹出赏心悦目的曲子”。然而他用手中的笔完成了自我的生命延续．有限与无限、完满与不完满等一系列生命课题的上下求索和不懈追问在他笔下一一书写．那张苍白的人生白纸上又重新焕发出了色彩．勾勒出了一幅“史铁生式”走向过程的生命美学的历电面兼 相似文献
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Piccolino M 《Endeavour》1999,23(4):175-179
All his life, Marcello Malpighi (1628–1694), the founder of modern microscopic anatomy, was unwillingly involved in difficult debates within a reactionary medical milieu that questioned the significance of modern science and its utility to medicine. Malpighi's responses to his detractors, included in posthumous works first published in 1697 by the Royal Society, offer an important insight into a critical phase of scientific progress in the 17th century and help to reveal the prevailing conception of science. In some ways, Malpighi's views predate important ideas in modern biology. 相似文献
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托马斯·库恩是20世纪最伟大的科学哲学家和科学史学家。由他划时代著作《科学革命的结构》产生出来的"范式"和"范式转换"已经成为我们的日常生活用语。一方面,库恩自认在哲学上的最大贡献是"不可通约性",但这一点遭到多方非议。另一方面,当他被认为是"科学知识社会学"(SSK)强纲领的思想先驱时,他却拒绝承认SSK的主张;他在学术上的同路人少得可怜,与他在思想界的巨大影响完全不成比例。库恩从登上学术舞台开始,就遭到不同程度的误解,他一直在寻找自己的身份定位。本文试图通过梳理矛盾的库恩形象,他与学生的关系以及影响他的思想形成的几大事件,从"误解"与"被误解"的角度来阐释库恩的心路历程。我们的目的不是"去魅",更不想树立新的偶像,而是试图还原一个真实的库恩。 相似文献
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在各门课中,英语较弱的学生比较多。又有谁来点燃这些英语差生心中的那盏灯呢？自信和勤奋可以说是一把双刃剑,成功的道路上总是挤满了勤奋的人,但学要得法,方能事半功倍。请点燃这些英语后进生心中的那盏灯,让他们已经黑暗的心灵燃起生命的火焰。 相似文献
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The classical problem of broadband matching was first studied by Bode (1) and developed later by Fano (2); however, Fano's solution, although very elegant, has a practical limitation. The key idea is to replace the load Z2(S) by its Darlington equivalent ending in 1 ohm, but the optimum design is, in general, not very simple. Youla (3) proposed an alternative method where it is relatively easy to find the optimum network even for the more complex impedance load. The paper shows that maximization of the gainbandwidth product, in the presence of load or source variations, depends on the choice of the reflection coefficient zeros, either in the left half-plane or in the right half-plane. 相似文献
9.
Fara P 《Endeavour》2004,28(1):12-13
J.B.S. Haldane's photographs reveal that this eminent geneticist was also a militant political agitator. Deeply engaged in left-wing British politics, Haldane eventually joined the Communist party, but found it increasingly difficult to reconcile his scientific beliefs with his Marxist commitments. During the controversy over Stalin's rejection of genetics in favour of Trofim Lysenko's agricultural reforms, Haldane's activities were critically interpreted from various different perspectives. 相似文献
10.
Galison P 《Isis; an international review devoted to the history of science and its cultural influences》2004,95(4):610-613
As Einstein's portrait comes increasingly to resemble an icon, we lose more than detail--his writings and actions lose all reference. This is as true for his physics as it is for his philosophy and his politics; the best of recent work aims to remove Einstein's interventions from the abstract sphere of Delphic pronouncements and to insert them in the stream of real events, real arguments. Politically, this means attending to McCarthyism, Paul Robeson, the Arab-Israeli conflict. Philosophically, it means tying his concerns, for example, to late nineteenth-century neo-Kantian debates and to his own struggles inside science. And where physics is concerned, it means attending both in the narrow to his responses to others' work and his reactions to his own sometimes misfired early work on, for example, general relativity and to the wider context of technological developments. Einstein remains and will remain a magnet for historians, philosophers, and scientists; the essays assembled here represent a strong sampling--but only a sampling--of a fascinating new generation of work on this perennial figure. 相似文献
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舞蹈是一种表现力和技术技巧性很强的艺术表演形式,它通过肢体的表现,美化人们的形体,并且可以提升艺术修养。孩子从开始掌握初步表演技能,到完成一定难度的舞段,再到高难度的舞蹈技巧,并用舞蹈抒发内心的情感,不是一件轻而易举的事情。因为舞蹈的表演不仅是肢体的运动,必须遵循有规律的、科学的、恒久性的训练,努力地去理解舞蹈的内涵、所要表达的主题,才能掌握舞蹈的表演技艺。随着我国经济的发展,素质教育也被大力提倡。少儿舞蹈学习已经不再是单纯地作为孩子将来谋生的一门技术,而是被人们作为锻炼孩子的体能、提高孩子艺术修养的一种手段。 相似文献
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芥川龙之介因为受中国古典文学的影响．所以认为中国是一个神秘、美好的国家．中国人都是充满英雄色彩的豪杰．但是在他的中国之行后．这种认识发生了变化——对当时的中国现状及中国人感到了失望．这种对中国认识的变化影响了芥川的文学创作。本文试在前人研究的基础上探寻芥川对中国认识的变化过程并分析对其文学创作的影响。 相似文献
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人文环境对科学技术发展的影响分析——兼论世界科学活动中心转移的人文因素 总被引：3，自引：0，他引：3
本文在界定科学技术发展人文环境的基础上,详细地分析了人文环境对科学技术发展的影响。指出,人文学科的普遍繁茂必然会促进科学技术的昌盛;民族文化传统对科学技术发展的方式和道路将产生深刻影响;社会价值观念对科学技术的发展具有导向作用;科学家个人的人文素养直接影响着其创造力的高低 相似文献
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语文对于中学生而言更多的是需要理解和学会应用,单纯的记忆是很难把初中语文学好的。对于教师而言,要想在有限的授课时间内让学生在语文学习上能够取得很快的进步,就需要在授课内容和课程内容安排上进行积极的思考和改进。如何在课堂教学效率方面得到提高是众多中学语文老师思考的问题。课堂教学效率的优化是最近几年大家提倡的在教学中特别关注的话语,笔者就自己实践工作经验进行相关问题的简单阐述。 相似文献
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This paper intends to introduce briefly the thematic progression patterns in Systemic- Functional Grammar, then analyze its application in "The Great Learning" which is one of the classics of the Confucius and his disciples. The analysis of the thematic progression patterns of "The Great Learning" is meaningful for both understanding and appreciating "The Great Learning". 相似文献
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自然与设计关系密切,本文通过探讨自然与设计、文化之间既简单又复杂的关系,呈现设计不仅要仿制自然,而且要进入自然,它如同人类社会一样需要将自己的生命力延续下去。求证设计本身仅仅是一个被功能化了的概念,艺术家的某些职责也因此被界定在为＂自然＂存亡而服务的范围之内。 相似文献
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分析吴有训在上世纪30年前后开展的X射线散射研究及这些研究的学术价值和背景,论证其与当时中国“学术独立”的关系,指出这些研究是中国物理学走向“学术独立”的第一步,并为中国科学的“学术独立”起到了很好的推动和示范作用。 相似文献
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本文系统地总结了班主任的工作任务和对学生应该起到的积极教化作用,探究了21世纪优秀班主任应该具备的自身素质和工作能力。优秀班主任,应该为学生的美好前程打下坚实的基础,应该酿造出学生健康的精神、伟大的心灵和利人利己利社会的行为。 相似文献