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921.
OROZCO Rubén 《浙江大学学报(A卷英文版)》2006,7(10):1748-1756
INTRODUCTION Deconvolution of ultrasonic signals is defined as the solution of the inverse problem of convolving an input signal, known as the system function h(n), with a medium reflectivity function x(n) and can be rep- resented by y(n)=h(n)*x(n) η(n), (1) where y(n) is the measured signal, * denotes the convolution operation and η(n) is the additive noise. Recovering x(n) from the observation y(n) leads to improving the appearance and the axial resolution of the RF-signals by removin… 相似文献
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中国教育私营化的机遇与挑战 总被引:4,自引:0,他引:4
中国各层次的民办学校正在大规模增长。本文正是要设定一种情景 ,从而更多地理解和引导这种现象。作者首先解释了在拥有庞大公立教育系统的国家缘何出现私立学校。基于埃斯特尔·詹姆斯的划分 ,私立学校是对过度需求、差异需求以及非营利组织大量出现的回应。中国的特点是在公共教育资源短缺的地方存在过度需求 ,特别是在中学阶段那些无法就学或是达不到中学教育和高等教育入学标准的学生中 ;差异需求也明显存在 ,民办精英学校的出现为学生在现有公立教育体系之外提供了另一种选择。其次 ,作者讨论了评价私立学校功能和运作的四个目标 :自由选择权、效率、公平和社会凝聚力。再次 ,他提出三个政策性工具以使私立学校达到上述目标 ,即财政、法规和支持性服务。最后作者考察了中国民办教育中存在的一些问题 ,特别是公平性问题。虽然中国在努力实现这些目标 ,但是对于民办学校的定位和监管法律依然含糊不清。今后需要澄清和完善这个民办教育的框架。 相似文献
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The problem of presenting advanced project work in distance teaching is discussed and criteria established for its success. An evaluation of empirical research projects involved in an advanced course on research methods in education and social science is described and some principles put forward for sound project design in distance teaching. Finally, three models suggesting different combinations of distance teaching and conventional institution-based teaching are proposed which incorporate advanced project work. It is suggested that conventional teaching institutions working in isolation can all benefit from a distance teaching element in their programmes. 相似文献
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OBJECTIVE: The aim of the study was to identify the general, common, and specific developmental risk factors for pedophilia, exhibitionism, rape, and multiple paraphilia, and to address five methodological issues observed in this area of research. METHOD: This study involved 64 sex offenders and 33 nonsex, nondrug-related, and nonviolent property offenders. The group of 64 sex offenders was further divided into eight subgroups, some of which overlapped in memberships because of multiple diagnoses. To overcome the methodological problem associated with overlapping group memberships, a special approach involving comparisons of sets of logistic regression analyses was adopted. Offenders were clinically assessed for evidence of paraphilias, and their adverse childhood experiences were measured by a battery of tests. RESULTS: Childhood Emotional Abuse and Family Dysfunction, Childhood Behavior Problems, and Childhood Sexual Abuse were found to be general developmental risk factors for paraphilias. Furthermore, Childhood Emotional Abuse and Family Dysfunction was found to be a common developmental risk factor for pedophilia, exhibitionism, rape, or multiple paraphilia. Additional analyses revealed that childhood emotional abuse contributed significantly as a common developmental risk factor compared to family dysfunction. Besides, Childhood Sexual Abuse was found to be a specific developmental risk factor for pedophilia. CONCLUSIONS: The study has supported the value of conceptualizing certain childhood adversities as developmental risk factors for paraphilic behaviors. The role of childhood emotional abuse as an important developmental risk contributor, and the relationship between childhood sexual abuse and pedophilia are of theoretical significance. Furthermore, the results have significant implications for the prevention of childhood abuse and treatment of sex offenders. 相似文献
928.
Henry Lieberman 《Instructional Science》1986,14(3-4):277-292
Making a good programming environment for beginning programmers is an enterprise which can exploit the strong connections between machine learning and human learning. Applying what we know about teaching and learning to improve the programming environment can result in a system which allows beginners to more readily acquire programming skills.Surprisingly, a universally accepted principle of good teaching and good learning has not been taken seriously enough in designing programming environments-learning by example. A good teacher presents examples of how to solve problems, and points out what is important about the examples. The student generalizes from the examples to learn principles and techniques. This paper describes a programming environment called Tinker, in which a beginning programmer presents examples to the machine, distinguishing accidental and essential aspects of the examples. The programmer demonstrates how to handle the specific examples, and the machine formulates a procedure for handling the general case. Because people are much better at thinking about concrete examples than they are at thinking about abstractions, and because examples provide immediate feedback, Tinker is a more congenial environment for a beginner than conventional programming systems. 相似文献
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In 2 studies, we address young children's understanding of the origin and representational relations of imagination, a fictional mental state, and contrast this with their understanding of knowledge, an epistemic mental state. In the first study, 54 3- and 4-year-old children received 2 tasks to assess their understanding of origins, and 4 stories to assess their understanding of representational relations. Children of both ages understood that, whereas perception is necessary for knowledge, it is irrelevant for imagination. Results for children's understanding of representational relations revealed intriguing developmental differences. Although children understood that knowledge represents reality more truthfully than imagination, 3-year-olds often claimed that imagination reflected reality. The second study provided additional evidence that younger 3-year-olds judge that imaginary representations truthfully reflect reality. We propose that children's responses indicate an early understanding of the distinction between mental states and the world, but also a confusion regarding the extent to which mental contents represent the physical world. 相似文献