全文获取类型
收费全文 | 2465篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
教育 | 1608篇 |
科学研究 | 358篇 |
各国文化 | 25篇 |
体育 | 211篇 |
综合类 | 1篇 |
文化理论 | 29篇 |
信息传播 | 249篇 |
出版年
2021年 | 32篇 |
2020年 | 37篇 |
2019年 | 85篇 |
2018年 | 144篇 |
2017年 | 105篇 |
2016年 | 101篇 |
2015年 | 53篇 |
2014年 | 72篇 |
2013年 | 461篇 |
2012年 | 47篇 |
2011年 | 49篇 |
2010年 | 51篇 |
2009年 | 42篇 |
2008年 | 54篇 |
2007年 | 46篇 |
2006年 | 37篇 |
2005年 | 33篇 |
2004年 | 28篇 |
2003年 | 23篇 |
2002年 | 22篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 26篇 |
1998年 | 27篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 27篇 |
1991年 | 27篇 |
1990年 | 27篇 |
1989年 | 30篇 |
1988年 | 26篇 |
1987年 | 18篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 19篇 |
1982年 | 26篇 |
1980年 | 18篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1967年 | 17篇 |
1941年 | 19篇 |
1939年 | 23篇 |
1937年 | 41篇 |
1936年 | 40篇 |
排序方式: 共有2481条查询结果,搜索用时 6 毫秒
71.
Sequence learning in pigeons was studied in asimultaneous chaining paradigm: all stimuli and the opportunity to respond to each stimulus were available simultaneously. In contrast to the traditionalsuccessive chaining paradigm, a simultaneous chaining paradigm provides no differential feedback following each response (except the last). Subjects were first trained to perform on sequences of two (AB), then three (ABC), and then four colors (ABCD). Performance greatly exceeded that predicted by models of random choice. Generalization to novel arrays of three and four colors was complete. After training with a four-color sequence, the subjects were tested with subsequences consisting of all possible combinations of two and three of the four training colors (e.g., BD, AD, BC, ACD, BCD, etc.). The successful completion of these subsequences showed that the organization of the original sequence did not entail overt pecks to successive elements of that sequence. That subjects can respond accurately on nonadjacent subsets is not readily explained by a chaining theory, or by any theory that assumes that responding to element n provides a cue for responding to element n+1. 相似文献
72.
Scott O. Moore 《History of education》2019,48(3):336-355
This article examines Austria’s efforts to reform teacher education during the period of the Dual Monarchy, 1867–1914. It offers insight into the role of teachers in Austrian society and how this role changed over time. It demonstrates that, during this period, teaching became an institutionalised and professionalised occupation. This process of professionalisation brought teachers firmly under state control, leading to conflict between teachers and the Austrian educational bureaucracy. This process also led to the development of a robust network of teachers’ associations to represent the interest of Austrian teachers and to contribute to their professional development. This article utilises documents from the Austrian educational bureaucracy, printed curriculum and pedagogical journals to illustrate that Austrian teacher training reforms offer crucial insight into the development of public education in the late nineteenth century. 相似文献
73.
Research in Higher Education - State financial aid grant programs are commonly categorized as either need-based, merit-based, or both, but their initial eligibility requirements include many more... 相似文献
74.
75.
The purpose of this paper is to compute the Hankel transform Fn(y) of order n of a function f(x) and its inverse transform using rationalized Haar wavelets. The integrand is replaced by its wavelet decomposition. Thus representing Fn(y) as a Fourier-Bessel series with coefficients depending strongly on the local behavior of the function , thereby getting an efficient algorithm for their numerical evaluation. Numerical evaluations of test functions with known analytical Hankel transforms illustrate the proposed algorithm. 相似文献
76.
Gergely Simon Caroline Busch Marco A. B. Andrade Julien Reboud Jonathan M. Cooper Marc P. Y. Desmulliez Mathis O. Riehle Anne L. Bernassau 《Biomicrofluidics》2021,15(1)
Separation and sorting of biological entities (viruses, bacteria, and cells) is a critical step in any microfluidic lab-on-a-chip device. Acoustofluidics platforms have demonstrated their ability to use physical characteristics of cells to perform label-free separation. Bandpass-type sorting methods of medium-sized entities from a mixture have been presented using acoustic techniques; however, they require multiple transducers, lack support for various target populations, can be sensitive to flow variations, or have not been verified for continuous flow sorting of biological cells. To our knowledge, this paper presents the first acoustic bandpass method that overcomes all these limitations and presents an inherently reconfigurable technique with a single transducer pair for stable continuous flow sorting of blood cells. The sorting method is first demonstrated for polystyrene particles of sizes 6, 10, and 14.5 μm in diameter with measured purity and efficiency coefficients above 75 ± 6% and 85 ± 9%, respectively. The sorting strategy was further validated in the separation of red blood cells from white blood cells and 1 μm polystyrene particles with 78 ± 8% efficiency and 74 ± 6% purity, respectively, at a flow rate of at least 1 μl/min, enabling to process finger prick blood samples within minutes. 相似文献
77.
Size-dependent trajectories of DNA macromolecules due to insulative dielectrophoresis in submicrometer-deep fluidic channels 总被引:1,自引:0,他引:1
Gea O. F. Parikesit Anton P. Markesteijn Oana M. Piciu Andre Bossche Jerry Westerweel Ian T. Young Yuval Garini 《Biomicrofluidics》2008,2(2)
In this paper, we demonstrate for the first time that insulative dielectrophoresis can induce size-dependent trajectories of DNA macromolecules. We experimentally use λ (48.5 kbp) and T4GT7 (165.6 kbp) DNA molecules flowing continuously around a sharp corner inside fluidic channels with a depth of 0.4 μm. Numerical simulation of the electrokinetic force distribution inside the channels is in qualitative agreement with our experimentally observed trajectories. We discuss a possible physical mechanism for the DNA polarization and dielectrophoresis inside confining channels, based on the observed dielectrophoresis responses due to different DNA sizes and various electric fields applied between the inlet and the outlet. The proposed physical mechanism indicates that further extensive investigations, both theoretically and experimentally, would be very useful to better elucidate the forces involved at DNA dielectrophoresis. When applied for size-based sorting of DNA molecules, our sorting method offers two major advantages compared to earlier attempts with insulative dielectrophoresis: Its continuous operation allows for high-throughput analysis, and it only requires electric field strengths as low as ∼10 V∕cm. 相似文献
78.
Richard O. Welsh 《Journal of Education for Students Placed at Risk》2018,23(1-2):70-92
ABSTRACTMobile students and absent students are important subsets of at-risk students in schools and districts nationwide. As such, student mobility and school absenteeism are two challenges in K-12 education with significant policy and equity implications. Although both issues are at the nexus of schooling and society and there is an apparent overlap in the attributes of these student subgroups, school absenteeism and student mobility are often discussed in separate conversations. This article connects the two disparate literatures in hopes of forging stronger ties that may benefit policymakers, researchers, educators, and students. The limited empirical evidence is mixed but suggests that school absenteeism and student mobility are correlated and absenteeism plays a small mediating role in the relationship between student mobility and student outcomes. The reasons underlying student mobility and student absenteeism are interrelated but not all reasons are common. The overlapping causes of student mobility and chronic absenteeism indicate that economic and social circumstances are important underlying factors. In particular, poverty is a key shared reason for missing or switching schools. Although both phenomena contribute to disparities in educational opportunities, experiences, and outcomes, this study posits that changing schools and missing school provide instructive examples of how inequality in society may be reproduced in districts and schools. Recommendations to address both phenomena and directions for future research are discussed. 相似文献
79.
John O’Neill 《教育政策杂志》2013,28(1):17-31
This paper examines recent privatisation practices in New Zealand public schooling. The standard political rhetoric is that free publicly provided schooling is guaranteed by statute. This position may be challenged by reference to two apparently insignificant practical examples of the way in which policy gives effect to privatisation in public schooling: (1) the commissioning of national assessment strategy policy advice, and (2) the award of contestable funding for the provision of support services to schools. It is argued that such practices advance neoliberal theories of schooling at the expense of the previous social democratic liberal settlement. The paper considers some possible consequences of increased privatisation of policy advice and service provision for understandings of and commitments to public schooling. 相似文献
80.