首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   991篇
  免费   21篇
  国内免费   8篇
教育   696篇
科学研究   93篇
各国文化   26篇
体育   84篇
综合类   1篇
文化理论   7篇
信息传播   113篇
  2023年   3篇
  2022年   15篇
  2021年   18篇
  2020年   33篇
  2019年   46篇
  2018年   73篇
  2017年   79篇
  2016年   63篇
  2015年   24篇
  2014年   47篇
  2013年   227篇
  2012年   41篇
  2011年   46篇
  2010年   34篇
  2009年   31篇
  2008年   38篇
  2007年   27篇
  2006年   24篇
  2005年   19篇
  2004年   16篇
  2003年   19篇
  2002年   9篇
  2001年   6篇
  2000年   12篇
  1999年   6篇
  1998年   5篇
  1997年   6篇
  1996年   7篇
  1995年   1篇
  1994年   5篇
  1993年   3篇
  1992年   4篇
  1991年   1篇
  1989年   3篇
  1988年   4篇
  1987年   1篇
  1986年   1篇
  1985年   4篇
  1984年   5篇
  1983年   3篇
  1982年   2篇
  1981年   1篇
  1979年   2篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1967年   1篇
  1966年   1篇
  1964年   1篇
排序方式: 共有1020条查询结果,搜索用时 15 毫秒
61.
If instructional designers hold limited views about their practice they sometimes adopt formulaic routines that do not help them accomplish the goals they believe are important, or develop instruction of a quality envisioned by the field??s innovative theorists. Fortunately, designers can avoid these unfavorable results in part by understanding and exemplifying the creative spirit of design. In this article the author examines the creative spirit of design, exploring its imaginative, creation-oriented, and inter-disciplinary character. The author also describes how the creative spirit can help instructional designers remain flexible and perceptive in their practice, and by so doing be better able to create effective and innovative instruction of a quality consistent with their ultimate ideals.  相似文献   
62.
Research on categories and markets suggests that audiences rely on categorical distinctions to make sense of market offerings. Market offerings that deviate from category norms risk devaluation. Although literature in this area has led to valuable insights, scholars have begun to question whether there has been an overemphasis on conformity, leaving existing theories ill-equipped to account for innovation. Within this context, we argue that research on authenticity in cultural sociology offers a useful platform for theorizing. We draw on the work of Peterson (1997), who underscores the importance of signals in evaluation. Objective features of market offerings (e.g., quality) matter, but particularly for innovations, these features are not readily visible. Because authentic producers are typically thought to be more committed, capable, and intrinsically motivated, when visibility of such objective features is lacking, authenticity may serve as an alternative indicator of value. Appearing authentic requires signaling believability with respect to category norms, while also being distinctive. Using data on 684 firms from five high technology sectors, we explore the relationship between authenticity and investor perceptions of value. Focusing on three different proxies for signals of authenticity—networks, governance, and narratives—we find a curvilinear association between conformity/distinctiveness and Tobin's q. Consistent with our view of authenticity as a signal, we also find that this relationship flattens as firms gain better track records and face stiffer competition.  相似文献   
63.
A number of recent studies have measured the extent and timing of segment rotation during the golf swing. A promising technique, instantaneous screw axis (ISA) theory, could provide a better expression of segment rotation. In Part 1 of this two-part study, the objectives are to identify the ISA of the pelvis, shoulders and left arm during the downswing, compute segment angular velocity relative to that segment’s ISA and verify that ISA theory is a valid tool to analyse segment rotation during the golf swing. Results indicate that for all subjects, at least 71% of marker velocity is a result of rotation about their respective ISA, when averaging results over the duration of the downswing, confirming that motion is primarily rotational. Furthermore, ISA position and orientation of each segment approaches, on average, the expected gross axis of rotation, confirming that motion about the ISA is representative of joint motion.  相似文献   
64.
Running is the most important discipline for Olympic triathlon success. However, cycling impairs running muscle recruitment and performance in some highly trained triathletes; though it is not known if this occurs in elite international triathletes. The purpose of this study was to investigate the effect of cycling in two different protocols on running economy and neuromuscular control in elite international triathletes. Muscle recruitment and sagittal plane joint angles of the left lower extremity and running economy were compared between control (no preceding cycle) and transition (preceded by cycling) runs for two different cycle protocols (20-minute low-intensity and 50-minute high-intensity cycles) in seven elite international triathletes. Muscle recruitment and joint angles were not different between control and transition runs for either cycle protocols. Running economy was also not different between control and transition runs for the low-intensity (62.4 +/- 4.5 vs. 62.1 +/- 4.0 ml/min/kg, p > 0.05) and high-intensity (63.4 +/- 3.5 vs. 63.3 +/- 4.3 ml/min/kg, p > 0.05) cycle protocols. The results of this study demonstrate that both low- and high-intensity cycles do not adversely influence neuromuscular control and running economy in elite international triathletes.  相似文献   
65.
66.
The successful encapsulation of human hepatocellular carcinoma (HepG2) cells would greatly assist a broad range of applications in tissue engineering. Due to the harsh conditions during standard chitosan fiber fabrication processes, encapsulation of HepG2 cells in chitosan fibers has been challenging. Here, we describe the successful wet-spinning of chitosan-alginate fibers using a coaxial flow microfluidic chip. We determined the optimal mixing conditions for generating chitosan-alginate fibers, including a 1:5 ratio of 2% (w∕w) water-soluble chitosan (WSC) solution to 2% (w∕w) alginate solution. Ratio including higher than 2% (w∕w) WSC solution increased aggregation throughout the mixture. By suspending cells in the WSC-alginate solution, we successfully fabricated HepG2 cell-laden fibers. The encapsulated HepG2 cells in the chitosan-alginate fibers were more viable than cells encapsulated in pure alginate fibers, suggesting that cross-linked chitosan provides a better environment for HepG2 cells than alginate alone. In addition, we found that the adhesion of HepG2 cells on the chitosan-alginate fiber is much better than that on the alginate fibers.  相似文献   
67.
Herein is described the fabrication and use of a plastic multilayer 3-channel microfluidic fixture. Multilayer devices were produced by laser machining of plastic polymethylmethacrylate and polyethyleneterapthalate laminates by ablation. The fixture consisted of an array of nine individually addressable gold or gold/ITO working electrodes, and a resistive platinum heating element. Laser machining of both the fluidic pathways in the plastic laminates, and the stencil masks used for thermal evaporation to form electrode regions on the plastic laminates, enabled rapid and inexpensive implementation of design changes. Electrochemiluminescence reactions in the fixture were achieved and monitored through ITO electrodes. Electroaddressable aryl diazonium chemistry was employed to selectively pattern gold electrodes for electrochemical multianalyte DNA detection from double stranded DNA (dsDNA) samples. Electrochemical detection of dsDNA was achieved by melting of dsDNA molecules in solution with the integrated heater, allowing detection of DNA sequences specific to breast and colorectal cancers with a non-specific binding control. Following detection, the array surface could be renewed via high temperature (95 °C) stripping using the integrated heating element. This versatile and simple method for prototyping devices shows potential for further development of highly integrated, multi-functional bioanalytical devices.  相似文献   
68.
In this article, the authors present the fabrication of an enzyme-entrapped alginate hollow fiber using a microfluidic device. Further use of enzyme-entrapped alginate hollow fibers as a biocatalytic microchemical reactor for chemical synthesis is also deliberated in this article. To ensure that there is no enzyme leaching from the fiber, fiber surfaces were coated with chitosan. To confine the mobility of reactants and products within the porous hollow fibers the entire fibers were embedded into a transparent polydimethylsiloxane (PDMS) matrix which also works as a support matrix. A vanadium-containing bromoperoxidase enzyme isolated from Corallina confusa was used as a model enzyme to demonstrate the use of these alginate hollow-fiber reactors in bromo-oxidation of phenol red to bromophenol blue at different dye flow rates. Stability of the entrapped enzyme at different temperatures and the effect of the chitosan coating on the reaction conversion were also studied. It was observed that molecules as big as 27 kDa can be retained in the matrix after coating with chitosan while molecules with molecular-weight of around 378 Da can still diffuse in and out of the matrix. The kinetic conversion rate in this microfluidic bioreactor was more than 41-fold faster when compared with the standard test-tube procedure.  相似文献   
69.
Educational Psychology Review - The purpose of this systematic review is to describe the state of the art of sequential multiple-assignment randomized trials in education research. An iterative,...  相似文献   
70.

Online collaborative and content-focused professional development (PD) is becoming an increasingly important setting for supporting mathematics teachers’ professional learning. The purpose of this study was to better understand the process by which a community emerges in such a PD setting by examining how the cohesiveness of 21 mathematics teachers’ social network evolves and associated shifts in the quality of mathematics teachers’ mathematical discourse. We employed social network analysis (SNA) to examine the evolving cohesiveness of mathematics teachers’ social network and coding procedures to examine teachers’ mathematical discourse. A key finding was the documentation of an emergent divide between participation in the core and periphery during initial weeks of the PD and then a reduced divide and emergence of a social network that resembles a community. We argue that the instructor’s pattern of participation that included distributing their interactions across the subgroups while sending a common message regarding expectations for mathematical discourse in the PD may have contributed to the community formation process. We propose the Interaction Assessment Model, which outlines an approach for PD facilitators to use SNA as a feedback mechanism to differentiate facilitation of online collaborative and content-focused PD and build online communities.

  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号