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   4596篇
  免费   57篇
  国内免费   53篇
教育   3469篇
科学研究   395篇
各国文化   8篇
体育   376篇
综合类   333篇
文化理论   6篇
信息传播   119篇
  2024年   1篇
  2023年   15篇
  2022年   16篇
  2021年   45篇
  2020年   60篇
  2019年   70篇
  2018年   56篇
  2017年   52篇
  2016年   59篇
  2015年   109篇
  2014年   259篇
  2013年   350篇
  2012年   367篇
  2011年   394篇
  2010年   291篇
  2009年   251篇
  2008年   299篇
  2007年   375篇
  2006年   349篇
  2005年   297篇
  2004年   234篇
  2003年   214篇
  2002年   210篇
  2001年   149篇
  2000年   84篇
  1999年   38篇
  1998年   18篇
  1997年   10篇
  1996年   10篇
  1995年   6篇
  1994年   6篇
  1993年   5篇
  1992年   3篇
  1991年   2篇
  1990年   1篇
  1957年   1篇
排序方式: 共有4706条查询结果,搜索用时 15 毫秒
1.
This study investigates the sociomaterial movements of student engagement in a school's makerspace. Here, we understand sociomaterial movements as emergent and relational, comprising complex dynamics of agency across students, teachers and materials in situated, culturally framed activities. Our study draws on data comprising 85 hours of video recordings of 9–12-year-old students' (N = 94) engagement in a technology-rich makerspace in a Finnish elementary school. The video data were transcribed and analyzed qualitatively using a multimodal interaction analysis. The sociomaterial movements were found to be displayed across a tension-laden continuum between (1) procedural activity—analysis and reflection; (2) individual activity—collaboration; (3) “doing school”—empowerment; and d) alienation—identification. Together, the study offers a potential approach for investigating and understanding the often overlooked workings of sociomateriality that constitutes students' emergent engagement and learning opportunities in science, technology, engineering and mathematics (STEAM) learning contexts.  相似文献   
2.
Mothers who use substances need integrated, multi-sectoral intervention services to support substance use discontinuation. We explored mothers’ service use at Breaking the Cycle, an early intervention and prevention program for pregnant and parenting women and their young children in Toronto, Canada. We conducted retrospective analyses of families’ service records and client charts (N = 160). Aims were to 1) describe women’s use of service, 2) examine how early engagement of pregnant women related to postnatal service use, and 3) examine the circumstances in which women ended their service relationship with Breaking the Cycle. Specifically, we examined circumstances at service ending relating to women’s service goals; custody status with children; and global substance-use, parent-child relationship, and child development outcomes. We found that these vulnerable women were actively engaged in many services and for a long duration, early engagement was associated with greater service use, and greater service use was associated with more positive circumstances upon ending service. Results provide support for a relational approach to service that promotes not only the relationship between mother and child, and mother and service provider, but also highlights relationships among staff, between staff and management, and between community partners as integral to effective service delivery. Integrating positive relationships at all levels is critical to support vulnerable families with complex needs.  相似文献   
3.
计算流体力学在搅拌混合过程模拟中的应用   总被引:4,自引:0,他引:4  
张永震  韩振为 《科技通报》2005,21(3):332-336
计算流体力学包括反应器中流体的质量、动量、能量守恒方程和反映所研究问题的辅助方程的数值解。它在搅拌式反应器的设计与放大中起着重要的作用。概述了模拟搅拌式反应器中流场的各种方法:搅拌桨边界条件法,内外迭代法,多重参照系法,滑动网格法,快速照相法和大涡模拟法。并通过分析各种方法的优缺点提出了进一步的研究方向:修正湍流模型,发展大涡模拟法等。  相似文献   
4.
This paper is concerned with the problem of global asymptotical tracking of single-input single-output (SISO) nonlinear time-delay control systems. Based on the input-output feedback linearization technique and Lyapunov method for nonlinear state feedback synthesis, a robust globally asymptotical output tracking controller design methodology for a broad class of nonlinear time-delay control systems is developed. The underlying theoretical approaches are the differential geometry approach and the composite Lyapunov approach. One utilizes the parameterized co-ordinate transformation to transform the original nonlinear system into singularly perturbed model and the composite Lyapunov approach is then applied for output tracking. For the view of practical application, the proposed control methodology has been successfully applied to the famous nonlinear automobile idle-speed control system.  相似文献   
5.
比较了传统技术价值评估方法与实物期权法的不同特征,给出了运用实物期权评估技术价值的逻辑框架,重点分析了评估中的困境和可能的解决方法,对实物期权评估技术价值的管理学涵义做了阐释。  相似文献   
6.
技术跨越的本质就是一种非连续性的技术进步方式,旨在迅速提高技术水平,缩短与技术领先者的差距。技术跨越的实现主要有三种途径:自主、引进、合作。理论和实践经验证明,政府的干预是实现技术跨越的重要条件,但是在不同创新阶段,政府工作的重点有所不同。  相似文献   
7.
齐悦 《中国科技信息》2007,(11):252-254
本文综述了支持口语教学改革的理论基础,探讨了非英语专业大学生英语口语课堂教学模式,并提出在口语教学改革中需要注意的几点,从而为英语教学改革提供一些新的思路及可能性。  相似文献   
8.
From a number of ML estimators (typically unbiased) of practical interest which include the variance for a Gaussian distribution, the standard deviation for a Laplace distribution, the variance for a Rayleigh distribution and a “spread parameter” for a Cauchy distribution, we design robust estimators according to an emphasis balance between normalized performance and normalized robustness. We measure performance with inverted MSE and robustness with a differential geometric approach.  相似文献   
9.
随着商务英语教学的发展,交际语言教学法已普遍运用到语言和商务相结合的复合课程中来,体现了“以学习者为中心”的教学思想。小组讨论作为交际教学法的一种典型教学手段,在当今商务英语教学中得到了广泛的运用。在长期的教学实践中,对讨论法在教学过程中的准备、引导、评价等方面作了一个简要而有效的探讨。  相似文献   
10.
分段函数求导问题的多种解法   总被引:1,自引:0,他引:1  
求分段函数在分段点处的导数,不能直接利用求导公式或求导法则;但是可以借助其它数学工具,如导数极限定理、泰勒公式等等,将问题转化,进而得到求解该问题的多种方法。  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