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   19972篇
  免费   532篇
  国内免费   381篇
教育   11574篇
科学研究   4751篇
各国文化   24篇
体育   559篇
综合类   924篇
文化理论   7篇
信息传播   3046篇
  2024年   4篇
  2023年   114篇
  2022年   275篇
  2021年   395篇
  2020年   574篇
  2019年   460篇
  2018年   377篇
  2017年   340篇
  2016年   454篇
  2015年   688篇
  2014年   1453篇
  2013年   1290篇
  2012年   1794篇
  2011年   1801篇
  2010年   1123篇
  2009年   1102篇
  2008年   1191篇
  2007年   1410篇
  2006年   1313篇
  2005年   1198篇
  2004年   990篇
  2003年   824篇
  2002年   665篇
  2001年   497篇
  2000年   275篇
  1999年   98篇
  1998年   45篇
  1997年   47篇
  1996年   15篇
  1995年   17篇
  1994年   17篇
  1993年   7篇
  1992年   10篇
  1991年   7篇
  1990年   3篇
  1989年   4篇
  1979年   1篇
  1978年   1篇
  1957年   6篇
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
881.
考虑到电动汽车动力电池回收量、回收技术水平等参数的不确定性,以逆向物流网络总利润最高和环境影响最小为目标,建立多目标模糊规划模型,进行电动汽车动力电池逆向物流网络设计。利用基于可信性测度的模糊求解方法处理模型中的模糊参数。引入决策者偏好系数,采用加权理想点法将多目标模型转化为单目标模型进行求解,得到考虑不确定性的逆向物流网络设施的选址、数量以及设施间的废旧动力电池流量分配方案。通过数值算例验证模型和算法的可行性和有效性。对回收量、回收技术水平和决策者偏好系数进行灵敏度分析,结果表明:随着回收量的增加,逆向物流网络利润增加;回收技术水平的提升和决策者选择合适的偏好系数可以提高逆向物流网络的经济效益和环境效益。  相似文献   
882.
While expert teachers remain a frequent focus of research in education, to date there have been very few attempts to conduct systematic reviews of this literature. This paper presents the findings of the first systematic metasummary of research on teacher expertise in K12 education (primary/elementary and secondary levels), based on analysis of 106 empirical studies from 16 countries involving 1124 teachers identified as experts. The inductively-developed coding framework was applied independently by both authors to the dataset to generate agreement counts for specific coding themes, firstly for specific domains of teacher expertise, and then stratified to compare primary and secondary studies. We present 73 specific features organised into six domains in our expert teacher prototype. Salient findings indicate that, with regard to professional practice, expert teachers reflect extensively and often critically on their practice, help their colleagues frequently, and are continuous learners throughout their careers. Concerning knowledge, we find that expert teachers have well-developed pedagogical content knowledge and knowledge about their learners. In the domain of pedagogic practice, we observe that expert teachers display flexibility in the classroom, build strong interpersonal relationships with their learners, whom they engage through their choice of activities and content, and frequently make use of strategies typically emphasised in both constructivist and learner-centred education literatures. We offer our prototype as a useful initial sketch of family resemblance among expert teachers rather than a checklist of necessary or expected features of expertise, also cautioning that the prototype remains far from complete.  相似文献   
883.
Although the effectiveness of peer review has been examined, few have tested the joint benefits of providing and receiving feedback features and quality in L2 contexts. The present study investigated variation in key features and quality of feedback provided and received by high and low L2 proficiency students and its benefits on revision in the authentic setting of students experiencing both roles of providing and receiving peer feedback in English academic writing. Analyses on two drafts from 50 students, 1356 idea units of anonymous implementable peer feedback and back-evaluation ratings revealed that the combined effect of providing and receiving feedback on revision was prominent for all students. But the bilateral benefits of providing and receiving feedback features were more significant for high proficiency students, while providing feedback features and quality benefited low proficiency students more. The study implies that students need more bilateral training with both providing and receiving feedback.  相似文献   
884.
通过对社交网络所产生的海量用户以及数据的挖掘与分析,判断用户不同的特征与喜好,从而为用户定制个性化知识服务,达到用户的需求,增强其对产品与服务的使用黏性,这不仅满足了企业的商业目的,同时也提高了用户的满意度。论文在深入了解我国社交网络的运营模式、分析社交网络中用户行为特征的前提下,提出从用户兴趣模型出发的个性化知识服务,并建立了基于个人兴趣和兴趣传播推荐的个性化知识服务模型。  相似文献   
885.
《去图书馆约会》是一位文化类杂志编辑写的图书馆文化普及读物.论文总结了该书的写作特色,归纳出三点可读价值,认为值得一读.  相似文献   
886.
研究发现,图书情报领域的合著率处于人文社会科学的中等水平,且以2~3人的小规模合著为主导模式;同时发现基金论文有着较高的合著率,基金项目、科研团队、论文产出之间有深刻的内在联系,共同承担重大基金项目往往成为团队形成的内在机制.近年来,图书情报学已经形成“三主多辐”型庞大合著网络,跨省区、跨机构合著、区域学术融合仍亟待加强.  相似文献   
887.
《城镇企业职工基本养老保险关系转移接续暂行办法》并没有摆脱社会保障的制度陷阱、不公平陷阱和低水平陷阱,反而又延伸出了社会保障的流动陷阱和踢皮球陷阱。这些陷阱形成的主要原因不是人口和社会保障的流动造成的,而是社会保障的模式、现行财政制度和相关政策体系以及区域经济社会发展不均衡联合导致的。要摆脱这些陷阱,实现人口和社会保障的自由流动,我们需要以建立健全全国社会保障模式弹性统一为主线,以加强社会保障网络信息化建设为基础,以提高社会保障统筹层次为重点,以衔接城乡二元社会保障制度为突破口,以建立健全社会保障均等化服务转移支付政策体系为支撑,最终实现"全民覆盖、弹性统一、服务均衡、流转自由、可持续发展"的社会保障制度。  相似文献   
888.
Government-led interorganizational alliance networks present a sensible opportunity to overcome many societal challenges through collaborative governance. In particular, few researchers have studied alliance networks in the field of energy conservation in commercial buildings—a sector with unique barriers to greater diffusion of innovative cost-saving strategies. We applied an analytic inductive case-based method and social network analysis to study one particular alliance network: the United States Commercial Building Energy Alliances representing interests from retail, commercial real estate, and healthcare sectors. This alliance network was initiated by the United States Department of Energy, with assistance from several federally funded research laboratories in the United States, to promote the diffusion of knowledge and ultimately encourage greater deployment of energy efficiency and clean energy strategies in commercial buildings. We draw upon interview data from 28 cases of private, non-profit, and governmental organizations and complete network data from the alliance participants. We honed in on eight focal cases of governmental organizations to provide insight on how the four forms of energy and environmental data, information, and knowledge shared within an alliance network address the challenge of a vastly underutilized energy resource, namely conservation. Further, we identify and discuss the public's four roles—Commissioner, Interpreter, Marketer, and User—in providing balance to the diffusion of both private and public goods in a network.  相似文献   
889.
This paper deals with the problem of adaptive output feedback neural network controller design for a SISO non-affine nonlinear system. Since in practice all system states are not available in output measurement, an observer is designed to estimate these states. In comparison with the existing approaches, the current method does not require any information about the sign of control gain. In order to handle the unknown sign of the control direction, the Nussbaum-type function is utilized. In order to approximate the unknown nonlinear function, neural network is firstly exploited, and then to compensate the approximation error and external disturbance a robustifying term is employed. The proposed controller is designed based on strict-positive-real (SPR) Lyapunov stability theory to ensure the asymptotic stability of the closed-loop system. Finally, two simulation studies are presented to demonstrate the effectiveness of the developed scheme.  相似文献   
890.
近年来,全球汽车市场的发展总体呈现出有起有伏、强弱转换的格局。作为汽车产业的一个发展方向,电动汽车的发展则是迎来了前所未有的新契机。总体来说,电动汽车的发展在逐步向原有的发展预期靠拢,特别是在一些关键技术上已经有所突破,不可否认发展电动汽车是全球汽车业未来发展的一个支点。在电动汽车创新网络组织方面已有多家企业表现出良好的发展态势,并且已经取得了一定的进展。在这强者鼎立的格局中,美国电动汽车企业特斯拉携电动汽车Model S走入大众的视野并且成功杀出重围。从知识共享导向的角度分析创新网络构成和各主体特征,基于电动汽车创新网络的特点和电动汽车产业内知识共享的特性分析研究,对电动汽车创新网络组织的演化发展以及网络组织内各要素特点的研究结论将为合作创新和网络结构理论的发展提供新视角。  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