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   4589篇
  免费   90篇
  国内免费   153篇
教育   3396篇
科学研究   771篇
各国文化   3篇
体育   241篇
综合类   292篇
文化理论   3篇
信息传播   126篇
  2023年   13篇
  2022年   57篇
  2021年   90篇
  2020年   128篇
  2019年   96篇
  2018年   84篇
  2017年   89篇
  2016年   107篇
  2015年   152篇
  2014年   312篇
  2013年   417篇
  2012年   356篇
  2011年   354篇
  2010年   264篇
  2009年   287篇
  2008年   280篇
  2007年   298篇
  2006年   281篇
  2005年   209篇
  2004年   198篇
  2003年   176篇
  2002年   156篇
  2001年   108篇
  2000年   79篇
  1999年   52篇
  1998年   30篇
  1997年   42篇
  1996年   29篇
  1995年   16篇
  1994年   25篇
  1993年   11篇
  1992年   12篇
  1991年   7篇
  1990年   9篇
  1989年   3篇
  1988年   1篇
  1986年   1篇
  1977年   1篇
  1976年   1篇
  1957年   1篇
排序方式: 共有4832条查询结果,搜索用时 31 毫秒
1.
农村公共体育服务作为农村体育中的基本组成部分,其发展与治理是实现乡村振兴的重要内容,是提升体育治理能力现代化和实现体育强国梦的必经之路。运用文献资料、专家访谈等研究方法,结合乡村振兴战略的时代背景,基于协同治理的基本理论,把握农村公共体育服务协同治理的现实动因,分析农村公共体育服务协同治理中存在的均等化供给落实不到位、服务管理体制结构失衡、市场经济模式功能缺失、农民需求表达体系欠缺等现实问题。通过构建农村公共体育服务多元主体协同治理模型,确保治理公正平等、完善政府职能结构、促进机制融合发展、激发需求主体活力等方面实现农村公共体育服务有效治理。  相似文献   
2.
To cope with ambiguous and/or underspecified queries, search result diversification (SRD) is a key technique that has attracted a lot of attention. This paper focuses on implicit SRD, where the subtopics underlying a query are unknown. Many existing methods appeal to the greedy strategy for generating diversified results. A common practice is using a heuristic criterion for making the locally optimal choice at each round. As a result, it is difficult to know whether the failures are caused by the optimization criterion or the setting of parameters. Different from previous studies, we formulate implicit SRD as a process of selecting and ranking k exemplar documents through integer linear programming (ILP). The key idea is that: for a specific query, we expect to maximize the overall relevance of the k exemplar documents. Meanwhile, we wish to maximize the representativeness of the selected exemplar documents with respect to the non-selected documents. Intuitively, if the selected exemplar documents concisely represent the entire set of documents, the novelty and diversity will naturally arise. Moreover, we propose two approaches ILP4ID (Integer Linear Programming for Implicit SRD) and AP4ID (Affinity Propagation for Implicit SRD) for solving the proposed formulation of implicit SRD. In particular, ILP4ID appeals to the strategy of bound-and-branch and is able to obtain the optimal solution. AP4ID being an approximate method transforms the target problem as a maximum-a-posteriori inference problem, and the message passing algorithm is adopted to find the solution. Furthermore, we investigate the differences and connections between the proposed models and prior models by casting them as different variants of the cluster-based paradigm for implicit SRD. To validate the effectiveness and efficiency of the proposed approaches, we conduct a series of experiments on four benchmark TREC diversity collections. The experimental results demonstrate that: (1) The proposed methods, especially ILP4ID, can achieve substantially improved performance over the state-of-the-art unsupervised methods for implicit SRD. (2) The initial runs, the number of input documents, query types, the ways of computing document similarity, the pre-defined cluster number and the optimization algorithm significantly affect the performance of diversification models. Careful examinations of these factors are highly recommended in the development of implicit SRD methods. Based on the in-depth study of different types of methods for implicit SRD, we provide additional insight into the cluster-based paradigm for implicit SRD. In particular, how the methods relying on greedy strategies impact the performance of implicit SRD, and how a particular diversification model should be fine-tuned.  相似文献   
3.
目前在文献中有很多关于多响应比较的研究方法,但是对带协变量调整的非参数检验的研究较少。一种直观的想法是将数据先投影到协变量的正交空间中,然后再利用秩和检验、调整的秩和检验或最大值检验方法。但是,功效普遍不高。在调整的秩和检验和伪F检验两种方法基础上,构建MIN2检验。大量模拟和实际数据表明,MIN2检验的效果优于现有的非参数检验方法。  相似文献   
4.
This study employed fixed effects regression that controls for selection bias, omitted variables bias, and all time-invariant aspects of parent and child characteristics to examine the simultaneous associations between neighborhood disorganization, maternal spanking, and aggressive behavior in early childhood using data from the Fragile Families and Child Wellbeing Study (FFCWS). Analysis was based on 2,472 children and their mothers who participated in Wave 3 (2001–2003; child age 3) and Wave 4 (2003–2006; child age 5) of the FFCWS. Results indicated that higher rates of neighborhood crime and violence predicted higher levels of child aggression. Maternal spanking in the past year, whether frequent or infrequent, was also associated with increases in aggressive behavior. This study contributes statistically rigorous evidence that exposure to violence in the neighborhood as well as the family context are predictors of child aggression. We conclude with a discussion for the need for multilevel prevention and intervention approaches that target both community and parenting factors.  相似文献   
5.
刘晓文 《美育学刊》2020,11(1):13-18
2013年教育部开始着手制定《中国学生发展核心素养》,由此启动普通高中美术课程标准的修订,这也标志中国的教育已经进入了核心素养时代。美术鉴赏是高中美术课程中重要的内容,但实际教学效果却不尽人意。教与学是一方主导、一方被动的分离状态,表现为教师为教而教,学生为知识而学习。学生无暇顾及与高考无关的课程,往往浅表性、单向度地接受碎片化知识的输入,因而不能有效地对情境中的图像进行识读和判断。核心素养下的高中美术鉴赏需要唤醒教与学双方主体的课程意识,同时也对教师的专业素质提出了更高的要求。创新教学过程和学生的学习方法是实现学生核心素养形成的必经桥梁,是值得专家学者和广大一线教师不断地去探究、发掘的重要环节。  相似文献   
6.
为研究全渠道零售的配送系统对企业物流成本的影响,综合考虑时间窗、车型选择等因素,以运输成本最低为目标,建立高度协同的全渠道零售场景下的物流配送模型。该模型采用自适应遗传算法求解,利用MATLAB进行算例分析。结果显示:全渠道零售模式下的车辆调度方案能迅速响应消费者需求,与一般配送模式相比可以减少物流成本,优化车辆配置。与粒子群优化算法相比,自适应遗传算法的运行时间更短、优化结果更好,这验证了模型和算法的可行性和有效性。  相似文献   
7.
鉴于大型交通线路建设项目的物资需求随时间变化(在初期阶段需求较低;在后续阶段项目全面展开,需求显著上升),本文采用线积分对沿线连续分布的线状物资需求进行刻画,构建两阶段设施选址模型,第一阶段进行部分设施的选址,第二阶段对剩余设施选址,以实现系统总成本最低的目标。针对模型特点,设计基于Voronoi图的两阶段交替定位-分配(alternative location-allocation,ALA)算法进行求解,并进行实例分析,比较两阶段模型与传统模型的异同。研究表明,将两阶段设施选址模型应用于交通线路建设项目多物流节点选址,能节约运营成本,并缓解初期资金压力。  相似文献   
8.
In this digital ITEMS module, Dr. Jeffrey Harring and Ms. Tessa Johnson introduce the linear mixed effects (LME) model as a flexible general framework for simultaneously modeling continuous repeated measures data with a scientifically defensible function that adequately summarizes both individual change as well as the average response. The module begins with a nontechnical overview of longitudinal data analyses drawing distinctions with cross-sectional analyses in terms of research questions to be addressed. Nuances of longitudinal designs, timing of measurements, and the real possibility of missing data are then discussed. The three interconnected components of the LME model—(1) a model for individual and mean response profiles, (2) a model to characterize the covariation among the time-specific residuals, and (3) a set of models that summarize the extent that individual coefficients vary—are discussed in the context of the set of activities comprising an analysis. Finally, they demonstrate how to estimate the linear mixed effects model within an open-source environment (R). The digital module contains sample R code, diagnostic quiz questions, hands-on activities in R, curated resources, and a glossary.  相似文献   
9.
心理距离视角下网络舆情传播意愿影响因素研究   总被引:1,自引:1,他引:0  
[目的/意义]网络舆情传播意愿的形成是网民的一种心理活动,与心理距离密不可分。了解影响网络舆情传播意愿的主要因素,有助于监督管控部门更加卓有成效地对网络舆情进行预警和治理。[方法/过程]通过对心理距离理论的深层次剖析,对其构成进行阐述,并从时间距离、空间距离、社会距离、概率4个维度出发,做出系列理论假设,利用调查问卷法和最优尺度回归分析法,识别出主要影响因素及其重要程度。[结果/结论]最终归纳出7个影响网民改变其自身传播意愿的主要因素,即报道时间、家乡相关、向往地相关、生活相关、亲戚朋友发布、媒体官方发布、企业官方发布,从这7个影响因素出发监控舆情,可以帮助舆情管控部门更有针对性地掌控舆情的传播方向。  相似文献   
10.
The study evaluated the relationship among teaching, leadership, teacher certification, student and teacher number related factors, and index of economic, social and cultural status (ESCS), and science literacy from an international comparative perspective. 2015 dataset of the Programme for International Student Assessment for Turkey, Singapore, the United States, Korea, Italy, and Brazil was used. Two-level hierarchical linear models were established for analysis. Results revealed that school ESCS was the best predictor of science literacy across six countries and additionally teacher-related factors came to the forefront of science literacy performance. The study underlined policymakers should focus primarily on policies that increase equity in education. Furthermore, the effectiveness of investments made in factors related to leadership, teacher certification, the number of students and teachers, which contribute very little to science literacy performance, need to be more questioned. Inferences about the findings were discussed in detail, and recommendations for further research were made.  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