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   8436篇
  免费   615篇
  国内免费   637篇
电工技术   155篇
技术理论   13篇
综合类   1222篇
化学工业   141篇
金属工艺   33篇
机械仪表   63篇
建筑科学   1240篇
矿业工程   141篇
能源动力   60篇
轻工业   202篇
水利工程   182篇
石油天然气   25篇
武器工业   7篇
无线电   404篇
一般工业技术   514篇
冶金工业   2954篇
自动化技术   2332篇
  2024年   24篇
  2023年   111篇
  2022年   167篇
  2021年   271篇
  2020年   309篇
  2019年   293篇
  2018年   294篇
  2017年   322篇
  2016年   342篇
  2015年   393篇
  2014年   532篇
  2013年   623篇
  2012年   447篇
  2011年   590篇
  2010年   524篇
  2009年   521篇
  2008年   488篇
  2007年   448篇
  2006年   435篇
  2005年   406篇
  2004年   337篇
  2003年   313篇
  2002年   259篇
  2001年   225篇
  2000年   77篇
  1999年   59篇
  1998年   26篇
  1997年   28篇
  1994年   24篇
  1993年   22篇
  1992年   26篇
  1990年   31篇
  1989年   21篇
  1988年   25篇
  1987年   21篇
  1986年   20篇
  1981年   18篇
  1966年   26篇
  1965年   28篇
  1964年   58篇
  1963年   47篇
  1962年   18篇
  1961年   45篇
  1960年   23篇
  1959年   31篇
  1958年   22篇
  1957年   34篇
  1956年   25篇
  1955年   47篇
  1954年   28篇
排序方式: 共有9688条查询结果,搜索用时 781 毫秒
71.
Nowadays, cities are the most relevant type of human settlement and their population has been endlessly growing for decades. At the same time, we are witnessing an explosion of digital data that capture many different aspects and details of city life. This allows detecting human mobility patterns in urban areas with more detail than ever before. In this context, based on the fusion of mobility data from different and heterogeneous sources, such as public transport, transport‐network connectivity and Online Social Networks, this study puts forward a novel approach to uncover the actual land use of a city. Unlike previous solutions, our work avoids a time‐invariant approach and it considers the temporal factor based on the assumption that urban areas are not used by citizens all the time in the same manner. We have tested our solution in two different cities showing high accuracy rates.  相似文献   
72.
An increasing number of individuals work in jobs with little standardization and repetition, that is, with high levels of job non‐routinization. At the same time, demands for creativity are high, which raises the question of how employees can use job non‐routinization to develop creativity. Acknowledging the importance of social processes for creativity, we propose that transformational leaders raise feelings of organizational identification in followers and that this form of identification then helps individuals to develop creativity in jobs with little routinization. This is because organizational members evaluate and promote those ideas as more creative, which are in line with a shared understanding of creativity within the organization. To investigate these relationships, we calculated a mediated moderation model with 173 leader–follower dyads from China. Results confirm our hypotheses that transformational leadership moderates the relationship between job non‐routinization on employee creativity through organizational identification. We conclude that raising feelings of social identity is a key task for leaders today, especially when working in uncertain and fast developing environments with little repetition and the constant need to develop creative ideas.  相似文献   
73.
针对目前已有社会化网络服务对社会影响的研究更侧重于青少年,对老年人群体研究相对较少的情况,本文研究了面向老年人的社会化网络服务平台,介绍了平台的体系结构,阐述了社交系统、数据分析和信息服务。此平台利用面向老年人的社交网络服务系统获得用户行为数据,在数据集成、时空数据仓库存储的基础上,通过建立老年人社会网络行为的数学模型,运用统计学方法进行建模分析,分析结果可为多层次人员提供不同的信息服务。  相似文献   
74.
There is huge scientific interest in the neuropeptide oxytocin (OXT) due to its putative capacity to modulate a wide spectrum of physiological and cognitive processes including motivation, learning, emotion, and the stress response. The present review seeks to increase the understanding of the role of OXT in an individual’s vulnerability or resilience with regard to developing a substance use disorder. It places specific attention on the role of social stress as a risk factor of addiction, and explores the hypothesis that OXT constitutes a homeostatic response to stress that buffers against its negative impact. For this purpose, the review summarizes preclinical and clinical literature regarding the effects of OXT in different stages of the addiction cycle. The current literature affirms that a well-functioning oxytocinergic system has protective effects such as the modulation of the initial response to drugs of abuse, the attenuation of the development of dependence, the blunting of drug reinstatement and a general anti-stress effect. However, this system is dysregulated if there is continuous drug use or chronic exposure to stress. In this context, OXT is emerging as a promising pharmacotherapy to restore its natural beneficial effects in the organism and to help rebalance the functions of the addicted brain.  相似文献   
75.
论大学生社会责任感的培养   总被引:17,自引:0,他引:17  
社会责任感的重要性在当今社会里凸显出来。可是,在多种因素的作用下,部分大学生的社会责任感却趋于淡化,这使大学生难以担负起历史的重任。对于部分大学生重才而轻德的现象,高等教育应该承担一定社会责任,这种社会责任就在于强化大学生的社会责任感。  相似文献   
76.
高等教育投资项目社会评价指标体系的分析与构建   总被引:4,自引:0,他引:4  
我国高等教育的高速发展对高等教育投资主体和资金来源多元化提出了新的要求。如何对高等教育投资项目的经济和社会效益进行合理评价 ,这既是各投资主体关注的重点 ,也是高等院校如何加快高等教育建设步伐的核心问题。由于高等教育所具有的特殊性 ,目前 ,我国对高等教育投资项目的效益问题研究甚少 ,而高等教育投资项目的社会评价问题更是刚刚起步。本文在深入研究教育经济学及建设项目评价相关知识的基础上 ,总结了高等教育投资项目社会评价的基本特点 ,进而构建了高等教育投资项目社会评价指标体系。这对建立和完善高等教育投资项目评价理论 ,正确进行高等教育投资决策奠定了坚实的基础。  相似文献   
77.
In this paper, we propose an album-oriented face-recognition model that exploits the album structure for face recognition in online social networks. Albums, usually associated with pictures of a small group of people at a certain event or occasion, provide vital information that can be used to effectively reduce the possible list of candidate labels. We show how this intuition can be formalized into a model that expresses a prior on how albums tend to have many pictures of a small number of people. We also show how it can be extended to include other information available in a social network. Using two real-world datasets independently drawn from Facebook, we show that this model is broadly applicable and can significantly improve recognition rates.  相似文献   
78.
Online learning has grown exponentially in recent years; however, dropout problem remains challenging for some online programmes. The dropout problem can be attributed to a number of reasons, with a lack of interaction between learners and the instructor constituting one of the main reasons. The lack of interaction also leads to learners' feeling of isolation. Learning communities can provide learners with an environment conducive to increased interactions and alleviate their feeling of isolation. Unfortunately, there are no clear rules that instructors can follow to help learners create learning communities. In this paper, we propose guidelines for online instructors to facilitate the development of learning communities in online courses. We first review the definition of a learning community, importance of a learning community and factors affecting the development of a learning community. Afterwards, based on a review of the existing guidelines and other relevant literature, we propose guidelines for facilitating the development of learning communities in online courses.  相似文献   
79.
Members of health social networks may be susceptible to privacy leaks by the amount of information they leave behind. The threat to privacy increases when members of these networks reuse their pseudonyms in other social networks. The risk of re‐identifying users from such networks requires quantitative estimates to evaluate its magnitude. The estimates will enable managers and members of health social communities to take corrective measures. We introduce a new re‐identification attack, the social network attack, that takes advantage of the fact that users reuse their pseudonyms. To demonstrate the attack, we establish links between MedHelp and Twitter (two popular social networks) based on matching pseudonyms. We used Bayesian networks to model the re‐identification risk and used stylometric techniques to identify the strength of the links. On the basis of our model 7‐11. 8% of the MedHelp members in the sample population who reused their pseudonyms in Twitter were re‐identifiable compared with 1% who did not. The risk estimates were measured at the 5% risk threshold. Our model was able to re‐identify users with a sensitivity of 41% and specificity of 96%. The potential for re‐identification increases as more data is accumulated from these profiles, which makes the threat of re‐identification more serious.  相似文献   
80.
华北平原地下水资源承载力评价   总被引:3,自引:0,他引:3       下载免费PDF全文
华北平原地下水严重超采,并带来一系列资源环境问题,地下水资源承载力的可持续性面临严重挑战。本研究定义了地下水资源承载力的概念,提出了一种定量评价地下水承载力的新方法,并对华北平原地下水承载力进行了评价。结果表明,华北平原地区地下水资源支撑的GDP从2003年的15 608.18亿元迅速提高到2011年的37 584.9亿元,33.3%的地市位于未超采未超载区;华北平原整体及57.2%的地市均位于超采未超载区,已发生地下水超采,但通过提高用水效率,未来社会经济规模仍有发展空间;9.5%的地市位于超采超载区。最后探讨地下水资源的承载力的提高途径,主要包括增加地下水资源可利用量和提高用水效率两方面,其中提高用水效率效果更显著。  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