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   25096篇
  免费   2229篇
  国内免费   1153篇
电工技术   1471篇
技术理论   3篇
综合类   1528篇
化学工业   4320篇
金属工艺   1507篇
机械仪表   1631篇
建筑科学   1845篇
矿业工程   987篇
能源动力   839篇
轻工业   1717篇
水利工程   555篇
石油天然气   1557篇
武器工业   165篇
无线电   2723篇
一般工业技术   3136篇
冶金工业   1354篇
原子能技术   245篇
自动化技术   2895篇
  2024年   116篇
  2023年   480篇
  2022年   786篇
  2021年   1108篇
  2020年   822篇
  2019年   702篇
  2018年   841篇
  2017年   853篇
  2016年   793篇
  2015年   993篇
  2014年   1297篇
  2013年   1582篇
  2012年   1599篇
  2011年   1721篇
  2010年   1532篇
  2009年   1391篇
  2008年   1395篇
  2007年   1295篇
  2006年   1246篇
  2005年   1096篇
  2004年   769篇
  2003年   708篇
  2002年   719篇
  2001年   606篇
  2000年   554篇
  1999年   608篇
  1998年   493篇
  1997年   419篇
  1996年   391篇
  1995年   319篇
  1994年   298篇
  1993年   228篇
  1992年   173篇
  1991年   118篇
  1990年   66篇
  1989年   67篇
  1988年   74篇
  1987年   46篇
  1986年   35篇
  1985年   22篇
  1984年   14篇
  1983年   7篇
  1982年   14篇
  1981年   10篇
  1980年   7篇
  1979年   11篇
  1977年   5篇
  1975年   5篇
  1954年   4篇
  1947年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
陈玉明  童超  任兵  陈卫国 《机电工程技术》2021,50(5):105-108,128
针对无人艇群协同作业能力的评价缺少有效测评方法问题,设计了一种无人艇群协同作业测评系统.采用信息优势度量法作为测评方法,根据无人艇群协同作业的特点,提出包含5个不同评价指标、将无人艇群协同作业能力水平评价转变为可以细分度量的数据值.采用MatlabGUI可视化面板构建可与用户交互的测评系统面板并进行验证实验.结果表明,测评系统能够对测试数据给出符合预期的处理结果,对无人艇群协同作业能力提升具有指导价值.  相似文献   
992.
针对大功率压接式功率器件的散热需求,进行用于其冷却的水冷基板设计与研究.根据压接式功率器件用水冷基板结构特点和技术要求,设计内部冷却流道为螺旋线结构,使用UG软件建立三维模型,应用仿真软件计算得出其温度场分布云图和压力分布云图,并对产品进行热性能试验和压接试验.结果显示,表面研制的水冷基板仿真计算结果与试验结果相近,热阻和流阻参数指标满足技术条件要求,功率模块区域均温性良好,且产品可靠性满足设计及实际运用要求.该研究内容为类似结构水冷基板设计提供参考.  相似文献   
993.
A new dialogue management model for affective dialogue system, which aims to provide a service of information inquiry and affective interaction, is proposed in this paper. First, we construct two finite state machines (TFSM) to model the user and the system, respectively, and simulate the dialogue process as an information exchange between the two state machines. All possible state transitions in dialogue and its probabilities of the user are summarized as a user model, which is helpful for the system to inference and predict the user's internal states. Second, we further discuss the implementation methods of information inquiry and emotional response modules. Finally, we employ the return function of partially observable Markov decision processes (POMDP) model to analyze and evaluate the TFSM‐based dialogue management model. The experimental results not only show the relationships between the average returns, recognition error rates, and state transition probabilities but also confirm that our TFSM‐based dialogue management model outperforms the conventional FSM model. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
994.
A self‐adaptive 3D pairwise view registration method is presented. Coarse registration of neighboring views is achieved according to their common continuous nonflat areas. These areas are calculated by local least‐square (LS) surface fitting. Then, the principle of point‐to‐surface projection is used to search for the corresponding points, where the local moving least‐square (MLS) surface is employed. Finally, multidimensional optimization based on the technique of hill‐climbing is performed to refine the coarse registration. Experimental results show that this method gives good noise immunity and requires simple computation process and very few manual interventions. Thus it is suitable for large‐scale free‐form surfaces lacking obvious geometric characteristics. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
995.
The popular social networking service Twitter provides rapidly updated information and online trends, which enriches and benefits people's daily life. At the same time, how to find out the really interesting and relevant topics from the massive streams of tweets, to provide precise topic recommendation for users, becomes a challenging problem in the real world. Previous collaborative filtering methods give solutions to traditional recommendation tasks considering users' positive reviews to help recommend items. However, to the problem ‘what is interesting to whom’ in Twitter, positive opinions toward a topic do not imply that the user will be interested in it with high probability, for the user probably prefers to know those controversial topics or hot events with a large number of negative posts. In this paper, we exploit the characteristics of topical opinion distribution for improving the performance of recommendation. The experimental results on a real‐world Twitter dataset show that the proposed opinion‐distribution‐aware topic recommendation (ODA‐TR) approach outperforms the state‐of‐the‐art collaborative recommendation methods. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
996.
In long‐term evolution, the service area is partitioned into several tracking areas (TAs), which comprise one or more cells (the radio coverages of base stations). The TAs are grouped into TA list (TAL). When an incoming call arrives, the network attempts to connect to the user equipment (UE) by paging the cells in the UE's TAL, which may incur large paging traffic that significantly consumes the limited radio resources. To resolve this issue, this paper proposes a dynamic paging scheme that determines the paging sequence of cells in real time according to the UE movement and call behavior. We compare the performance of the dynamic paging with that of the previously proposed Cell‐TA‐TAL (CTT) paging. Our study indicates that the dynamic paging outperforms the CTT paging when movement pattern is regular and the UE moves frequently. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
997.
The PM10 collection efficiency of a wire-cylinder electrostatic precipitator (ESP) was studied by means of a developed mathematical model, including the multi-field coupling between the gas flow field, the particle dynamic field and the electric field, and applying the Deutsch–Anderson Equation. The diffusion charging mechanism was considered due to the diameter range of PM10. The investigated variables were the applied potential, the gas velocity and the particle distribution. Numerical results indicate that the diffusion charging has significant influence on PM10 removal performance and the effect is more obvious with the decreasing diameter, and that the PM10 collection efficiency increases with the increasing applied potential and the increment of collection efficiency is more significant at lower voltage. Moreover, as the gas velocity at inlet decreases, collection efficiency of PM10 will increase. Finally, the overall efficiency increases with increasing the mean diameter of particle distribution. The research results can provide theoretical and technical references for the design of novel ESP aiming at economy and environment protection.  相似文献   
998.
One important reason for low hydrogen production from protein wastewater is due to the native folded conformation of protein. In this study the enhancement of bio-hydrogen production from protein wastewater by altering protein conformation via pretreatment was reported. Firstly, the effect of different pretreatment methods (acid, alkali, heat, and ultraviolet) on hydrogen production from synthetic protein wastewater was compared. The hydrogen production from the ultraviolet pretreated wastewater was 111.3 mL/g-protein, which was 3.79-, 3.73-, 3.54-, and 1.36-fold of that from the unpretreated (blank), acid, alkali, and heat pretreated wastewater, respectively. Then, the reasons for ultraviolet pretreatment showing significantly higher hydrogen production than other pretreatments were investigated. It was found that all pretreatments did not cause the cleavage of peptide bond, but the ultraviolet one caused much greater damage of hydrogen bonding networks and unfolding of protein. Thus, during anaerobic fermentation much higher protease activity and protein utilization were observed, which resulted in the bio-hydrogen production being remarkably improved. Further studies indicated that the photo-oxidization of aromatic residues in protein was not the reason for ultraviolet pretreatment remarkably improving bio-hydrogen production. Finally, the application of ultraviolet pretreatment to enhance hydrogen production from real protein wastewater was testified.  相似文献   
999.
近年来,南京城市空间、人口规模快速增长,新的形势对城乡医疗卫生设施的布局提出了新的要求。南京市结合卫生行业发展规划,开展了医疗卫生设施专项规划研究,通过公共医疗卫生体系的分类,确定合理的配置标准,完善医疗服务设施及公共卫生服务设施的规划布局,落实用地选址,以图则形式将规划成果纳入规划管理平台。  相似文献   
1000.
养老既是家庭的义务,也是社会的服务,亦是政府的职责.随着我国老龄化社会进程加快,在自有住房拥有率较高,小型化家庭赡养能力减弱,而社会养老机构供给不足的情况下,传统的家庭养老已变成社区居家养老.为实现山地城市社区居家养老,需要配套构建相关基础服务设施.文章在分析老年人居家养老的心理行为特点的基础上,提出社区应建设的养老基础设施类型,论述配套建设方法策略.  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