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   4822篇
  免费   184篇
  国内免费   85篇
电工技术   89篇
技术理论   2篇
综合类   345篇
化学工业   772篇
金属工艺   278篇
机械仪表   283篇
建筑科学   347篇
矿业工程   26篇
能源动力   93篇
轻工业   283篇
水利工程   37篇
石油天然气   31篇
武器工业   9篇
无线电   127篇
一般工业技术   552篇
冶金工业   1090篇
原子能技术   37篇
自动化技术   690篇
  2024年   8篇
  2023年   47篇
  2022年   129篇
  2021年   164篇
  2020年   107篇
  2019年   96篇
  2018年   98篇
  2017年   91篇
  2016年   97篇
  2015年   106篇
  2014年   187篇
  2013年   327篇
  2012年   197篇
  2011年   361篇
  2010年   294篇
  2009年   324篇
  2008年   283篇
  2007年   300篇
  2006年   318篇
  2005年   259篇
  2004年   210篇
  2003年   166篇
  2002年   138篇
  2001年   120篇
  2000年   75篇
  1999年   59篇
  1998年   39篇
  1997年   53篇
  1996年   48篇
  1995年   32篇
  1994年   46篇
  1993年   35篇
  1992年   30篇
  1991年   15篇
  1990年   31篇
  1989年   29篇
  1988年   17篇
  1987年   25篇
  1986年   15篇
  1985年   11篇
  1984年   11篇
  1983年   6篇
  1982年   8篇
  1981年   6篇
  1979年   5篇
  1971年   6篇
  1965年   5篇
  1963年   6篇
  1961年   6篇
  1955年   4篇
排序方式: 共有5091条查询结果,搜索用时 15 毫秒
71.
在Lω-空间中引入了Lω-分离性的概念,主要包括ωS-1、ωS0、次ωS0分离性,讨论了它们的一些基本的拓扑性质.给出了ωS-分离性的几个等价刻划,讨论了它们之间的关系.  相似文献   
72.
本文旨在运用相关理论分析本次世界经济危机对我国中小型家族企业的影响,并针对实现经济危机的环境下,家族企业如何进一步发展探寻对策并提供相关建议。  相似文献   
73.
Exploitation of coal seams in the Upper Silesian Coal Basin is conducted in complex and difficult conditions. These difficulties are connected with the occurrence of many natural mining hazards and limitations resulting from the existing in this area surface infrastructure. One of the most important problems of Polish mining is the rock burst hazard and reliable evaluation of its condition. During long-years' mining practice in Poland a comprehensive system of evaluation and control of this hazard was de-veloped. In the paper the main aspects of rock burst hazard state evaluation will be presented, comprising: 1) rock mass inclination for rock bursts, I.e., rock strength properties investigation, comprehensive parametric evaluation of rock mass inclination for rock bursts, prognosis of seismic events induced by mining operations, methods of computer-aided modelling of stress and rock mass deformation parameters distribution, strategic rock mass classification under rock burst degrees; 2) immediate seismic and rock burst hazard state evaluation, I.e., low diameter test drilling method, seismologic and seismoacoustic method, comprehensive method of rock burst hazard state evaluation, non-standard methods of evaluation; 3) legal aspects of rock burst hazard state evaluation. Selected elements of the hazard state evaluation system are illustrated with specific practical examples of their applica-tion.  相似文献   
74.
地月系共线平动点附近的Halo轨道族,能够提供从L1点至月球再至L2点的广泛空间的多种轨道应用需要,但2个轨道族内轨道的稳定性差异较大。文章引入稳定系数和线性稳定阶数2个指标来判断轨道的稳定性,并用数值模拟分别分析了百米和千米量级的初始轨道误差在数天后所引起的轨道偏差,得出结论:两轨道族内接近平动点的部分轨道稳定性较差,其余部分轨道稳定性相差不大,L1点附近Halo轨道族内轨道较为稳定的是0.85~0.92之间的轨道,L2点较为稳定的是1.02~1.1之间的轨道。  相似文献   
75.
家庭暴力是近年来我国婚姻领域的突出问题,家庭暴力事件呈上升趋势,男尊女卑、父权制的封建陋习造成家庭暴力的受害者多为女性,而家庭暴力行为的隐秘性、残暴性、反复性,使得反家庭暴力存在困难。立足于中国的实际,文章以家庭暴力的法律规制为切入点,反思家庭暴力的产生原因,并对防止和制裁家庭暴力问题展开深入的理论研究,以期为我国的家庭暴力规制制度的完善尽一份绵薄之力。  相似文献   
76.
The synthesis of the title complexes was achieved via the reaction of -p-dichlorobenzene- -cyclopentadienyliron cations with 4,4′-bis(4-hydroxyphenyl)valeric acid to produce the diiron complexes which were then reacted with a number of arylazo dyes to give cationic bis(cyclopentadienyliron)arene complexes containing the arylazo dyes. These iron-containing monomers were subsequently polymerized via nucleophilic aromatic substitution using 1,8-octanedithiol, 4,4′-thiobisbenzenethiol, or bisphenol A to produce the desired coloured cationic organoiron polymers. The weight – average molecular weights were estimated to range from 11,800 to 31,600. UV–vis studies conducted in dimethylformamide (DMF) showed that the metallated polymers exhibited of 412–491 nm. Addition of HCl to the polymer solution caused a bathochromic shift into the range of 515–530 nm. Thermogravimetric analysis (TGA) revealed that the iron moieties were cleaved between 205 and 248 °C while the polyether/thioether backbone degraded between 380 and 613 °C. Differential scanning calorimetry (DSC) showed that the polymers exhibited glass transition temperatures (Tg) ranging from 106 to 184°C.This paper is dedicated to Professor Richard J. Puddephatt in recognition of his outstanding contribution to the field of metal-containing polymers.  相似文献   
77.
当今纳米科学技术飞速发展,其中纳米管已构成了纳米材料的一个非常重要的类别。本文介绍近几年来由化学键结合的纳米管以及由分子间力形成的一些纳米或具有中观尺度的管状结构材料的合成研究进展。  相似文献   
78.
军校学员作为未来的军官,是否具有较好的职业道德,关系到未来军队干部队伍的道德水平。当今世界,国际思潮日益复杂化,对军校学员的职业道德影响不容忽视。计算机系统与网络课程及时顺应了改革的需求,授课过程中深入挖掘有关职业道德课程思政的资源,塑造军校学员的军人素养,使军校学员职业道德素养的培养大力推进,对我军的全面建设和长远发展具有重要意义。  相似文献   
79.
Product family design and product configuration based on data mining technology is identified as an intelligent and automated means to improve the efficiency of product development. However, few of previous literatures have proposed systematic product family design method based on data mining technology. To make up for this deficiency, this research put forward a systematic data-mining-based method for product family design and product configuration. First, the customer requirement information and product engineering information in the historical order are formatted into structural data. Second, principal component analysis is performed on historical orders to extract the customers' differentiated needs. Third, association rule algorithm is introduced to mine the rules between differentiated needs and module instances in the historical orders, thus obtained the configuration knowledge between customer needs and product engineer. Forth, the mined rules are used to construct association rule-based classifier (CBA) that is employed to sort out the best product configuration schemes as popular product variants. Fifth, sequence alignment technique is employed to identify modules for popular product variants, so that the module instances are divided into optional, common and special module, respectively, thereby the product platform is generated based on common modules. Finally, according to new customer needs, the CBA classifier is used to recommend the best configuration schemes, and then popular product variants are configured based on the product platform. The feasibility of the proposed method is demonstrated by the product family design example of desktop computer hosts.  相似文献   
80.
Recent museum exhibitions are becoming a means by which to satisfy visitor demands. In order to provide visitor-centric exhibitions, artwork must be analyzed based on the behavior of visitors, and not merely according to museum professionals' points of view. This study aims to analyze the relationship between museum visitors and artwork via a network analysis based on visitor behavior using object detection techniques. Cameras installed in a museum recorded visitors, and an object detector with a content-based image-retrieval technique tracked visitors from the videos. The durations spent with different artworks were measured, and the data was converted into a bipartite graph. The relationships between different artwork types were analyzed with a visitor-centered artwork network. Based on the visitors’ behavior, significant artworks were identified and the artwork network was compared to the arrangement of the museum. The tendency of edges in the artwork network was also examined considering visitors' preferences for artworks. The method used here makes it possible to collect quantitative data, with the results possibly used as a basis and for reference when analyzing artwork in a visitor-centered approach.  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