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   26784篇
  免费   766篇
  国内免费   560篇
电工技术   811篇
技术理论   2篇
综合类   1079篇
化学工业   2258篇
金属工艺   1509篇
机械仪表   3235篇
建筑科学   5187篇
矿业工程   534篇
能源动力   791篇
轻工业   1351篇
水利工程   313篇
石油天然气   729篇
武器工业   145篇
无线电   1603篇
一般工业技术   2119篇
冶金工业   865篇
原子能技术   226篇
自动化技术   5353篇
  2024年   36篇
  2023年   184篇
  2022年   283篇
  2021年   431篇
  2020年   432篇
  2019年   295篇
  2018年   364篇
  2017年   400篇
  2016年   566篇
  2015年   654篇
  2014年   1299篇
  2013年   1414篇
  2012年   1656篇
  2011年   1859篇
  2010年   1401篇
  2009年   1418篇
  2008年   1223篇
  2007年   1605篇
  2006年   1652篇
  2005年   1525篇
  2004年   1320篇
  2003年   1349篇
  2002年   1131篇
  2001年   865篇
  2000年   816篇
  1999年   771篇
  1998年   655篇
  1997年   497篇
  1996年   422篇
  1995年   368篇
  1994年   275篇
  1993年   223篇
  1992年   168篇
  1991年   125篇
  1990年   80篇
  1989年   83篇
  1988年   57篇
  1987年   35篇
  1986年   23篇
  1985年   32篇
  1984年   34篇
  1983年   21篇
  1982年   13篇
  1981年   9篇
  1980年   7篇
  1979年   9篇
  1978年   5篇
  1976年   8篇
  1975年   4篇
  1971年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
赵玉娟 《信息技术》2003,27(2):32-33,,35
针对综合布线系统工程设计与施工中存在的问题作一简单的归纳,并提出相应的解决办法。其中解决的办法包括几点重要的内容:设计时注意用户的需求和系统的可扩展性,施工时严格按照规范施工,工程结束后要做出详细的测试方案。接地问题和线缆敷设管路的弯曲问题是在施工时很重要的。测试时应测试的内容有:远端串扰、近端串扰、综合近端串扰、结构回波损耗等。  相似文献   
82.
介绍了设计文件标准化审查的内容,指出了存在的问题,并提出了解决的措施。  相似文献   
83.
空间的塑造--厦门海湾公园设计   总被引:1,自引:1,他引:0  
海湾公园利用植物、地形、大海与湖泊的周边环境等景观要素,运用隐喻、对比的手法,创造丰富、神秘、变化的空间,注重空间灵活的使用功能及其良好的人性化.  相似文献   
84.
Clathrate compounds are crystalline materials formed by a physical interaction between host and relatively light guest molecules. Various types of nano-sized cages surrounded by host frameworks exist in the highly unique crystalline structures and free guest molecules are entrapped in an open host-guest network. Recently, we reported two peculiar phenomena, swapping and tuning, naturally occurring in the hydrate cages. Helium, one of the smallest light guest molecules, must be the challengeable material in the sense of physics and moreover possesses versatile applications in the field of superconductivity technology and thermonuclear industry. In this regard, we attempted for the first time to synthesize helium hydrates at moderate temperature and pressure conditions. According to inclusion phenomena, helium itself normally cannot form clathrate hydrates due to being too small molecularly without the help of hydrate former molecules (sI, sII, and sH formers). In this study, the hydrate equilibria of the binary clathrate hydrate containing tetrahydrofuran, helium, and water were determined at 2, 3, 5.56 THF mol%. Direct volumetric measurements were also carried out to confirm the exact amount of helium captured in the hydrate cages. Finally, the crystalline structure of the formed mixed hydrates was identified by powder X-ray diffraction, resulting in structure II.  相似文献   
85.
In this paper, we present the findings from an extensive study of the use of virtual reality (VR) models in large construction projects. The study includes two parts: The first part presents a quantitative questionnaire designed to investigate how VR models are experienced and assessed by the workforce at a building site. The second part includes a qualitative field survey of how VR models can be applied and accepted by professionals in the design and planning process of a large pelletizing plant. Through mainly studying persons who had little or no experience with advanced information technology (IT), we hoped to reveal the attitudes of the average person working at a construction site rather than of an IT expert. In summary, the study shows that the VR models in both projects have been very useful and well accepted by the users. Today’s information flow is, from a general point of view, considered to be insufficient and the hypothesis is that using VR models in the construction process have the potential to minimize waste of resources and improve the final result.  相似文献   
86.
Yeon Seok Kim 《Polymer》2008,49(2):570-578
Monodispersed copolymer emulsions with different glass transition temperatures were synthesized to investigate the effect of room temperature polymer matrix modulus on the electrical properties of carbon black (CB) filled segregated network composites. The emulsion with the highest modulus at room temperature produced composites with the lowest percolation threshold. The threshold for a composite made from a copolymer latex containing an equal ratio of butyl acrylate and methyl methacrylate (BA5) is 1.5 vol%, while the percolation threshold for the much lower modulus BA7 (7:3 BA/MMA ratio) is 4.93 vol%. The microstructure of each composite shows significant differences in the level of CB dispersion within the polymer matrix. Higher modulus polymer particles push the CB more efficiently into the interstitial space between them, resulting in a lower percolation threshold. This modulus effect was confirmed by increasing the drying temperature, where the moduli of latexes (BA5, BA5.5, and BA6) were more similar and the percolation thresholds for three composites also become closer to one another.  相似文献   
87.
针对混铁炉使用过程中出现的各种侵蚀状况,设计采用砖砌十浇注复合炉衬结构,特别对前墙拐角和后墙中段等侵蚀快的关键部位作了有针对性的技术改进;在运行管理上,制定推行全新的工艺操作规程,取得了显著的使用效果。  相似文献   
88.
Multiresolution is currently one of the main schemes used in CAD modeling for representing objects, particularly when large-scale geometric data must be transferred interactively over a network, as in the case of collaborative design. Increasingly complex products and growing competition have turned design into a collaborative team effort. Furthermore, the widespread development of Internet viewers has also necessitated the transfer and display of large-scale CAD models over networks. In order to reduce the volume of transferred data, efforts have been made to transfer CSG (Constructive Solid Geometry) models rather than those based on B_rep (Boundary Representation). This paper presents an original new method for speeding up data transfer by using multiresolution CSG models at different levels of details (LOD). The multiresolution CSG algorithm generates a hierarchy of multiresolution CSG trees; at each level, the shape is further approximated and represented by a smaller number of CSG primitives. The paper analyzes the proposed algorithm, and demonstrates its feasibility.  相似文献   
89.
90.
方海  杨宇峤 《时代建筑》2003,(6):112-117
本文通过对主要设计成员凯萨·布隆斯泰德和沃迪·凯威的背景,以及对私人住宅、餐馆、办公楼、图书馆、精品屋等案例的阐释,向读者介绍了这家十分活跃的芬兰设计事务所,同时展现了北欧的室内设计风格。  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