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   45800篇
  免费   7615篇
  国内免费   1951篇
电工技术   4406篇
技术理论   2篇
综合类   4040篇
化学工业   6236篇
金属工艺   3120篇
机械仪表   3250篇
建筑科学   3738篇
矿业工程   2009篇
能源动力   1600篇
轻工业   3638篇
水利工程   1396篇
石油天然气   2296篇
武器工业   702篇
无线电   5373篇
一般工业技术   4735篇
冶金工业   1865篇
原子能技术   792篇
自动化技术   6168篇
  2025年   90篇
  2024年   1031篇
  2023年   935篇
  2022年   1720篇
  2021年   2380篇
  2020年   1807篇
  2019年   1396篇
  2018年   1434篇
  2017年   1729篇
  2016年   1527篇
  2015年   2221篇
  2014年   2742篇
  2013年   3088篇
  2012年   3685篇
  2011年   3721篇
  2010年   3436篇
  2009年   3366篇
  2008年   3346篇
  2007年   3187篇
  2006年   2783篇
  2005年   2270篇
  2004年   1593篇
  2003年   1102篇
  2002年   1038篇
  2001年   899篇
  2000年   762篇
  1999年   550篇
  1998年   332篇
  1997年   284篇
  1996年   214篇
  1995年   159篇
  1994年   131篇
  1993年   106篇
  1992年   65篇
  1991年   64篇
  1990年   40篇
  1989年   29篇
  1988年   17篇
  1987年   14篇
  1986年   9篇
  1985年   4篇
  1984年   5篇
  1983年   5篇
  1982年   4篇
  1981年   12篇
  1980年   10篇
  1979年   6篇
  1959年   9篇
  1953年   2篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
We propose and evaluate a medium-access control (MAC) protocol for synchronous cellular packet direct-sequence code-division multiple-access (DS/CDMA). The protocol is designed for handling a variety of multimedia traffic types in an integrated wireless-access network (IWAN). For instance, the protocol is suited for carrying multiple traffic types of different priorities. An analytical model for the equilibrium state has been developed for the proposed protocol. A comparative evaluation of the protocol is done for three different radio frequency bandwidths currently under consideration for personal communication services (PCS), i.e., 1.25 MHz, 5 MHz, and 10 MHz. Our results demonstrate that the proposed protocol is both robust and flexible for the intended IWAN applications. It offers a significant multiplexing gain as the bandwidth increases  相似文献   
2.
Hard and wear resistant coatings for the moulding and embossing of glasses at elevated temperatures Hard and wear resistant coatings of Titanium Aluminium Nitride TiAlN were deposited on various substrates by the application of different reactive deposition processes: RF-magnetron-sputtering, ion beam-sputtering and by the energetic cluster impact (ECI) process. The deposition of the coatings was performed under variation of biasing conditions and of process parameters such as pressures and flow rates of the process gases argon and nitrogen as well as of energies of species hitting the substrate surfaces. The microstructure particularly the growth morphology of several films was investigated by pictures of film cross sections recorded by transmission electron microscopy. Residual intrinsic film stresses were analyzed by measuring deflections of substrates in an interference optical microscope before and after the deposition of the coatings. By heating coated substrates and in-situ observation of deflections at elevated temperatures dependencies of thermally induced stresses on temperatures and variations of intrinsic stresses due to changes within the films could be analyzed and related to microstructure and growth conditions. In the paper specific characteristics of the deposition processes occuring on the scale both of atoms and of clusters which may contain several thousand of atoms are described and related to microstructure, residual stress states and damaging conditions. Different contributions to residual film stresses are analyzed on the base of theoretical considerations taking into account deposition kinetics and thermomecanical properties. The significance of achieved film properties for application, i. e. for the coating of tools for the manufacturing of optical components by moulding and embossing of glasses is discussed.  相似文献   
3.
张强 《江苏水利》2021,(1):65-69
水利信息化作为水利现代化的基础和标志,是防洪减灾、水资源管理、水环境监测和水土保持的重要手段和技术支撑,是提高水利管理工作效率和效能、实现水利服务社会的重要途径和必然要求,是改造传统水利、促进水利改革与发展的重要措施和迫切需要.阐述了目前水利工程现状和非工程措施建设现状,存在的问题及需求分析,并提出相关解决对策.  相似文献   
4.
5.
6.
Wang  Kun  Tian  Qiang  Hu  Haiyan 《Multibody System Dynamics》2021,51(1):1-19
Multibody System Dynamics - Computational prediction of 3D crutch-assisted walking patterns is a challenging problem that could be applied to study different biomechanical aspects of crutch walking...  相似文献   
7.
Segmenting human faces automatically is very important for face recognition and verification, security system, and computer vision. In this paper, we present an accurate segmentation system for cutting human faces out from video sequences in real-time. First, a learning based face detector is developed to rapidly find human faces. To speed up the detection process, a face rejection cascade is constructed to remove most of negative samples while retaining all the face samples. Then, we develop a coarse-to-fine segmentation approach to extract the faces based on a min-cut optimization. Finally, a new matting algorithm is proposed to estimate the alpha-matte based on an adaptive trimap generation method. Experimental results demonstrate the effectiveness and robustness of our proposed method that can compete with the well-known interactive methods in real-time.  相似文献   
8.
本文将人工免疫原理应用到网络安全态势评估的研究中.通过对入侵检测模型中有关自体、非自体、抗原的形式化描述,建立了抗体细胞的演化机制、动态免疫记忆、免疫监视等免疫机制.依据人体免疫系统抗体浓度的变化与病原体入侵强度的对应关系,建立了网络安全态势实时定量计算模型.  相似文献   
9.
Guo  Chenchen  Zhao  Xiaoming  Zou  Qiang 《Applied Intelligence》2022,52(10):11394-11406
Applied Intelligence - In recent years, person re-identification (re-ID) has become a widespread research topic that focuses on retrieving target pedestrians from a set of images, typically taken...  相似文献   
10.
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