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   105950篇
  免费   10469篇
  国内免费   6809篇
电工技术   7950篇
技术理论   3篇
综合类   8316篇
化学工业   15413篇
金属工艺   6744篇
机械仪表   7411篇
建筑科学   8281篇
矿业工程   3289篇
能源动力   3365篇
轻工业   7512篇
水利工程   2601篇
石油天然气   4746篇
武器工业   1285篇
无线电   13266篇
一般工业技术   11793篇
冶金工业   4076篇
原子能技术   1586篇
自动化技术   15591篇
  2024年   446篇
  2023年   1402篇
  2022年   2802篇
  2021年   4103篇
  2020年   3056篇
  2019年   2582篇
  2018年   2786篇
  2017年   3296篇
  2016年   3144篇
  2015年   4460篇
  2014年   5743篇
  2013年   6683篇
  2012年   7894篇
  2011年   8742篇
  2010年   8106篇
  2009年   7777篇
  2008年   7811篇
  2007年   7479篇
  2006年   6976篇
  2005年   5555篇
  2004年   4114篇
  2003年   3391篇
  2002年   3290篇
  2001年   2794篇
  2000年   2209篇
  1999年   1604篇
  1998年   1002篇
  1997年   840篇
  1996年   696篇
  1995年   571篇
  1994年   424篇
  1993年   332篇
  1992年   236篇
  1991年   195篇
  1990年   141篇
  1989年   141篇
  1988年   75篇
  1987年   69篇
  1986年   64篇
  1985年   30篇
  1984年   24篇
  1983年   27篇
  1982年   21篇
  1981年   21篇
  1980年   15篇
  1979年   10篇
  1978年   5篇
  1977年   8篇
  1959年   17篇
  1951年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
The periodic steady state of power distribution system loads is studied for electronically switched, time varying cases. Many loads of this type appear on contemporary power systems as energy saving and controllable demands. Several alternative methods of calculating the periodic steady state are discussed and a new method is proposed based on the frequency modulation property of the discrete Fourier transform. The new method is termed the gain-shift formula (GSF) because the format of the technique entails adding frequency shifted terms which represent the parameter to be calculated. An example of a triac-switched load on the distribution system is given. The main advantages of the GSF are: rapid calculation of the periodic steady state; and efficient calculation of the frequency spectrum of voltages and currents in the periodic steady state  相似文献   
32.
This paper investigates the stability analysis and antiwindup design problem for a class of discrete-time switched linear systems with time-varying norm-bounded uncertainties and saturating actuators by using the switched Lyapunov function approach.Supposing that a set of linear dynamic output controllers have been designed to stabilize the switched system without considering its input saturation,we design antiwindup compensation gains in order to enlarge the domain of attraction of the closed-loop system in the presence of saturation.Then,in terms of a sector condition,the antiwindup compensation gains which aim to maximize the estimation of domain of attraction of the closed-loop system are presented by solving a convex optimization problem with linear matrix inequality(LMI)constraints.A numerical example is given to demonstrate the effectiveness of the proposed design method.  相似文献   
33.
从SAN(存储区域网)的安全隐患出发,分析了SAN在应用环境中受到的三种典型威胁。结合现行的入侵检测技术给出一个可行的解决方案。  相似文献   
34.
35.
Luan  Yu  Shi  Yuhang  Wu  Wanyin  Liu  Zhiyao  Chang  Hai  Cheng  Jun 《Knowledge and Information Systems》2021,63(10):2791-2814
Knowledge and Information Systems - In the past decade, human activity recognition (HAR) has grown in popularity due to its applications in security and entertainment. As recent years have...  相似文献   
36.
Identifying the key factors of the disaster-related information propagation process can provide decision support for disaster management. This study characterizes the effects of content types, location, and social capital of social media users on the virality of disaster-related information. We found through the Weibo dataset of the Yiliang earthquake that the virality of different types of information can vary on the basis of the social capital of users who post the information. This study fills the current research gaps by examining the individual and joint effects of the content and creator characteristics on the virality of disaster-related information.  相似文献   
37.
Xue  Xia  Gao  Yi  Liu  Meng  Sun  Xia  Zhang  Wenyu  Feng  Jun 《Applied Intelligence》2021,51(7):4730-4743
Applied Intelligence - Personnel performance is a key factor to maintain core competitive advantages. Thus, predicting personnel future performance is a significant research domain in human...  相似文献   
38.
Morphology and geometry of melted zones, cooling rates, microstructure and microhardness in the laser-glazed Fe-4%C-10%Sn alloy have been investigated. The computer simulation on the basis of the moving gaussian source model was used successfully to predict the maximum width and depth of the melted zone and the cooling rate. The microstructure from the surface to the bottom of the laser-melted zone is a non-crystalline phase, dendritic grains and a microcrystalline zone successively. Values of the averaged-spacing of the non-crystalline phase are 0.2056 and 0.1219nm, respectively; twinned martensites, having an axial ratioc/a of 1.128, existed in dendritic grains, and carbides of Fe3 C at the interdendritic regions; the microcrystalline zone was composed of -Fe and a new bet (a=0.415 nm,c=0.955 nm) phase. The different microstructure in the melted zone can be explained by the results of the heat flow calculation. A fine eutectic structure (-Fe + Fe3C) was observed in heat-affected zones. Microhardness of the eutectic structure can be predicted by the empirical relation of fracture stress to the interlamellar spacing of pearlite.  相似文献   
39.
1 INTRODUCTIONTheorthorhombicalloysareofgreattech nolog icalinterestinhightemperatureapplicationssincetheyhaveagoodbalanceamongst  相似文献   
40.
Qiu  Jun  Wang  Yueting  Wu  Peng  Jiang  Shan  Cui  Kaibo  Chen  Guowei  Liu  Dongliang  Cui  Guangwen 《Journal of Porous Materials》2021,28(6):1675-1687
Journal of Porous Materials - The dynamics and thermodynamics of adsorption of hexadecyl ammonium with different numbers of carbon chains in montmorillonite (Mt) with different layer charge density...  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