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   64963篇
  免费   6049篇
  国内免费   3436篇
电工技术   4739篇
技术理论   6篇
综合类   4689篇
化学工业   10080篇
金属工艺   3811篇
机械仪表   3786篇
建筑科学   5655篇
矿业工程   1644篇
能源动力   1904篇
轻工业   4134篇
水利工程   1200篇
石油天然气   3344篇
武器工业   559篇
无线电   8005篇
一般工业技术   7987篇
冶金工业   2757篇
原子能技术   826篇
自动化技术   9322篇
  2024年   351篇
  2023年   1216篇
  2022年   2004篇
  2021年   2886篇
  2020年   2068篇
  2019年   1701篇
  2018年   1878篇
  2017年   2112篇
  2016年   1874篇
  2015年   2606篇
  2014年   3165篇
  2013年   3816篇
  2012年   4175篇
  2011年   4412篇
  2010年   3969篇
  2009年   3717篇
  2008年   3846篇
  2007年   3642篇
  2006年   3627篇
  2005年   3012篇
  2004年   2152篇
  2003年   1954篇
  2002年   2029篇
  2001年   1826篇
  2000年   1597篇
  1999年   1654篇
  1998年   1225篇
  1997年   1068篇
  1996年   1036篇
  1995年   845篇
  1994年   701篇
  1993年   511篇
  1992年   459篇
  1991年   341篇
  1990年   230篇
  1989年   189篇
  1988年   167篇
  1987年   105篇
  1986年   70篇
  1985年   58篇
  1984年   37篇
  1983年   23篇
  1982年   33篇
  1981年   19篇
  1980年   21篇
  1979年   8篇
  1978年   2篇
  1959年   3篇
  1951年   8篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
91.
An electro-optically modulated intensity interrogation method based on tunable waveguide coupled surface plasmon resonance sensors has been proposed. It has been theoretically and experimentally demonstrated that the proposed scheme can enable sensitive measurement of measurand variations. By modulating the refractive index in the waveguide layer, this interrogation method yields modulated signal whose amplitude is related to measurand's refractive index. This amplitude modulated signal offers a higher signal to noise ratio and eliminates additive noise in the sensor system. A preliminary investigation using saline buffers with different NaCl concentrations shows a resolution of 2.3 × 10?6 refractive index unit by our approach. Resolution can be controlled by the amplitude of the applied modulation voltage and can be further enhanced by optimizing the device structure or improving the electro-optical (E-O) coefficient of the E-O material. This approach is simple, stable, and promising for low-cost or multi-channel SPR biosensor applications.  相似文献   
92.
In many applications, such as intelligent decision systems, there are usually random perturbations caused by the constant changing of real situations, thus the analysis of the robustness with respect to random perturbations is practically important. In the side of fuzzy methods, a corresponding problem arises: will a small random perturbation of fuzzy input cause a big variance of fuzzy output? This paper study the robustness of fuzzy schemes in environments with random perturbations. It focuses on fuzzy algebraic operators, and proposes two methods to analyze their robustness in environments with random perturbations. The effectiveness and features of the methods are shown by simulations.  相似文献   
93.
94.
With the rapid development of network technologies and deteriorating of network environment, traditional single-net security system cannot satisfy the security requirement. The excellent security performance of biological systems impels the bio-inspired network security theory to be a hot research area currently. Based on Bio-inspired Multidimensional Network Security Model we have put forward, we have advanced Bio-inspired Multi-Net Security system by implementing the functional distribution of different subnets of different transient states in Multi-Net Paralleling structure. Firstly, parameter estimation and modified algorithms of Hidden Markov Model are introduced to construct the mathematical mode of B-MNS; secondly, the integrated performance of our modified B-MNS has been tested and its simulation has been carried out. So the feasibility, validity and high efficiency of our model have been demonstrated theoretically, and practically.  相似文献   
95.
磁悬浮系统是复杂的强耦合系统,研究中未充分考虑轨道的弹性形变,会造成磁浮列车和轨道之间产生耦合振动的现象,而考虑这一因素对系统的影响无疑增加了研究的难度;为了便于问题的求解,采用非线性系统理论解耦的方法,对单电磁铁悬浮系统进行纵向解耦控制,并对解耦后的子系统进行极点配置使其满足要求的性能指标;仿真结果表明该方法有效地使复杂问题简单化,并且能够实现系统的全局稳定和良好的动态性能.  相似文献   
96.
“Emergency medicine” is the front line of medical service a hospital provides; also it is the department people seek medical care from immediately after an emergency happens. The statistics by the Department of Health, Executive Yuan, indicate that over years, the number of people at the emergency department has been increasing. The US has introduced and practiced the triage system in the emergency medicine in 1960, whereby to aid the emergency department in allocating the patients, to give them appropriate medical care by the fast decision of the nurses and doctors in case of the patients’ seriousness through their judgment.This study takes on the knowledge contained in the massive data of unknown characteristics in the triage database at a Taiwanese regional hospital, using the cluster analysis and the rough set theory as tools for data mining to extract, with the analysis software ROSE2 (Rough Sets Data Explorer) and through rule induction technique, the imprecise, uncertain and vague information of rules from the massive database, and builds the model that is capable of simplifying massive data while maintaining the accuracy in classifying rules. After analyzing and evaluating the knowledge obtained from relevant mining in the hospitals past medical data for the consumption of emergency medical resources, this thesis proposes suggestions as reference for the hospitals in subsequent elevation of medical quality and decrease in operative costs.  相似文献   
97.
98.
99.
100.
This paper addresses the food distribution decision from a wholesaler's perspective, as the wholesalers are often faced with thorny issues such as when, where, how to deliver products at the lowest costs to best satisfy the retailers’ changing needs. This research relies on a distribution problem encountered at Northern Grocery Company in Beijing as an example to develop a two-stage solution procedure and subsequent computer-enabled programs for identifying efficient vehicle routing alternatives. The solution process, which integrates heuristic search algorithms and an integer programming model, can be applied to a wide range of distribution problems with specified route durations and a circular transportation network structure as exemplified by City of Beijing.  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