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   39199篇
  免费   3296篇
  国内免费   1571篇
电工技术   2286篇
技术理论   1篇
综合类   2663篇
化学工业   6732篇
金属工艺   2083篇
机械仪表   2082篇
建筑科学   3013篇
矿业工程   978篇
能源动力   1276篇
轻工业   2608篇
水利工程   700篇
石油天然气   2042篇
武器工业   220篇
无线电   4660篇
一般工业技术   4856篇
冶金工业   2021篇
原子能技术   443篇
自动化技术   5402篇
  2024年   148篇
  2023年   604篇
  2022年   1031篇
  2021年   1512篇
  2020年   1094篇
  2019年   1005篇
  2018年   1053篇
  2017年   1190篇
  2016年   1099篇
  2015年   1411篇
  2014年   1867篇
  2013年   2264篇
  2012年   2389篇
  2011年   2518篇
  2010年   2194篇
  2009年   2196篇
  2008年   2165篇
  2007年   2021篇
  2006年   2052篇
  2005年   1745篇
  2004年   1355篇
  2003年   1520篇
  2002年   1841篇
  2001年   1477篇
  2000年   1022篇
  1999年   955篇
  1998年   789篇
  1997年   650篇
  1996年   586篇
  1995年   494篇
  1994年   419篇
  1993年   277篇
  1992年   250篇
  1991年   171篇
  1990年   120篇
  1989年   96篇
  1988年   124篇
  1987年   61篇
  1986年   59篇
  1985年   37篇
  1984年   41篇
  1983年   26篇
  1982年   31篇
  1981年   16篇
  1980年   19篇
  1979年   22篇
  1977年   5篇
  1976年   10篇
  1974年   4篇
  1965年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This research uses the object extracting technique to extract the index, middle and ring fingers from the hand images. The algorithm developed in this research can find the precise locations of the different fingers' fingertips and the finger-to-finger-valleys. After finding the positions of the fingertips and finger-valleys, the index, middle and ring fingers can be extracted from the hand images by using morphological technique. The extracted index, middle and ring fingers contain many useful geometry features. One can use these features to do the person's identification. The orientations of the index, middle and ring fingers are found in this research. Image rotating, image shifting, and image interpolating techniques are used to align different persons' index, middle and ring fingers. Image subtraction is used to exam the difference of two index, middle and ring finger images. In this research so far only use the index, middle and the ring fingers as the features to identify different persons. This work was supported by National Science Council under grant NSC 93-2213-E-212-011.  相似文献   
82.
Wet adhesion is widely adopted in biological adhesion systems in nature. Wet adhesion is studied in this paper with the focus on the effect of different contact shapes (flat, concave, convex, and ring-like) on the adhesion force. The evolution of the liquid bridge between a fiber tip and substrate during the detaching process shows two transition points. The first transition from the radius-controlled to the contact-angle controlled process is critical to influence the strength and robustness of adhesion. We show that a concave shape is more effective than a flat one, while a convex shape has no advantage. A ring-like contact shape has advantages in a hydrophobic environment and on a rough surface.  相似文献   
83.
84.
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range of modulus ratio between inclusion and matrix material.  相似文献   
85.
面向企业信息化实现管理现代化   总被引:1,自引:0,他引:1  
为适应社会信息化技术的发展,必须积极推行企业信息化,企业信息化引发管理革命,从而丰富了企业管理现代化的内容。本文论述了上述三方面的内部及演化关系,指出只有面向企业信息化,才能充分实现企业管理现代化。  相似文献   
86.
柴淑玲  任明霞 《山西建筑》2003,29(8):133-134
对智能电动机控制器的情况作了介绍,结合工作实践提出了维护要点和建议,并对该控制器的参数设置进行了说明,这对使用该设备的工业企业有一定的指导意义。  相似文献   
87.
随着采液时间的延长,电潜泵井事故不断增加,仅辽河油田每年就有30口左右的电泵井需要转大修.由于没有专用的打捞工具,作业设备的能力有限,其处理事故的周期往往较长,效果不理想.因此,在已有φ139.7mm套管内电泵打捞工具的基础上,研制开发了φ177.8 mm套管内电泵打捞工具,解决了油田电泵打捞的难题.  相似文献   
88.
Based on the optimal fusion estimation algorithm weighted by scalars in the linear minimum variance sense, a distributed optimal fusion Kalman filter weighted by scalars is presented for discrete‐time stochastic singular systems with multiple sensors and correlated noises. A cross‐covariance matrix of filtering errors between any two sensors is derived. When the noise statistical information is unknown, a distributed identification approach is presented based on correlation functions and the weighted average method. Further, a distributed self‐tuning fusion filter is given, which includes two stage fusions where the first‐stage fusion is used to identify the noise covariance and the second‐stage fusion is used to obtain the fusion state filter. A simulation verifies the effectiveness of the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
89.
Liquid–liquid two‐phase epoxidation from cyclohexene and cyclooctene in aqueous potassium peroxymonosulfate (commercially available as Oxone®) solution was studied as an application in pollution prevention. To avoid potential emissions of volatile organic compounds an aqueous solution was employed to replace the usual chlorinated solvents used in epoxide production. A droplet column reactor and stirred tank reactor were used to investigate two‐phase synthesis of epoxide. An aqueous Oxone® solution was used to oxidize a dispersion of alkene droplets and form epoxide. The study of aqueous epoxidation in both reactors showed that the epoxidation of alkenes can be represented as a first order reaction with respect to alkene. The salting out effect of Oxone® concentration was studied in both reactors and found to be very similar at optimal conditions. In comparing the two reactors, it was found that the droplet column reactor produces larger quantities of product per unit reactor volume for the same reaction time. The objective of this study is to provide an alternative reactor design and synthesis route that can meet pollution prevention goals. Copyright © 2004 Society of Chemical Industry  相似文献   
90.
基于因特网的远程校准技术进展   总被引:3,自引:0,他引:3  
远程校准是信息技术特别是计算机网络技术与传统的计量测试技术结合的必然产物。本文介绍与之有关的一些概念及国外开展相应项目的情况。结合我们自己的一个实验装置.对在我国开展远程校准工作的必要性和可行性提出一些看法。  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