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   74472篇
  免费   9210篇
  国内免费   7100篇
电工技术   5591篇
技术理论   10篇
综合类   8672篇
化学工业   1558篇
金属工艺   804篇
机械仪表   4254篇
建筑科学   7988篇
矿业工程   2077篇
能源动力   958篇
轻工业   752篇
水利工程   1924篇
石油天然气   6050篇
武器工业   912篇
无线电   9450篇
一般工业技术   4373篇
冶金工业   1217篇
原子能技术   840篇
自动化技术   33352篇
  2024年   397篇
  2023年   1072篇
  2022年   2210篇
  2021年   2674篇
  2020年   2978篇
  2019年   2337篇
  2018年   2172篇
  2017年   2499篇
  2016年   2863篇
  2015年   3175篇
  2014年   5082篇
  2013年   4610篇
  2012年   5597篇
  2011年   6026篇
  2010年   4506篇
  2009年   4530篇
  2008年   4922篇
  2007年   5488篇
  2006年   4674篇
  2005年   4260篇
  2004年   3610篇
  2003年   3040篇
  2002年   2361篇
  2001年   1824篇
  2000年   1569篇
  1999年   1158篇
  1998年   908篇
  1997年   759篇
  1996年   608篇
  1995年   528篇
  1994年   448篇
  1993年   312篇
  1992年   236篇
  1991年   233篇
  1990年   186篇
  1989年   147篇
  1988年   99篇
  1987年   78篇
  1986年   67篇
  1985年   89篇
  1984年   62篇
  1983年   76篇
  1982年   62篇
  1981年   39篇
  1980年   48篇
  1979年   47篇
  1978年   12篇
  1977年   20篇
  1976年   13篇
  1959年   11篇
排序方式: 共有10000条查询结果,搜索用时 2 毫秒
51.
52.
A Search for Hidden Relationships: Data Mining with Genetic Algorithms   总被引:1,自引:0,他引:1  
This paper presents an algorithm that permits the search for dependencies among sets of data (univariate or multivariate time-series, or cross-sectional observations). The procedure is modeled after genetic theories and Darwinian concepts, such as natural selection and survival of the fittest. It permits the discovery of equations of the data-generating process in symbolic form. The genetic algorithm that is described here uses parts of equations as building blocks to breed ever better formulas. Apart from furnishing a deeper understanding of the dynamics of a process, the method also permits global predictions and forecasts. The algorithm is successfully tested with artificial and with economic time-series and also with cross-sectional data on the performance and salaries of NBA players during the 94–95 season.  相似文献   
53.
Effective management of construction projects depends on good access to and control of data, especially data pertaining to cost and schedule control functions. However, the proper design and development of automated mechanisms have not had the facility to acquire and store quality data in a timely manner. The purpose of this paper, then, is to discuss a prototype, automated data acquisition system that was developed to support an integrated project management system. The data acquisition system is composed of an integrated set of electronic forms used in conjunction with a bar coding data-entry tool.  相似文献   
54.
The analysis of recently collected wind data at five sites in Saudi Arabia namely, Dhulum, Arar, Yanbu, Gassim and Dhahran is presented. The five sites represent different geographically and climatologically conditions. The data collected over a period spanned between 1995 and 2002 with different collection periods for each site. Daily, monthly and frequency profiles of the wind speed at the sites showed that Dhulum and Arar sites have higher wind energy potential with annual wind speed average of 5.7 and 5.4 m/s and speeds higher than 5 m/s for 60 and 47% of the time, respectively. The two sites are candidates for remote area wind energy applications. The costal site's, i.e. Yanbu and Dhahran wind speed data indicated that the two sites have lower annual wind speed averages and wind blows at speed higher than 5 m/s during afternoon hours. That makes the two sites candidates for grid connected wind systems for electrical load peak shaving. The data of Gassim site showed that the site has the lowest wind energy potential compared to the others. The annual energy produced by a Nordex N43 wind machine is estimated to be 1080, 990, 730, 454 and 833 MWh for Dhulum, Arar, Yanbu, Gassim and Dhahran, respectively. The analysis showed that the estimated annual energy produced by the machine based on 10 min averaged data is 2.5% higher than the estimated energy based on 30 min averaged data.  相似文献   
55.
56.
基于中间件技术的HTML业务系统设计与实现   总被引:1,自引:0,他引:1  
介绍了欧洲的MHP标准,并在HTML技术方面提出了改进方案。在此方案的基础上设计了一个基于HTML的从前端数据封装到终端数据接收的完整业务系统,并对其应用前景提出了一些看法。  相似文献   
57.
从数据结构角度为旅游胜地设计导游系统。向游人提供景点的信息查询服务,根据指定的景点提供相关的景点信息。任意给定起点和终点,查询两点之间的最短路径。  相似文献   
58.
Non-redundant data clustering   总被引:6,自引:6,他引:0  
Data clustering is a popular approach for automatically finding classes, concepts, or groups of patterns. In practice, this discovery process should avoid redundancies with existing knowledge about class structures or groupings, and reveal novel, previously unknown aspects of the data. In order to deal with this problem, we present an extension of the information bottleneck framework, called coordinated conditional information bottleneck, which takes negative relevance information into account by maximizing a conditional mutual information score subject to constraints. Algorithmically, one can apply an alternating optimization scheme that can be used in conjunction with different types of numeric and non-numeric attributes. We discuss extensions of the technique to the tasks of semi-supervised classification and enumeration of successive non-redundant clusterings. We present experimental results for applications in text mining and computer vision.  相似文献   
59.
本文所提出的投影域重建——再投影迭代算法可以恢复不完整的扇形束投影数据,从而实现从有限的投影数据重建图象。这种算法把滤波——反投影图象重建过程和再投影的过程纳入一个公式,仅在投影域上估算未知的投影数据,因此避免了重建过程和反投影过程中的插值运算,改善了收敛性,提高了计算精度,缩短了运算时间。模拟实验表明:即使有70%的投影数据丢失,经过两次迭代就能以令人满意的精度恢复丢失的投影数据。  相似文献   
60.
Experimentally determined p,V,T data are reported for toluene, trichloromethane, dichloromethane, acetonitrile, aniline, and n-dodecane at 278, 288, 298, 313, and 323 K, except for dichloromethane, for which the highest temperature was 298 K. At each temperature, measurements were done at pressures up to about 280 MPa or (for aniline and n-dodecane) at a lower pressure slightly below the freezing pressure at the temperature of measurement. Values of the isobaric expansivity isothermal compressibility and (for toluene, trichloromethane, dichloromethane, and acetonitrile) internal pressure, derived from the p,V,T data, are presented.  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