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   15747篇
  免费   1317篇
  国内免费   703篇
电工技术   940篇
综合类   856篇
化学工业   2613篇
金属工艺   872篇
机械仪表   1042篇
建筑科学   1163篇
矿业工程   399篇
能源动力   490篇
轻工业   902篇
水利工程   246篇
石油天然气   1034篇
武器工业   100篇
无线电   2153篇
一般工业技术   1982篇
冶金工业   795篇
原子能技术   130篇
自动化技术   2050篇
  2024年   61篇
  2023年   286篇
  2022年   480篇
  2021年   687篇
  2020年   488篇
  2019年   407篇
  2018年   454篇
  2017年   483篇
  2016年   463篇
  2015年   616篇
  2014年   807篇
  2013年   970篇
  2012年   963篇
  2011年   1124篇
  2010年   935篇
  2009年   847篇
  2008年   925篇
  2007年   801篇
  2006年   881篇
  2005年   800篇
  2004年   504篇
  2003年   438篇
  2002年   341篇
  2001年   327篇
  2000年   309篇
  1999年   443篇
  1998年   405篇
  1997年   296篇
  1996年   272篇
  1995年   202篇
  1994年   189篇
  1993年   131篇
  1992年   105篇
  1991年   71篇
  1990年   62篇
  1989年   42篇
  1988年   31篇
  1987年   11篇
  1986年   23篇
  1985年   7篇
  1984年   15篇
  1983年   7篇
  1982年   16篇
  1981年   9篇
  1980年   9篇
  1979年   5篇
  1977年   4篇
  1976年   5篇
  1975年   3篇
  1959年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
本文在N—S方程涡量一流函数形式的经典ADI格式和SOR松驰迭代公式的基础上,对其“外来项”进行平均化处理,构造出了平均化差分格式及迭代求解程序。对雷诺数Re=100,1000,10000的空腔流动分别进行了数值计算,并与各数值方法的结果及实验资料进行了比较,结果令人满意。  相似文献   
32.
用医药工业的副产物乙酰基次黄嘌呤(Ⅰ)在弱酸条件下水解,生成次黄嘌呤(Ⅱ),经三氟氧磷在吡啶溶液中缩合,生成6-吡啶盐中间体(Ⅲ),再与苄胺反应,制得高效植物细胞分裂素6-BA(Ⅳ)。  相似文献   
33.
We present an approach for animating cracks and fractures in cartoon style. In our method we take a 2D hand-drawn object as input and then construct a 2.5D model of the object in order to approximate the object volume. Next, we generate the Voronoi textures on the 2.5D object model for visual abstraction of cartoon cracks. Further, cracking gaps on the Voronoi textures are widened progressively until Voronoi cells split apart and finally fall onto ground according to simplified physical rules. With minimum user intervention, our model is able to generate cartoon cracks and fractures animations procedurally, as demonstrated by examples given in the paper.  相似文献   
34.
This paper presents a hybrid chaos search (CS), immune algorithm (IA)/genetic algorithm (GA), and fuzzy system (FS) method (CIGAFS) for solving short-term thermal generating unit commitment (UC) problems. The UC problem involves determining the start-up and shut-down schedules for generating units to meet the forecasted demand at the minimum cost. The commitment schedule must satisfy other constraints such as the generating limits per unit, reserve, and individual units. First, we combined the IA and GA, then we added the CS and the FS approach. This hybrid system was then used to solve the UC problems. Numerical simulations were carried out using three cases: 10, 20, and 30 thermal unit power systems over a 24 h period. The produced schedule was compared with several other methods, such as dynamic programming (DP), Lagrangian relaxation (LR), standard genetic algorithm (SGA), traditional simulated annealing (TSA), and traditional Tabu search (TTS). A comparison with an immune genetic algorithm (IGA) combined with the CS and FS was carried out. The results show that the CS and FS all make substantial contributions to the IGA. The result demonstrated the accuracy of the proposed CIGAFS approach.  相似文献   
35.
This paper presents a new route about producing carbon black,by wich the natural gas cracking is carried out in the absence of oxygen thanks to an electric energy supply externally given by a plasma jet.The carbon black produced by this process has a narrow size distribution and a small average diameter of 38nm as well as a highly branched aggregate.The higher DBP value of 1.40ml/g shows it should be a high structure carbon black.The FTIR spectra shows that there are lots of aromatic c-c bonds and a large amount of nitrogen-coutaining functional groups on the carbon blacks surface,such as-NH,-CN as we3ll as -CH,-OH,-COOH groups.  相似文献   
36.
本文主要介绍了广钢汽拖AV40-11轴流压缩机组的结构和特点,控制系统概要、应用效果。  相似文献   
37.
High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal mines and providing scientific guidance for the respiratory protection of miners.Based on the self-designed in-situ PM2.5collector,controllable PM2.5generator,human breathing simulator,and respirator simulation testing system,under the simulated deep mine working ...  相似文献   
38.
微电网技术研究现状   总被引:10,自引:0,他引:10       下载免费PDF全文
首先阐释了微网的概念、结构及特点,然后对当前美国、欧盟和日本等国的微网研究现状进行了介绍,并介绍了微网运行方式,最后着重探讨了现阶段微电网研究中的关健问题和相关研究现状。  相似文献   
39.
膨胀土地区开挖渠道滑坡的规律与特征   总被引:3,自引:0,他引:3  
在安徽省近百处开挖渠道滑坡分析的基础上,结合工程地质条件,对膨胀土地区开挖渠道滑坡在滑动面的形态及其形成、滑坡过程和滑坡分布等方面的规律和特征进行了研究。  相似文献   
40.
Modeling and finite element analysis of rod and wire steel rolling process   总被引:2,自引:0,他引:2  
Two thermomechanical coupled elastic-plastic finite element (FE) models were developed for predicting the 12-pass continuous rolling process of GCrl 5 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by interpolation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.  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