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   405050篇
  免费   38462篇
  国内免费   15052篇
电工技术   21037篇
技术理论   60篇
综合类   23255篇
化学工业   77027篇
金属工艺   21199篇
机械仪表   24306篇
建筑科学   30356篇
矿业工程   12336篇
能源动力   11568篇
轻工业   28007篇
水利工程   6366篇
石油天然气   24609篇
武器工业   2922篇
无线电   46455篇
一般工业技术   53537篇
冶金工业   20710篇
原子能技术   3704篇
自动化技术   51110篇
  2024年   1437篇
  2023年   5734篇
  2022年   9898篇
  2021年   14144篇
  2020年   12030篇
  2019年   11473篇
  2018年   12727篇
  2017年   14380篇
  2016年   13616篇
  2015年   17046篇
  2014年   21081篇
  2013年   25725篇
  2012年   24993篇
  2011年   26985篇
  2010年   23882篇
  2009年   22746篇
  2008年   21998篇
  2007年   21163篇
  2006年   21770篇
  2005年   19096篇
  2004年   12951篇
  2003年   12019篇
  2002年   11572篇
  2001年   10473篇
  2000年   10249篇
  1999年   10981篇
  1998年   8788篇
  1997年   7288篇
  1996年   6781篇
  1995年   5724篇
  1994年   4671篇
  1993年   3278篇
  1992年   2685篇
  1991年   2127篇
  1990年   1619篇
  1989年   1329篇
  1988年   1098篇
  1987年   723篇
  1986年   575篇
  1985年   370篇
  1984年   261篇
  1983年   216篇
  1982年   212篇
  1981年   141篇
  1980年   155篇
  1979年   77篇
  1978年   40篇
  1977年   46篇
  1976年   60篇
  1975年   22篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The thick film of Zn-Sb-O was prepared by coating the paste of nanoparticles mixture (Sb2O3:ZnO=1:3) on the alumina substrate, followed by sintering at 500-900 °C for 2 h in air. The electrical resistance and gas-sensing properties to benzene, alcohol and acetone of Zn-Sb-O films were found to be dependent on the change of phase structure caused by sintering temperature.  相似文献   
102.
Polyurethane elastomer composites were developed using milled fiberglass and their mechanical properties were studied. In particular, the organically chemical treatment of the milled fiberglass was investigated in detail. It was demonstrated that both strength and toughness of the resulting elastomer composites were improved considerably with the addition content of fiberglass. Furthermore, it was indicated that the optimal properties can be achieved by the proper addition of milled fiberglass that was chemically treated using coupling agent.  相似文献   
103.
Generalized difference control of parallel streams temperatures   总被引:1,自引:0,他引:1  
A furnace with multiple parallel passes and multiple burners is commonly seen in petroleum refineries. In order to maintain the furnace running in a safe, stable, and high-efficiency state it is necessary to control the outlet temperatures of the multiple passes to be the same. Due to the fact that the process of the oil heating in such furnace is nonlinear, multivariable, time varying, has serious coupling among passes, has frequent dynamic changes and a large time delay, traditional control methods have trouble in controlling these temperatures, and some advanced control methods, including predictive control, adaptive control, and robust control, are usually too complex for convenient use. In this paper, a control technique, called differences control technique (DsCT), is proposed to distribute the stream flowrates such that the stream temperatures are as identical as possible. The principle of the proposed technique is explained and demonstrated, and the results of its application to a real-life petroleum refinery furnace are also reported. The DsCT technique has the following advantages: it does not need complicated design procedures, the controller structure is simple, it is easy to apply, and it can be canonically applied to furnaces with different number of passes.  相似文献   
104.
105.
介绍并分析了春光油田现代油藏经营管理模式的构建与运作及实施效果.  相似文献   
106.
107.
Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X‐ray diffraction (XRD) analysis indicated that the crystallinity of PAA‐treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers. Copyright © 2008 Society of Chemical Industry  相似文献   
108.
印染废水处理工艺研究及实例   总被引:1,自引:0,他引:1  
本文简要介绍了印染废水水质特征,提出了处理工艺,并利用两个工程实例说明了该工艺的可行性.  相似文献   
109.
110.
氩等离子体辐照反相乳液接枝改性涤纶织物的研究   总被引:1,自引:0,他引:1  
首次提出了在等离子体辐照后再用反相乳液接枝改性涤纶织物的新方法,探讨了接枝颗粒特征以及织物各项物理力学性能.接枝织物的结构及性能的测试结果表明:接枝物的尺寸远小于纤维的直径,在提高织物吸湿性的同时,对织物透气性能和强力等无明显影响;实验也证实了乳液中未接枝单体可以再次聚合.  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