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   79614篇
  免费   9692篇
  国内免费   6164篇
电工技术   7004篇
技术理论   6篇
综合类   8229篇
化学工业   11043篇
金属工艺   4028篇
机械仪表   4666篇
建筑科学   5404篇
矿业工程   2684篇
能源动力   3919篇
轻工业   4960篇
水利工程   2797篇
石油天然气   2274篇
武器工业   705篇
无线电   7820篇
一般工业技术   9890篇
冶金工业   2408篇
原子能技术   706篇
自动化技术   16927篇
  2024年   480篇
  2023年   2481篇
  2022年   3419篇
  2021年   3539篇
  2020年   3586篇
  2019年   2929篇
  2018年   2999篇
  2017年   3229篇
  2016年   3449篇
  2015年   3470篇
  2014年   4887篇
  2013年   5778篇
  2012年   7658篇
  2011年   7938篇
  2010年   6003篇
  2009年   6018篇
  2008年   3833篇
  2007年   6427篇
  2006年   5735篇
  2005年   2458篇
  2004年   1183篇
  2003年   917篇
  2002年   901篇
  2001年   718篇
  2000年   702篇
  1999年   642篇
  1998年   513篇
  1997年   422篇
  1996年   424篇
  1995年   368篇
  1994年   260篇
  1993年   257篇
  1992年   207篇
  1991年   184篇
  1990年   143篇
  1989年   120篇
  1988年   173篇
  1987年   348篇
  1986年   300篇
  1985年   72篇
  1984年   46篇
  1983年   44篇
  1982年   34篇
  1981年   33篇
  1980年   34篇
  1979年   45篇
  1978年   27篇
  1977年   12篇
  1976年   15篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
本文根据90年代以来新材料技术的新进展,高度概括地评述了世界新材料技术发展的新趋势,以期对跟踪世界高新技术提供依据。  相似文献   
53.
54.
In conformity with the principle of Design for Manufacture,feature-based design strate-(?)es have been developed.As the“feature”is relevant to the“macro process plan”and“macro NCprograms”,obviously,“feature”is beyond the power of conventional solid modellers.Neverthe-less,substantial breakthrough has not been made in the solid modeling field,except“feature at-taching”or“feature recognizing”methods have been taken on.In this paper,the theory,concepts,system architecture,and algorithm principles of solid modeling tool system have beenrepresented.The practice of Feature Solid Modeling Tool System (FSMTS) developed atHuazhong University has proved that the tool may be a new foundation of Feature-Based Design.  相似文献   
55.
It is one of important measures for the sustainable development of cement industry to utilize industrial wastes. High-strength composite portland cement with a large amount of granulated blast furnace slag (GBFS), fly ash and limestone was prepared by separate grinding method, optimizing gypsum and using activators. The total amounts of blending materials are between 45% and 65% and the strength grades of cements reach 525 or even 625 according to Chinese national standard for composite portland cement. Besides setting time and strength, the hydration heat, drying shrinkage and sulfate resistance were also determined.  相似文献   
56.
Nanowires made of aluminum borate formed of Al18B4O33 have been synthesized in high yield by improving the traditional chemical flux method for the growth of aluminum borate with the fibrous structure. In this study, aluminum powder was added into the aluminum oxide and boron oxide reactants as an additive in order to control the morphology of the final products. The chemical method reported here is utilized to decrease the diameters of traditional aluminum borate fiber into nanoscale and to increase their lengths. The optimum experimental parameters and possible growth mechanism for the compound nanowires have been presented.  相似文献   
57.
58.
In order to investigate the galvanic anodic protection (GAP) of ferrous metals (such as 410, 304 and 316 stainless steels) in acid solutions by doped polyaniline (PANi), separate doped PANi powder-pressed electrodes with different surface areas (the area ratio of the PANi electrode to stainless steel is between 1:1 and 1:2) have been prepared. These were coupled with ferrous metal in the following solutions: 5 M sulphuric acid, 5 M phosphoric acid and industrial phosphoric acid (containing 5 M phosphoric acid and 0.05% chloride ion) to construct a galvanic cell, in which PANi is cathode while ferrous metal is anode. The results indicate that a PANi electrode with sufficient area can provide corrosion protection to stainless steel in these acidic solutions. A pilot scale coupling experiment was carried out. The results indicate that PANi is a promising material as an electrode for the anodic protection of ferrous metals in acidic solutions in industrial situations.  相似文献   
59.
低碳微合金钢中的晶内铁素体及组织控制   总被引:1,自引:0,他引:1  
回顾和评述了晶内铁素体的发现、发展及其与组织控制的关系.介绍了晶内铁素体的形核机制和影响晶内铁素体形成的因素,讨论了晶内铁素体的三维形态和长大动力学,并从以上几方面分析了晶内铁素体对低碳微合金钢组织细化的重要作用和影响.  相似文献   
60.
The mechanical stability of the electrode plays a very important role in the long-term stability of electrochemical behavior. In this paper, multi-wall carbon nanotubes (MWCNTs) electrodes were prepared in the holes of glass directly by microwave plasma chemical vapor deposition and the electrochemical behavior of catechol at the integrated MWCNT electrodes was investigated. The oxygen plasma treated CNTs had excellent electrochemical behavior for the analysis of catechol. The catechol was detected in the linear concentration range of 1.0 × 10 6 mol L 1–1.0 × 10 3 mol L 1. And because CNTs were integrated directly on the substrate, the stable response to catechol solution showed that the carbon nanotubes electrodes had long-term stability.  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