全文获取类型
收费全文 | 140392篇 |
免费 | 15803篇 |
国内免费 | 10556篇 |
专业分类
电工技术 | 12940篇 |
技术理论 | 3篇 |
综合类 | 13503篇 |
化学工业 | 17457篇 |
金属工艺 | 9262篇 |
机械仪表 | 10017篇 |
建筑科学 | 10748篇 |
矿业工程 | 4554篇 |
能源动力 | 3964篇 |
轻工业 | 15872篇 |
水利工程 | 5442篇 |
石油天然气 | 4325篇 |
武器工业 | 1885篇 |
无线电 | 14893篇 |
一般工业技术 | 13321篇 |
冶金工业 | 5612篇 |
原子能技术 | 2401篇 |
自动化技术 | 20552篇 |
出版年
2024年 | 858篇 |
2023年 | 2285篇 |
2022年 | 5047篇 |
2021年 | 6455篇 |
2020年 | 4777篇 |
2019年 | 3386篇 |
2018年 | 3556篇 |
2017年 | 4169篇 |
2016年 | 3804篇 |
2015年 | 5875篇 |
2014年 | 7301篇 |
2013年 | 8980篇 |
2012年 | 10733篇 |
2011年 | 11234篇 |
2010年 | 10800篇 |
2009年 | 10518篇 |
2008年 | 10911篇 |
2007年 | 10760篇 |
2006年 | 9397篇 |
2005年 | 7750篇 |
2004年 | 5848篇 |
2003年 | 4287篇 |
2002年 | 4313篇 |
2001年 | 4043篇 |
2000年 | 3088篇 |
1999年 | 1608篇 |
1998年 | 834篇 |
1997年 | 722篇 |
1996年 | 626篇 |
1995年 | 573篇 |
1994年 | 432篇 |
1993年 | 331篇 |
1992年 | 285篇 |
1991年 | 212篇 |
1990年 | 187篇 |
1989年 | 162篇 |
1988年 | 139篇 |
1987年 | 81篇 |
1986年 | 73篇 |
1985年 | 62篇 |
1984年 | 30篇 |
1983年 | 19篇 |
1982年 | 26篇 |
1981年 | 28篇 |
1980年 | 35篇 |
1979年 | 29篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1959年 | 21篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
汽车离合器从动盘自由行程检测机的改进 总被引:1,自引:0,他引:1
介绍了对法国瓦雷奥(VELEO)公司生产的汽车离合器从动盘自由行程检测机的半自动化改进方案,同时,介绍了改进后的自由行程检测机的结构、工作过程以及原理. 相似文献
992.
993.
994.
缓蚀剂对316L不锈钢在酸性氯离子溶液中应力腐蚀开裂的作用 总被引:2,自引:2,他引:2
研究表明316L不锈钢在55℃的1mol/L HCl+1mol/L NaCl溶液中对SCC比较敏感。316L不锈钢在所研究的体系中处于活化溶解状态。对添加缓蚀剂的体系的电化学参数的测试和分析表明,缓蚀剂抑制SCC的能力与缓蚀剂抑制阳极反应有关。 相似文献
995.
A composite catalyst Nafion-Pt-HxMoO3 was prepared on a glassy carbon by cyclic voltammetry methods in sulfuric acid solution containing Na2MoO4, H2PtCl6 and Naton, and its activity for the methanol oxidation was studied with Pt-HxMoO3 as comparison. It is found that the electrocatalytic activity and the stability of Pt-HxMoO3 are improved by the Nation. The activity of Pt-HxMoO3 reaches its maximum when the content of Nation in the preparation solution is 0.012%(mass fraction). In this case the oxidation peak current of methanol on Nation-Pt-HxMoO3 is 1.76 times larger than that on Pt-HxMoO3 and keeps unchanged when the potential is set at 0.3 V (vs Hg-Hg2SO4) for 5 000 s in 1 mol/LCH3OH+0.5 mol/L U2SO4 solution. The results from energy dispersive spectroscopy show that the content of Nation in the composite is 0.57%. The results from scanning electron spectroscopy show that the composite of Nafion-Pt-HxMoO has a gain size of about 90 nm and distributes more uniformly than Pt-HxMoO3. 相似文献
996.
997.
998.
ZHAO Xuehui ) HUANG Kelong) JIAO Feipeng) LI Zhiaojian) and PENG Xiahui) ) College of Chemistry Chemical Engineering Central South University Changsha China ) Chemistry Department Hunan Technology BOE Science University Zhuzhou China 《稀有金属(英文版)》2006,(2)
1. Introduction Rare earth elements have an important function inlife process. The fluorescence enhancement of lan-thanides in aqueous solutions has therefore becomean area of active study in trace-level estimation oflanthanides using spectrofluorimetry [1]. Its possiblemechanism and application as fluorescence probesin biological systems have also attracted attention inrecent years [2]. Generally, fluorescence enhance-ment can be achieved through ligand sensitization.Various ligands have bee… 相似文献
999.
Characteristics of graphite felt electrode electrochemically oxidized for vanadium redox battery application 总被引:2,自引:0,他引:2
The graphite felt was oxidized at a positive electrode potential in sulfuric acid solution.The electrochemical performance of the treated graphite felt served as electrode for vanadium redox battery was investigated with FT-IR,SEM,XPS,BET,cyclic voltammetry and testing VRB system,respectively.The results show that the molar ratio of O to C increases from 0.085 to 0.15 due to the increase of—COOH functional groups during electrochemical oxidation treatment,and the GF surface is eroded by electrochemical oxidation,resulting in the surface area increase from 0.33 m2/g to 0.49 m 2/g.The VRB with modified GF electrode exhibits excellent performance under a current density of 30 mA/cm 2 .The average current efficiency reaches 94%and average voltage efficiency reaches 85%.The improvement of electrochemical activity for the electrode is ascribed to the increase of the number of—COOH group and the special surface of GF. 相似文献
1000.
The deformation behavior of AZ31B magnesium alloy as extruded under hot compression conditions was characterized in the temperature range of 200 - 400 ℃ and strain rate range of 0. 001 - 1 s^-1. The processing maps were obtained at different strains. The results show that the map exhibits flow instabilities as two domains. The domain at beyond 300 ℃ and strain rate of 1 s^-1 appears with a peak efficiency of power dissipation about 56% occurring. This domain is expected to happen in a hot process, such as hot rolling, hot extrusion and hot forging. There is high efficiency of power dissipation at temperature beyond 350 ℃ and strain rate 0. 001 s^-1. Such domains suggest the occurrence of superplastic deformation. 相似文献