全文获取类型
收费全文 | 118946篇 |
免费 | 9865篇 |
国内免费 | 4998篇 |
专业分类
电工技术 | 7109篇 |
技术理论 | 7篇 |
综合类 | 7617篇 |
化学工业 | 20526篇 |
金属工艺 | 6620篇 |
机械仪表 | 7346篇 |
建筑科学 | 9704篇 |
矿业工程 | 3457篇 |
能源动力 | 3515篇 |
轻工业 | 7773篇 |
水利工程 | 2105篇 |
石油天然气 | 7343篇 |
武器工业 | 884篇 |
无线电 | 13441篇 |
一般工业技术 | 14342篇 |
冶金工业 | 5539篇 |
原子能技术 | 1293篇 |
自动化技术 | 15188篇 |
出版年
2024年 | 558篇 |
2023年 | 2048篇 |
2022年 | 3552篇 |
2021年 | 4905篇 |
2020年 | 3748篇 |
2019年 | 3160篇 |
2018年 | 3394篇 |
2017年 | 3941篇 |
2016年 | 3315篇 |
2015年 | 4734篇 |
2014年 | 5740篇 |
2013年 | 6797篇 |
2012年 | 7458篇 |
2011年 | 8035篇 |
2010年 | 7007篇 |
2009年 | 6691篇 |
2008年 | 6448篇 |
2007年 | 6136篇 |
2006年 | 6379篇 |
2005年 | 5551篇 |
2004年 | 3786篇 |
2003年 | 3316篇 |
2002年 | 3103篇 |
2001年 | 2814篇 |
2000年 | 2962篇 |
1999年 | 3187篇 |
1998年 | 2682篇 |
1997年 | 2281篇 |
1996年 | 2105篇 |
1995年 | 1836篇 |
1994年 | 1477篇 |
1993年 | 1060篇 |
1992年 | 862篇 |
1991年 | 677篇 |
1990年 | 491篇 |
1989年 | 437篇 |
1988年 | 355篇 |
1987年 | 245篇 |
1986年 | 167篇 |
1985年 | 97篇 |
1984年 | 65篇 |
1983年 | 49篇 |
1982年 | 63篇 |
1981年 | 39篇 |
1980年 | 35篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
一种晶闸管整流器全关断检测电路 总被引:1,自引:0,他引:1
本文提出并介绍了欧姆逻辑无环流检测的一种方案——晶闸管流器全关断检测,并与软件检测和电流互联器检测进行比较分析,最终得出晶闸管全关断检测方案准确可行的结论。全关断的输出信号与上述两种信号进行综合利用,从而准确可靠地实现了欧姆的逻辑无环流控制。 相似文献
992.
Jianfeng Gao Xiangjun Xu Junpin Lin Xiping Song Yanli Wang Guoliang Chen 《北京科技大学学报(英文版)》2005,12(6):535-539
The effect of strain rate on the yield strength of high Nb containing TiAl alloy was studied. The results show that the strain rate sensitivity varies with the test temperature, and the yield strength is not sensitive to the strain rate at room temperature but significantly sensitive to the strain rate at high temperature. An increase of the strain rate or a decrease of the temperature results in an obvious change of fracture mode. It is found that the strain rate sensitivity of this alloy varying with temperature is due to the dislocation climb generated at high temperature. 相似文献
994.
Xingbo Liu Ever Barbero Jing Xu Matthew Burris Keh-Minn Chang Vinod Sikka 《Metallurgical and Materials Transactions A》2005,36(8):2049-2058
Corrosion tests of 316L and two intermetallic compounds Fe3Al and FeCrSi in industrial Galvanizing (Zn-0.18Al), GALFAN (Zn-5Al), GALVALUME (Zn-55Al), and Aluminizing (Al-8Si) baths
and lab-scale static baths were conducted. In on-line tests in industrial hot-dip baths, 316L steel shows better corrosion
resistance than Fe3Al in Galvanizing, GALFAN, and GALVALUME baths. The corrosion resistance of 316L and Fe3Al is similar in Aluminizing bath. In static tests, FeCrSi shows the best corrosion resistance in pure Zn, Zn-55Al, and Al-8Si
baths. The corrosion resistance of 316L is better than that of Fe3Al. In Zn-5Al bath, 316L shows no thickness loss after the test. For the same bath composition, the corrosion rates of the
alloys in industrial baths are higher than those in static baths. Bath temperature and chemical composition play important
roles in corrosion and intermetallic layer formation. Increasing bath temperature accelerates the corrosion process and changes
the nature of intermetallic layers. A small amount of aluminum reduces the corrosion process by reducing the activity of Zn
and forming inhibition layer. However, after aluminum content reaches the critical point, the dominant corrosion process changes
from Zn-Fe reaction to Al-Fe reaction, and, consequently, the corrosion process accelerates by increasing aluminum content
in the bath. 相似文献
995.
Lai Huasheng Chen Baojiu Wang Linsheng Xu Wu Wang Xiaojun Xie Yihua Ren Xinguang Di Weihua 《中国稀土学报(英文版)》2005,23(6)
White body-color (Y, Gd)BxV1- xO4-x :Eu3 phosphors were prepared by coprecipitation reaction. Under VUV excitation at 147 nm, the red emission colorimetric purity of (Y, Gd)BxV1- xO4-x :Eu3 phosphor is much better than that of commercial PDP (plasma display panels) phosphor (Y, Gd)BO3:Eu3 . But its relative emission intensity is only about 90% of the commercial phosphor. 相似文献
996.
A new method, the concentrated sulfuric acid acidolysis and water leaching (SAWL) of nickeliferous oxide ores, is proposed and the optimal conditions for recovery of nickel, cobalt and copper from a low-grade Chinese nickeliferous oxide ore are presented. A series of experiments were conducted which examined the effect of acid charge, acid curing temperature and acid curing time. Recoveries of up to 95%, 83% and 95% for Ni, Cu and Co, respectively were obtained with only the sulfuric acid at ambient temperature and atmospheric pressure. Comparing the percolation leaching with agitation leaching showed that percolation leaching was capable of extracting the valuable metals with water. The SAWL method was scaled to three-stages counter-current leaching tests using 1 kg of ore. The results indicate greater than 90% extraction for nickel and cobalt. 相似文献
997.
借鉴了国内外的一些研究成果。从概念、组成等角度分析了员工流动成本。提出了狭义和广义的员工流动成本计算公式,最后就降低员工流动成本提出了若干措施。 相似文献
998.
After the investigation on partial remelting of thixotropic magnesium serial alloys (ZK60) by near non-equilibrium liquidus casting (NNLC), the primary solid grains of ZK60-2Ca alloy spheroidized notably during partial remelting processing, however, coarsening and polygonization as occurred holding time prolonged. The refining and globularity of the thixotropic alloys are promoted after further alloyed by Y, RE, Nd and/or Ag, and the results vary with those addition. The remelting structure of ZK60-2Ca-1Y alloy is finer than its base alloy. And the effect of RE, especially Ag, on the refinement of microstrueture is notable, but Nd does nothing on it. There is little impact of remelting temperature fluctuation on partial remelted microstrueture as holding time in general. On the contrary, it is more sensitive at longer holding time. The quality thixotropic silver-contained alloy can be achieved by remelted partially at 600℃ for 10 min. 相似文献
999.
国企改制是一次根本性的变革,它必将对企业制度、企业管理及企业员工等方方面面产生深远的影响。国有企业实行股份制改造的进程中,企业办公室也应该跟上时代发展的步伐。要不断创新工作方法,充分发挥主观能动性,增强工作的主动性和预见性。 相似文献
1000.
Lanthanidemetalsarethe 5 7thto 71thelementsintheperiodictable ,thetrivalentionsforlanthanideareofvalenceelectronshell 4f0~ 14 6s2 ,whicharefairlystablewhenthe 4felectronsub layerisemptyoral mostempty ,halffullorfull .Becauseofbigenergydifferencebetweenba… 相似文献