全文获取类型
收费全文 | 205967篇 |
免费 | 2337篇 |
国内免费 | 565篇 |
专业分类
电工技术 | 3510篇 |
综合类 | 141篇 |
化学工业 | 31823篇 |
金属工艺 | 10267篇 |
机械仪表 | 7010篇 |
建筑科学 | 3994篇 |
矿业工程 | 2161篇 |
能源动力 | 4632篇 |
轻工业 | 12873篇 |
水利工程 | 2920篇 |
石油天然气 | 7726篇 |
武器工业 | 22篇 |
无线电 | 21498篇 |
一般工业技术 | 45171篇 |
冶金工业 | 34381篇 |
原子能技术 | 6620篇 |
自动化技术 | 14120篇 |
出版年
2021年 | 2051篇 |
2019年 | 1998篇 |
2018年 | 3678篇 |
2017年 | 3716篇 |
2016年 | 3998篇 |
2015年 | 2232篇 |
2014年 | 3781篇 |
2013年 | 8737篇 |
2012年 | 5677篇 |
2011年 | 7214篇 |
2010年 | 5855篇 |
2009年 | 6487篇 |
2008年 | 6611篇 |
2007年 | 6491篇 |
2006年 | 5569篇 |
2005年 | 5116篇 |
2004年 | 4629篇 |
2003年 | 4553篇 |
2002年 | 4366篇 |
2001年 | 4472篇 |
2000年 | 4185篇 |
1999年 | 4198篇 |
1998年 | 10183篇 |
1997年 | 7181篇 |
1996年 | 5500篇 |
1995年 | 4131篇 |
1994年 | 3597篇 |
1993年 | 3838篇 |
1992年 | 2983篇 |
1991年 | 2995篇 |
1990年 | 2890篇 |
1989年 | 2852篇 |
1988年 | 2865篇 |
1987年 | 2509篇 |
1986年 | 2568篇 |
1985年 | 2854篇 |
1984年 | 2687篇 |
1983年 | 2554篇 |
1982年 | 2300篇 |
1981年 | 2269篇 |
1980年 | 2345篇 |
1979年 | 2359篇 |
1978年 | 2382篇 |
1977年 | 2487篇 |
1976年 | 2876篇 |
1975年 | 2188篇 |
1974年 | 2068篇 |
1973年 | 2166篇 |
1972年 | 1940篇 |
1971年 | 1755篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
I. N. Polandov V. K. Novik O. K. Gulish B. P. Bogomolov V. B. Morozov 《Measurement Techniques》1989,32(9):888-890
Translated from Izmeritel'naya Tekhnika, No. 9, pp. 34–35, September, 1989. 相似文献
242.
Thin films on aluminum-tungsten alloys were prepared by co-deposition of pure aluminum and pure tungsten, each sputtered by an independently controlled magnetron source, on glass and sapphire substrates. Completely amorphous films were obtained in the Al80W20-Al67W33 composition range. Passivity and corrosion behavior of amorphous Al-W alloys were investigated in 1 M deaerated hydrochloric acid solution using polarization and impedance spectroscopy measurements and have been correlated with the properties of pure alloy components. Tungsten and sputter-deposited Al-W thin films are inherently passive materials while aluminum undergoes pitting corrosion in hydrochloric acid solution. The passive film formed at the OCP on each alloy possesses excellent electric and dielectric properties comparable to those of the isolating film on tungsten. The absolute impedance increases with increasing tungsten content in the alloy. According to electrochemical polarization measurements, alloying Al with W in solid solution significantly enhances the material's resistance to pitting corrosion by shifting the breakdown potential above 2000 mV (Al67W33) and lowering the corrosion rate at the OCP by more than two orders of magnitude. The most likely mechanism explaining the passivity of amorphous Al-W alloys, the Solute Vacancy Interaction Model (SVIM), involves the formation of complexes between highly oxidized solute atoms (W+6) and mobile cation vacancies, which restrict the transport of Cl− through the oxide film and inhibit its breakdown in hydrochloric acid solution. The role that film stress relaxation effects and microscopic defects in amorphous Al-W films, of the some composition, and deposited on various substrates play in their corrosion resistance is discussed. 相似文献
243.
244.
245.
V. L. Ozol' L. F. Kandyba N. T. Bychenkov L. A. Zbarskii B. E. Koropov 《Metallurgist》1989,33(8):156-156
Lenin Dnepropetrovsk Pipe Plant. Translated from Metallurg, No. 8, p. 39, August, 1989. 相似文献
246.
A. M. Pristrem N. I. Danilovich V. A. Labunov 《Journal of Engineering Physics and Thermophysics》1987,53(6):1464-1472
By using integral transform methods, an approach is developed to the solution of a problem on the temprature distribution in multilayer structures heated by cw scanning laser radiation, with phase transitions in the layers taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 6, pp. 1000–1010, December, 1987. 相似文献
247.
R. Breil T. Fries J. Garnaes J. Haycocks D. Hüser J. Joergensen W. Kautek L. Koenders N. Kofod K. R. Koops R. Korntner B. Lindner W. Mirand A. Neubauer J. Peltonen G. B. Picotto M. Pisani H. Rothe M. Sahre M. Stedman G. Wilkening 《Precision Engineering》2002,26(3)
Comparison measurements on reference standards are reported in which 13 partners with different instruments took part. A set of prototype standards which had been produced and calibrated within a European project were used for the measurements. Here, results of measurements on a 240 nm step height standard and a two-dimensional lateral standard with a nominal pitch of 1 μm are reported. 相似文献
248.
M. N. Magomedov 《Technical Physics Letters》2002,28(5):430-433
Expressions for the calculation of the parameters of self-diffusion in a crystal of simple substance at temperatures close
to absolute zero are derived. It is established that, in “loose” crystal structures (with the first coordination number below
12), the amount of atoms involved in diffusion motion exceeds the number of vacant sites in the crystal lattice at T=0 K. The results of calculations of the vacancy and diffusion parameters at T=0 K for ten cryocrystals show that the phenomenon of “nonvacancy self-diffusion at T=0 K” can take place only in bcc helium. 相似文献
249.
A. N. Utkina Yu. Yu. Cherkis M. N. Kozlova V. L. Kozlov 《Metal Science and Heat Treatment》1982,24(4):270-273
Conclusion To ensure the required characteristics of the diffusion layer in heat-resistant steels, it is recommended to subject them to two-stage nitriding: saturation at 950°C for 2 h in endogas with an addition of 12% natural gas and 4% ammonia, lowering the temperature to 900°C, holding for 5 h in endogas with an addition of 6% natural gas and 4% ammonia; exchange of gas 6 times.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 34–36, April, 1982. 相似文献
250.
New fundamental solutions which automatically satisfy boundary conditions at the interfaces of an elastic plate perfectly bonded to two elastic halfspaces are implemented in a 3-D boundary element method (BEM) for crack problems. The BEM features a new integration scheme for highly singular kernels. The capability is achieved through a part analytic and part numerical integration procedure, such that the analytic part of the integration is similar for all slip/opening variations, ‘Part-through’ elliptic cracks in an elastic plate with traction-free surfaces are analysed and the stress intensity factor (SIF) values along the crack front are found to compare favourably with widely accepted numerically obtained SIF results by Raju and Newman.1 相似文献