全文获取类型
收费全文 | 571912篇 |
免费 | 10343篇 |
国内免费 | 1596篇 |
专业分类
电工技术 | 10196篇 |
综合类 | 774篇 |
化学工业 | 87896篇 |
金属工艺 | 21031篇 |
机械仪表 | 16142篇 |
建筑科学 | 15183篇 |
矿业工程 | 2468篇 |
能源动力 | 15719篇 |
轻工业 | 52432篇 |
水利工程 | 5611篇 |
石油天然气 | 9603篇 |
武器工业 | 50篇 |
无线电 | 62909篇 |
一般工业技术 | 110270篇 |
冶金工业 | 111830篇 |
原子能技术 | 10913篇 |
自动化技术 | 50824篇 |
出版年
2022年 | 3317篇 |
2021年 | 5978篇 |
2020年 | 4310篇 |
2019年 | 5421篇 |
2018年 | 9025篇 |
2017年 | 8758篇 |
2016年 | 9355篇 |
2015年 | 6840篇 |
2014年 | 10806篇 |
2013年 | 27037篇 |
2012年 | 16932篇 |
2011年 | 22884篇 |
2010年 | 17922篇 |
2009年 | 19793篇 |
2008年 | 20485篇 |
2007年 | 19990篇 |
2006年 | 17400篇 |
2005年 | 15782篇 |
2004年 | 14907篇 |
2003年 | 14548篇 |
2002年 | 13760篇 |
2001年 | 13539篇 |
2000年 | 12586篇 |
1999年 | 13347篇 |
1998年 | 34375篇 |
1997年 | 24023篇 |
1996年 | 18383篇 |
1995年 | 13760篇 |
1994年 | 11940篇 |
1993年 | 11633篇 |
1992年 | 8386篇 |
1991年 | 7762篇 |
1990年 | 7642篇 |
1989年 | 7396篇 |
1988年 | 6820篇 |
1987年 | 6137篇 |
1986年 | 6011篇 |
1985年 | 6699篇 |
1984年 | 6297篇 |
1983年 | 5523篇 |
1982年 | 5204篇 |
1981年 | 5294篇 |
1980年 | 4994篇 |
1979年 | 4864篇 |
1978年 | 4634篇 |
1977年 | 5603篇 |
1976年 | 7425篇 |
1975年 | 3995篇 |
1974年 | 3733篇 |
1973年 | 3851篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
This paper explains the principle of a method which avoids printing of phantom resist lines due to undesired intensity minima appearing on Cr-less edge line phase-shifting masks. The method combines principles of grey-tone lithography and attenuated phase-shifting masks to give, what we call, a Cr-Less Attenuated Phase-shifting mask (CLAP). Rules for generating a CLAP design and a paradigm setup of a CLAP mask are presented. The capabilities and possible limitations of the CLAP method based on simulated results for a standard wafer stepper setup using the SOLID lithography simulator are being assessed. 相似文献
922.
923.
924.
V. M. Raikovic A. J. Miloslawlevic V. M. Shijachki-Zherawcic K. C. Kovacevic B. M. Andelic 《Metal Science and Heat Treatment》1996,38(8):345-346
Investigation of continuously cast low-carbon aluminum-killed steel has great practical importance. Its structure and properties depend on the reeling temperature after hot rolling. After reeling at a low temperature the steel exhibits a capacity for deep drawing, whereas after reeling at a high temperature it is suitable for enameling.Translated from Metallovedenie i Tetmicheskaya Obrabotka Metallov, No. 8, pp. 23 – 24, August, 1996. 相似文献
925.
Particles and gases can deposit from the atmosphere to polar snow by several mechanisms. Dry deposition can be considered to consist of three steps: aerodynamic transport from the free atmosphere to the viscous sublayer near the surface, boundary layer transport across the sublayer, and interactions with the surface. The particle dry deposition mass flux is dominated by the largest particles present in a size distribution. Wet deposition includes in-cloud and below-cloud scavenging, where the former refers to uptake of particles during nucleation of cloudwater as well as scavenging of particles and gases by existing droplets and ice crystals. Of all the wet deposition mechanisms, nucleation scavenging is often the most important mechanism for particles in the polar regions. Finally, incorporation of particles and gases into fog droplets and subsequent settling of the fog to the snow surface can be an important removal process in regions of frequent fog. For Summit, Greenland, the total deposition of MSA, SO42-, Na+, K+, and Ca2+ during May 24-July 13, 1993 was dominated by wet deposition: this mechanism accounted for an average of 62% of the total deposition for these species. Fog and dry deposition accounted for 21% and 17% of the total, respectively. These results suggest that all three mechanisms may need to be considered when estimating total deposition of certain chemical species to polar snow. 相似文献
926.
M Pacifici 《Canadian Metallurgical Quarterly》1995,14(9):689-698
In comparison to the vast literature on articular cartilage structure and function, relatively little is known about how articular cartilage forms during embryogenesis and is endowed with unique phenotypic properties, most notably the ability to persist and function throughout postnatal life. In this minireview, we summarize recent studies from our laboratory suggesting that the extracellular matrix protein tenascin-C is involved in the genesis and function of articular chondrocytes. These and other data have led us to propose that tenascin-C may be part of in vivo mechanisms whereby articular chondrocytes develop at the epiphysis of long bone models, remain functional throughout postnatal life, and avoid the endochondral ossification process undertaken by the bulk of chondrocytes located in the metaphysis and diaphysis of skeletal models. 相似文献
927.
G Chessa Ricotti R Cutrì A De Bernardi M Funis S Frediani 《Canadian Metallurgical Quarterly》1995,17(3):271-273
The authors describe 5 cases, 3 boys and 2 girls, with idiopathic growth hormone deficiency in prepubertal age, treated with human growth hormone. In four of five cases the response to treatment with GH was relevant. Only in one case (F1) the response was negative. The results of this study confirm that rhGH is a safe and effective therapy in children with GHD. 相似文献
928.
929.
The superior high temperature mechanical strength and oxidation resistance of ferritic oxide dispersion strengthened (ODS) tubular alloys are compromised by the difficulties encountered in joining. Conventional fusion welding techniques generate a weld fusion zone which is devoid of the mechanical strength exhibited by the base material. Therefore, more sophisticated solid state joining techniques, such as diffusion bonding, must be employed when joining ODS materials. This paper describes a series of solid state diffusion bonding experiments carried out between two tubular ferritic ODS alloys and two high temperature austenitic alloys. Careful control of bonding conditions produced pressure retaining joints between one of the tubular ODS alloys and both austenitic alloys. The successful joint design was incorporated into the manufacture of a tubular creep component, which enabled a series of internally pressurized creep tests to be carried out. The microstructure developed at the bond interface of each of the four separate material couples is described and the high temperature performance of the pressure retaining joints is discussed. 相似文献
930.
This paper deals with a new application of the time-domain windowed (smoothed version) of the pseudo Wigner-Ville distribution (PWD), that can be easily implemented in a dedicate digital instrument to be used as a spectral analyzer for time-frequency analysis of nonstationary signals. New computational algorithms are studied and developed to attain high time-frequency resolution, accuracy, flexibility and computational efficiency. Particularly, to reduce the negative effects due to leakage during frequency changes, a new interpolation formula is derived by using the windowing theory. The suggested technique allows the users to perform optimal evaluations of the instantaneous amplitudes and frequencies of analyzed signals 相似文献