全文获取类型
收费全文 | 687111篇 |
免费 | 7915篇 |
国内免费 | 1482篇 |
专业分类
电工技术 | 12584篇 |
综合类 | 575篇 |
化学工业 | 107819篇 |
金属工艺 | 28590篇 |
机械仪表 | 21865篇 |
建筑科学 | 15292篇 |
矿业工程 | 5348篇 |
能源动力 | 17577篇 |
轻工业 | 54014篇 |
水利工程 | 8568篇 |
石油天然气 | 17936篇 |
武器工业 | 52篇 |
无线电 | 73270篇 |
一般工业技术 | 141524篇 |
冶金工业 | 118405篇 |
原子能技术 | 17360篇 |
自动化技术 | 55729篇 |
出版年
2021年 | 6567篇 |
2019年 | 6242篇 |
2018年 | 10776篇 |
2017年 | 10951篇 |
2016年 | 11547篇 |
2015年 | 7202篇 |
2014年 | 12153篇 |
2013年 | 31325篇 |
2012年 | 18767篇 |
2011年 | 25163篇 |
2010年 | 20073篇 |
2009年 | 22538篇 |
2008年 | 22842篇 |
2007年 | 22479篇 |
2006年 | 19510篇 |
2005年 | 17742篇 |
2004年 | 16838篇 |
2003年 | 16436篇 |
2002年 | 15828篇 |
2001年 | 15517篇 |
2000年 | 14859篇 |
1999年 | 14664篇 |
1998年 | 34893篇 |
1997年 | 25039篇 |
1996年 | 19483篇 |
1995年 | 14851篇 |
1994年 | 13363篇 |
1993年 | 13206篇 |
1992年 | 10191篇 |
1991年 | 9887篇 |
1990年 | 9669篇 |
1989年 | 9405篇 |
1988年 | 9143篇 |
1987年 | 8167篇 |
1986年 | 8022篇 |
1985年 | 9098篇 |
1984年 | 8245篇 |
1983年 | 7934篇 |
1982年 | 7136篇 |
1981年 | 7183篇 |
1980年 | 6984篇 |
1979年 | 7090篇 |
1978年 | 6974篇 |
1977年 | 7666篇 |
1976年 | 9447篇 |
1975年 | 6263篇 |
1974年 | 6000篇 |
1973年 | 6136篇 |
1972年 | 5315篇 |
1971年 | 4957篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
For pt.I see ibid., vol.17, no.1, p.95-101 (2002). This paper proposes a method for lateral stabilization of the levitated linear induction motor and also gives the analysis for calculating the stabilizing force in detail. The calculated force has been experimentally verified using the laboratory prototype described previously 相似文献
992.
M Flores-Díaz A Alape-Girón B Persson P Pollesello M Moos C von Eichel-Streiber M Thelestam I Florin 《Canadian Metallurgical Quarterly》1997,272(38):23784-23791
We previously isolated a mutant cell that is the only mammalian cell reported to have a persistently low level of UDP-glucose. In this work we obtained a spontaneous revertant whose UDP-glucose level lies between those found in the wild type and the mutant cell. The activity of UDP-glucose pyrophosphorylase (UDPG:PP), the enzyme that catalyzes the formation of UDP-glucose, was in the mutant 4% and in the revertant 56% of the activity found in the wild type cell. Sequence analysis of UDPG: PP cDNAs from the mutant cell showed one missense mutation, which changes amino acid residue 115 from glycine to aspartic acid. The substituted glycine is located within the largest stretch of strictly conserved residues among eukaryotic UDPG:PPs. The analysis of the cDNAs from the revertant cell indicated the presence of an equimolar mixture of the wild type and the mutated mRNAs, suggesting that the mutation has reverted in only one of the alleles. In summary, we demonstrate that the G115D substitution in the Chinese hamster UDPG:PP dramatically impairs its enzymatic activity, thereby causing cellular UDP-glucose deficiency. 相似文献
993.
A high-speed monolithic optical interface switch LSI is developed using a GaAs MSM photodetector and large-scale integrated electric circuits. This LSI operates universally as a 1.8 Gb/s optical-input/optical-output four-channel time-division switch, a 1.8 Gb/s optical-input/electrical-output 1:4 demultiplexer, a 2.0 Gb/s electrical-output 4:1 multiplexer, and a 2.8 Gb/s electrical-input/electrical-output 4×4 space-division switch. It uses a new multistage 2×2 switch block with small hardware and high-speed operation. It can be expanded to a 16×16 optical-input/optical-output time-division switch operating at up to 1.8 Gb/s for broadband-ISDN 相似文献
994.
995.
Evolution of the capillary network in a reactive powder concrete during hydration process 总被引:7,自引:0,他引:7
V. Morin F. Cohen-Tenoudji A. Feylessoufi P. Richard 《Cement and Concrete Research》2002,32(12):1907-1914
Ultrasonic waves in echographic mode, combined with autogenous shrinkage measurements, were used to study the evolution of the capillary network of reactive powder concrete (RPC) from the time after the mixing. Two characteristic porous classes have been identified: the first, between 10 and 20 nm, begins when the material reaches its solid hyperstatic state, and the second about 1 or 2 nm. The first class is associated with the porous space between the C-S-H hydrate clusters and the second with the internal porosity of the hydrate. The evolution of the active capillary radius as a function of the degree of hydration allows us to understand the strong interaction between the capillary network size and the chemical activity given by the dissipated calorimetric power curve. Indeed, the maximum point of the chemical activity marks the transition of the first class of pores to the second one. Finally, measurements of electrical conductivity through RPC samples show that after the maximum of the dissipated power, the curve of this electrical conductivity presents the same evolution as the capillary radius. As the electrical conductivity clearly depends on the evolution of the capillary network, the similarity between the results confirms our analysis in pore classes. 相似文献
996.
997.
998.
999.
Khomyakov A. P. Kashcheev I. D. Komolikov Yu. I. 《Refractories and Industrial Ceramics》2003,44(6):424-426
Results of an experimental study of the aerodynamics and spray density distribution of a liquid dispersed by an airstream atomizer inside a drying chamber. Velocity components of the drying agent and their radial distributions as a function of the distance from the spray plane are determined. Relationships for the distribution of dispersed liquid inside the drying chamber are derived. Interactions between the drying agent and the product in the drying chamber are analyzed. 相似文献
1000.