全文获取类型
收费全文 | 376642篇 |
免费 | 4086篇 |
国内免费 | 1144篇 |
专业分类
电工技术 | 7121篇 |
综合类 | 256篇 |
化学工业 | 54419篇 |
金属工艺 | 16541篇 |
机械仪表 | 11739篇 |
建筑科学 | 7615篇 |
矿业工程 | 2709篇 |
能源动力 | 8748篇 |
轻工业 | 25631篇 |
水利工程 | 4335篇 |
石油天然气 | 9517篇 |
武器工业 | 29篇 |
无线电 | 45367篇 |
一般工业技术 | 77252篇 |
冶金工业 | 73536篇 |
原子能技术 | 9490篇 |
自动化技术 | 27567篇 |
出版年
2021年 | 3092篇 |
2019年 | 3059篇 |
2018年 | 5384篇 |
2017年 | 5449篇 |
2016年 | 5738篇 |
2015年 | 3495篇 |
2014年 | 5982篇 |
2013年 | 15709篇 |
2012年 | 9475篇 |
2011年 | 12473篇 |
2010年 | 10083篇 |
2009年 | 11478篇 |
2008年 | 11945篇 |
2007年 | 11838篇 |
2006年 | 10462篇 |
2005年 | 9694篇 |
2004年 | 9233篇 |
2003年 | 9024篇 |
2002年 | 8700篇 |
2001年 | 9052篇 |
2000年 | 8505篇 |
1999年 | 8949篇 |
1998年 | 23519篇 |
1997年 | 16055篇 |
1996年 | 12510篇 |
1995年 | 9233篇 |
1994年 | 8042篇 |
1993年 | 8210篇 |
1992年 | 5922篇 |
1991年 | 5840篇 |
1990年 | 5691篇 |
1989年 | 5478篇 |
1988年 | 5235篇 |
1987年 | 4441篇 |
1986年 | 4549篇 |
1985年 | 5109篇 |
1984年 | 4669篇 |
1983年 | 4290篇 |
1982年 | 3915篇 |
1981年 | 4024篇 |
1980年 | 3874篇 |
1979年 | 3791篇 |
1978年 | 3802篇 |
1977年 | 4243篇 |
1976年 | 5243篇 |
1975年 | 3373篇 |
1974年 | 3227篇 |
1973年 | 3263篇 |
1972年 | 2874篇 |
1971年 | 2547篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
David N. Johnson Alan A. Johnson 《Fatigue & Fracture of Engineering Materials & Structures》1985,8(3):287-294
The results of Stan ton and Bairstow (1908) have been reanalyzed to yield information on the composition dependence of the low cycle impact fatigue properties of pearlitic plain carbon steels. It has been found that the energy absorbed per impact, Ei, and the number of impacts are failure, Nf, are related by the equation: In this equation q is determined by the carbon, manganese and silicon contents of the steel; Eo is the impact endurance limit; and C and D are constants. The curve represented by this equation intersects that representing the Johnson-Keller high cycle impact fatigue equation at a value of logeNf equal to 1/C. Thus, the transition from low to high cycle impact fatigue occurs at this value of logeNf. 相似文献
992.
993.
Watson B. Kim J. Moher T. Hindo C. Mceneany T. Gomez L.M. Fransen S. 《Potentials, IEEE》2005,24(2):42-46
The StoryGrid project undertook studying the role new interface technologies might play in education, particularly at the high school level. Unfortunately, technology often seizes center stage in high school classrooms; i.e., it becomes the topic of instruction. We believe that learning about technology would be most successful when technology is not the topic, but simply a tool used during instruction. StoryGrid, therefore, was designed to support and to enhance existing narrative activity in classrooms by adhering to the following goals: trigger reflection and interpretation, accommodate individual expression and encourage student discourse. 相似文献
994.
995.
996.
997.
We study the nonlinear propagation of light in optical fibers in the strong nonlinearity limit. In this limit, the transverse guiding properties are altered and cannot be decoupled from the longitudinal part of the wave equation. We consider a refractive index profile with no bound modes at low intensities and show that stable self-guiding occurs at a critical intensity. This critical intensity is a property of the guide and can be made much lower than the threshold for unstable self-focusing. We consider a particular design for which self-guiding occurs at three orders of magnitude lower than the self-focusing threshold. 相似文献
998.
999.
A. O. Skomorokhov V. N. Kutinsky M. T. Slepov 《Pattern Recognition and Image Analysis》2006,16(1):85-88
The paper describes a few modifications of the classification tree construction algorithm that have proved to be useful for
solving tasks of noise spectra processing with reference to NPP diagnostics.
The article was translated by the authors. 相似文献
1000.