全文获取类型
收费全文 | 730篇 |
免费 | 58篇 |
国内免费 | 15篇 |
专业分类
化学 | 39篇 |
晶体学 | 1篇 |
力学 | 71篇 |
综合类 | 3篇 |
数学 | 44篇 |
物理学 | 333篇 |
综合类 | 312篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 19篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 58篇 |
2013年 | 48篇 |
2012年 | 34篇 |
2011年 | 57篇 |
2010年 | 30篇 |
2009年 | 48篇 |
2008年 | 43篇 |
2007年 | 61篇 |
2006年 | 26篇 |
2005年 | 47篇 |
2004年 | 36篇 |
2003年 | 34篇 |
2002年 | 33篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有803条查询结果,搜索用时 15 毫秒
81.
金属成型特殊非协调大变形有限元数值模拟 总被引:2,自引:0,他引:2
在金属成型领域,一种较新的特殊非协调大变形有限元法,即增强假设应变有限元法(简称EASM)已被研究用于进行数值模拟.为使该方法可适用于分析压缩大变形问题,对原由Simo提出的EASM列式进行了修正并编制了用于数值模拟变形过程的增强假设应变有限元程序EAS.FOR,通过2个标准算例来验证该方法的可行性和有效性. 相似文献
82.
A rationally mode-locked 10 GHz erbium fiber laser stabilized by a simple technique for extended time operation is described. The laser generates stable ~ 5 ps pulses that can be used in communications experiments. Back-to-back bit error rate (BER) measurements confirmed error-free operation for 6-8 hours, giving an error floor below 10 -14 . A receiver sensitivity of -19.7 dBm was achieved for BER of 10 -9 . 相似文献
83.
Shenping Li K. T. Chan Hao Ding Zujie Fang 《Fiber and Integrated Optics》1998,17(2):113-118
Electrical wavelength switching of picosecond pulses was demonstrated in an actively mode-locked Er-doped fiber ring laser with fiber gratings by changing the electrical driving frequency of the modulator. Laser pulses switchable between two wavelengths spaced from 0.5 to 18 nm apart were achieved. The switching speed between the two wavelengths was of the order of several hundred kilohertz. 相似文献
84.
85.
K. U. Schreiber J. -P. R. Wells G. E. Stedman 《General Relativity and Gravitation》2008,40(5):935-943
Large ring lasers with a cavity Q well above 1012 are characterized by extremely narrow line-widths and high coherence. At this point, active Sagnac interferometers do not
quite reach the quantum limit. In this paper, we will explore the current status of this technology and look at the various
noise processes involved with large ring lasers rigidly mounted to the Earth crust. 相似文献
86.
Masoud Kasraian 《International Journal of Infrared and Millimeter Waves》1994,15(11):1923-1936
An analytical treatment of the second-order Bragg interaction is presented for the transverse magnetic mode of a dielectric film waveguide having gratings on both the film-cover and the film-substrate interfaces. Four canonical equations that describe the interactions of two guided waves propagating in the opposite directions in the film and the normally incident and radiated free waves in the cover and the substrate are deduced. 相似文献
87.
D. von der Linde 《Applied Physics A: Materials Science & Processing》1973,2(6):281-296
This article reviews some aspects of the generation of very short optical pulses using mode-locked lasers, with the emphasis
laid on pulsed laser systems. Active and passive mode-locking is discussed, and the problem of measuring ultrashort light
pulses is considered. A survey of some commonly used sources and techniques for the generation of ultrashort light pulses
follows. The paper concludes with a short account of limitations in the generation and propagation of these pulses. 相似文献
88.
89.
A surface wave of frequency lying within bulk band of transverse waves is found in an elastic medium coated with a thin layer endowed with a surface mass density, surface Young's modulus and surface bending modulus. The wave is a particular case of surface resonance with infinite lifetime. In materials with negative Poisson's ratio (auxetics) the wave exists even for coating material with zero bending modulus, whereas with positive Poisson's ratio it requires the surface bending modulus to be larger than the surface Young's modulus. The manifestation of this wave in the reflection coefficient seems promising for fabrication of devices showing monochromator properties. 相似文献
90.
李世红 《广西民族大学学报》2004,10(3):90-92
该文分析了民族院校教育信息化的外部环境和内在因素与东部院校的差别,对民族院校在教育信息化过程中应用教育技术的方式、措施与经验进行了总结与探讨,并对民族院校应用教育技术的模式进行了探索. 相似文献