全文获取类型
收费全文 | 87296篇 |
免费 | 1443篇 |
国内免费 | 1300篇 |
专业分类
化学 | 30483篇 |
晶体学 | 883篇 |
力学 | 7137篇 |
综合类 | 92篇 |
数学 | 32732篇 |
物理学 | 18712篇 |
出版年
2024年 | 131篇 |
2023年 | 230篇 |
2022年 | 378篇 |
2021年 | 457篇 |
2020年 | 505篇 |
2019年 | 579篇 |
2018年 | 10733篇 |
2017年 | 10539篇 |
2016年 | 6534篇 |
2015年 | 1334篇 |
2014年 | 867篇 |
2013年 | 1001篇 |
2012年 | 4607篇 |
2011年 | 11250篇 |
2010年 | 6194篇 |
2009年 | 6503篇 |
2008年 | 7113篇 |
2007年 | 9242篇 |
2006年 | 635篇 |
2005年 | 1623篇 |
2004年 | 1749篇 |
2003年 | 2177篇 |
2002年 | 1264篇 |
2001年 | 490篇 |
2000年 | 430篇 |
1999年 | 335篇 |
1998年 | 314篇 |
1997年 | 225篇 |
1996年 | 272篇 |
1995年 | 169篇 |
1994年 | 136篇 |
1993年 | 152篇 |
1992年 | 104篇 |
1991年 | 113篇 |
1990年 | 90篇 |
1989年 | 92篇 |
1988年 | 80篇 |
1987年 | 76篇 |
1986年 | 69篇 |
1985年 | 54篇 |
1984年 | 48篇 |
1983年 | 45篇 |
1982年 | 44篇 |
1980年 | 48篇 |
1979年 | 46篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
We apply the recently improved version of the 0–1 test for chaos to real experimental time series of laser droplet generation process. In particular two marginal regimes of dripping are considered: spontaneous and forced dripping. The outcomes of the test reveal that both spontaneous and forced dripping time series can be characterized as chaotic, which coincides with the previous analysis based on nonlinear time series analysis. 相似文献
52.
A review is given of the StandardSU(5) supergravity model. This model has passed an important check regarding unification of the electro-weak and the strong couplings using high precision LEP data. It is shown that for a significant domain of the parameter space the model also satisfies constraints on the SUSY spectrum from CDF and LEP, as well as proton stability and cosmological relic density constraints. 相似文献
53.
X. L. Zhang X. Y. Zhang Q. P. Wang C. Wang H. H. Xu Y. Tang L. Li Z. J. Liu X. H. Chen S. Z. Fan Z. T. Jia X. T. Tao 《Laser Physics》2011,21(6):1047-1050
A diode-side-pumped continuous-wave Nd:GGG laser operating at dual-wavelength (1110 and 1105 nm) and single wavelength of 1110 nm is demonstrated for the first time. The maximum output power of the 1110 and 1105 nm dual-wavelength operation is 13.2 W. By adjusting the orientation of an insertion mirror, the relative intensities of the two wavelengths can be changed. Thus single wavelength operation at 1110 nm is obtained, and the output power is 9.6 W. 相似文献
54.
Jia Li Yanru Chen Shixue Xu Yongqing Wang Muchun Zhou Qi Zhao Yu Xin Feinan Chen 《Optics & Laser Technology》2011,43(1):152-157
Based on the vector angular spectrum representation of electromagnetic beams and the method of stationary phase, the vectorial structure of a Hermite-cosine-Gaussian (HcosG) beam in the far field is derived in analytical form. Energy flux distributions for the TE term, TM term and the whole beam are represented. The vectorial structures of HcosG beams with different Hermite models are depicted. The effects of cosine displacement parameters on the vectorial structure are also demonstrated. The results may provide a flexible approach to manipulate HcosG beams in free space. 相似文献
55.
56.
V. P. Silva Neto C. F. L. Vasconcelos M. R. M. L. Albuquerque A. G. D’Assunção 《Applied Physics A: Materials Science & Processing》2014,115(2):421-425
This work presents an analysis of the microstrip bandpass filter on metamaterial substrates. The filter is composed of two ring resonators with quarter-wavelength side-coupled sections. The filter input is provided, as well as the output port, using a quarter-wavelength side-coupled microstrip line section. Simulations by finite element method have been carried out to verify the effect of the metamaterial substrate properties on the filter performance, and to compare these results to those obtained considering isotropic substrate. 相似文献
57.
58.
59.
Tianqing Jia Motoyoshi Baba Fuli Zhao Xiaojun Wu Masayuki Suzuki Zhizhan Xu 《Solid State Communications》2007,141(11):635-638
We present a simple route for ZnSe nanowire growth in the ablation crater on a ZnSe crystal surface. The crystal wafer, which was horizontally dipped in pure water, was irradiated by femtosecond laser pulses. No furnace, vacuum chamber or any metal catalyst were used in this experiment. The size of the nanowires is about 1-3 μm long and 50-150 nm in diameter. The growth rate is 1-3 μm/s, which is much higher than that achieved with molecular-beam epitaxy and chemical vapor deposition methods. Our discovery reveals a rapid and simple way to grow nanowires on designed micro-patterns, which may have potential applications in microscopic optoelectronics. 相似文献
60.
We model and study the asymmetric long-range surface-plasmon waveguides using the finite-element method. We introduce two types of asymmetric structures and discuss their modal properties compared to traditional long-range surface-plasmon waveguides. Although the propagation distance is decreased, the energy-confinement capability is improved for asymmetric long-range waveguiding structures when the geometrical parameters are properly selected. Our simulation result offers guidance for tuning properties of plasmonic waveguides and providing ways for enhancing electromagnetic energy confinement in long-range surface-plasmon waveguides. 相似文献