全文获取类型
收费全文 | 155116篇 |
免费 | 6262篇 |
国内免费 | 5924篇 |
专业分类
化学 | 71500篇 |
晶体学 | 1586篇 |
力学 | 11360篇 |
综合类 | 586篇 |
数学 | 39691篇 |
物理学 | 42579篇 |
出版年
2025年 | 108篇 |
2024年 | 917篇 |
2023年 | 1755篇 |
2022年 | 2539篇 |
2021年 | 2992篇 |
2020年 | 3312篇 |
2019年 | 3069篇 |
2018年 | 12145篇 |
2017年 | 11769篇 |
2016年 | 8879篇 |
2015年 | 4063篇 |
2014年 | 4103篇 |
2013年 | 5260篇 |
2012年 | 9615篇 |
2011年 | 16154篇 |
2010年 | 9528篇 |
2009年 | 9812篇 |
2008年 | 10594篇 |
2007年 | 12292篇 |
2006年 | 3797篇 |
2005年 | 4388篇 |
2004年 | 4008篇 |
2003年 | 3822篇 |
2002年 | 2687篇 |
2001年 | 1782篇 |
2000年 | 1737篇 |
1999年 | 1746篇 |
1998年 | 1550篇 |
1997年 | 1323篇 |
1996年 | 1435篇 |
1995年 | 1204篇 |
1994年 | 1098篇 |
1993年 | 983篇 |
1992年 | 840篇 |
1991年 | 736篇 |
1990年 | 633篇 |
1989年 | 574篇 |
1988年 | 456篇 |
1987年 | 419篇 |
1986年 | 361篇 |
1985年 | 354篇 |
1984年 | 246篇 |
1983年 | 214篇 |
1982年 | 186篇 |
1981年 | 157篇 |
1980年 | 132篇 |
1979年 | 94篇 |
1978年 | 99篇 |
1975年 | 74篇 |
1973年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
172.
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
173.
174.
A. Jullien X. Chen A. Ricci J.-P. Rousseau R. Lopez-Martens L. P. Ramirez D. Papadopoulos A. Pellegrina F. Druon P. Georges 《Applied physics. B, Lasers and optics》2011,102(4):769-774
A 80???J, 6?fs, CEP-stable high-contrast injector is demonstrated. The device relies on standard pulse post-compression in hollow-core fiber followed by a temporal filter based on cross-polarized wave generation. Pulses with a Gaussian spectrum over 350?nm, centered at 750?nm, are generated. Temporal measurements show that the contrast of the few-cycle pulses is enhanced on a femtosecond and picosecond time scale. The carrier-envelope phase stability is preserved (0.3?rad RMS). These performances make the system an ideal seed laser for high-power, high-contrast OPCPA systems. 相似文献
175.
We present comprehensive studies on thin diffraction lenses made of arrays of subwavelength, parallel nanoslits in a gold film. Such a nanoslit lens can operate either as a conventional convex or concave lens. The lenses can be designed to focus linearly polarized light with polarization either perpendicular (TM-lens) or parallel to the slits (TE-lens), while the orthogonal polarization diverges when passing through the lens. The designs of each lens are initially built on the dispersion relations for wave propagation through a parallel-plate waveguide. Both TM- and TE-lenses were realized experimentally, and full-wave numerical simulations fully support the experimental results. 相似文献
176.
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
177.
178.
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
179.
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
180.
The surface profiler has become a basic metrology tool for the characterization of high-quality optical surfaces. The unknown effective resolution of the surface profiler is problematic in using the instrument, as it distorts the measured surface profile. In this paper, we suggest and describe the use of a fractal surface as a standard test surface with which to calibrate the effective resolution of a surface profiler. Fractal surfaces have the characteristics of irregularity, self-similarity and low correlation, with the correlation length being approximately equal to the length of the profile; therefore, a log-log plot of the power spectral density curve is a straight line. The power spectral density curves of fractal surfaces, which can be acquired through surface characterization techniques such as atomic force microscopy, are fitted to a straight line to act as a standard with which to calibrate an optical profiler in different ranges. Through calibration, we can obtain the effective resolution of the optical profiler, and the surface profiler is found to have good transmission capacity within the effective spatial frequency range. 相似文献