全文获取类型
收费全文 | 11737篇 |
免费 | 2200篇 |
国内免费 | 1378篇 |
专业分类
化学 | 8019篇 |
晶体学 | 162篇 |
力学 | 822篇 |
综合类 | 105篇 |
数学 | 1250篇 |
物理学 | 4957篇 |
出版年
2024年 | 39篇 |
2023年 | 279篇 |
2022年 | 469篇 |
2021年 | 535篇 |
2020年 | 498篇 |
2019年 | 506篇 |
2018年 | 431篇 |
2017年 | 385篇 |
2016年 | 623篇 |
2015年 | 590篇 |
2014年 | 705篇 |
2013年 | 842篇 |
2012年 | 1074篇 |
2011年 | 1029篇 |
2010年 | 803篇 |
2009年 | 738篇 |
2008年 | 718篇 |
2007年 | 633篇 |
2006年 | 648篇 |
2005年 | 565篇 |
2004年 | 370篇 |
2003年 | 310篇 |
2002年 | 311篇 |
2001年 | 231篇 |
2000年 | 211篇 |
1999年 | 211篇 |
1998年 | 177篇 |
1997年 | 204篇 |
1996年 | 180篇 |
1995年 | 163篇 |
1994年 | 138篇 |
1993年 | 99篇 |
1992年 | 88篇 |
1991年 | 80篇 |
1990年 | 78篇 |
1989年 | 69篇 |
1988年 | 53篇 |
1987年 | 29篇 |
1986年 | 44篇 |
1985年 | 32篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1975年 | 7篇 |
1973年 | 4篇 |
1972年 | 7篇 |
1965年 | 6篇 |
1964年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
871.
Wang X. Li P. Yang H. Jiang T. Ma Y. Fan Z. Niu G. Yu J. Wang A. Zhang Z. 《Laser Physics》2011,21(11):1941-1944
An all-fiber high-energy nonlinear chirped-pulse amplification system with two-stage double-cladding fiber amplifiers is presented
in this paper. It generates pulses with the energy up to 10 μJ at 20 kHz repetition rate and total accumulated nonlinear phase
shift as large as 12.8π. The pulses can be compressed to 137 fs with the compensation of mismatched third-order dispersion
by self-phase modulation in the fiber amplifiers. 相似文献
872.
A passively Q-switched 1.06 μm laser with Cr4+:YAG saturable absorber by direct 879 nm diode pumping grown-together composite GdVO4/Nd:GdVO4 crystal to the emitting level was demonstrated in this paper. The characteristics of pulsed laser were investigated by using
two kinds of Cr4+:YAG crystal with the initial transmissivity of 80 and 90%, respectively. When the T
0 = 90% Cr4+:YAG was used, an average output power of 1.59 W was achieved at an incident pump power of 10 W. The pulse width and repetition
rate were 64.5 ns and 170 kHz, respectively. The thermal lens effect of laser crystal was analyzed. 相似文献
873.
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
874.
Fabien Durand Ai-Hua Fan Andrei Yu. Khrennikov Dongdai Lin Franco Vivaldi Yuefei Wang 《P-Adic Numbers, Ultrametric Analysis, and Applications》2011,3(4):359-362
On the occasion of the 60th birthday of Professor Vladimir Sergeevich Anashin, we present a review of his significant scientific
research and related activities. 相似文献
875.
Ye-jun Xu Jun Song Hong-yi Fan Qiu-yu Liu 《International Journal of Theoretical Physics》2011,50(3):744-751
By virtue of deformation quantization methods we introduce the q-deformed coordinate representation. A new set of completeness and orthogonality relations composed of the ket and bra which
are not mutually Hermitian conjugates are derived. Further, using the eigenket and eigenbra for q-deformed coordinate some important quantum gate operators for continuum variables are realized and their properties are discussed. 相似文献
876.
Zhengang Lu Jiubin Tan Jing Qi Zhigang Fan Luyang Zhang 《Optics Communications》2011,284(16-17):3855-3861
In order to analyze the Fraunhofer diffractive characteristics and modulation transfer function (MTF) of a tilted ring metallic mesh, an optical intensity distribution model of Fraunhofer diffraction is built using Huygens–Fresnel diffraction theory and the diffraction integral is carried out directly in the tilted mesh plane. The diffraction characteristics of the tilted ring metallic mesh are in good agreement with experimental results, which proves the correctness of the model established. MTF of an optical system with metallic mesh is calculated based on the model established and Fourier transform. Analysis shows that the degradation of MTF caused by diffraction of a ring mesh is much less than that of a square mesh whether they are vertical or tilted to the optical axis. Therefore, ring mesh can provide higher imaging quality than square mesh when they are used as high-pass filters in optical windows. A tilted array diffraction modulating factor is abstracted and believed useful in the analysis of diffractive characteristics of tilted square mesh and ring mesh, and it can be extended to Fraunhofer diffractive characteristics analysis of other tilted diffraction arrays. 相似文献
877.
A class of active fiber is presented as gain mediums of fiber lasers, where a silica layer with spoke-like air slits is introduced between the active core and cladding to obtain birefringence. With an appropriate choice of the design parameters, the fiber can support only the HE11 and TM01 modes. Furthermore, the numerical results show that, corresponding to the optimal rare earth doping profile, the fiber lasers can output a pure TM01 mode with about 79% slope efficiency without using other mode-selective elements. 相似文献
878.
879.
We experimentally demonstrate cavity phase matching for the first time using a sheet optical parametric oscillator which is made of an x-cut KTiOPO(4) crystal sheet. This microcavity presents 220 kW peak power capability for near-frequency-degenerate parametric outputs with up to 23.8% slope efficiency. It also features unique spectral characteristics such as single-longitudinal-mode and narrow linewidth. These attractive properties predict broad applications of such a mini-device, such as terahertz generation, photonic integration, spectroscopy, and quantum information, etc. 相似文献
880.
We computationally study shear-induced segregation of different-sized particles in vertical chute flow. We find that, for low solid fractions, large particles segregate toward regions of low shear rates where the granular temperature (velocity variance) is low. As the solid fraction increases, this trend reverses, and large particles segregate toward regions of high shear rates and temperatures. We find that this is a global phenomenon: local segregation trends reverse at high system solid fractions even where local solid fractions are small. The reversal corresponds to the growth of a single enduring cluster of 30%-60% of the particles that we propose changes the segregation dynamics. 相似文献