全文获取类型
收费全文 | 5055篇 |
免费 | 544篇 |
国内免费 | 411篇 |
专业分类
化学 | 1575篇 |
晶体学 | 40篇 |
力学 | 1194篇 |
综合类 | 115篇 |
数学 | 1118篇 |
物理学 | 1968篇 |
出版年
2024年 | 8篇 |
2023年 | 31篇 |
2022年 | 128篇 |
2021年 | 142篇 |
2020年 | 133篇 |
2019年 | 124篇 |
2018年 | 114篇 |
2017年 | 156篇 |
2016年 | 198篇 |
2015年 | 148篇 |
2014年 | 220篇 |
2013年 | 336篇 |
2012年 | 314篇 |
2011年 | 309篇 |
2010年 | 261篇 |
2009年 | 321篇 |
2008年 | 334篇 |
2007年 | 277篇 |
2006年 | 319篇 |
2005年 | 222篇 |
2004年 | 245篇 |
2003年 | 192篇 |
2002年 | 191篇 |
2001年 | 190篇 |
2000年 | 144篇 |
1999年 | 142篇 |
1998年 | 110篇 |
1997年 | 102篇 |
1996年 | 92篇 |
1995年 | 81篇 |
1994年 | 61篇 |
1993年 | 53篇 |
1992年 | 45篇 |
1991年 | 43篇 |
1990年 | 43篇 |
1989年 | 39篇 |
1988年 | 18篇 |
1987年 | 27篇 |
1986年 | 22篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 16篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1975年 | 2篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有6010条查询结果,搜索用时 15 毫秒
121.
Yangsheng Yuan Yangjian Cai Jun Qu Halil T. Eyyubo?lu Yahya Baykal 《Optics & Laser Technology》2010,42(8):1344-1348
Based on the extended Huygens–Fresnel integral and the second-order moments of the Wigner distribution function, an analytical formulae for the propagation factors (M2-factors) of coherent and partially coherent one-dimensional Hermite–Gaussian beams in a turbulent atmosphere are derived. Evolution properties of the M2-factor of the Hermite–Gaussian beam in a turbulent atmosphere are studied numerically in detail. Our results show that the M2-factor of the Hermite–Gaussian beam increases upon propagation in a turbulent atmosphere. The M2-factor of the Hermite–Gaussian beam with larger beam order (or lower coherence) increases slower that of the Hermite–Gaussian beam with smaller beam order (or higher coherence) in a turbulent atmosphere, which means that the Hermite–Gaussian beam with a larger beam order and lower coherence is less affected by a turbulent atmosphere. Our results will be useful in long-distance free-space optical communications. 相似文献
122.
123.
Akira ICHIHARA 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(7):707-716
This article summarizes my research over 40 years. The main theme of my work is nitrogen metabolism of amino acids, though later I focused on protein turnover in the cell. In the first years of my research work, I was busy dissecting the pathways involved in the metabolism of certain amino acids and their related enzymes. Then I became interested in the physiology and regulation of matabolism of these amino acids. For that, I used primary cultured hepatocytes, which contain many liver-specific enzymes. However, this play field was very rough around 1970 and hence I had to smooth them (differentiated) first. We discovered a specific growth factor (hepatocyte growth factor, HGF) in rat platelets. Exceptionally, I also worked on branched chain amino acids (valine, leucine and isoleucine). These amino acids are not efficiently metabolized in the liver, so I had to consider the physiology of extrahepatic tissues as well. Finally, I came across a huge protease complex, the proteasome. Whether these players, small amino acid metabolizing enzymes and the huge protease complex, danced well in harmony on my playground or not, I still do not know. 相似文献
124.
1.IntroductionInthepastfe\\'ycarsltllcil1tcnsity-momentsmethodandtheM2factorhavebeenre-vea1edtobeveryuscfulrotlcscribethepropagationlawandthebeamqualityofastaticlightbeam[l~Jj.Rccent1y,1ncji:1sctal.generalizedtheintensitymomentsmethodfortheSCLQ(speetral1y`"el1-centcrcdandlocallyquasi-monochromatic)pulsedlightboms[5j.Itisapparentthatthosercsu]tsubtainedinreferenceL5]areon1yvalidfortheso-calledquasi-monochromaticlightbeamsandarenotvalidforgeneralpolychromaticpulsedlightbeams,esPeciallyaredono… 相似文献
125.
Huey-Wen Lin 《中国物理 C》2009,33(12):1238-1243
In this proceeding, I review the attempts to calculate the Nucleon resonance (including Roper as first radially excited state of nucleon and other excited states) using lattice quantum chromodynamics (QCD). The latest preliminary results from Hadron Spectrum Collaboration (HSC) with mπ≈ 380 MeV are reported. The Sachs electric form factor of the proton and neutron and their transition with the Roper at large Q2 are also updated in this work. 相似文献
126.
127.
128.
M. Fujita T. Endo A. Yamazaki T. Sonada T. Miyake E. Tanaka T. Shinozuka T. Suzuki A. Goto Y. Miyashita N. Sato Y. Wakabayashi N. Hokoiwa M. Kibe Y. Gono T. Fukuchi A. Odahara 《Hyperfine Interactions》2004,159(1-4):245-249
The g-factor of the 27− isomer state of 152Dy has been measured using the Time-Integral Perturbed Angular Distribution (TIPAD) method. The high-spin states of 152Dy have been populated by 141Pr(16O,p4n)152Dy reaction at E = 115 MeV from the AVF cyclotron at CYRIC. The paramagnetic correction factor of Dy ions in Pr has been determined to be
4.2(5) by the Time-Differential Perturbed Angular Distribution (TDPAD) measurement of the 21− state of 152Dy. As a result, the g-factor of the 27− isomer state of 152Dy has been obtained to be +0.09(5). This shows the smaller value than the expected one of +0.39 deduced from a fully aligned
configuration of π(h
11/2
2) ⊗ ν(f
7/2
2
h
9/2
i
13/2). 相似文献
129.
SHI Yingtian SHI Bingren 《核工业西南物理研究院年报(英文版)》2004,(1):133-134
The safety most important factor profile is one of the the plasma discharge. For limiter configuration, people usually use the following cylindrical approximation formula to calculate it q(r)=5r^2BT/RIp where r is the minor radius of the plasma toms, R is the major radius (in m) , BT is the toroidal magnetic field (in T), Ip is the total toroidal current(in MA). 相似文献
130.
Transient saturation absorption spectroscopy excited near the band gap at high excitation carrier density in GaAs 下载免费PDF全文
Transient saturation absorption spectroscopy in GaAs thin films was investigated using femtosecond pump and supercontinuum probe technique at excitation densities higher than 1×10^{19}cm^{-3}. The Coulomb enhancement factor of the electron-hole plasma results in a spectrum hole at the pump wavelength. Two distinct transmission peaks at two sides of the pump wavelength are observed, arising from the bleaching of transitions from the heavy- and light-hole bands to the conduction band. The dynamic process of the transient saturation absorption is fitted using a bi-exponential function. The fast decay process is dominated by the carrier-phonon scattering and the slow process may be attributed to the electron-hole recombination. 相似文献