全文获取类型
收费全文 | 490071篇 |
免费 | 4119篇 |
国内免费 | 1467篇 |
专业分类
化学 | 252858篇 |
晶体学 | 7363篇 |
力学 | 24102篇 |
综合类 | 15篇 |
数学 | 57755篇 |
物理学 | 153564篇 |
出版年
2020年 | 4150篇 |
2019年 | 4764篇 |
2018年 | 6299篇 |
2017年 | 6376篇 |
2016年 | 9008篇 |
2015年 | 5372篇 |
2014年 | 8614篇 |
2013年 | 21287篇 |
2012年 | 16704篇 |
2011年 | 20253篇 |
2010年 | 14417篇 |
2009年 | 14582篇 |
2008年 | 18790篇 |
2007年 | 18878篇 |
2006年 | 17707篇 |
2005年 | 15966篇 |
2004年 | 14909篇 |
2003年 | 13216篇 |
2002年 | 13076篇 |
2001年 | 14932篇 |
2000年 | 11304篇 |
1999年 | 8767篇 |
1998年 | 7261篇 |
1997年 | 7157篇 |
1996年 | 6692篇 |
1995年 | 6134篇 |
1994年 | 5878篇 |
1993年 | 5732篇 |
1992年 | 6298篇 |
1991年 | 6554篇 |
1990年 | 6176篇 |
1989年 | 6084篇 |
1988年 | 6027篇 |
1987年 | 5989篇 |
1986年 | 5619篇 |
1985年 | 7483篇 |
1984年 | 7736篇 |
1983年 | 6397篇 |
1982年 | 6790篇 |
1981年 | 6602篇 |
1980年 | 6262篇 |
1979年 | 6549篇 |
1978年 | 6819篇 |
1977年 | 6902篇 |
1976年 | 6990篇 |
1975年 | 6583篇 |
1974年 | 6483篇 |
1973年 | 6765篇 |
1972年 | 4651篇 |
1971年 | 3823篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 212–217, August, 1989. 相似文献
42.
43.
We demonstrate a method that permits to obtain generalized solutions for some quasilinear equations and systems of hyperbolic
type. The corresponding variational principle is constructed using the theory of equilibrium of a potential in an external
field.
Dedicated to the memory of B. M. Levitan
Supported by RFBR grants Nos. 05-01-00522 and NSh-1551.2003.1, by Program No. 1 of the Branch of Mathematics, Russian Academy
of Sciences, and by INTAS project No. 03-51-6637. 相似文献
44.
T. Kumita Y. Kamiya M. Babzien I. Ben-Zvi K. Kusche I. V. Pavlishin I. V. Pogorelsky D. P. Siddons V. Yakimenko T. Hirose T. Omori J. Urakawa K. Yokoya D. Cline F. Zhou 《Laser Physics》2006,16(2):267-271
Thomson scattering of high-power laser and electron beams is a good test of electrodynamics in the high-field region. We demonstrated production of high-intensity X-rays in the head-on collision of a CO2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. The energy of an X-ray photon was limited at 6.5 keV in the linear (lowest order) Thomson scattering, but the nonlinear (higher order) process produces higher energy X-rays. We measured the angular distribution of the high-energy X-rays and confirmed that it agrees with theoretical predictions. 相似文献
45.
General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
D.T. Son 《Annals of Physics》2006,321(1):197-224
We show that the Lagrangian for interacting nonrelativistic particles can be coupled to an external gauge field and metric tensor in a way that exhibits a nonrelativistic version of general coordinate invariance. We explore the consequences of this invariance on the example of the degenerate Fermi gas at infinite scattering length, where conformal invariance also plays an important role. We find the most general effective Lagrangian consistent with both general coordinate and conformal invariance to leading and next-to-leading orders in the momentum expansion. At the leading order the Lagrangian contains one phenomenological constant and reproduces the results of the Thomas-Fermi theory and superfluid hydrodynamics. At the next-to-leading order there are two additional constants. We express various physical quantities through these constants. 相似文献
46.
The spatial structure of Bragg angles and the transfer functions of an acousto-optic cell are calculated for the cases of isotropic and anisotropic light diffraction in a uniaxial crystal. Their change with ultrasound frequency is traced. The possibility of image processing by acousto-optic filtration of the spatial spectrum of an image is considered. The results of experimental visualization of the transfer functions of a calcium molybdate crystal cell are presented. 相似文献
47.
The sound field in the region of a deep shadow behind an impedance cylinder is analyzed for the case of plane wave diffraction by the cylinder surface. The main part of the field is represented by a cylindrical wave that has a complex index determined from the boundary conditions and decays with the angular coordinate. An expression for the amplitude of this wave is determined by extracting it from the total field formed in the shadow region. It is demonstrated that this wave approximates more closely the total field behind the cylinder, as compared to the least damped wave in the field representation obtained on the basis of the Watson transform. A way to improve the sound barriers is indicated. 相似文献
48.
Using Wagner's polarization technique and EMF method the joinic and silver ionic transport number measurements of various
compositions of the mixed system CdI2-Ag2O-CrO3 have been made. The presence of AgI in these materials has been inferred from the typical β → α phase transition of AgI,
which is characterized by an endothermic peak at around 420 K in the DSC traces of these specimens. While the structural analysis
performed by means of powder X-ray diffraction has revealed the formation of ionic phases involving polycrystalline compounds,
the Fourier transform infrared (FTIR) spectroscopic results have indicated the presence of ionic species thus confirming the
ionic nature of the products. The complex impedance studies carried out in the frequency range 20 Hz - 1 MHz and over the
temperature range 294 – 442 K have revealed that the best conducting composition, namely 55%(CdI2) – 45%(Ag2O·CrO3), would exhibit a silver ionic conductivity of 1.3×10−5Scm−1 at 294 K. 相似文献
49.
Franz H. Asthalter T. Dommach M. Ehnes A. Messel K. Sergueev I. 《Hyperfine Interactions》2002,141(1-4):131-134
The present status of the new nuclear resonance beamline PETRA 1 at HASYLAB, DESY, Hamburg is described. Besides an overview
of the experimental setup some examples of recent experiments are given. Those cover the main applications, i.e., inelastic
scattering from iron alloys and quasielastic scattering from glass-forming liquids.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
50.