全文获取类型
收费全文 | 538937篇 |
免费 | 4598篇 |
国内免费 | 1284篇 |
专业分类
化学 | 276321篇 |
晶体学 | 7707篇 |
力学 | 26211篇 |
综合类 | 17篇 |
数学 | 69359篇 |
物理学 | 165204篇 |
出版年
2021年 | 5135篇 |
2020年 | 5628篇 |
2019年 | 6389篇 |
2018年 | 8522篇 |
2017年 | 8672篇 |
2016年 | 11993篇 |
2015年 | 6550篇 |
2014年 | 10842篇 |
2013年 | 24254篇 |
2012年 | 19136篇 |
2011年 | 22500篇 |
2010年 | 16866篇 |
2009年 | 16632篇 |
2008年 | 21320篇 |
2007年 | 21111篇 |
2006年 | 19260篇 |
2005年 | 17174篇 |
2004年 | 15923篇 |
2003年 | 14347篇 |
2002年 | 14195篇 |
2001年 | 14871篇 |
2000年 | 11488篇 |
1999年 | 8840篇 |
1998年 | 7673篇 |
1997年 | 7539篇 |
1996年 | 7028篇 |
1995年 | 6334篇 |
1994年 | 6322篇 |
1993年 | 6103篇 |
1992年 | 6445篇 |
1991年 | 6915篇 |
1990年 | 6623篇 |
1989年 | 6527篇 |
1988年 | 6366篇 |
1987年 | 6171篇 |
1986年 | 5934篇 |
1985年 | 7490篇 |
1984年 | 7833篇 |
1983年 | 6562篇 |
1982年 | 6873篇 |
1981年 | 6379篇 |
1980年 | 6066篇 |
1979年 | 6557篇 |
1978年 | 6794篇 |
1977年 | 6677篇 |
1976年 | 6638篇 |
1975年 | 6333篇 |
1974年 | 6163篇 |
1973年 | 6456篇 |
1972年 | 4730篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
391.
We show that, contrary to earlier reports, application of the one-parameter variational technique to the classical (image) model for H in front of an Al surface leads to energy shifts for the ground state which are very close to those obtained numerically with a more sophisticated model of the system. 相似文献
392.
393.
The effect of 57Fe hyperfine interaction radiofrequency (rf) modulation by external rotating magnetic field was studied in thin Permalloy foil by means of Mössbauer spectroscopy. The rf effect was investigated as a function of intensity for several rf field frequencies. The experiments show that the external rotating rf field causes considerable changes in the hyperfine pattern. The obtained spectra are in disagreement with those obtained by Perlow [Phys. Rev. 172 (1968) 319]. They also are inconsistent with magnetostriction hypothesis. Proceeding from the Mössbauer spectrum analysis one may conclude that the magnetization of investigated foil changes its direction in a complex manner. However, the undertaken experiments show that the essential number of Mössbauer nuclei experience the rotating magnetic field influence. 相似文献
394.
395.
A. V. Kashevarov 《Fluid Dynamics》1997,32(6):905-907
It is shown that the exact solution of the problem of convective heat exchange in a low-Prandtl-number fluid flow (Pr ? 1) can be obtained for a two-dimensional body of arbitrary shape provided that the conformal mapping relating the body contour with a circle is known. By way of example, the Joukowsky airfoil is considered. 相似文献
396.
Mössbauer spectroscopy was used to investigate the reactions of microbes with iron minerals in aqueous solutions and as components of rocks in banded iron formations and granite. A microbial biofilm that formed on a wall of an excavated granite vault in a deep underground laboratory initiated this research. At the aerobic face of the biofilm, iron was found in a form of ferrihydrite; in the anaerobic face against the rock, iron was found as very small siderite particles. Laboratory incubations of the biofilm microbial consortium showed different mineral species could be formed. When the microbial consortium from the biofilm was incubated with magnetite grains, up to about 10% of the iron was altered in three weeks to hematite. The ability of the consortium to precipitate iron both as Fe2+ and Fe3+ in close proximity may have a bearing on the deposition of banded iron formations. These reactions could also be important in microbially induced corrosion. 相似文献
397.
A. V. Tsyganov 《Theoretical and Mathematical Physics》1998,115(1):377-395
A class of Hamiltonian dynamic systems integrated by the variable separation method is considered. The integration for this class is the inversion of an Abel mapping on hyperelliptic curves. We prove that the derivative of the Abel mapping is the Stäckel matrix, which determines a diagonal Riemannian metric and curvilinear orthogonal coordinate systems in a flat space. Lax representations with the spectral parameter are constructed. The corresponding classicalr-matrices are dynamic. It is shown how the class of pointwise canonical transformations can be naturally generalized using the Abel integral reduction theory. 相似文献
398.
A model kinetic equation is constructed for the transport of a massless Bose gas. This equation is applied to solve the boundary
value problem for the transport of radiation in the half-space occupied by a dispersive medium that is in local thermal equilibrium
with the radiation. It is shown that the difference in temperature between the dispersive medium and the incident radiation
substantially depends on the character of the scattering properties of the particles in the medium.
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 111, No. 3, pp. 462–472, June, 1997. 相似文献
399.
400.
R. Grac M. Pugnet J.H. Collet B. Lambert C. De Matos H. L'Haridon A. Le Corre J.O. White 《Superlattices and Microstructures》1997,22(4):505-509
We report new results on the diffraction properties of photoinduced gratings in InGaAs/InGaAsP MQW structures. The original feature of this device is that the QWs are enclosed in an asymmetric Fabry–Perot microcavity in order to increase the diffraction efficiency. We observe oscillations in the diffraction efficiency due to resonant effects in the microcavity. The experimental spectra are compared with theory. Diffraction efficiency at 1.55 μm attains a maximum value of 2.7% at a write beam fluence of 260 μ J cm−2, and then decreases at higher fluences. We explain this phenomenon by an absorption saturation at high excitation. 相似文献