全文获取类型
收费全文 | 644788篇 |
免费 | 6414篇 |
国内免费 | 1640篇 |
专业分类
化学 | 329414篇 |
晶体学 | 9338篇 |
力学 | 32310篇 |
综合类 | 27篇 |
数学 | 86250篇 |
物理学 | 195503篇 |
出版年
2021年 | 5979篇 |
2020年 | 6531篇 |
2019年 | 7430篇 |
2018年 | 10054篇 |
2017年 | 10122篇 |
2016年 | 14225篇 |
2015年 | 7797篇 |
2014年 | 12855篇 |
2013年 | 29042篇 |
2012年 | 22737篇 |
2011年 | 26811篇 |
2010年 | 20044篇 |
2009年 | 19943篇 |
2008年 | 25282篇 |
2007年 | 25094篇 |
2006年 | 22748篇 |
2005年 | 20340篇 |
2004年 | 19026篇 |
2003年 | 17022篇 |
2002年 | 16787篇 |
2001年 | 17799篇 |
2000年 | 13732篇 |
1999年 | 10637篇 |
1998年 | 9122篇 |
1997年 | 9045篇 |
1996年 | 8530篇 |
1995年 | 7618篇 |
1994年 | 7712篇 |
1993年 | 7418篇 |
1992年 | 7968篇 |
1991年 | 8350篇 |
1990年 | 8072篇 |
1989年 | 7958篇 |
1988年 | 7757篇 |
1987年 | 7487篇 |
1986年 | 7211篇 |
1985年 | 9254篇 |
1984年 | 9679篇 |
1983年 | 8048篇 |
1982年 | 8286篇 |
1981年 | 7854篇 |
1980年 | 7437篇 |
1979年 | 8025篇 |
1978年 | 8262篇 |
1977年 | 8244篇 |
1976年 | 8206篇 |
1975年 | 7837篇 |
1974年 | 7615篇 |
1973年 | 7990篇 |
1972年 | 5858篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
851.
Marcelo Queiroz Joaquim Jú dice Carlos Humes Jr.. 《Mathematics of Computation》2004,73(248):1849-1863
In this paper the Eigenvalue Complementarity Problem (EiCP) with real symmetric matrices is addressed. It is shown that the symmetric (EiCP) is equivalent to finding an equilibrium solution of a differentiable optimization problem in a compact set. A necessary and sufficient condition for solvability is obtained which, when verified, gives a convenient starting point for any gradient-ascent local optimization method to converge to a solution of the (EiCP). It is further shown that similar results apply to the Symmetric Generalized Eigenvalue Complementarity Problem (GEiCP). Computational tests show that these reformulations improve the speed and robustness of the solution methods.
852.
V. A. Alekseev 《Optics and Spectroscopy》2004,96(4):492-496
The absorption spectra of Xe + CF4 and Kr + CF4 mixtures in the vacuum ultraviolet region are presented. A considerable broadening of the short-wavelength wings of the atomic absorption lines is explained by a repulsive character of the Rg*-CF4 interaction potential. This repulsive character is also considered to be the most probable reason for the anomalously small cross sections of the quenching of electronically excited atoms of rare gases by CF4 molecules. The influence of CF4 on the emission rate of the trapped resonance radiation of Xe from the cell is discussed. 相似文献
853.
854.
The pure state space of Quantum Mechanics is investigated as Hermitian Symmetric Kähler manifold. The classical principles of quantum mechanics (Quantum Superposition Principle, Heisenberg Uncertainty Principle, Quantum Probability Principle) and Spectral Theory of observables are discussed in this non-linear geometrical context. 相似文献
855.
M. A. Nikitina 《Russian Physics Journal》2003,46(3):296-304
The h
2-persistent multiple-access communication networks with discrete and continuous strategy of control of conflict messages are investigated. 相似文献
856.
857.
X-ray diffraction patterns of nanocrystalline Fe-Cu-Nb-Si-B (FINEMET) alloys reveal that bcc α-Fe/α-FeSi crystallites with
the average grain size of 20(5) nm are dispersed in amorphous matrix. Enhanced electron—electron interaction (EEI) and quantum
interference (QI) effects as well as electron-magnon (and/or electron-spin fluctuation) scattering turn out to be the main
mechanisms that govern the temperature dependence of resistivity. Of all the inelastic scattering processes, inelastic electron-phonon
scattering is the most effective mechanism to destroy phase coherence of electron wave functions. The diffusion constant,
density of states at the Fermi level and the inelastic scattering time have been estimated, for the first time, for the alloys
in question
Article presented at the International Symposium on Advances in Superconductivity and Magnetism: Materials, Mechanisms and
Devices, ASMM2D-2001, 25–28 September 2001, Mangalore, India. 相似文献
858.
Structure and magnetic properties of the Zr1−xMnxCo2+δ alloys were studied for 0 x <0.7, δ=0, 0.45. The cubic C15 Laves phase structure shows Mn solubility up to x≈0.4. The other Laves phase with the hexagonal C36 structure found for x0.5 apparently has a small region of Mn solubility in the vicinity of Zr0.4Mn0.6Co2. Though the parent Mn-free compounds are known to be paramagnetic, the Mn-substituted alloys show ferromagnetic behavior with the Curie temperatures up to 625 K and the room-temperature saturation magnetization of about 100 emu/g. The onset of ferromagnetism with the Mn substitution for Zr may be caused by polarization of itinerant 3d electrons, like it was earlier supposed for the off-stoichiometric ZrCo2+δ. The universal composition dependencies of the intrinsic magnetic properties for different δ can be obtained, if plotted against the amount of zirconium atoms missing in its sublattice. The room-temperature anisotropy with the noticeable anisotropy field of 24 kOe and the 1 1 0 easy magnetization direction laying in a basal plane was found in the hexagonal Zr0.5Mn0.5Co2. 相似文献
859.
S. J. Cheng W. Sheng P. Hawrylak S. Raymond S. Studenikin A. Sachrajda Z. Wasilewski A. Babinski M. Potemski G. Ortner M. Bayer 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):211
We present results of calculations and experiments on electron–hole complexes in InGaAs/GaAs self-assembled quantum dots in high magnetic field (B). Due to hidden symmetries, the chemical potential of an N-exciton system at special B fields becomes insensitive to the exciton number as well as the magnetic field. This results in plateau regions of high intensity in measured magneto-PL spectrum. Theoretical calculations using exact diagonalization techniques successfully explain the measured magneto-photoluminescence spectrum with B fields up to 28 T. 相似文献
860.
Jeroen J. L. M. Cornelissen W. Sander Graswinckel Alan E. Rowan Nico A. J. M. Sommerdijk Roeland J. M. Nolte 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1725-1736
The conformational properties of polymers derived from isocyanodipeptides have been investigated with a combination of model calculations, X‐ray diffraction, and circular dichroism spectroscopy. Depending on the configuration of the side chains, defined arrays of hydrogen bonds along the polymeric backbone are formed. This leads to a well‐defined conformation as, for example, expressed in the formation of lyotropic liquid‐crystalline phases and increased helical stability. Upon the disruption of the hydrogen bonds by a strong acid, a less well‐defined macromolecular conformation is observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1725–1736, 2003 相似文献