全文获取类型
收费全文 | 202958篇 |
免费 | 2513篇 |
国内免费 | 663篇 |
专业分类
化学 | 106363篇 |
晶体学 | 2589篇 |
力学 | 8222篇 |
综合类 | 12篇 |
数学 | 24507篇 |
物理学 | 64441篇 |
出版年
2021年 | 1636篇 |
2020年 | 1860篇 |
2019年 | 1941篇 |
2018年 | 2452篇 |
2017年 | 2474篇 |
2016年 | 3903篇 |
2015年 | 2513篇 |
2014年 | 3870篇 |
2013年 | 8978篇 |
2012年 | 7330篇 |
2011年 | 8726篇 |
2010年 | 6056篇 |
2009年 | 5975篇 |
2008年 | 8071篇 |
2007年 | 7992篇 |
2006年 | 7558篇 |
2005年 | 7376篇 |
2004年 | 6895篇 |
2003年 | 5884篇 |
2002年 | 5393篇 |
2001年 | 6008篇 |
2000年 | 4677篇 |
1999年 | 3417篇 |
1998年 | 2874篇 |
1997年 | 2786篇 |
1996年 | 2747篇 |
1995年 | 2582篇 |
1994年 | 2491篇 |
1993年 | 2453篇 |
1992年 | 2698篇 |
1991年 | 2573篇 |
1990年 | 2445篇 |
1989年 | 2370篇 |
1988年 | 2370篇 |
1987年 | 2359篇 |
1986年 | 2227篇 |
1985年 | 2943篇 |
1984年 | 2953篇 |
1983年 | 2585篇 |
1982年 | 2732篇 |
1981年 | 2524篇 |
1980年 | 2498篇 |
1979年 | 2640篇 |
1978年 | 2699篇 |
1977年 | 2578篇 |
1976年 | 2640篇 |
1975年 | 2527篇 |
1974年 | 2516篇 |
1973年 | 2679篇 |
1972年 | 1688篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
The differential systems satisfied by orthogonal polynomials with arbitrary semiclassical measures supported on contours in
the complex plane are derived, as well as the compatible systems of deformation equations obtained from varying such measures.
These are shown to preserve the generalized monodromy of the associated rank-2 rational covariant derivative operators. The
corresponding matrix models, consisting of unitarily diagonalizable matrices with spectra supported on these contours are
analyzed, and it is shown that all coefficients of the associated spectral curves are given by logarithmic derivatives of
the partition function or, more generally, the gap probabilities. The associated isomonodromic tau functions are shown to
coincide, within an explicitly computed factor, with these partition functions.
Research supported in part by the Natural Sciences and Engineering Research Council of Canada, the Fonds FCAR du Québec and
EC ITH Network HPRN-CT-1999-000161. 相似文献
992.
B. I. Suleimanov 《Journal of Experimental and Theoretical Physics》2002,95(5):944-956
Solutions of the equations v x+v 3?tv+x=0 and v xx=v 3? tv+x, which describe the nucleation of domain walls occurring in the neighborhood of cusps of slowly varying equilibriums, are analyzed. Examples related to the diffusion in smoothly inhomogeneous media are considered. 相似文献
993.
994.
M. Piana M. Arrabito S. Bodoardo A. D'Epifanio D. Satolli F. Croce B. Scrosati 《Ionics》2002,8(1-2):17-26
Solid State Reaction was employed to prepare phospho-olivines LiMPO4 (where M=Fe, Co) as pure phase and LiNiPO4 in presence of foreign phases, as cathodic materials for lithiumions batteries. The relationship between structural, morphological
and electrochemical properties were investigated in the case of LiFePO4. Structural investigation has been carried out by means of X-ray powder diffraction (XRPD) and Rietveld refinement. The influence
on the morphology of annealing temperature, different flowing gas mixture and addition of ascorbic acid during the synthesis,
has been analysed via scanning electron microscopy. The electrochemical cycling performances on LiFePO4 showed to be positively affected by the modifications of the experimental conditions. Cyclic voltammetry showed a good reversibility
during insertion-extraction mechanism, in particular in presence of additives. LiCoPO4 and LiNiPO4 are interesting as high voltage cathode materials for Li-ion batteries and have been taken into account, but their electrochemical
operating conditions are still to be optimised. In the case of LiNiPO4 it is very difficult to obtain, by solid state synthesis, suitable purity powders, having a grain size small enough to exploit
it usefully as cathodic material for Li-ion cells.
Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16 – 22, 2000. 相似文献
995.
Remco van der Hofstad Gerard Hooghiemstra Piet Van Mieghem 《Random Structures and Algorithms》2002,20(4):519-539
In this paper we study the covariance structure of the number of nodes k and l steps away from the root in random recursive trees. We give an analytic expression valid for all k, l and tree sizes N. The fraction of nodes k steps away from the root is a random probability distribution in k. The expression for the covariances allows us to show that the total variation distance between this (random) probability distribution and its mean converges in probability to zero. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20: 519–539, 2002 相似文献
996.
997.
A differential equation is obtained that describes the change in the energy of a charged particle in the field of a slow wave (with phase velocity not equal to unity) as a function of the distance traversed. Analysis of this equation yields the amplitude and period of the change in the particle's energy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 97–102, February, 1981. 相似文献
998.
999.
1000.
A. A. Karabutov V. A. Larichev G. A. Maksimov I. M. Pelivanov N. B. Podymova 《Acoustical Physics》2006,52(5):582-588
The first experimental observation of the propagation dynamics of a short broadband acoustic pulse in a resonance medium with gas bubbles is carried out. The probing pulse is generated using the optoacoustic effect. It is shown that the theory of short pulse propagation in media with generalized resonance relaxation adequately and accurately describes the dynamics of short pulse dispersion. A possibility to determine the relaxation and resonance parameters of media by the pulsed testing technique is demonstrated. 相似文献