全文获取类型
收费全文 | 542828篇 |
免费 | 6646篇 |
国内免费 | 2569篇 |
专业分类
化学 | 275862篇 |
晶体学 | 8130篇 |
力学 | 25144篇 |
综合类 | 98篇 |
数学 | 75962篇 |
物理学 | 166847篇 |
出版年
2021年 | 3125篇 |
2020年 | 3593篇 |
2019年 | 3790篇 |
2018年 | 12123篇 |
2017年 | 12937篇 |
2016年 | 10728篇 |
2015年 | 6102篇 |
2014年 | 7717篇 |
2013年 | 21013篇 |
2012年 | 19756篇 |
2011年 | 30218篇 |
2010年 | 19286篇 |
2009年 | 19049篇 |
2008年 | 27006篇 |
2007年 | 30031篇 |
2006年 | 17310篇 |
2005年 | 21665篇 |
2004年 | 17152篇 |
2003年 | 15479篇 |
2002年 | 13558篇 |
2001年 | 14082篇 |
2000年 | 10899篇 |
1999年 | 8480篇 |
1998年 | 6935篇 |
1997年 | 6607篇 |
1996年 | 6667篇 |
1995年 | 6084篇 |
1994年 | 5835篇 |
1993年 | 5610篇 |
1992年 | 6284篇 |
1991年 | 6083篇 |
1990年 | 5801篇 |
1989年 | 5596篇 |
1988年 | 5819篇 |
1987年 | 5533篇 |
1986年 | 5281篇 |
1985年 | 7447篇 |
1984年 | 7602篇 |
1983年 | 6341篇 |
1982年 | 6750篇 |
1981年 | 6616篇 |
1980年 | 6401篇 |
1979年 | 6628篇 |
1978年 | 6727篇 |
1977年 | 6552篇 |
1976年 | 6542篇 |
1975年 | 6385篇 |
1974年 | 6227篇 |
1973年 | 6566篇 |
1972年 | 3992篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We consider the inverse problem of finding the unknown time-dependent leading coefficient and the free term in a parabolic equation. Boundary conditions and overdetermination conditions are local. We find conditions for the uniqueness and local existence. 相似文献
992.
A facile, rapid and regioselective method for the 1-O-deacylation of peracylated glycopyranoses is described which occurs under mild conditions by absorption onto alumina using microwave irradiation. 相似文献
993.
J. Kidawa-Kukla 《Journal of sound and vibration》2003,262(4):865-876
This paper considers the problem of the transverse vibrations of a beam induced by a mobile heat source. The formulation of the problem is based on the differential equations of heat conduction and transverse vibrations of the beam, which are complemented by suitable initial and boundary conditions. The effect of internal and external damping on the vibrations of the beam is considered. The solution to the problem in analytical form is obtained by using the properties of the Green functions. A time partitioning method has been used to avoid the difficulties associated with the slow convergence of the series occurring in the solution to the heat conduction problem. The numerical results of the thermally induced vibration of the beam are presented. 相似文献
994.
R. M. Sardarly O. A. Samedov I. Sh. Sadykhov V. A. Aliev 《Physics of the Solid State》2003,45(6):1118-1121
The relaxor properties of Fe-doped TlInS2 crystals are investigated. It is shown that Fe-doped TlInS2 compounds exhibit all features inherent in relaxor ferroelectric materials. The temperature range of existence of the microdomain (relaxor) state and the temperature of the transition from this state to a macro-domain state are determined. 相似文献
995.
V. L. Tsymbalenko 《JETP Letters》2003,78(8):493-496
The kinetics of formation of an anomalous phase from a solution with a small 3He impurity was studied in the temperature range 0.2–0.7 K up to a supersaturation of ~30 mbar. The phase diagram was determined for normal and anomalous growths. It is found that, in the presence of impurities, the formation of a fast-growing state is retarded. This experimental fact indicates that the dissipative processes in fluids have an appreciable effect on the phase formation kinetics. The retardation is, possibly, caused by the direct interaction of an impurity with the crystal surface. 相似文献
996.
G. M. Maksimova A. L. Chuvilin E. M. Moroz V. A. Likholobov K. I. Matveev 《Kinetics and Catalysis》2004,45(6):870-878
Conditions for the preparation of stable aqueous monometallic and bimetallic colloidal solutions (sols) of noble metals (Ru, Rh, Pd, Pt, Ir, Ag, and Au) in the presence of polyoxometalates containing W, Mo, V, and Nb were found. The stability of sols against coagulation at room temperature was studied. The metal/C samples prepared by metal adsorption from sols were studied by powder X-ray diffraction analysis and transmission electron microscopy. The following factors of importance for the preparation of a stable sol are discussed: (1) the formation of a sol of a metal polyhydroxo complex stabilized by a polyoxometalate (preliminary stage) and (2) the formation of polyoxometalate-metal clusters in the course of reduction of polyhydroxo complexes.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 921–929.Original Russian Text Copyright © 2004 by Maksimova, Chuvilin, Moroz, Likholobov, Matveev. 相似文献
997.
The corrugation stability of the flat surface of a fast magnetohydrodynamic shock wave in a perfect monoatomic gas with a
constant heat capacity is studied with numerical techniques. The magnetic field makes an arbitrary angle with the plane of
discontinuity. It is shown that the shock wave remains stable only if it is strictly perpendicular to the magnetic field.
At any other angle between the fast shock wave and magnetic field, the former may spontaneously radiate outwardly propagating
magnetohydrodynamic waves under certain conditions. Incoming flow characteristics at which these waves are induced are determined. 相似文献
998.
A. M. Yakunin A. Yu. Silov P. M. Koenraad W. Van Roy J. De Boeck J. H. Wolter 《Superlattices and Microstructures》2003,34(3-6):539
An individual Mn acceptor in GaAs is mapped by cross-sectional scanning tunneling microscopy (X-STM) at room temperature and a strongly anisotropic shape of the acceptor state is observed. An acceptor state manifests itself as a cross-like feature which we attribute to a valence hole weakly bound to the Mn ion forming the (Mn2+3d5+hole) complex. We propose that the observed anisotropy of the Mn acceptor wavefunction is due to the d-wave present in the acceptor ground state. 相似文献
999.
The reasons for the existence of various scenarios for structural transformations in disordered condensed media, such as liquids and amorphous substances, where both smeared transformations and sharp first-order transitions may occur, were analyzed. The ratio between the spatial scale of structural correlations and the size of the smallest possible region occupied by a new phase in the matrix of initial modification is the key parameter determining the scenario for equilibrium phase transformations in liquids. In amorphous substances, the experimentally observed transformations occur far from equilibrium, and the possible size of the region occupied by the new phase corresponds to the minimal nucleus size. For some amorphous solids, quantitative analysis of the transformation width was carried out and the main classes of covalent substances, in which the smeared or sharp transitions occur, were revealed. Specific features of the interparticle interactions determining various transformation scenarios are discussed. 相似文献
1000.
The European Physical Journal E - Recently, the chain dynamics of molten polymers in confined geometries has been investigated, using NMR. Some of these experiments have been performed on... 相似文献