全文获取类型
收费全文 | 557610篇 |
免费 | 5080篇 |
国内免费 | 1498篇 |
专业分类
化学 | 288719篇 |
晶体学 | 7875篇 |
力学 | 26583篇 |
综合类 | 18篇 |
数学 | 73300篇 |
物理学 | 167693篇 |
出版年
2021年 | 5369篇 |
2020年 | 5949篇 |
2019年 | 6708篇 |
2018年 | 8768篇 |
2017年 | 8889篇 |
2016年 | 12433篇 |
2015年 | 6876篇 |
2014年 | 11299篇 |
2013年 | 24939篇 |
2012年 | 20105篇 |
2011年 | 23708篇 |
2010年 | 17514篇 |
2009年 | 17281篇 |
2008年 | 22535篇 |
2007年 | 22200篇 |
2006年 | 20310篇 |
2005年 | 18183篇 |
2004年 | 16805篇 |
2003年 | 15062篇 |
2002年 | 14945篇 |
2001年 | 15139篇 |
2000年 | 11755篇 |
1999年 | 9102篇 |
1998年 | 7940篇 |
1997年 | 7832篇 |
1996年 | 7308篇 |
1995年 | 6530篇 |
1994年 | 6583篇 |
1993年 | 6307篇 |
1992年 | 6624篇 |
1991年 | 7113篇 |
1990年 | 6790篇 |
1989年 | 6672篇 |
1988年 | 6509篇 |
1987年 | 6320篇 |
1986年 | 6034篇 |
1985年 | 7716篇 |
1984年 | 8050篇 |
1983年 | 6784篇 |
1982年 | 7121篇 |
1981年 | 6572篇 |
1980年 | 6262篇 |
1979年 | 6711篇 |
1978年 | 6942篇 |
1977年 | 6816篇 |
1976年 | 6767篇 |
1975年 | 6467篇 |
1974年 | 6268篇 |
1973年 | 6536篇 |
1972年 | 4781篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We study elliptic boundary-value problems in improved scales of functional Hilbert spaces on smooth manifolds with boundary. The isotropic Hörmander-Volevich-Paneyakh spaces are elements of these scales. The local smoothness of a solution of an elliptic problem in an improved scale is investigated. We establish a sufficient condition under which this solution is classical. Elliptic boundary-value problems with parameter are also studied. 相似文献
992.
A. M. Samoilenko 《Ukrainian Mathematical Journal》2007,59(2):243-292
We present results of the investigation of the local behavior of smooth functions in neighborhoods of their regular and critical
points and prove theorems on the mean values of the functions considered similar to the Lagrange finite-increments theorem.
We also study the symmetry of the derivative of an analytic function in the neighborhood of its multiple zero, prove new statements
of the Weierstrass preparation theorem related to the critical point of a smooth function with finite smoothness, determine
a nongradient vector field of a function in the neighborhood of its critical point, and consider one critical case of stability
of an equilibrium position of a nonlinear system.
__________
Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, No. 2, pp. 231–267, February, 2007. 相似文献
993.
Most of the few known examples of compact Riemannian manifolds with positive sectional curvature are the total space of a
Riemannian submersion. In this article we show that this is true for all known examples, if we enlarge the category to orbifold
fibrations. For this purpose we study all almost free isometric circle actions on positively curved Eschenburg spaces, which
give rise to principle orbifold bundle structures, and we examine in detail their geometric properties. In particular, we
obtain a new family of 6-dimensional orbifolds with positive sectional curvature whose singular locus consists of just two
points.
相似文献
994.
We analyze the well-posedness of the initial value problem for the dissipative quasi-geostrophic equations in the subcritical
case. Mild solutions are obtained in several spaces with the right homogeneity to allow the existence of self-similar solutions.
While the only small self-similar solution in the strong
Lp{\cal L}^{p}
space is the null solution, infinitely many self-similar solutions do exist in weak-
Lp{\cal L}^{p}
spaces and in a recently introduced [7] space of tempered distributions. The asymptotic stability of solutions is obtained
in both spaces, and as a consequence, a criterion of self-similarity persistence at large times is obtained. 相似文献
995.
996.
P.A. Postigo A.R. Alija L.J. Martínez M.L. Dotor D. Golmayo J. Snchez-Dehesa C. Seassal P. Viktorovitch M. Galli A. Politi M. Patrini L.C. Andreani 《Photonics and Nanostructures》2007,5(2-3):79-85
Two-dimensional photonic crystal lasers have been fabricated on III–V semiconductor slabs. Tuning of the spontaneous emission in micro and nanocavities has been achieved by accurate control of the slab thickness. Different structures, some of them of new application to photonic crystal lasers, have been fabricated like the Suzuki-phase or the coupled-cavity ring-like resonators. Laser emission has been obtained by pulsed optical pumping. Optical characterization of the lasing modes have been performed showing one or more laser peaks centred around 1.55 μm. Far field characterization of the emission pattern has been realized showing different patterns depending on the geometrical shape of the structures. These kinds of devices may be used as efficient nanolaser sources for optical communications or optical sensors. 相似文献
997.
A. V. Kalinin 《Radiophysics and Quantum Electronics》2004,47(12):955-965
We consider a method of far-zone wideband antenna measurements performed at discrete frequencies with subsequent synthesis of the tested-antenna response in the time domain for separating the useful signal and interference due to scattering. Experimental results of a study of the scattered fields arising during the measurements of characteristics of centimeter-wave horn antennas on a standard facility in an anechoic chamber are presented.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 47, No. 12, pp. 1066–1077, December, 2004. 相似文献
998.
The effect of annealing in a hydrogen atmosphere on the transmission spectra of GaP:N light-emitting diodes at temperatures of 550, 570, and 590 °C has been investigated. Temperature-induced rearrangement of defects has been observed. The band gap of the material studied is determined. The dependence of the transmission and difference transmission spectra on the annealing temperature and the effect of annealing on the electroluminescence spectra are shown. 相似文献
999.
Calibration of the relationship between height and phase is of uttermost importance to perform accurate 3D measurements in phase measurement profilometry. This work reports a different approach to this problem by first looking at the analytical expression for this relationship and determining the regime spanned by the fringe analysis method. The conclusions thus ascertained, amply justify confronting the analytical expression with a simple normalization procedure of the experimental data, with a remarkable matching between both results. In light of this, a linear calibration procedure with just one plane is proposed and verified experimentally. 相似文献
1000.
We propose an explanation for the experimentally observed [1] giant temperature hysteresis of the ultrasound velocity and internal friction in single crystals of lanthanum manganite (La0.8Sr0.2MnO3). The effect is interpreted within the framework of a phenomenological model based on the notion of two coexisting sublattices of the oxygen octahedra performing cooperative tilting-rotational oscillations in bistable potential fields. 相似文献