全文获取类型
收费全文 | 547642篇 |
免费 | 5238篇 |
国内免费 | 1359篇 |
专业分类
化学 | 269716篇 |
晶体学 | 8765篇 |
力学 | 26943篇 |
综合类 | 16篇 |
数学 | 74582篇 |
物理学 | 174217篇 |
出版年
2021年 | 4111篇 |
2020年 | 4537篇 |
2019年 | 5099篇 |
2018年 | 12689篇 |
2017年 | 13326篇 |
2016年 | 12604篇 |
2015年 | 6320篇 |
2014年 | 9533篇 |
2013年 | 22541篇 |
2012年 | 20037篇 |
2011年 | 29362篇 |
2010年 | 20076篇 |
2009年 | 20087篇 |
2008年 | 25889篇 |
2007年 | 28304篇 |
2006年 | 17020篇 |
2005年 | 19649篇 |
2004年 | 16151篇 |
2003年 | 14769篇 |
2002年 | 13189篇 |
2001年 | 14544篇 |
2000年 | 11108篇 |
1999年 | 8426篇 |
1998年 | 6969篇 |
1997年 | 6783篇 |
1996年 | 6538篇 |
1995年 | 5797篇 |
1994年 | 5635篇 |
1993年 | 5353篇 |
1992年 | 6255篇 |
1991年 | 6370篇 |
1990年 | 6119篇 |
1989年 | 6112篇 |
1988年 | 5874篇 |
1987年 | 5985篇 |
1986年 | 5637篇 |
1985年 | 7203篇 |
1984年 | 7274篇 |
1983年 | 5939篇 |
1982年 | 6125篇 |
1981年 | 5941篇 |
1980年 | 5654篇 |
1979年 | 6205篇 |
1978年 | 6259篇 |
1977年 | 6271篇 |
1976年 | 6144篇 |
1975年 | 5708篇 |
1974年 | 5585篇 |
1973年 | 5648篇 |
1972年 | 3965篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
We investigate the existence and stability of solutions for higher-order two-point boundary value problems in case the differential
operator is not necessarily positive definite, i.e. with superlinear nonlinearities. We write an abstract realization of the
Dirichlet problem and provide abstract existence and stability results which are further applied to concrete problems. 相似文献
992.
We consider a shock-type wave solution of the modified quintic complex Ginzburg-Landau equation and make a numerical study
of its spatiotemporal stability. Discussions related to the behavior of this front wave are introduced and it is shown how
the velocities of the wave can be used to collect information concerning the pattern formation in the system.
Published in Neliniini Kolyvannya, Vol. 10, No. 2, pp. 270–276, April–June, 2007. 相似文献
993.
S. V. Tyshkevich 《Mathematical Notes》2007,81(5-6):851-853
994.
A nonlocal difference scheme for the heat conduction equation with a real parameter γ > 1 or γ < 0 in the boundary condition is considered. Thus, the analysis of this problem is generalized to all real values of the parameter in the boundary condition. The spectrum of the spatial operator of the scheme is studied. The results obtained are used to formulate a stability criterion for the difference scheme. The case γ = ?1 proves to be special, because the system of eigenfunctions of the operator does not form a basis in the space of grid functions. 相似文献
995.
R.G. Abhilash Kumar K. Vinod U. Syamaprasad 《Applied Physics A: Materials Science & Processing》2007,88(2):243-247
MgB2/Fe wires were prepared by electrical self-heating of in situ powder-in-tube wires for the first time at ambient conditions.
Characterization of the wires processed at 750 °C, 800 °C and 850 °C for 15 min by XRD, SEM, ϱ–T, susceptibility and JC measurements shows that the MgB2 formed is of high quality particularly with respect to phase purity and transport JC. The method considerably reduces the overall energy consumption vis-à-vis the production cost, simplifies the complexity
of the fabrication procedure and is promising for manufacture of high-quality MgB2 superconducting wires.
PACS 74.70.Ad; 74.62.Bf; 74.25.Fy; 74.25.Ha; 81.20.Hy 相似文献
996.
In this paper, we apply a three-stage-DEA model to the Spanish Professional Football League, which means separating the teams’
economic behaviour into three components: operating efficiency—of the offence and defence—athletic or operating effectiveness,
and social effectiveness. The results showed that the technical inefficiency of the defence is greater than that of the offence,
both being caused by aspects linked to the poor management of players’ abilities and by the football team’s size. Teams showed
a favourable evolution of their offensive and defensive efficiency during the 2004/2005 season and to a lesser extent in the
season before. The point system assigned by the professional football league regulations evaluates the teams’ athletic effectiveness,
but we detected that the teams with the most experience perform athletically in a more effective manner. Their social effectiveness
is strongly related to the level of play in itself and to factors linked to their PFL ranking: participation in international
competitions for important football teams; or the struggle of minor football teams to stay in the first division. 相似文献
997.
998.
999.
We introduce a random perturbed version of the classical fidelity and we show that it converges with the same rate of decay
of correlations, but not uniformly in the noise. This makes the classical fidelity unstable in the zero-noise limit. 相似文献
1000.
Neutral Community Theory: How Stochasticity and Dispersal-Limitation Can Explain Species Coexistence
Neutral community theory explains biodiversity, i.e. the coexistence of several species, as the result of a stochastic balance
between immigration and extinction on a local level, and between speciation and extinction on a regional level. The most popular
model, presented by Hubbell in 2001, has seen many analytical developments in recent years, which can be used in model analysis,
model testing and model comparison. We review these developments here, and present alternative derivations and shine previously
unnoticed lights on them. 相似文献