全文获取类型
收费全文 | 335184篇 |
免费 | 11382篇 |
国内免费 | 7154篇 |
专业分类
化学 | 166400篇 |
晶体学 | 4968篇 |
力学 | 18488篇 |
综合类 | 518篇 |
数学 | 51799篇 |
物理学 | 111547篇 |
出版年
2022年 | 3145篇 |
2021年 | 3599篇 |
2020年 | 3888篇 |
2019年 | 3961篇 |
2018年 | 12769篇 |
2017年 | 13452篇 |
2016年 | 10062篇 |
2015年 | 5794篇 |
2014年 | 6845篇 |
2013年 | 12554篇 |
2012年 | 15650篇 |
2011年 | 24793篇 |
2010年 | 15994篇 |
2009年 | 15967篇 |
2008年 | 20884篇 |
2007年 | 23876篇 |
2006年 | 9683篇 |
2005年 | 15018篇 |
2004年 | 10797篇 |
2003年 | 9733篇 |
2002年 | 7430篇 |
2001年 | 6776篇 |
2000年 | 5534篇 |
1999年 | 4533篇 |
1998年 | 3828篇 |
1997年 | 3539篇 |
1996年 | 3608篇 |
1995年 | 3267篇 |
1994年 | 3164篇 |
1993年 | 2934篇 |
1992年 | 3128篇 |
1991年 | 2968篇 |
1990年 | 2807篇 |
1989年 | 2669篇 |
1988年 | 2571篇 |
1987年 | 2550篇 |
1986年 | 2391篇 |
1985年 | 3015篇 |
1984年 | 2984篇 |
1983年 | 2644篇 |
1982年 | 2717篇 |
1981年 | 2498篇 |
1980年 | 2453篇 |
1979年 | 2580篇 |
1978年 | 2625篇 |
1977年 | 2461篇 |
1976年 | 2552篇 |
1975年 | 2467篇 |
1974年 | 2424篇 |
1973年 | 2647篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Julie Clutterbuck Oliver C. Schnürer Felix Schulze 《Calculus of Variations and Partial Differential Equations》2007,29(3):281-293
We prove stability of rotationally symmetric translating solutions to mean curvature flow. For initial data that converge
spatially at infinity to such a soliton, we obtain convergence for large times to that soliton without imposing any decay
rates.
The authors are members of SFB 647/B3 “Raum – Zeit – Materie: Singularity Structure, Long-time Behaviour and Dynamics of Solutions
of Non-linear Evolution Equations”. 相似文献
992.
Tatiana B. Mikenas Vladimir A. Zakharov Lyudmila G. Echevskaya Mikhail A. Matsko 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5057-5066
The effects of polymerization temperature, polymerization time, ethylene and hydrogen concentration, and effect of comonomers (hexene‐1, propylene) on the activity of supported catalyst of composition LFeCl2/MgCl2‐Al(i‐Bu)3 (L = 2,6‐bis[1‐(2,6‐dimethylphenylimino)ethyl] pyridyl) and polymer characteristics (molecular weight (MW), molecular‐weight distribution (MWD), molecular structure) have been studied. Effective activation energy of ethylene polymerization over LFeCl2/MgCl2‐Al(i‐Bu)3 has a value typical of supported Ziegler–Natta catalysts (11.9 kcal/mol). The polymerization reaction is of the first order with respect to monomer at the ethylene concentration >0.2 mol/L. Addition of small amounts of hydrogen (9–17%) significantly increases the activity; however, further increase in hydrogen concentration decreases the activity. The IRS and DSC analysis of PE indicates that catalyst LFeCl2/MgCl2‐Al(i‐Bu)3 has a very low copolymerizing ability toward propylene and hexene‐1. MW and MWD of PE produced over these catalysts depend on the polymerization time, ethylene and hexene‐1 concentration. The activation effect of hydrogen and other kinetic features of ethylene polymerization over supported catalysts based on the Fe (II) complexes are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5057–5066, 2007 相似文献
993.
M. K. Richharia 《Pramana》2007,68(6):1007-1012
The cosmic ray (CR) intensity data recorded in Deep River Neutron Monitoring Station have been investigated on quietest days
(QD) for third harmonics of daily variation during solar cycles 21 and 22. It has been observed that in spite of abrupt change
in the amplitude and phase of tri-diurnal anisotropy in CR intensity, the amplitude is quite significant throughout the period
of investigation with larger amplitude during the years 1980 and 1985. Thus, tri-diurnal anisotropy clearly shows 11-year
variation at the mid latitude neutron monitoring station.
相似文献
994.
995.
In this paper, we propose and analyze an SQP-type method for solving linearly constrained convex minimization problems where the objective functions are too complex to be evaluated exactly. Some basic results for global convergence and local superlinear convergence are obtained according to the properties of the approximation sequence. We illustrate the applicability of our approach by proposing a new method for solving two-stage stochastic programs with fixed recourse. 相似文献
996.
In previous work the authors consider the dynamic assignment problem, which involves solving sequences of assignment problems over time in the presence of uncertain information about the future. The algorithm proposed by the authors provides generally high-quality but non-optimal solutions. In this work, though, the authors prove that if the optimal solution to a dynamic assignment problem in one of two problem classes is unique, then the optimal solution is a fixed point under the algorithm. 相似文献
997.
Brandau C. Bartsch T. Böhm S. Böhme C. Hoffknecht A. Kieslich S. Knopp H. Schippers S. Shi W. Müller A. Grün N. Scheid W. Steih T. Bosch F. Franzke B. Kozhuharov C. Krämer A. Mokler P. H. Nolden F. Steck M. Stöhlker T. Stachura Z. 《Hyperfine Interactions》2003,146(1-4):41-45
Hyperfine Interactions - An overview of measurements of dielectronic recombination (DR) with the heaviest lithiumlike ions is presented. The experiments have been carried out at the heavy ion... 相似文献
998.
The grain boundary is an interface and the surface tension is one of its important thermodynamic properties. In this paper,
the surface tension of the ∑9 grain boundary for α-Fe at various temperatures and pressures is calculated by means of Computer
Molecular Dynamics (CMD). The results agree satisfactorily with the experimental data. It is shown that the contribution of
entropy to surface tension of grain boundary can be ignored.
The project supported by the National Natural Science Foundation of China and the Science Foundation of Chinese Academy of
Sciences. 相似文献
999.
On the exact distribution of linear combinations of order statistics from dependent random variables 总被引:2,自引:0,他引:2
We study the exact distribution of linear combinations of order statistics of arbitrary (absolutely continuous) dependent random variables. In particular, we examine the case where the random variables have a joint elliptically contoured distribution and the case where the random variables are exchangeable. We investigate also the particular L-statistics that simply yield a set of order statistics, and study their joint distribution. We present the application of our results to genetic selection problems, design of cellular phone receivers, and visual acuity. We give illustrative examples based on the multivariate normal and multivariate Student t distributions. 相似文献
1000.
Eulerian limit for 2D Navier-Stokes equation and damped/driven KdV equation as its model 总被引:1,自引:0,他引:1
S. B. Kuksin 《Proceedings of the Steklov Institute of Mathematics》2007,259(2):128-136
We discuss the inviscid limits for the randomly forced 2D Navier-Stokes equation (NSE) and the damped/driven KdV equation.
The former describes the space-periodic 2D turbulence in terms of a special class of solutions for the free Euler equation,
and we view the latter as its model. We review and revise recent results on the inviscid limit for the perturbed KdV and use
them to suggest a setup which could be used to make a next step in the study of the inviscid limit of 2D NSE. The proposed
approach is based on an ergodic hypothesis for the flow of the 2D Euler equation on iso-integral surfaces. It invokes a Whitham
equation for the 2D Navier-Stokes equation, written in terms of the ergodic measures.
Dedicated to Vladimir Igorevich Arnold on his 70th birthday 相似文献