全文获取类型
收费全文 | 4216篇 |
免费 | 124篇 |
国内免费 | 19篇 |
专业分类
化学 | 2706篇 |
晶体学 | 31篇 |
力学 | 161篇 |
数学 | 764篇 |
物理学 | 697篇 |
出版年
2023年 | 19篇 |
2022年 | 57篇 |
2021年 | 81篇 |
2020年 | 69篇 |
2019年 | 57篇 |
2018年 | 58篇 |
2017年 | 45篇 |
2016年 | 128篇 |
2015年 | 116篇 |
2014年 | 109篇 |
2013年 | 204篇 |
2012年 | 249篇 |
2011年 | 276篇 |
2010年 | 168篇 |
2009年 | 145篇 |
2008年 | 238篇 |
2007年 | 245篇 |
2006年 | 236篇 |
2005年 | 201篇 |
2004年 | 159篇 |
2003年 | 152篇 |
2002年 | 130篇 |
2001年 | 56篇 |
2000年 | 58篇 |
1999年 | 41篇 |
1998年 | 38篇 |
1997年 | 51篇 |
1996年 | 76篇 |
1995年 | 37篇 |
1994年 | 50篇 |
1993年 | 37篇 |
1992年 | 44篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 33篇 |
1988年 | 29篇 |
1987年 | 33篇 |
1986年 | 28篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 28篇 |
1982年 | 39篇 |
1981年 | 22篇 |
1980年 | 29篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 15篇 |
1975年 | 14篇 |
1973年 | 16篇 |
排序方式: 共有4359条查询结果,搜索用时 62 毫秒
1.
2.
3.
BIT Numerical Mathematics - In this article we address the problem of minimizing a strictly convex quadratic function using a novel iterative method. The new algorithm is based on the well-known... 相似文献
4.
5.
It is long known that the Fokker-Planck equation with prescribed constant coefficients of diffusion and linear friction describes
the ensemble average of the stochastic evolutions in velocity space of a Brownian test particle immersed in a heat bath of
fixed temperature. Apparently, it is not so well known that the same partial differential equation, but now with constant
coefficients which are functionals of the solution itself rather than being prescribed, describes the kinetic evolution (in
the N→∞ limit) of an
isolated
N-particle system with certain stochastic interactions. Here we discuss in detail this recently discovered interpretation.
An erratum to this article can be found at 相似文献
6.
Guido Wauters Jacques Dewaele Carlo Vandecasteele Richard Dams 《Mikrochimica acta》1989,98(4-6):157-162
Proton activation analysis was used for the determination of cadmium and lead in three sediment reference materials. The method is based on the111,112Cd(p, xn)111 In and the206,207,208Pb(p, xn)206Bi reactions.111In and206Bi were chemically separated by anion exchange. The results obtained were taken into account for the certification of the materials and are in the excellent agreement with the certified values. 相似文献
7.
8.
R. Pizzoferrato L. Lagonigro T. Ziller A. Di Carlo R. Paolesse F. Mandoj A. Ricci C. Lo Sterzo 《Chemical physics》2004,300(1-3):217-225
We study the infrared emission at 1.54 μm of an organolanthanide complex, Er(III)-tetraphenylporphyrin [Er(TPP)acac], both as a result of direct optical excitation and via energy transfer from host π-conjugate polymers of type poly(arylene–ethynylene) [PAE]. In the first case, the emission of the neat complex is characterized in inert transparent materials and a value of the quantum yield at 1.54 μm φIR=4×10−4 is measured. Then, fluorescence resonance transfer is investigated in blends of Er(TPP)acac with PAEs by monitoring the quenching of the polymer fluorescence along with the enhancement of both the visible emission of the ligand and the near-infrared band of Er3+. These different procedures allow a detailed analysis of the transfer efficiency within a specific implementation of the Förster model for polymeric donors. The experimental values of the critical radius R0, ranging from 1.3 to 2.5 nm for the different blends, are in good agreement with theory for a wide interval of the physical and spectroscopic parameters. This suggests that other mechanisms for excitation transfer do not play a significant role in these materials. 相似文献
9.
10.
Jayanth R. Banavar Oscar Gonzalez John H. Maddocks Amos Maritan 《Journal of statistical physics》2003,110(1-2):35-50
Physical strands or sheets that can be modelled as curves or surfaces embedded in three dimensions are ubiquitous in nature, and are of fundamental importance in mathematics, physics, biology, and engineering. Often the physical interpretation dictates that self-avoidance should be enforced in the continuum model, i.e., finite energy configurations should not self-intersect. Current continuum models with self-avoidance frequently employ pairwise repulsive potentials, which are of necessity singular. Moreover the potentials do not have an intrinsic length scale appropriate for modelling the finite thickness of the physical systems. Here we develop a framework for modelling self-avoiding strands and sheets which avoids singularities, and which provides a way to introduce a thickness length scale. In our approach pairwise interaction potentials are replaced by many-body potentials involving three or more points, and the radii of certain associated circles or spheres. Self-interaction energies based on these many-body potentials can be used to describe the statistical mechanics of self-interacting strands and sheets of finite thickness. 相似文献