全文获取类型
收费全文 | 542篇 |
免费 | 60篇 |
国内免费 | 55篇 |
专业分类
化学 | 160篇 |
晶体学 | 2篇 |
力学 | 113篇 |
综合类 | 6篇 |
数学 | 131篇 |
物理学 | 245篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 2篇 |
2020年 | 11篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 27篇 |
2013年 | 32篇 |
2012年 | 35篇 |
2011年 | 32篇 |
2010年 | 30篇 |
2009年 | 39篇 |
2008年 | 37篇 |
2007年 | 44篇 |
2006年 | 39篇 |
2005年 | 30篇 |
2004年 | 23篇 |
2003年 | 29篇 |
2002年 | 22篇 |
2001年 | 26篇 |
2000年 | 20篇 |
1999年 | 18篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
排序方式: 共有657条查询结果,搜索用时 290 毫秒
41.
Einar L. Hinrichsen Jens Feder Torstein Jøssang 《Journal of statistical physics》1986,44(5-6):793-827
By sequentially adding line segments to a line or disks to a surface at random positions without overlaps, we obtain configurations of the one- and two-dimensional random sequential adsorption (RSA) problem. We have simulated the one- and two-dimensional problem with periodic boundary condition. The one-dimensional simulations are compared with the exact analytical solutions to give an estimate of the accuracy of the simulation. In two dimensions the geometrical properties of the RSA configuration are discussed and in addition known results of the RSA process are reproduced. Various statistical distributions of the Voronoi-Dirichlet (VD) network corresponding to the RSA disk configuration are analyzed. In order to characterize pores in the RSA configuration, we introduce circular holes. There is a direct correspondence between vertices of the VD network and these holes, and also between direct/indirect geometrical neighbors and these holes. The hole size distribution is found to be a parabola. We also find general relations that connect the asymptotic behavior of the surface coverage, the correlation function, and the hole size distribution. 相似文献
42.
自由电子激光器要求高亮度、低能散度的电子束注入波荡器(Undulator)。本文叙述提供高亮度电子束的高频电子直线加速器中的注入器部分的设计计算。注入器由L波段(1300MHz)的十二分频和三分频两个谐振腔预聚束器和一个基波频率的变相速聚束器组成。粒子运动方程中考虑了空间电荷效应和束流负载效应。电子枪的注入参数:脉冲宽度T=4ns;电流I=5A;电子的初始动能E_0=100keV;电子束分布为高斯型。参数优化设计结果:单束团宽度小于25ps,峰值电流达400A以上,电子的平均归一化能量>4,束团内的能量差小于200keV。 相似文献
43.
设D是R~2中的Jordan域,本文证明了D是b-John圆当且仅当存在常数c≥1,对任意的x_1,x_2∈D,有k_D(x_1,x_2)≤cH_D(x_1,x_2),这里kD(x_1,x_2)表示D中x_1与x_2二点的拟双曲距离,H_D(x_1,x_2)=1/2log(1+(l(γ))/(d(x_1,■D)))(1+(l(γ))/(d(x_2,■D))),其中l(γ)为D中连结x_1与x_2二点的拟双曲测地线的欧几里德长度. 相似文献
44.
45.
46.
The three dimensional problem of steady fluid deposition on an inclined rotating disk is solved by similarity transform. For a given spraying rate there may be one, two or no steady state solution. The inclination causes a downward draining flow and a lateral flow. Perturbation solutions compare well with exact similarity solutions when the fluid film is thin. 相似文献
47.
A simple and reproducible method for the rapid extraction and determination of trace amounts of copper(Ⅱ) ions using octadecyl-bonded silica membrane disks modified by 1,5-diphenylcarbazide (DPC) and atomic absorption spectrometry was presented, which was based on complex formation on the surface of the ENVI-18 DISK^TM disks followed by stripping of the retained species by minimum amounts of appropriate organic solvents. The elution was efficient and quantitative. The effect of potential interfering ions, pH, ligand amount, stripping solvent, and sample flow rate were also investigated. Under the optimal experimental conditions, the break-through volume was found to be about 1000 mL providing a preconcentration factor of 400. The maximum capacity of the disks was found to be (255±5) lag for Cu^2+, and the limit of detection of the proposed method was 5 ng per 1000 mL. The method was applied to the extraction and recovery of copper in different water samples. 相似文献
48.
49.
In this paper we characterize John domains in terms of John domain decomposition property. In addition, we also show that
a domain D in ℔
n
is a John domain if and only if D\P is a John domain, where P is a subset of D containing finitely many points of D. The best possibility and an application of the second result are also discussed. 相似文献
50.
A set of invariants describing the limit regimes of braking disk-type wound composite flywheels is suggested. The limit regime is determined by using a linear failure criterion. It is shown that, for generating short-time impulses of very high power, a set of small identical flywheels is more effective than one large flywheel with an equivalent mass. Particular examples illustrating the theory considered are discussed. 相似文献