全文获取类型
收费全文 | 27161篇 |
免费 | 1190篇 |
国内免费 | 884篇 |
专业分类
化学 | 7600篇 |
晶体学 | 309篇 |
力学 | 1219篇 |
综合类 | 129篇 |
数学 | 11187篇 |
物理学 | 8791篇 |
出版年
2023年 | 140篇 |
2022年 | 265篇 |
2021年 | 193篇 |
2020年 | 265篇 |
2019年 | 599篇 |
2018年 | 411篇 |
2017年 | 441篇 |
2016年 | 310篇 |
2015年 | 302篇 |
2014年 | 417篇 |
2013年 | 1354篇 |
2012年 | 685篇 |
2011年 | 1209篇 |
2010年 | 702篇 |
2009年 | 1022篇 |
2008年 | 1143篇 |
2007年 | 1165篇 |
2006年 | 1100篇 |
2005年 | 807篇 |
2004年 | 1206篇 |
2003年 | 1333篇 |
2002年 | 1906篇 |
2001年 | 1885篇 |
2000年 | 1750篇 |
1999年 | 1925篇 |
1998年 | 1644篇 |
1997年 | 1027篇 |
1996年 | 525篇 |
1995年 | 298篇 |
1994年 | 262篇 |
1993年 | 126篇 |
1992年 | 127篇 |
1991年 | 110篇 |
1990年 | 188篇 |
1989年 | 163篇 |
1988年 | 116篇 |
1987年 | 102篇 |
1986年 | 149篇 |
1985年 | 205篇 |
1984年 | 189篇 |
1983年 | 78篇 |
1982年 | 148篇 |
1981年 | 243篇 |
1980年 | 236篇 |
1979年 | 118篇 |
1978年 | 178篇 |
1977年 | 112篇 |
1976年 | 76篇 |
1975年 | 83篇 |
1974年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
Kasper K. Berthelsen Jesper Møller 《Bulletin of the Brazilian Mathematical Society》2002,33(3):351-367
This primer provides a self-contained exposition of the case where spatial birth-and-death processes are used for perfect
simulation of locally stable point processes. Particularly, a simple dominating coupling from the past (CFTP) algorithm and
the CFTP algorithms introduced in [13], [14], and [5] are studied. Some empirical results for the algorithms are discussed.
Received: 30 June 2002 相似文献
13.
We consider immersions: and construct a subspace of which corresponds to a set of embedded manifolds which are either parallel to f, tubes around f or, in general, partial tubes around f. This space is invariant under the action of the normal holonomy group, We investigate the case where is non-trivial and obtain some results on the number of connected components of .
Received 24 March 2000. 相似文献
14.
Fundamental processes in long air gap discharges 总被引:2,自引:0,他引:2
I. Gallimberti G. Bacchiega Anne Bondiou-Clergerie Philippe Lalande 《Comptes Rendus Physique》2002,3(10):854
The development of atmospheric lightning is initiated and sustained by the formation in virgin air of ‘streamer corona’ and ‘leader’ discharges, very similar to those observed in laboratory long sparks. Therefore, the experimental and theoretical investigations of these laboratory discharges have become of large interest to improve the physical knowledge of the lightning process and to develop self-consistent models that could be applied to new protection concepts.In the present paper the fundamental processes of the subsequent phases of long air gap discharges are analyzed, from the first corona inception and development to the leader channel formation and propagation. For all these processes simulations models are discussed that have been essentially derived and simplified by the authors, in order to develop sequential time-dependent simulation of the laboratory breakdown, with both positive and negative voltages. The possibility of extending these models to the case of natural lightning is discussed in the companion paper, presented in this same volume. To cite this article: I. Gallimberti et al., C. R. Physique 3 (2002) 1335–1359. 相似文献
15.
Summary In this paper a Gauss-Jordan algorithm with column interchanges is presented and analysed. We show that, in contrast with Gaussian elimination, the Gauss-Jordan algorithm has essentially differing properties when using column interchanges instead of row interchanges for improving the numerical stability. For solutions obtained by Gauss-Jordan with column interchanges, a more satisfactory bound for the residual norm can be given. The analysis gives theoretical evidence that the algorithm yields numerical solutions as good as those obtained by Gaussian elimination and that, in most practical situations, the residuals are equally small. This is confirmed by numerical experiments. Moreover, timing experiments on a Cyber 205 vector computer show that the algorithm presented has good vectorisation properties. 相似文献
16.
The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar+ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate. 相似文献
17.
The paper provides significant simplifications and extensions of results obtained by Gorsich, Genton, and Strang (J. Multivariate Anal. 80 (2002) 138) on the structure of spatial design matrices. These are the matrices implicitly defined by quadratic forms that arise naturally in modelling intrinsically stationary and isotropic spatial processes. We give concise structural formulae for these matrices, and simple generating functions for them. The generating functions provide formulae for the cumulants of the quadratic forms of interest when the process is Gaussian, second-order stationary and isotropic. We use these to study the statistical properties of the associated quadratic forms, in particular those of the classical variogram estimator, under several assumptions about the actual variogram. 相似文献
18.
An experimental method for determining the real-time depth of laser-drilled holes is presented. The proposed method involves
detecting the laser-induced optoacoustic waves generated during the interaction of the laser beam with the material. Our optodynamic
study involved measuring the propagation times of these waves as they traveled through the material and analyzing their temporal
behavior during the drilling process. The experimental observations revealed an exponential relationship between the propagation
time of the longitudinal stress wave and the number of consecutive laser pulses.
Received: 25 October 2001 / Accepted: 27 October 2001 / Published online: 20 December 2001 相似文献
19.
Nicolas Bergeron 《Mathematische Zeitschrift》2002,241(1):101-125
Let M be an arithmetic hyperbolic manifold and be a codimension 1 geodesic cycle. In this paper, we study the asymptotic growth of the -norm of the lifts of F in the congruence tower above M. We obtain an explicit value for the growth rate of this norm. In particular, we provide a new proof of a celebrated result
of Millson [Mi] on the homology of the arithmetic hyperbolic manifolds. The method is quite general and gives a new way of
getting non zero homology classes in certain locally symmetric spaces.
Received: 20 April 2001; in final form: 26 September 2001 / Published online: 28 February 2002 相似文献
20.
Chuanming Zong 《Monatshefte für Mathematik》2002,134(3):247-255
In this article we study the simultaneous packing and covering constants of two-dimensional centrally symmetric convex domains.
Besides an identity result between translative case and lattice case and a general upper bound, exact values for some special
domains are determined. Similar to Mahler and Reinhardt’s result about packing densities, we show that the simultaneous packing
and covering constant of an octagon is larger than that of a circle.
(Received 17 January 2001; in revised form 13 July 2001) 相似文献