全文获取类型
收费全文 | 70748篇 |
免费 | 5269篇 |
国内免费 | 6539篇 |
专业分类
化学 | 28086篇 |
晶体学 | 336篇 |
力学 | 6415篇 |
综合类 | 1241篇 |
数学 | 25269篇 |
物理学 | 21209篇 |
出版年
2023年 | 548篇 |
2022年 | 829篇 |
2021年 | 1219篇 |
2020年 | 1331篇 |
2019年 | 1573篇 |
2018年 | 1318篇 |
2017年 | 1566篇 |
2016年 | 1789篇 |
2015年 | 1631篇 |
2014年 | 2346篇 |
2013年 | 4549篇 |
2012年 | 2773篇 |
2011年 | 3117篇 |
2010年 | 2710篇 |
2009年 | 3869篇 |
2008年 | 4300篇 |
2007年 | 4512篇 |
2006年 | 4208篇 |
2005年 | 3592篇 |
2004年 | 3305篇 |
2003年 | 3338篇 |
2002年 | 3389篇 |
2001年 | 2614篇 |
2000年 | 2544篇 |
1999年 | 2273篇 |
1998年 | 2139篇 |
1997年 | 1748篇 |
1996年 | 1472篇 |
1995年 | 1421篇 |
1994年 | 1314篇 |
1993年 | 1133篇 |
1992年 | 1088篇 |
1991年 | 840篇 |
1990年 | 696篇 |
1989年 | 606篇 |
1988年 | 557篇 |
1987年 | 432篇 |
1986年 | 379篇 |
1985年 | 442篇 |
1984年 | 433篇 |
1983年 | 213篇 |
1982年 | 345篇 |
1981年 | 404篇 |
1980年 | 304篇 |
1979年 | 296篇 |
1978年 | 221篇 |
1977年 | 208篇 |
1976年 | 156篇 |
1974年 | 109篇 |
1973年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
71.
Abstract
In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is
fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining
part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under
the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global
attractor. More precisely, we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence
of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the
non-autonomous case by the limiting global attractor.
* Project supported by the MIUR-COFIN 2004 research program on “Mathematical Modelling and Analysis of Free Boundary Problems”. 相似文献
72.
Wei Gengping~ Shen Jianhua~ 《高校应用数学学报(英文版)》2006,21(3):320-326
This paper studies the nonautonomous nonlinear system of difference equationsΔx(n)=A(n)x(n)+f(n,x(n)),n∈Z,(*) where x(n)∈R~N,A(n)=(a_(ij)(n))N×N is an N×N matrix,with a-(ij)∈C(R,R) for i,j= 1,2,3,...,N,and f=(f_1,f_2,...,f_N)~T∈C(R×R~N,R~N),satisfying A(t+ω)=A(t),f(t+ω,z)=f(t,z) for any t∈R,(t,z)∈R×R~N andωis a positive integer.Sufficient conditions for the existence ofω-periodic solutions to equations (*) are obtained. 相似文献
73.
WANG Libin 《数学年刊B辑(英文版)》2002,23(4):439-454
The author gets a blow-up result of C1 solution to the Cauchy problem for a first order quasilinear non-strictly hyperbolic system in one space dimension. 相似文献
74.
利用Riccati变换求解同谐谐振子的定态薛定谔方程,求得了能谱及态函数
关键词:
同调谐振子
本征值谱
Riccati变换法 相似文献
75.
We report the results of experiments on electrically driven convection that occurs in a thin, freely suspended film of smectic A liquid crystal when an electric field is applied in the plane of the film. Convection in a vortex pattern is found above a well-defined critical voltage. The film behaves as a two-dimensional isotropic liquid: neither its thickness nor the director field are modified by the flow. We present measurements of the critical voltage at the onset of convection in two experimental configurations—one which allows the injection of charges into the film from the electrodes, and one which does not. When injection is present, the critical voltage for the onset of flow increases monotonically with increasing frequency of applied field. With no injection, there is no instability at DC and the critical voltage diverges there. The nature of the flow pattern observed at onset changes with frequency. Below a certain frequency the film flows in vortices that extend over the width of the film; above this frequency the flow is confined to two lines of smaller vortices localized along the electrodes. We present a simple discussion of the mechanisms which drive the convection. 相似文献
76.
77.
78.
79.
NA序列部分和的矩完全收敛性 总被引:4,自引:0,他引:4
讨论了NA序列部分和的矩完全收敛性,在一定条件下获得了NA序列矩完全收敛的充要条件,显示了矩完全收敛和矩条件之间的关系,将独立同分布随机变量序列矩完全收敛的结果推广到NA序列,得到了与独立随机变量序列情形类似的结果. 相似文献
80.
Maria Kordaki Athanasia Balomenou 《International Journal of Computers for Mathematical Learning》2006,11(1):99-135
This study focuses on the constructions in terms of area and perimeter in equivalent triangles developed by students aged 12–15 years-old, using the tools provided by Cabri-Geometry II [Labore (1990). Cabri-Geometry (software), Université de Grenoble]. Twenty-five students participated in a learning experiment where they were asked to construct: (a) pairs of equivalent triangles “in as many ways as possible” and to study their area and their perimeter using any of the tools provided and (b) “any possible sequence of modifications of an original triangle into other equivalent ones”. As regards the concept of area and in contrast to a paper and pencil environment, Cabri provided students with different and potential opportunities in terms of: (a) means of construction, (b) control, (c) variety of representations and (d) linking representations, by exploiting its capability for continuous modifications. By exploiting these opportunities in the context of the given open tasks, students were helped by the tools provided to develop a broader view of the concept of area than the typical view they would construct in a typical paper and pencil environment. 相似文献