全文获取类型
收费全文 | 8543篇 |
免费 | 1206篇 |
国内免费 | 493篇 |
专业分类
化学 | 429篇 |
晶体学 | 27篇 |
力学 | 244篇 |
综合类 | 138篇 |
数学 | 2566篇 |
物理学 | 1604篇 |
无线电 | 5234篇 |
出版年
2024年 | 50篇 |
2023年 | 167篇 |
2022年 | 298篇 |
2021年 | 285篇 |
2020年 | 291篇 |
2019年 | 278篇 |
2018年 | 209篇 |
2017年 | 338篇 |
2016年 | 416篇 |
2015年 | 402篇 |
2014年 | 598篇 |
2013年 | 606篇 |
2012年 | 580篇 |
2011年 | 589篇 |
2010年 | 419篇 |
2009年 | 470篇 |
2008年 | 519篇 |
2007年 | 545篇 |
2006年 | 425篇 |
2005年 | 384篇 |
2004年 | 318篇 |
2003年 | 302篇 |
2002年 | 236篇 |
2001年 | 220篇 |
2000年 | 216篇 |
1999年 | 155篇 |
1998年 | 159篇 |
1997年 | 128篇 |
1996年 | 101篇 |
1995年 | 74篇 |
1994年 | 69篇 |
1993年 | 47篇 |
1992年 | 41篇 |
1991年 | 41篇 |
1990年 | 21篇 |
1989年 | 16篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 30篇 |
1984年 | 33篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1974年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Bernard Bialecki 《Numerical Algorithms》1994,8(2):167-184
Cyclic reduction and Fourier analysis-cyclic reduction (FACR) methods are presented for the solution of the linear systems which arise when orthogonal spline collocation with piecewise Hermite bicubics is applied to boundary value problems for certain separable partial differential equations on a rectangle. On anN×N uniform partition, the cyclic reduction and Fourier analysis-cyclic reduction methods requireO(N
2log2
N) andO(N
2log2log2
N) arithmetic operations, respectively. 相似文献
12.
T. K. Melik-Barkhudarov 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2007,42(5):173-177
An approach is discussed which allows one to describe within the framework of the single model the aggregative states of a system of atoms obeying the Fermi statistics. A phase diagram is obtained containing both the critical point where the distinctions between the liquid and vapor vanish and the triple point where the liquid, vapor, and crystal are in equilibrium. 相似文献
13.
E. Hernández L. Rodríguez-Marín 《Journal of Optimization Theory and Applications》2007,134(1):119-134
In this paper, we study optimization problems where the objective function and the binding constraints are set-valued maps
and the solutions are defined by means of set-relations among all the images sets (Kuroiwa, D. in Takahashi, W., Tanaka, T.
(eds.) Nonlinear analysis and convex analysis, pp. 221–228, 1999). We introduce a new dual problem, establish some duality theorems and obtain a Lagrangian multiplier rule of nonlinear type
under convexity assumptions. A necessary condition and a sufficient condition for the existence of saddle points are given.
The authors thank the two referees for valuable comments and suggestions on early versions of the paper. The research of the
first author was partially supported by Ministerio de Educación y Ciencia (Spain) Project MTM2006-02629 and by Junta de Castilla
y León (Spain) Project VA027B06. 相似文献
14.
本篇文章首先定义了向量变分不等式的严格可行点概念,其次在假设了映射是强(D)-伪单调的情况下,证明了向量变分不等式解集非空有界与其严格可行点存在的等价性问题,推广了在数量变分不等式上得到的相应结果. 相似文献
15.
本文首先根据文本中各个字符的颜色相似的特性,确定已知文本块的文本的颜色,利用文本的颜色信息二值化文本图像以得到文本块中的字符数、字符的尺寸和间距;其次,根据视频图像的大小和视频的播放速度确定搜索窗口的大小,并利用文本的运动信息来预测搜索窗口的位置;第三,根据在相邻两帧中具有相同内容文本的颜色相似的特性,提出了一个可以解决脉冲噪声和部分缺损或遮挡问题的稳健匹配准则来跟踪文本块;最后,确定跟踪输出的文本的颜色、尺寸和运动方式。本文方法可以很好地跟踪平移、缩小或放大、旋转、淡入淡出和部分被遮挡的水平或倾斜排列的文本,并且可以记录文本平移、旋转和缩放的速度。 相似文献
16.
17.
18.
Marlies Gerber 《Geometriae Dedicata》2003,98(1):123-160
We establish some criteria for the existence or nonexistence of focal points near closed geodesics on surfaces. These criteria are in terms of the curvature of the manifold along the closed geodesic and the average values of the partial derivatives of the curvature in the direction perpendicular to the geodesic. Our criteria lead to a new family of examples of surfaces with no focal points. We also show that if S is a compact surface with no focal points and an inequality relating the curvature of the surface to the curvature of the horocycles holds, then the horocycles (considered as curves in S) are uniformly C
2+Lipschitz. 相似文献
19.
This study investigates the robust output tracking problem for a class of uncertain linear systems. The uncertainties are assumed to be time invariant and to satisfy the matching conditions. According to the selected nominal parameters, an optimal solution with a prescribed degree of stability is determined. Then, an auxiliary input via the use of an adapting factor, connected to the nominal optimal control, is introduced to guarantee the robustness and prescribed degree of stability for the output tracking control of the uncertain linear systems. This method is very simple and effective and can reject bounded uncertainties imposed on the states. A maglev vehicle model example is given to show its effectiveness. 相似文献
20.
In a recent work (Int. J. Solids Struct. 37 (2000) 1561) by one of the authors, an extended system for calculating critical points of equilibrium paths in imperfect structures was presented. However, the extremum nature of these points was not analyzed explicitly in that paper. In this note, we will fill in the gap and establish a sufficient condition for determining the buckling strength of imperfect structures. 相似文献