全文获取类型
收费全文 | 4176篇 |
免费 | 219篇 |
国内免费 | 264篇 |
专业分类
化学 | 351篇 |
晶体学 | 2篇 |
力学 | 285篇 |
综合类 | 14篇 |
数学 | 2642篇 |
物理学 | 1365篇 |
出版年
2024年 | 7篇 |
2023年 | 34篇 |
2022年 | 70篇 |
2021年 | 59篇 |
2020年 | 103篇 |
2019年 | 101篇 |
2018年 | 118篇 |
2017年 | 126篇 |
2016年 | 112篇 |
2015年 | 82篇 |
2014年 | 227篇 |
2013年 | 330篇 |
2012年 | 181篇 |
2011年 | 262篇 |
2010年 | 209篇 |
2009年 | 276篇 |
2008年 | 321篇 |
2007年 | 277篇 |
2006年 | 212篇 |
2005年 | 172篇 |
2004年 | 156篇 |
2003年 | 148篇 |
2002年 | 126篇 |
2001年 | 78篇 |
2000年 | 85篇 |
1999年 | 82篇 |
1998年 | 99篇 |
1997年 | 78篇 |
1996年 | 77篇 |
1995年 | 47篇 |
1994年 | 37篇 |
1993年 | 35篇 |
1992年 | 40篇 |
1991年 | 25篇 |
1990年 | 19篇 |
1989年 | 34篇 |
1988年 | 26篇 |
1987年 | 27篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1973年 | 5篇 |
排序方式: 共有4659条查询结果,搜索用时 15 毫秒
1.
2.
Lu Chuanrong 《数学年刊B辑(英文版)》1997,18(1):71-78
Let $\{\xi_{\bold t}, {\bold t}
\in {\bold Z}^d\}$ be a nonuniform $\varphi$-mixing strictly stationary
real random field with
$E\xi_{\bold 0}=0, E|\xi_{\bold 0}|^{2+\delta}<\infty$ for some
$0<\delta<1$. A sufficient
condition is given for the sequence of partial sum set-indexed process
$\{Z_n(A),\ A\in \Cal A\}$ to converge to Brownian motion. By a direct
calculation, the author shows
that the result holds for a more general class of set index ${\Cal A}$, where
${\Cal A}$ is assumed only to have the metric entropy exponent $r, 0相似文献
3.
An Improved Gradient Projection-based Decomposition Technique for Support Vector Machines 总被引:2,自引:0,他引:2
Luca Zanni 《Computational Management Science》2006,3(2):131-145
In this paper we propose some improvements to a recent decomposition technique for the large quadratic program arising in
training support vector machines. As standard decomposition approaches, the technique we consider is based on the idea to
optimize, at each iteration, a subset of the variables through the solution of a quadratic programming subproblem. The innovative
features of this approach consist in using a very effective gradient projection method for the inner subproblems and a special
rule for selecting the variables to be optimized at each step. These features allow to obtain promising performance by decomposing
the problem into few large subproblems instead of many small subproblems as usually done by other decomposition schemes. We
improve this technique by introducing a new inner solver and a simple strategy for reducing the computational cost of each
iteration. We evaluate the effectiveness of these improvements by solving large-scale benchmark problems and by comparison
with a widely used decomposition package. 相似文献
4.
5.
6.
考虑约束最优化问题:minx∈Ωf(x)其中:f:R^n→R是连续可微函数,Ω是一闭凸集。本文研究了解决此问题的梯度投影方法,在步长的选取时采用了一种新的策略,在较弱的条件下,证明了梯度投影响方法的全局收敛性。 相似文献
7.
On the average complexity of 3D-Voronoi diagrams of random points on convex polytopes 总被引:1,自引:0,他引:1
It is well known that the complexity, i.e. the number of vertices, edges and faces, of the 3-dimensional Voronoi diagram of n points can be as bad as Θ(n2). It is also known that if the points are chosen Independently Identically Distributed uniformly from a 3-dimensional region such as a cube or sphere, then the expected complexity falls to O(n). In this paper we introduce the problem of analyzing what occurs if the points are chosen from a 2-dimensional region in 3-dimensional space. As an example, we examine the situation when the points are drawn from a Poisson distribution with rate n on the surface of a convex polytope. We prove that, in this case, the expected complexity of the resulting Voronoi diagram is O(n). 相似文献
8.
9.
Random copolymers of poly{(methacrylamide)-co-(vinyl trimethoxysilane)} and poly{(methacrylic acid)-co-(vinyl trimethoxysilane)} were synthesized via a free radical polymerization reaction. Acid catalyzed sol-gel process of tetraethylorthosilicate (TEOS) with aforementioned polymers in the presence of methyl xanthine class of alkaloid like caffeine resulted in the formation of highly transparent monoliths. Solvent extraction of the template leaves behind the recognition sites intact with high selectivity towards the print molecule. The ionic and non-specific adsorptions, which are considered to be the main disadvantages of the molecularly imprinted polymers (MIP), are prevented to a considerable extent by the end capping of surface silanol groups. The template binding efficiencies of MIP were determined by HPLC analysis. 相似文献
10.