全文获取类型
收费全文 | 20079篇 |
免费 | 2227篇 |
国内免费 | 2026篇 |
专业分类
化学 | 2237篇 |
晶体学 | 30篇 |
力学 | 1745篇 |
综合类 | 505篇 |
数学 | 13857篇 |
物理学 | 5958篇 |
出版年
2024年 | 21篇 |
2023年 | 157篇 |
2022年 | 250篇 |
2021年 | 351篇 |
2020年 | 406篇 |
2019年 | 420篇 |
2018年 | 444篇 |
2017年 | 572篇 |
2016年 | 648篇 |
2015年 | 500篇 |
2014年 | 1026篇 |
2013年 | 1275篇 |
2012年 | 1055篇 |
2011年 | 1269篇 |
2010年 | 1129篇 |
2009年 | 1405篇 |
2008年 | 1361篇 |
2007年 | 1459篇 |
2006年 | 1292篇 |
2005年 | 1239篇 |
2004年 | 1011篇 |
2003年 | 917篇 |
2002年 | 778篇 |
2001年 | 719篇 |
2000年 | 664篇 |
1999年 | 569篇 |
1998年 | 516篇 |
1997年 | 483篇 |
1996年 | 350篇 |
1995年 | 291篇 |
1994年 | 246篇 |
1993年 | 184篇 |
1992年 | 157篇 |
1991年 | 131篇 |
1990年 | 138篇 |
1989年 | 91篇 |
1988年 | 88篇 |
1987年 | 82篇 |
1986年 | 69篇 |
1985年 | 86篇 |
1984年 | 69篇 |
1983年 | 46篇 |
1982年 | 64篇 |
1981年 | 61篇 |
1980年 | 39篇 |
1979年 | 35篇 |
1978年 | 31篇 |
1977年 | 28篇 |
1976年 | 30篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
901.
将多元复分析中一种复偏微分方程组的解与复Clifford分析中双曲调和函数联系起来,并研究了双曲调和函数的几个性质。 相似文献
902.
Yasuhiro Gotoh 《Proceedings of the American Mathematical Society》1999,127(5):1443-1451
Let denote the space of all positive superharmonic functions on a domain . Lindqvist showed that is a bounded subset of . Using this, we give a characterization of finitely connected -dimensional uniform domains and remarks on Hölder domains.
903.
Consider a closed Jackson type network in which each queue has a single exponential server. Assume that N customers are moving among k queues. We establish simple closed form bounds on the network throughput (both lower and upper), which are sharper than those that are currently available. Numerical evaluation indicates that the improvements are significant. 相似文献
904.
905.
Piotr Hajlasz 《Proceedings of the American Mathematical Society》1999,127(2):417-423
If is an open set with the sufficiently regular boundary, then the Hardy inequality holds for and , where . The main result of the paper is a pointwise inequality , where on the right hand side there is a kind of maximal function. The pointwise inequality combined with the Hardy-Littlewood maximal theorem implies the Hardy inequality. This generalizes some recent results of Lewis and Wannebo.
906.
以大肠杆菌启动子探测质粒pKK232-8 为载体,用4 组限制性内切酶分别消化古生菌盐生盐杆菌R1(Halobacterium halobium )的染色体DNA,在体外进行重组,转化E.coliDH-5α感受态细胞,得到12 个转化子(T1~T12),其抗性水平分布在10~500 m g/L的区间内. 将这些转化子所含质粒分别命名为pSX1~pSX12,限制性酶切分析表明,这些质粒各插入了一段不同的外源DNA 片段,杂交分析表明,抗性最强的转化子T11 所含质粒pSX11 上插入了一段来源于盐生盐杆菌R1 染色体的DNA 片段. 该DNA 片段在大肠杆菌中具有启动子功能. 相似文献
907.
We examine connections between A-hypergeometric differential equations and the theory of integer programming. In the first part, we develop a hypergeometric sensitivity analysis for small variations of constraint constants with creation operators and b-functions. In the second part, we study the indicial polynomial (b-function) along the hyperplane xi=0 via a correspondence between the optimal value of an integer programming problem and the roots of the indicial polynomial. Gröbner bases are used to prove theorems and give counter examples. 相似文献
908.
Given a continuous P0-function F : Rn Rn, we describe a method of constructing trajectories associated with the P0-equation F(x) = 0. Various well known equation-based reformulations of the nonlinear complementarity problem and the box variational inequality problem corresponding to a continuous P0-function lead to P0-equations. In particular, reformulations via (a) the Fischer function for the NCP, (b) the min function for the NCP, (c) the fixed point map for a BVI, and (d) the normal map for a BVI give raise to P0-equations when the underlying function is P0. To generate the trajectories, we perturb the given P0-function F to a P-function F(x, ); unique solutions of F(x, ) = 0 as varies over an interval in (0, ) then define the trajectory. We prove general results on the existence and limiting behavior of such trajectories. As special cases we study the interior point trajectory, trajectories based on the fixed point map of a BVI, trajectories based on the normal map of a BVI, and a trajectory based on the aggregate function of a vertical nonlinear complementarity problem. 相似文献
909.
Gianni Di Pillo Stefano Lucidi Laura Palagi 《Computational Optimization and Applications》1999,12(1-3):157-188
In this paper we describe a Newton-type algorithm model for solving smooth constrained optimization problems with nonlinear objective function, general linear constraints and bounded variables. The algorithm model is based on the definition of a continuously differentiable exact merit function that follows an exact penalty approach for the box constraints and an exact augmented Lagrangian approach for the general linear constraints. Under very mild assumptions and without requiring the strict complementarity assumption, the algorithm model produces a sequence of pairs
converging quadratically to a pair
where
satisfies the first order necessary conditions and
is a KKT multipliers vector associated to the linear constraints. As regards the behaviour of the sequence x
k alone, it is guaranteed that it converges at least superlinearly. At each iteration, the algorithm requires only the solution of a linear system that can be performed by means of conjugate gradient methods. Numerical experiments and comparison are reported. 相似文献
910.
Shigehiko Kuratsubo 《Proceedings of the American Mathematical Society》1999,127(10):2987-2994
We prove the pointwise convergence of the Fourier series for radial functions in several variables, which in the case is the Dirichlet-Jordan theorem itself. In our proof the method for the case of the indicator function of the ball is very useful.