全文获取类型
收费全文 | 6942篇 |
免费 | 673篇 |
国内免费 | 577篇 |
专业分类
化学 | 836篇 |
晶体学 | 22篇 |
力学 | 505篇 |
综合类 | 180篇 |
数学 | 3827篇 |
物理学 | 2822篇 |
出版年
2024年 | 12篇 |
2023年 | 96篇 |
2022年 | 131篇 |
2021年 | 187篇 |
2020年 | 164篇 |
2019年 | 175篇 |
2018年 | 160篇 |
2017年 | 231篇 |
2016年 | 274篇 |
2015年 | 218篇 |
2014年 | 364篇 |
2013年 | 488篇 |
2012年 | 340篇 |
2011年 | 382篇 |
2010年 | 303篇 |
2009年 | 443篇 |
2008年 | 492篇 |
2007年 | 442篇 |
2006年 | 434篇 |
2005年 | 347篇 |
2004年 | 303篇 |
2003年 | 272篇 |
2002年 | 309篇 |
2001年 | 253篇 |
2000年 | 251篇 |
1999年 | 180篇 |
1998年 | 174篇 |
1997年 | 148篇 |
1996年 | 108篇 |
1995年 | 52篇 |
1994年 | 77篇 |
1993年 | 43篇 |
1992年 | 47篇 |
1991年 | 38篇 |
1990年 | 25篇 |
1989年 | 36篇 |
1988年 | 28篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 21篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1975年 | 7篇 |
排序方式: 共有8192条查询结果,搜索用时 0 毫秒
991.
Dongho Byeon 《The Ramanujan Journal》2006,11(2):159-163
Let g be an odd positive integer and X be a positive real number. We shall show that for any ∊ > 0, the number of imaginary quadratic fields with discriminant ≥
− X and ideal class group having a subgroup isomorphic to ℤ/g ℤ× ℤ/g ℤ is ≫ X1/g−∊.
2000 Mathematics Subject Classification Primary—11R11, 11R29
This work was supported by KRF-R08-2003-000-10243-0 and partially by KRF-2002-003-C00001. 相似文献
992.
Summary A new high-powered ultraviolet laser system is proposed. The system doubles the infrared light from a Nd-Yag laser mode-locked
at 100 MHz, injects this light into a storage-ring cavity to accumulate a high power in the visible and then doubles this
into the ultraviolet at 2600 ?. The power levels anticipated at this wavelength are much larger than those of commercially
available c.w. lasers. The new system can have a far-reaching impact in basic research and, even more so, in a great many
industrial applications. 相似文献
993.
Simulating eight lattices for Pomeau's cellular automata simultaneously through bit-per-bit operations, a vectorized Fortran program reached 30 million updates per second and per Cray YMP processor. We give the full innermost loops. 相似文献
994.
This paper deals with generalized vector quasi-equilibrium problems. By virtue of a nonlinear scalarization function, the
gap functions for two classes of generalized vector quasi-equilibrium problems are obtained. Then, from an existence theorem
for a generalized quasi-equilibrium problem and a minimax inequality, existence theorems for two classes of generalized vector
quasi-equilibrium problems are established.
This research is partially supported by the Postdoctoral Fellowship Scheme of The Hong Kong Polytechnic University and the
National Natural Science Foundation of China. 相似文献
995.
Influence of the bias current on the output characteristics of a mode-locked fiber ring laser consisting of two SOAs 总被引:2,自引:0,他引:2
In this paper, after obtaining the mode-locked pulse shape with self-reproduction theory, the influence of the bias current on the output characteristics of a backward-optical-injection harmonic mode-locked fiber ring laser consisting of two semiconductor optical amplifiers (SOAs) has been numerically investigated. The results show that the mode-locked pulse with high peak power and narrow width can be obtained through reasonably adjusting the bias currents of the two SOAs. 相似文献
996.
有限域上互反本原正规元的存在性 总被引:1,自引:0,他引:1
设q是素数方幂,n是正整数,Fqn是qn个元素的有限域.本文证明了:当正整数n≥32时,对任意的素数方幂q,存在Fqn中的本原元ξ满足ξ和ξ-1都是Fqn 在Fq上的正规元,也即{ξ,ξq,…,ξqn-1}和{ξ-1,ξ-q,…,ξ-qn-1)都构成Fqn在Fq 上的本原正规基. 相似文献
997.
Vector Ordinal Optimization 总被引:2,自引:0,他引:2
Ordinal optimization is a tool to reduce the computational burden in simulation-based optimization problems. So far, the major effort in this field focuses on single-objective optimization. In this paper, we extend this to multiobjective optimization and develop vector ordinal optimization, which is different from the one introduced in Ref. 1. Alignment probability and ordered performance curve (OPC) are redefined for multiobjective optimization. Our results lead to quantifiable subset selection sizes in the multiobjective case, which supplies guidance in solving practical problems, as demonstrated by the examples in this paper.This paper was supported in part by Army Contract DAAD19-01-1-0610, AFOSR Contract F49620-01-1-0288, and a contract with United Technology Research Center (UTRC). The first author received additional funding from NSF of China Grants 60074012 and 60274011, Ministry of Education (China), and a Tsinghua University (Beijing, China) Fundamental Research Funding Grant, and the NCET program of China.The authors are grateful to and benefited from two rounds of reviews from three anonymous referees. 相似文献
998.
电介质的频域特性与测量 总被引:4,自引:0,他引:4
从物质的分子结构基本模型出发,简要介绍了介电频域理论,提出了有关新的测量方法。 相似文献
999.
利用连通集上有关上半连续点集映射的连通性质,本文证明了拓扑向量空间中向量最优化问题的弱锥-有效解集与相应目标空间中的弱锥-有效点集连通性之间的一个等价定理. 相似文献
1000.
关于3维Minkowski空间中类空曲面的若干结果 总被引:2,自引:0,他引:2
在本文,我们证明2维黎曼流形能实现为L3中的类空极大曲面的充要条件是相应的Ricci条件成立,此外还确定了L3中其平均曲率向量h满足条件△h=λh(λ∈R)的类空曲面 相似文献