全文获取类型
收费全文 | 3038篇 |
免费 | 805篇 |
国内免费 | 130篇 |
专业分类
化学 | 518篇 |
晶体学 | 12篇 |
力学 | 416篇 |
综合类 | 177篇 |
数学 | 851篇 |
物理学 | 1999篇 |
出版年
2024年 | 3篇 |
2023年 | 26篇 |
2022年 | 64篇 |
2021年 | 56篇 |
2020年 | 79篇 |
2019年 | 53篇 |
2018年 | 73篇 |
2017年 | 109篇 |
2016年 | 147篇 |
2015年 | 112篇 |
2014年 | 194篇 |
2013年 | 195篇 |
2012年 | 191篇 |
2011年 | 197篇 |
2010年 | 161篇 |
2009年 | 159篇 |
2008年 | 193篇 |
2007年 | 215篇 |
2006年 | 188篇 |
2005年 | 178篇 |
2004年 | 155篇 |
2003年 | 171篇 |
2002年 | 168篇 |
2001年 | 151篇 |
2000年 | 84篇 |
1999年 | 90篇 |
1998年 | 102篇 |
1997年 | 80篇 |
1996年 | 59篇 |
1995年 | 65篇 |
1994年 | 49篇 |
1993年 | 42篇 |
1992年 | 42篇 |
1991年 | 25篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有3973条查询结果,搜索用时 15 毫秒
41.
42.
Hossam A. Zaki 《Computational Optimization and Applications》1995,4(1):23-45
State-of-the-art computational results have shown that the shortest augmenting path (SAP) methods are more efficient than other primal-dual and primal-simplex based methods for solving the linear assignment problem on uniprocessor computers. There is, however, some controversy concerning their merits when compared with Bertsekas' auction algorithm on multiprocessor computers. In this study we investigate the performance of these competing methods on the Alliant FX/8. For each method, theoretical motivation, sources of parallelism and computational results are presented. 相似文献
43.
The method of demodulation with two parallel matched fiber Bragg gratings( FBGs)system is introduced to enlarge the range of strain that can be detected by the FBG sensor system. 相似文献
44.
Wengu Chen Yixin Lai 《分析论及其应用》2006,22(2):195-200
Let μ be a Borel measure on Rd which may be non doubling. The only condition that μ must satisfy is μ(Q) ≤ col(Q)n for any cube Q () Rd with sides parallel to the coordinate axes and for some fixed n with 0 < n ≤ d. The purpose of this paper is to obtain a boundedness property of fractional integrals in Hardy spaces H1 (μ). 相似文献
45.
In hardware design, it is necessary to simulate the anticipated behavior of the integrated circuit before it is actually cast in silicon. As simulation procedures are long due to the great number of tests to be performed, optimization of the simulation code is of prime importance. This paper describes two mathematical models for the minimization of the memory access times for a cycle-based simulator.An integrated circuit being viewed as a directed acyclic graph, the problem consists in building a graph order on the vertices, compatible with the relation order induced by the graph, in order to minimize a cost function that represents the memory access time. For both proposed cost functions, we show that the corresponding problems are NP-complete. However, we show that the special cases where the graphs are in-trees or out-trees can be solved in polynomial time. 相似文献
46.
In this short communication, we have evaluated the effect of thermal velocity of the plasma particles on the energy of resonantly
interacting energetic electrons with the propagating whistler mode waves as a function of wave frequency and L-value for the
normal and disturbed magnetospheric conditions. During the disturbed conditions when the magnetosphere is depleted in electron
density, the resonance energy of the electron enhances by an order of magnitude at higher latitudes, whereas the effect is
small at low latitudes. An attempt is made to explain the enhanced wave activity observed during magnetic storm periods. 相似文献
47.
切变模量和转动惯量实验的改进 总被引:2,自引:1,他引:1
设计了一种基于垂直轴定理的新型吊钩,对切变模量和转动惯量实验进行了改进,使之成为既可测定金属丝切变模量和环、柱等刚体的转动惯量,又可验证反映转动惯量重要性质的平行轴定理及垂直轴定理的多功能实验仪. 相似文献
48.
49.
采用模匹配方法,研究了非均匀磁场下开放的四端量子波导中的电子输运性质. 结果表明,从一端入射的电子可以透射到两个与之垂直的输出端和一个与之平行的输出端. 在没有外加磁场的情况下,两个垂直输出端的输运概率是相同的,但垂直端与水平端的输运概率不同;在外加磁场下,由于磁边缘态效应,两个垂直输出端的输运概率也有着相当大的差别. 通过施加不同的磁场,我们能获得丰富的电子输运结构,如台阶,宽谷,尖峰等;通过调节磁场的大小和比例以及结构参数可控制该量子结构在各输出端的输运概率.
关键词:
电子输运
介观体系
磁效应 相似文献
50.