全文获取类型
收费全文 | 20080篇 |
免费 | 3990篇 |
国内免费 | 3422篇 |
专业分类
化学 | 15429篇 |
晶体学 | 319篇 |
力学 | 1128篇 |
综合类 | 323篇 |
数学 | 2336篇 |
物理学 | 7957篇 |
出版年
2024年 | 66篇 |
2023年 | 403篇 |
2022年 | 701篇 |
2021年 | 821篇 |
2020年 | 870篇 |
2019年 | 916篇 |
2018年 | 734篇 |
2017年 | 691篇 |
2016年 | 969篇 |
2015年 | 1137篇 |
2014年 | 1293篇 |
2013年 | 1606篇 |
2012年 | 1872篇 |
2011年 | 1888篇 |
2010年 | 1480篇 |
2009年 | 1486篇 |
2008年 | 1624篇 |
2007年 | 1450篇 |
2006年 | 1354篇 |
2005年 | 1060篇 |
2004年 | 865篇 |
2003年 | 733篇 |
2002年 | 703篇 |
2001年 | 538篇 |
2000年 | 428篇 |
1999年 | 323篇 |
1998年 | 257篇 |
1997年 | 181篇 |
1996年 | 171篇 |
1995年 | 135篇 |
1994年 | 119篇 |
1993年 | 111篇 |
1992年 | 95篇 |
1991年 | 71篇 |
1990年 | 62篇 |
1989年 | 44篇 |
1988年 | 39篇 |
1987年 | 41篇 |
1986年 | 36篇 |
1985年 | 33篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1970年 | 3篇 |
1959年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
In this paper, we discuss the controllability of a nonlinear degenerate parabolic system with bilinear control. Based on the shrinking property of the solutions, we prove that the system is not globally approximately controllable. Furthermore, we give an approximate null controllability result. We also prove that the system is not globally exactly null controllable by a comparison principle. 相似文献
62.
Thin films of oxide materials are playing a growing role as critical elements in optoelectronic devices and nanoscale devices. In this work, thin films of some typical oxides such as WO3, Ga2O3 and SrTiO3 were investigated. We present measurements of those films, using various optical techniques like photoconductivity transients over a wide time range and photo-Hall measurements. Analysis of the photo-Hall and photoconductivity data permits the determination of the contribution to the photoconductivity made by the carrier mobility and concentration. A model for dispersive carrier transport was proposed to explain the relaxation of the photoconductivity in oxide thin films. In addition, photoluminescence characterization was used to study microstructures and energy band in oxide thin films. The broad emission from oxide host, consisting of several band peaks, was likely due to a recombination process with several possible paths. The dependence of the luminescent intensity on the annealing atmosphere was associated with the presence of oxygen vacancies. It is suggested that our optical analysis efforts have improved the understanding of oxide thin films, and this should lead to the necessary advancements in a variety of devices. 相似文献
63.
基于完全信息博弈理论,阐述了寡头垄断市场的排污收费古诺模型.建立了具有政府宏观调控机制的博弈模型,并对调控效果进行了分析. 相似文献
64.
Generalized KKM Type Theorems in FC-Spaces with Applications (I) 总被引:1,自引:0,他引:1
Xie Ping Ding 《Journal of Global Optimization》2006,36(4):581-596
The class KKM(X,Y) (resp., s-KKM(X,Y,Z)) of set-valued mappings with KKM (resp., s-KKM) property is introduced in FC-spaces without any convexity structure. Some generalized KKM (resp., s-KKM) type theorems are proved in FC-spaces under much weak assumptions. As applications, some new section theorems and coincidence theorems are established in FC-spaces. These theorems generalize many known results in literature. The further applications of these results will be given in a follow-up paper. 相似文献
65.
Jing Ping YANG Shi Hong CHENG Xiao Qian WANG 《数学学报(英文版)》2007,23(3):467-478
This paper investigates bivariate recursive equations on excess-of-loss reinsurance. For an insurance portfolio, under the assumptions that the individual claim severity distribution has bounded continuous density and the number of claims belongs to R1 (a, b) family, bivariate recursive equations for the joint distribution of the cedent's aggregate claims and the reinsurer's aggregate claims are obtained. 相似文献
66.
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
67.
根据能量变分的思想,将双原子分子离子XY 的新解析势能函数ECMI势和关于离子XY 的能量自洽法(Energy-consistent-method for ion, ECMI)推广到双原子分子离子XY-的势能函数研究之中,具体研究了双原子分子离子SiC-激发态A2∏的势能函数,并与将中性双原子分子的势能函数如Morse势和Huxley-Murrrell-Sorbie (HMS)势直接用于双原子分子离子XY-的结果和ab initio计算结果进行了比较.结果表明,ECMI势和ECMI方法对双原子分子离子XY-的势能函数研究同样是成功的,在重要的渐近区和离解区优于中性势能函数,与精确的ab initio结果一致. 相似文献
68.
69.
Chuncheng Hao Zuolin Cui Yansheng Yin Zhikun Zhang 《Journal of nanoparticle research》2002,4(1-2):107-110
Nanostructured Fe3Al intermetallic compounds were produced by using hydrogen arc plasma method. The transmission electron microscopy experiments showed that the average particle size of the as-synthesized was about 40-nm. The change in hardness of Fe3Al nanostructured intermetallic compounds with annealing temperatures was observed and evaluated. 相似文献
70.
He Ping LIU Xuan Yuan ZHENG 《数学学报(英文版)》2006,22(2):425-430
We consider the commutators of the HSrmander multiplier with CMO-functions on the Heisenberg group. The result of compactness on L^P spaces is proved. 相似文献