首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   149篇
  免费   9篇
  国内免费   11篇
化学   6篇
晶体学   1篇
力学   37篇
综合类   4篇
数学   100篇
物理学   21篇
  2023年   1篇
  2022年   3篇
  2021年   2篇
  2020年   2篇
  2019年   5篇
  2018年   1篇
  2017年   6篇
  2016年   3篇
  2015年   2篇
  2014年   7篇
  2013年   9篇
  2012年   3篇
  2011年   4篇
  2010年   6篇
  2009年   3篇
  2008年   5篇
  2007年   16篇
  2006年   9篇
  2005年   8篇
  2004年   5篇
  2003年   15篇
  2002年   6篇
  2001年   10篇
  2000年   9篇
  1999年   4篇
  1998年   3篇
  1997年   6篇
  1996年   3篇
  1995年   3篇
  1993年   3篇
  1991年   1篇
  1990年   2篇
  1987年   1篇
  1985年   1篇
  1983年   1篇
  1981年   1篇
排序方式: 共有169条查询结果,搜索用时 15 毫秒
41.
集值映射向量优化的Benson真有效性   总被引:11,自引:2,他引:9  
本文首先将单值映射的锥次类凸概念推广到集值映射,并对锥次类凸集值映射给出几个等价刻划和一个择一性定理。然后,利用这些概念与结果来确定拓扑线性空间中带集值映射的向量优化问题的Benson真有效性,获得两个标量化结果和两个Lagrange乘子定理,在定义了一个适当的集值Lagrange映射并对其引入真鞍点的概念之后,又建立了Benson真有效性的一个充分条件和一个充要条件,最后还讨论了两个对偶问题。  相似文献   
42.
We study discrete time Heath–Jarrow–Morton (HJM) type of interest rate curve models, where the forward interest rates – in contrast to the classical HJM models – are driven by a random field. Our main aim is to investigate the relationship between the discrete time forward interest rate curve model and its continuous time counterpart. We derive a general result on the convergence of discrete time models and we give special focus on the nearly unit root spatial autoregression model.  相似文献   
43.
We show that a non-symmetric nearly triply regular designD with and in which every line has at least q points is AG(n,q) for prime power q > 2 and positiveinteger n 3.  相似文献   
44.
Changes in the surface chemical state of a nearly equiatomic nickel–titanium (NiTi) alloy caused by immersion in aqueous solutions of HNO3 and H2SO4 as well as subsequent heating in air at 723 K were analyzed using X-ray photoelectron spectroscopy (XPS). An XPS analysis using angle-resolved technique and a mathematical deconvolution technique revealed that a passive layer formed in an ambient atmosphere contained TiO2 as a major state and Ni(OH)2 and NiO as minor states. The Ni(OH)2 on the alloy remained in the region even when heated in air at 723 K. Therefore, the resulting layer became a Ti-oxide layer with Ni segregated region at the surface, which was NiO formed via dehydration of Ni(OH)2. However, immersion in an aqueous solution of HNO3 or H2SO4 enables Ni(OH)2 state to dissolve in the passive layer of a NiTi alloy; thereby, the Ni segregated region rarely appeared in the oxide layer by heating. The Ni segregated region at the surface becomes an obstacle for the inward diffusion of oxygen; thus, the annihilation of such a segregated region results in an increase in the thickness of the oxide layer.  相似文献   
45.
The flat bands in a square kagome lattice containing square and triangle plaquettes, are respectively investigated, and the origin of the doubly degenerated completely flat bands and the corresponding compact localized states are elucidated. It is found that the introduction of external magnetic flux enriches the modulation parameters, making the system present many interesting results. In the case that the magnetic flux penetrates through each square plaquette, the tunable completely flat band has one more tunable parameter. And when the external magnetic flux penetrates through each triangle plaquette, excepting a completely flat band, the band dispersions of the system present the topological nearly flat band, which is very useful to realize the interesting fractional quantum Hall physics. The average density of states is also calculated to corroborate the completely FB generated by the highly localized eigenstates. Furthermore, the implementation of the square kagome lattice system based on the current photonic waveguide network technology is demonstrated. The scheme opens up a way to generate the tunable completely flat band and topological nearly flat band in square kagome lattice under multi-parameter variable conditions.  相似文献   
46.
Let Kn be a complete graph on n vertices. In this paper, we find the necessary conditions for the existence of a 6-cycle system of Kn - L for every nearly 2-regular leave L of Kn. This condition is also sufficient when the number of vertices of L is n - 4.  相似文献   
47.
Here, we are discussing the applicable ranges of one-equation and two-equation turbulence models with the viewpoint of similar theory. The criterions of determining the applicable ranges of these models are given.  相似文献   
48.
本文定义并讨论了近乎Sasakian流形的CR子流形,得到了关开这类子流形的微分几何方面的一些有意义的结果。  相似文献   
49.
The title compound,[Cu2(CH3COO)4(C8H10N2)]n·nCH3CN1 (C8H10N2,4,4'-bipy = 4,4'-bipyridine),has been solvothermally synthesized in CH3CN and characterized by X-ray diffraction.The crystal is of monoclinic,space group Cc with a = 22.626(6),b = 14.012(4),c =15.106(4) (A),β = 107.610(3)°,V = 4565(2) (A)3,C20H23Cu2N3O8,Mr = 560.49,Z = 8,Dc = 1.631 g/cm3,μ = 1.914 mm-1,Flack parameter = 0.48(1),F(000) = 2288,R = 0.042 and wR = 0.)98 for 8887 observed reflections (I > 2σ(I)).It consists of nearly linear one-dimensional chains [Cu2(CH3COO)4(C8H10N2)]n derived from paddle-wheel [Cu2(CH3COO)4] unit linked by 4,4'-bipy,and CH3CN as guest molecule regularly decorates between the chains.  相似文献   
50.
Summary The purpose of this paper is the derivation of reduced, finite-dimensional dynamical systems that govern the near-integrable modulations ofN-phase, spatially periodic, integrable wavetrains. The small parameter in this perturbation theory is the size of the nonintegrable perturbation in the equation, rather than the amplitude of the solution, which is arbitrary. Therefore, these reduced equations locally approximate strongly nonlinear behavior of the nearly integrable PDE. The derivation we present relies heavily on the integrability of the underlying PDE and applies, in general, to anyN-phase periodic wavetrain. For specific applications, however, a numerical pretest is applied to fix the truncation orderN. We present one example of the reduction philosophy with the damped, driven sine-Gordon system and summarize our present progress toward application of the modulation equations to this numerical study.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号