全文获取类型
收费全文 | 637篇 |
免费 | 73篇 |
国内免费 | 90篇 |
专业分类
化学 | 500篇 |
晶体学 | 13篇 |
力学 | 24篇 |
综合类 | 6篇 |
数学 | 80篇 |
物理学 | 177篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 27篇 |
2020年 | 29篇 |
2019年 | 26篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 31篇 |
2015年 | 40篇 |
2014年 | 35篇 |
2013年 | 52篇 |
2012年 | 55篇 |
2011年 | 41篇 |
2010年 | 38篇 |
2009年 | 30篇 |
2008年 | 22篇 |
2007年 | 30篇 |
2006年 | 32篇 |
2005年 | 27篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 24篇 |
1998年 | 17篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 4篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
排序方式: 共有800条查询结果,搜索用时 359 毫秒
41.
Mn(Ⅱ),Co(Ⅱ)与HSA相互作用的荧光光谱研究 总被引:5,自引:0,他引:5
用荧光光谱法研究了生理pH和等离子点(pH=5.30)时Mn(Ⅱ)、Co(Ⅱ)与HSA的相互作用。根据Forste非辐射能量转移理论,得到了不同pH时Mn(Ⅱ)、Co(Ⅱ)在HSA中的第一强结合位置与Trp-214残基间的距离。这一结果远大于文献报道值,根据Mn(Ⅱ)、Co(Ⅱ)在HSA中的结合部位及HSA的畴结构对这一显著差异进行了讨论。 相似文献
42.
非电离能损(NIEL)引起的位移损伤是导致空间辐射环境中新型光电器件失效的主要因素.由于低能时库仑相互作用占主导地位,一般采用Mott-Rutherford微分散射截面,但它没考虑核外电子库仑屏蔽的影响.为此,本文采用解析法和基于Monte-Carlo方法的SRIM程序计算了考虑库仑屏蔽效应后低能质子在半导体材料Si,GaAs中的NIEL,SRIM程序在计算过程中采用薄靶近似法, 并与其他作者的计算数据和实验数据进行了比较.结果表明:用SRIM程序计算NIEL时采用薄靶近似法处理是比较合理的,同时考虑库仑
关键词:
低能质子
非电离能损
硅
砷化镓 相似文献
43.
44.
This paper simulates the NLR7301 airfoil limit cycle oscillation (LCO) caused by fluid–structure interaction (FSI) using Reynolds averaged Navier–Stokes equations (RANS) coupled with Spalart–Allmaras (S–A) one-equation turbulence model. A low diffusion E-CUSP (LDE) scheme with 5th order weighted essentially nonoscillatory scheme (WENO) is employed to calculate the inviscid fluxes. A fully conservative 4th order central differencing is used for the viscous terms. A fully coupled fluid–structural interaction model is employed. For the case computed in this paper, the predicted LCO frequency, amplitudes, averaged lift and moment, all agree excellently with the experiment performed by Schewe et al. The solutions appear to have bifurcation and are dependent on the initial fields or initial perturbation. The developed computational fluid dynamics (CFD)/computational structure dynamics (CSD) simulation is able to capture the LCO with very small amplitudes measured in the experiment. This is attributed to the high order low diffusion schemes, fully coupled FSI model, and the turbulence model used. This research appears to be the first time that a numerical simulation of LCO matches the experiment. The simulation confirms several observations of the experiment. 相似文献
45.
46.
Serge Lawrencenko Michael D. Plummer Xiaoya Zha 《Discrete and Computational Geometry》2002,28(3):313-330
Abstract. Let G be an infinite locally finite plane graph with one end and let H be a finite plane subgraph of G . Denote by a(H) the number of finite faces of H and by l(H) the number of the edges of H that are on the boundary of the infinite face or a finite face not in H . Define the isoperimetric constant h (G) to be inf
H
l(H) / a(H) and define the isoperimetric constant h (δ) to be inf
G
h (G) where the infimum is taken over all infinite locally finite plane graphs G having minimum degree δ and exactly one end. We establish the following bounds on h (δ) for δ ≥ 7 :
相似文献
47.
ZHANG Zhenyue & ZHA Hongyuan Department of Mathematics Zhejiang University Yuquan Campus Hangzhou China Department of Computer Science Engineering The Pennsylvania State University University Park PA U.S.A. 《中国科学A辑(英文版)》2004,47(6):908-920
We present our recent work on both linear and nonlinear data reduction methods and algorithms: for the linear case we discuss results on structure analysis of SVD of column-partitioned matrices and sparse low-rank approximation; for the nonlinear case we investigate methods for nonlinear dimensionality reduction and manifold learning. The problems we address have attracted great deal of interest in data mining and machine learning. 相似文献
48.
49.
50.
Partitioned difference families (PDFs) arise from constructions of optimum constant composition codes. In this paper, a number of infinite classes of PDFs are constructed, based on known cyclotomic difference families in GF(q). A general approach which obtains PDFs from difference packings and coverings in abelian group is also presented. 相似文献