全文获取类型
收费全文 | 1893篇 |
免费 | 31篇 |
国内免费 | 11篇 |
专业分类
化学 | 1081篇 |
晶体学 | 7篇 |
力学 | 76篇 |
数学 | 486篇 |
物理学 | 285篇 |
出版年
2022年 | 25篇 |
2021年 | 20篇 |
2020年 | 14篇 |
2019年 | 30篇 |
2018年 | 26篇 |
2017年 | 29篇 |
2016年 | 51篇 |
2015年 | 49篇 |
2014年 | 60篇 |
2013年 | 108篇 |
2012年 | 95篇 |
2011年 | 95篇 |
2010年 | 73篇 |
2009年 | 70篇 |
2008年 | 118篇 |
2007年 | 111篇 |
2006年 | 99篇 |
2005年 | 73篇 |
2004年 | 59篇 |
2003年 | 54篇 |
2002年 | 61篇 |
2001年 | 12篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1996年 | 16篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 19篇 |
1989年 | 8篇 |
1985年 | 15篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 11篇 |
1927年 | 9篇 |
1926年 | 8篇 |
1912年 | 11篇 |
1910年 | 9篇 |
1909年 | 19篇 |
1903年 | 8篇 |
1898年 | 7篇 |
1890年 | 8篇 |
1885年 | 11篇 |
排序方式: 共有1935条查询结果,搜索用时 62 毫秒
1.
Chemical bonding in representative astrophysically relevant neutral,cation, and anion HCnH chains
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ioan Baldea 《中国物理 B》2022,31(12):123101-123101
Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths. Building on our recent work, in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis. Presently reported results include atomic charges, natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC2k/2k+1H chain family. They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes, e.g., electron removal from or electron attachment to a neutral chain. Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC2k/2k+1H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study. 相似文献
2.
Bucataru Ioan Constantinescu Oana Creţu Georgeta 《Annals of Global Analysis and Geometry》2022,62(4):815-827
Annals of Global Analysis and Geometry - We prove that in a Finsler manifold with vanishing $$\chi $$ -curvature (in particular with constant flag curvature) some non-Riemannian geometric... 相似文献
3.
Riad Hassani Patrick Hild Ioan Ionescu 《Mathematical Methods in the Applied Sciences》2004,27(1):47-67
We consider the Signorini problem with Coulomb friction in elasticity. Sufficient conditions of non‐uniqueness are obtained for the continuous model. These conditions are linked to the existence of real eigenvalues of an operator in a Hilbert space. We prove that, under appropriate conditions, real eigenvalues exist for a non‐local Coulomb friction model. Finite element approximation of the eigenvalue problem is considered and numerical experiments are performed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
5.
6.
We continue the studies on the so–called genuine Bernstein–Durrmeyer operators U
n
by establishing a recurrence formula for the moments and by investigating the semigroup T(t) approximated by U
n
. Moreover, for sufficiently smooth functions the degree of this convergence is estimated. We also determine the eigenstructure
of U
n
, compute the moments of T(t) and establish asymptotic formulas.
Received: January 26, 2007. 相似文献
7.
Using the linearization of Einstein's equations for weak gravitational fields, a specific model of gravito-magnetofluid is elaborated. The study of wave formation and propagation in such a medium is necessarily connected to the existence of the cosmological constant. 相似文献
8.
Ioan Tomescu 《Journal of Graph Theory》2003,43(3):210-222
In the set of graphs of order n and chromatic number k the following partial order relation is defined. One says that a graph G is less than a graph H if ci(G) ≤ ci(H) holds for every i, k ≤ i ≤ n and at least one inequality is strict, where ci(G) denotes the number of i‐color partitions of G. In this paper the first ? n/2 ? levels of the diagram of the partially ordered set of connected 3‐chromatic graphs of order n are described. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 210–222, 2003 相似文献
9.
10.
During irradiation of liquid samples of 1-vinylimidazole, 2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine and 1,1-diphenylethene
with positive muons, radicals of the type MuCH2ĊHAr (Ar=the appropriate aromatic group), and the MuCH2ĊPh2 radical were observed by transverse field μSR; the muon hyperfine couplings are considered in the context of the effectiveness
of the aryl groups in delocalising the unpaired electron. 相似文献