全文获取类型
收费全文 | 7117篇 |
免费 | 380篇 |
国内免费 | 187篇 |
专业分类
化学 | 4323篇 |
晶体学 | 76篇 |
力学 | 298篇 |
综合类 | 25篇 |
数学 | 1049篇 |
物理学 | 1913篇 |
出版年
2023年 | 70篇 |
2022年 | 173篇 |
2021年 | 182篇 |
2020年 | 191篇 |
2019年 | 188篇 |
2018年 | 172篇 |
2017年 | 150篇 |
2016年 | 225篇 |
2015年 | 223篇 |
2014年 | 249篇 |
2013年 | 489篇 |
2012年 | 442篇 |
2011年 | 492篇 |
2010年 | 309篇 |
2009年 | 279篇 |
2008年 | 360篇 |
2007年 | 304篇 |
2006年 | 310篇 |
2005年 | 263篇 |
2004年 | 198篇 |
2003年 | 208篇 |
2002年 | 177篇 |
2001年 | 159篇 |
2000年 | 140篇 |
1999年 | 108篇 |
1998年 | 67篇 |
1997年 | 64篇 |
1996年 | 72篇 |
1995年 | 52篇 |
1994年 | 91篇 |
1993年 | 65篇 |
1992年 | 77篇 |
1991年 | 62篇 |
1990年 | 57篇 |
1989年 | 45篇 |
1988年 | 46篇 |
1987年 | 41篇 |
1986年 | 43篇 |
1985年 | 63篇 |
1984年 | 63篇 |
1983年 | 38篇 |
1982年 | 62篇 |
1981年 | 53篇 |
1980年 | 57篇 |
1979年 | 51篇 |
1978年 | 58篇 |
1977年 | 51篇 |
1976年 | 46篇 |
1975年 | 37篇 |
1973年 | 39篇 |
排序方式: 共有7684条查询结果,搜索用时 15 毫秒
11.
Summary. In the context of the generalized ADI method, we are concerned with the problem of finding in the set of rational functions
r with numerator degree m and denominator degree n an element that minimizes where E,F are disjoint real intervals. By extending a recent analysis by Levin and Saff, we present an explicit formula for choosing
the pair (m,n) for given m +n. Furthermore, we provide a characterization of and a Remes type algorithm for its determination. Extensive numerical computations furnish some comparison of with asymptotically optimal solutions based on Fejér-Walsh and Leja-Bagby points.
Received September 6, 1996 / revised version received June 30, 1997 相似文献
12.
13.
C. Bréchignac Ph. Cahuzac F. Carlier C. Colliex M. de Frutos N. Kébaïli J. Le Roux A. Masson B. Yoon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):265-268
We studied shape relaxation of nano-fractal islands,
during annealing, after their growth from antimony cluster
deposition on graphite surface. Annealing at
180°C shows evidence of an increase
of the fractal branch width with time followed by branch
fragmentation, without changing the fractal dimension. The time
evolution of the width of the arm suggests the surface
self-diffusion mechanism as the main relaxation process. With
Monte Carlo simulations, we confirmed the observed behavior.
Comparison is done with our previous results on fragmentation of
nano-fractal silver islands when impurity added to the incident
cluster promotes rapid fragmentation by surface self-diffusion
enhancement [1]. 相似文献
14.
Khanh Le Chau Pham Duc Chinh 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1991,42(4):614-622
In this paper inequalities for the effective conductivity of isotropic composite materials are derived. These inequalities depend on several coefficients characterizing the microstructure of composites. The obtained coefficients can be exactly calculated for models of a two-component aggregate of multisized, coated ellipsoidal inclusions, packed to fill all space. As a result, new bounds for effective conductivity, considerably narrower than those of Hashin-Shtrikman, are established for such models of composite materials. 相似文献
15.
We investigate the dependence of the relaxation time of the current flowing in a nematic cell submitted to an external dc voltage on the physical properties of the substrate. We show that previously presented analyses of the same problem are not very useful for practical applications. We compare our theoretical predictions with experimental data, and show that the agreement is rather good. The influence of the adsorption-desorption phenomenon on the relaxation time is also discussed. 相似文献
16.
We study in this Note the continuum (macroscopic) limit for some atomistic models for crystals. The purpose is to derive densities of mechanical energies from microscopic models. In contrast to the setting of a previous study, where the microscopic structure was assumed to be periodic, it is modelled here by a stochastic lattice, which enjoys some stationarity and ergodicity properties, following notions previously introduced elsewhere. To cite this article: X. Blanc et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
17.
Tian Le LIN Bao Zhen YAN Gao Fei HU Mei WANG 《中国化学快报》2006,17(7):937-940
Complex formation between aluminium and quercetin(Q) in methanol was investigated by means of 27^Al solid-state, 13^C and 1^H NMR and MS(ESI), UV and IR spectra. Formation of the 1:2 complex was favored in methanol relative to all other solvent and the predominant species observed of Al(Ⅲ) has a 1:2 stoichiometry. The fine structure of 1:2 aluminum complex of quercetin was that the aluminum central atom chelated with two quereetin molecules and two methoxyl groups between two five membered rings, its coordination is six, the chelated site was 3-hydroxy-4-carbonyl. 相似文献
18.
M. Le Vassor D’yerville D. Monge D. Cassagne J. P. Albert 《Optical and Quantum Electronics》2002,34(5-6):445-454
We present here a tight-binding-like modelling of two-dimensional (2D) photonic crystals (PCs). Adopted from solid-state physics,
the concept of generalized Wannier functions is used to construct a localized state basis that allows a parameter-free ab
initio study of defects in PCs. We demonstrate here for a 2D triangular lattice of dielectric rods in air, the existence of
this localized basis and the possibility to study large scale complex dielectric structures deviating from periodicity. Specific
numerical simulations on a split waveguide embedded in this triangular lattice are performed, and they demonstrate the superiority
of this method over plane wave based techniques. 相似文献
19.
20.
Chepoi showed that every breadth first search of a bridged graph produces a cop-win ordering of the graph. We note here that Chepoi's proof gives a simple proof of the theorem that G is bridged if and only if G is cop-win and has no induced cycle of length four or five, and that this characterization together with Chepoi's proof reduces the time complexity of bridged graph recognition. Specifically, we show that bridged graph recognition is equivalent to (C4,C5)-free graph recognition, and reduce the best known time complexity from O(n4) to O(n3.376). 相似文献