全文获取类型
收费全文 | 430篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 261篇 |
晶体学 | 5篇 |
力学 | 11篇 |
数学 | 84篇 |
物理学 | 85篇 |
出版年
2023年 | 1篇 |
2022年 | 23篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 22篇 |
2013年 | 14篇 |
2012年 | 27篇 |
2011年 | 28篇 |
2010年 | 25篇 |
2009年 | 15篇 |
2008年 | 17篇 |
2007年 | 24篇 |
2006年 | 27篇 |
2005年 | 18篇 |
2004年 | 10篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有446条查询结果,搜索用时 234 毫秒
61.
One of the innovative technological directions for the high-temperature superconductors has been persued by fabricating the
heteroepitaxial multilayer structures such as superconductor-semiconductor heterostructures. In the present investigation,
metal/superconductor/semiconductor (Ag/Tl-2223/CdSe) hetero-nanostructures have successfully been fabricated using dc electrodeposition
technique and were characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy
(SEM) studies. The measurement of junction capacitance as a function of biasing voltage was used for the estimation of junction
built-in-potential (V
D) and to study the charge distribution in a heterojunction. The Mott-Schottky plots were measured for each junction in dark
and under the photo-irradiation. The effect of laser irradiation on C-V characteristics of hetero-nanostructure has been studied. 相似文献
62.
A highly efficient iodine-catalyzed allylation of 1,3-dicarbonyl compounds with a wide variety of allylic alcohols has been developed. The reaction is operationally straightforward and proceeds under very mild conditions at room temperature in good to excellent yields (up to 99%) and regioselectivity. 相似文献
63.
As a brief sequel to our previous stability analysis of dumbbell molecule in torsional flow [1] we demonstrate that the motion of a dumbbell molecule in a continuous squeezing flow is also unstable at sufficiently large. Weissenberg number. The cause of instability in the present case, however, is quite different from the previous case. The mechanism responsible for triggering the instability is mainly attributed to the additional elongational flow component over the basic shear flow. The present flow situation is also different from the previous case in that the system is stochasticaly non-stationary, hence no steady-state average quantities can be obtained statistically. 相似文献
64.
Poly(neopentyl glycol adipate), PDPA, was found to be miscible with poly(epichlorohydrin-co-ethylene oxide). PDPA also formed miscible blends with chlorinated polyethylene samples containing 48 and 42% by weight of chlorine. Chlorinated polyethylene with a lower chlorine content was not miscible with PDPA. 相似文献
65.
Chun Hung Cheng Chon-Huat Goh Anita Lee 《The Journal of the Operational Research Society》1996,47(6):794-802
Many existing solution methodologies for machine assignment problems in group technology do not consider factors such as part demand, operation sequence and cost of intercellular moves. We formulate a 0-1 quadratic programming model that takes into account these factors in machine assignment. Two approaches are proposed to solve this problem. The first is an A*-based approach that generates optimal solutions. The second is a heuristic approach developed to solve problems with large number of machines and/or parts. The heuristic approach is shown to be efficient in producing good solutions in a computational study. 相似文献
66.
and
provided a variety of
and
alkaloids as well as novel ring-opened indole alkaloids including leuconolam (6), rhazinilam (8) and 5,21-dihydrorhazinilam (9). Facile acid and base reactions of leuconolam lead to ring reclosure products. Physical and spectral data of norfluorocurarine (
), norfluorocurarine-Nb-oxide (
), eburnamine (2), kopsinine (5) and epileuconolam (7) as well as some derivatives of leuconolam are also provided. 相似文献
67.
68.
69.
We find that the fractal scaling in a class of scale-free networks originates from the underlying tree structure called a skeleton, a special type of spanning tree based on the edge betweenness centrality. The fractal skeleton has the property of the critical branching tree. The original fractal networks are viewed as a fractal skeleton dressed with local shortcuts. An in silico model with both the fractal scaling and the scale-invariance properties is also constructed. The framework of fractal networks is useful in understanding the utility and the redundancy in networked systems. 相似文献
70.
Ang CY Boeré RT Goh LY Koh LL Kuan SL Tan GK Yu X 《Chemical communications (Cambridge, England)》2006,(45):4735-4737
The title heterocyclic radicals coordinate to either 17e CpCr(CO)3 or 15e CpCr(CO)2 moieties as one-electron or as three-electron donors, respectively; in the former the bonding is via the perpendicular p orbital of the sulfur atom, while in the latter bonding is via p(pi) orbitals on both sulfur and nitrogen. 相似文献