全文获取类型
收费全文 | 550篇 |
免费 | 18篇 |
专业分类
化学 | 344篇 |
晶体学 | 10篇 |
力学 | 5篇 |
数学 | 80篇 |
物理学 | 129篇 |
出版年
2023年 | 3篇 |
2022年 | 19篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2019年 | 19篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 27篇 |
2015年 | 22篇 |
2014年 | 36篇 |
2013年 | 71篇 |
2012年 | 23篇 |
2011年 | 20篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 21篇 |
2007年 | 15篇 |
2006年 | 19篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 15篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1973年 | 5篇 |
1961年 | 2篇 |
1913年 | 2篇 |
1909年 | 2篇 |
排序方式: 共有568条查询结果,搜索用时 15 毫秒
471.
In this paper we answer a question of A. Lubotzky by giving examples of groups having property (T) without uniform Kazhdan
constants. We show that many lattices in Lie groups do not admit a Kazhdan constant which is independent of the generating
subset. 相似文献
472.
M. Pankov K. Prażmowski M. Żynel 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》2005,75(1):21-50
Transformations of spine spaces which preserve base subsets preserve also adjacency. They either preserve the two sorts of
projective adjacency or interchange them. Lines of a spine space can be defined in terms of adjacency, except one case where
projective lines have no proper extensions to projective maximal strong subspaces, and thus adjacency preserving transformations
are collineations. 相似文献
473.
J. Żochowski 《Few-Body Systems》2005,36(1-4):257-261
A novel consistent treatment of the light-front momentum integrals is proposed. The actual calculations are performed for the closed fermion loops in (1 + 1) dimensions, including Furry’s theorem. The regularization of Pauli-Villars is employed for the tadpole and two-leg diagrams. The problems with the light-front effective potentials are consistently solved. 相似文献
474.
475.
Dorota Maciejewska Paweł Kaźmierczak Jerzy Żabiński Irena Wolska Sylwia Popis 《Monatshefte für Chemie / Chemical Monthly》2006,137(9):1225-1240
Summary. The synthesis of four new 1,5-bis(4-amidinophenoxy)-3-oxapentane analogs is described. The structures of the obtained bis-amidines
and bis-nitriles in the solid state are evaluated on the basis of 13C CP/MAS NMR spectra and theoretical calculations at DFT level. A single crystal X-ray diffraction structure is presented
for 1,5-bis(4-amidinophenoxy)-3-oxapentane. A preliminary anticancer assay against three cell lines is also given. 相似文献
476.
Katarzyna Wińska Małgorzata Grabarczyk Wanda Mączka Barbara Żarowska Gabriela Maciejewska Mirosław Anioł 《Journal of Saudi Chemical Society》2018,22(3):363-371
Ten new derivatives of isophorone were obtained through a five-step synthesis. Among the products were several unsaturated, bicyclic lactones with three or four methyl groups. These lactones were used as the substrates for biotransformation mediated by selected fungal strains (Fusarium species, Syncephalastrum racemosum, Cunninghamella japonica, Penicillium species, Absidia species, and Pleurotus ostreatus). Four new hydroxylactones were obtained as a result of biotransformation. Because the unsaturated lactone with four methyl groups was a diastereoisomeric mixture, a structural analysis was conducted. The hydroxylactones were also included in this analysis. Both the unsaturated lactones and hydroxylactones were examined for their antimicrobial activity. It was found that some of these compounds exhibited growth inhibition against pathogenic strains of bacteria (Staphylococcus aureus, Pseudomonas fluorescens), yeasts (Candida albicans) and filamentous fungi (Alternaria sp., Penicillium sp.). All obtained compounds were also subjected to scent analysis. 相似文献
477.
Jerzy Żuchowski Łukasz Pecio Emilia Reszczyńska Anna Stochmal 《Helvetica chimica acta》2016,99(9):674-680
While lentil (Lens culinaris) seeds are phytochemically well characterized, very little is known about secondary metabolites from lentil roots. Our research on lentil roots led to isolation of five phenolic compounds and five group B soyasaponins. Their structures were established using NMR spectroscopy and mass spectrometry. Four phenolics have not been hitherto described in the literature: 4‐O‐β‐d ‐glucopyranosyl‐2‐methoxybenzoic acid, (αS)‐4,4′‐di‐O‐β‐d ‐glucopyranosyl‐α,2′‐dihydroxydihydrochalcone, (αS)‐4′‐O‐β‐d ‐glucopyranosyl‐α,2′,4‐trihydroxydihydrochalcone, and keto‐2‐hydroxyglycitein. The DPPH? radical‐scavenging activity of the purified phenolic compounds was additionally evaluated. 相似文献
478.
479.
The interaction of the diethyl(quinolin-2-ylmethyl)phosphonate (2-qmpe) ligand with CoCl2 · 2H2O unexpectedly leads to the formation of a compound with the formula [Co(2-qca)2(EtOH)2] (2-qca = quinoline-2-carboxylate). This compound is a product of the oxidative cleavage of the C–P bond in 2-qmpe and the formation of the 2-qca ligand. The title compound was characterized by infrared, ligand field, EPR spectroscopy and low temperature magnetic (1.8–300 K) studies. Particularly, the crystal and molecular structures were determined by the X-ray diffraction. The CoN2O4 chromophore shows an elongated octahedron geometry, resulting from the two didentate N,O-bonded chelate ligands and two ethanol molecules – quinolil nitrogen atoms are located in axial positions and oxygen atoms are positioned in the basal plane. The crystal packing is due to hydrogen bonds and π–π stacking interactions, which give rise to a three-dimensional (3D) polymeric network. The magnetic properties reflect the molecular character of the compound, with a very weak magnetic exchange interaction. The moments are enhanced due to an important orbital contribution via spin–orbit coupling. 相似文献
480.
Emilia Grodzka Joanna Grabowska Monika Wysocka-Żołopa Krzysztof Winkler 《Journal of Solid State Electrochemistry》2008,12(10):1267-1278
The electrochemically active polymers have been formed during electro-reduction carried out in solution containing fullerenes,
C60 or C70, and transition metal complexes of Pd(II), Pt(II), Rh(III), and Ir(I). In these films, fullerene moieties are covalently
bounded to transition metal atoms (Pd and Pt) or their complexes (Rh and Ir) to form a polymeric network. All films exhibit
electrochemical activity at negative potentials due to the fullerene cages reduction process. For all studied metal complexes,
yields of formation of films containing C70 are higher than yields of electrodeposition of their C60 analogs. C70
/M films also exhibit higher porosity in comparison to C60/M layers. The differences in film morphology and efficiency of polymer formation are responsible for differences in electrochemical
responses of these films in acetonitrile containing supporting electrolyte only. C70/M films shows more reversible voltammeric behavior in negative potential range. They also show higher potential range of electrochemical
stability. Processes of film formation and electrochemical properties of polymers depend on the transition metal ions or atoms
bonding fullerene cages into polymeric network. The highest efficiency of polymerization was observed for fullerene/Pd and
fullerene/Rh films. In the case of fullerene/Pd films, the charge transfer processes related to the fullerene moieties reduction
in negative potential range exhibit the best reversibility among all of the studied systems. Capacitance performances of C60/Pd and C70/Pd films deposited on the porous Au/quartz electrode were also compared. Capacitance properties of both films are significantly
affected by the conditions of electropolymerization. Only a fraction of the film having a direct contact with solution contributes
to pseudocapacitance. Capacitance properties of these films also depend on the size of cations of supporting electrolyte.
The C70/Pd film exhibits much better capacitance performance comparison to C60/Pd polymer. 相似文献