全文获取类型
收费全文 | 224篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 207篇 |
力学 | 1篇 |
数学 | 18篇 |
物理学 | 9篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 2篇 |
2013年 | 10篇 |
2012年 | 20篇 |
2011年 | 25篇 |
2010年 | 8篇 |
2009年 | 20篇 |
2008年 | 11篇 |
2007年 | 15篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 9篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有235条查询结果,搜索用时 15 毫秒
51.
Discovery of Highly Selective Alkyne Semihydrogenation Catalysts Based on First‐Row Transition‐Metallated Porous Organic Polymers 下载免费PDF全文
Dr. Kristine K. Tanabe Dr. Magali S. Ferrandon Dr. Nathan A. Siladke Dr. Steven J. Kraft Guanghui Zhang Dr. Jens Niklas Dr. Oleg G. Poluektov Dr. Susan J. Lopykinski Dr. Emilio E. Bunel Dr. Theodore R. Krause Dr. Jeffrey T. Miller Dr. Adam S. Hock Dr. SonBinh T. Nguyen 《Angewandte Chemie (International ed. in English)》2014,53(45):12055-12058
Five different first‐row transition metal precursors (VIII, CrIII, MnII, CoII, NiII) were successfully incorporated into a catechol porous organic polymer (POP) and characterized using ATR‐IR and XAS analysis. The resulting metallated POPs were then evaluated for catalytic alkyne hydrogenation using high‐throughput screening techniques. All POPs were unexpectedly found to be active and selective catalysts for alkyne semihydrogenation. Three of the metallated POPs (V, Cr, Mn) are the first of their kind to be active single‐site hydrogenation catalysts. These results highlight the advantages of using a POP platform to develop new catalysts which are otherwise difficult to achieve through traditional heterogeneous and homogeneous routes. 相似文献
52.
The reaction of cobalt(II), nickel(II), copper(II) chlorides and bromides with 3-thiophene aldehyde thiosemicarbazone (3TTSCH) leads to the formation of a series of new complexes: [Co(3TTSC)2], [Ni(3TTSC)2], [CuCl(3TTSC)]2, [CuBr(3TTSC)]2 and [CuBr2(3TTSCH)]. The crystal structures of the free ligand and of the compound [Ni(3TTSC)2] have been determined by X-ray diffraction methods. For all these complexes, the central ion is coordinated through the sulfur and the azomethine nitrogen atom of the thiosemicarbazone. [Co(3TTSC)2], [Ni(3TTSC)2] and [CuBr2(3TTSCH)] are mononuclear species, while [CuCl(3TTSC)]2 and [CuBr(3TTSC)]2 are binuclear complexes. 相似文献
53.
Fabien Lamoureux Jean-michel Gaulier François-Ludovic Sauvage Magali Mercerolle Christine Vallejo Gérard Lachâtre 《Analytical and bioanalytical chemistry》2009,394(7):1895-1901
The detection of ethyl-β-d-6-glucuronide (EtG), a stable phase II metabolite of ethanol, is of interest in both clinical and forensic contexts with
the aim of monitoring alcohol abuse. We present a liquid chromatography-electrospray ionisation-tandem mass spectrometry method
for the detection and quantification of EtG in hair. Thirty milligrams of washed and cut hair were cleaned up using solid-phase
extraction graphite cartridges. Separation was then performed using an Uptisphere-3SI column, and the detection was operated
in the negative mode. After validation, the method was applied to hair samples taken from four fatalities (F) with documented
excessive drinking habits, 12 heavy drinkers (HD) and seven social drinkers (SD). The method exhibits limits of detection
and quantification of 4 and 10 pg/mg, respectively. Intra- and inter-assay standard deviation and relative bias were less
than 20% over the calibrating range (10 to 3,000 pg/mg). EtG hair concentrations in SD were <10 pg/mg and >50 pg/mg for F
and HD (range, 54 to 497 pg/mg). The present assay appears convenient to carry out owing to the very small quantity of hair
samples required to determine an effective heavy alcohol consumption (EtG hair concentration >50 pg/mg). 相似文献
54.
Rodrigues MA Bemquerer MP Mohallem ND Politi MJ 《Langmuir : the ACS journal of surfaces and colloids》2006,22(21):8939-8944
A nanohybrid xerogel (XDPN) was obtained from a tetraethyl orthosilicate (TEOS) condensation reaction in the presence of N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (DPN). Physical and chemical characterization of the materials revealed that the XDPN morphology is quite different from that of xerogel without DPN (X). Photochemical and photophysical studies of the hybrid material showed that XDPN is efficient in promoting the photosensitization of tryptophan radical formation, and the radical species are stabilized due to the presence of DPN aggregates in the material. Radical stabilization can also be observed for DPN in solution but only for concentrations in the millimolar range. 相似文献
55.
Using a radial flow chamber, we study Saccharomyces cerevisiae kinetics of detachment from stainless steel substrates. Samples of similar surface chemistry, but with different surface topologies are compared: mirror polished and electro-chemically etched. Different grain sizes (20, 40 and 100 microm) and different etching depths (100-650 nm) are tested. Cells are removed from the substrate according to a first-order kinetics defining two macroscopic parameters that depend on the applied stress: the detachment efficiency and the detachment rate constant. Whatever the surface topology, detachment occurs above a threshold and its rate is strongly stimulated by the applied stress. The detachment efficiency is characterized by the shear stress at which half of the cells detach and is independent of surface topology. In contrast, detachment is faster from etched than mirror polished surfaces. Finally, we also show the preferential adhesion of yeast cells to grains of < 001 > crystallographic orientation with respect to the surface. 相似文献
56.
Albert J Cadena JM González A Granell J Solans X Font-Bardia M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(3):887-894
We report that the action of Lewis bases, such as triphenylphosphine, pyridine, or trimethylamine, on imine metallacycles derived from amino acids leads to the formation of the first organometallic compound of an NH aldimine, a highly reactive organic species, and the corresponding alpha-ketoester, in a deamination reaction that mimics the metabolism of alpha-amino acids. The synthesis of different cyclopalladated compounds by a reaction between palladium acetate and the Schiff bases 2,4,6-Me(3)C(6)H(2)CH=NCH(R(1))COOR(2) (R(1) = CH(2)Ph, R(2) = Et and R(1) = Ph, R(2) = Me) is also reported. 相似文献
57.
58.
Delogu G Fabbri D Dettori MA Sallé M Derf FL Blesa MJ Allain M 《The Journal of organic chemistry》2006,71(24):9096-9103
The synthesis of a family of biphenyl-tetrathiafulvalene (TTF) derivatives incorporating a binding site has been carried out in good to moderate yields through functionalization of the biphenyl scaffold. X-ray structure of one derivative (compound 3) of the series is provided and shows a dihedral angle of 74 degrees around the central Ar-Ar bond of the biphenyl unit in a cisoid conformation. (1)H NMR and cyclic-voltammetry studies demonstrate the critical importance of the nature of the substitution on the conformational rigidity and on the electrochemical behavior of the resulting biphenyl-TTF assemblies. This feature is underlined by an original electrochemical recognition process upon binding of Pb(2+), correlated to conformational changes occurring upon metal cation complexation. 相似文献
59.
Magali Bardet 《Applied mathematics and computation》2011,217(17):7318-7323
The C-Algorithm introduced in [5] is designed to determine isochronous centers for Lienard-type differential systems, in the general real analytic case. However, it has a large complexity that prevents computations, even in the quartic polynomial case.The main result of this paper is an efficient algorithmic implementation of C-Algorithm, called ReCA (Reduced C-Algorithm). Moreover, an adapted version of it is proposed in the rational case. It is called RCA (Rational C-Algorithm) and is widely used in [1] and [2] to find many new examples of isochronous centers for the Liénard type equation. 相似文献
60.
Abdelfattah Mahmoud Sebastien Caes Magali Brisbois Raphaël P. Hermann Loris Berardo Audrey Schrijnemakers Cédric Malherbe Gauthier Eppe Rudi Cloots Bénédicte Vertruyen Frédéric Boschini 《Journal of Solid State Electrochemistry》2018,22(1):103-112
In this work, Na2FePO4F-carbon composite powders were prepared by spray-drying a solution of inorganic precursors with 10 and 20 wt% added carbon black (CB) or carbon nanotubes (CNTs). In order to compare the effect of CB and CNT when added to the precursor solutions, the structural, electrochemical, and morphological properties of the synthesized Na2FePO4F-xCB and Na2FePO4F-xCNT samples were systematically investigated. In both cases, X-ray diffraction shows that calcination at 600 °C in argon leads to the formation of Na2FePO4F as the major inorganic phase. 57Fe Mössbauer spectroscopy was used as complementary technique to probe the oxidation states, local environment, and identify the composition of the iron-containing phases. The electrochemical performance is markedly better in the case of Na2FePO4F-CNT (20 wt%), with specific capacities of about 100 mAh/g (Na2FePO4F-CNT) at C/4 rate vs. 50 mAh/g for Na2FePO4F-CB (20 wt%). SEM characterization of Na2FePO4F-CB particles revealed different particle morphologies for the Na2FePO4F-CNT and Na2FePO4F-CB powders. The carbon-poor surface observed for Na2FePO4F-CB could be due to a slow diffusion of carbon in the droplets during drying. On the contrary, Na2FePO4F-CNT shows a better CNT dispersion inside and at the surface of the NFPF particles that improves the electrochemical performance. 相似文献