全文获取类型
收费全文 | 108篇 |
免费 | 2篇 |
专业分类
化学 | 41篇 |
数学 | 9篇 |
物理学 | 60篇 |
出版年
2016年 | 2篇 |
2015年 | 3篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 7篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1969年 | 1篇 |
1932年 | 1篇 |
1929年 | 1篇 |
1920年 | 4篇 |
1919年 | 1篇 |
1904年 | 2篇 |
排序方式: 共有110条查询结果,搜索用时 24 毫秒
1.
A Bioinspired Molybdenum Complex as a Catalyst for the Photo‐ and Electroreduction of Protons 下载免费PDF全文
Jean‐Philippe Porcher Thibault Fogeron Dr. Maria Gomez‐Mingot Dr. Etienne Derat Lise‐Marie Chamoreau Dr. Yun Li Prof. Marc Fontecave 《Angewandte Chemie (International ed. in English)》2015,54(47):14090-14093
A molybdenum–dithiolene–oxo complex was prepared as a model of some active sites of Mo/W‐dependent enzymes. The ligand, a quinoxaline–pyran‐fused dithiolene, mimics molybdopterin present in these active sites. For the first time, this type of complex was shown to be active as a catalyst for the photoreduction of protons with excellent turnover numbers (500) and good stability in aqueous/organic media and for the electroreduction of protons in acetonitrile with remarkable rate constants (1030 s?1 at ?1.3 V versus Ag/AgCl). DFT calculations provided insight into the catalytic cycle of the reaction, suggesting that the oxo ligand plays a key role in proton exchange. These results provide a basis to optimize this new class of H2‐evolving catalysts. 相似文献
2.
3.
Gottlieb-Röse Eichloff Grimmer Röhrig D. P. Ross van Lennep J. D. Ruys W. Bremer W. Greifenhagen C. Huyge A. A. Bonnema C. J. König W. C. Moog Orla-Jensen J. van Haarst M. Siegfeld O. Richter H. Droop Ross Gerber Wendler A. Sichler J. Golding Hesse Fr. Kundrat A. Rosam W. R. Bloor B. G. Lellan E. P. Harding G. Parkin Ch. Porcher A. A. A. Utt J. O. Halverson N. G. Redmond Klein Janoss H. F. Lichtenberg L. Fr. Rosengren Mats Weibull Rusche L. Lindet J. Boes H. Weyland 《Analytical and bioanalytical chemistry》1919,58(10-11):516-525
4.
Nd(5)CoSi(2) was obtained from the elements by arc-melting followed by annealing at 883 K. Its investigation by single-crystal x-ray and neutron powder diffraction shows that this ternary silicide crystallizes as Nd(5)Si(3) in a tetragonal structure deriving from the Cr(5)B(3)-type (I4/mcm space group; a = 7.7472(2) and c = 13.5981(5) ? as unit cell parameters). The structural refinements confirm the mixed occupancy on the 8h site between Si and Co atoms, as already observed for Gd(5)CoSi(2). Magnetization and specific heat measurements reveal a ferromagnetic behavior below T(C) = 55 K for Nd(5)CoSi(2). This magnetic ordering is further evidenced by neutron powder diffraction investigation revealing between 1.8 K and T(C) a canted ferromagnetic structure in the direction of the c-axis described by a propagation vector k = (0 0 0). At 1.8 K, the two Nd(3+) ions carry ordered magnetic moments equal respectively to 1.67(7) and 2.37(7) μ(B) for Nd1 and Nd2; these two moments exhibit a canting angle of θ = 4.3(6)°. This magnetic structure presents some similarities with that reported for Nd(5)Si(3). 相似文献
5.
Anthony JM Garrett 《Contemporary Physics》2013,54(2):163-165
The dynamic electronic structure of atoms and molecules can be directly observed by means of the (e, 2e) reaction, which measures the distribution of energies and momenta of two electrons in coincidence after a knockout reaction initiated by an electron beam of known momentum incident on a molecular gas target. The molecular state for each event is identified by the electron separation energy. The recoil momentum for each event is known from the difference of measured initial and final momenta. It has been verified that values of this momentum are equal under suitable conditions to the momentum of the electron in the target immediately before knockout. Thus the spherically-averaged electron momentum distribution for each molecular orbital is measured. This is directly related to molecular orbitals calculated by the methods of quantum chemistry. Properties obtained by this method for different types of molecules are discussed. 相似文献
6.
Kinani S Bouchonnet S Bourcier S Creusot N Porcher JM Aït-Aïssa S 《Rapid communications in mass spectrometry : RCM》2008,22(22):3651-3661
A sensitive and simple method based on ultrasonication extraction with a hexane/acetone (2:1, v/v) mixture, followed by clean up of the extract by solid-phase extraction (SPE) and gas chromatography/mass spectrometry (GC/MS) detection, has been developed and validated for the analysis of 20 estrogenic endocrine-disrupting chemicals (EEDCs) including phenolic xenoestrogens, synthetic and natural estrogens in river sediment. After extraction and purification, analytes are derivatised with a BSTFA/TMCS/pyridine (49:1:50, v/v/v) mixture and quantified by GC/MS. The GC/MS method involves switching between electron ionisation (EI) and chemical ionisation (CI); it also switches between selected ion storage and tandem mass spectrometry detection. The applicability of the method has been demonstrated by analysing extracts of French river sediments for which bioanalytical tests (in vitro) had already shown that they were impacted by estrogenic endocrine disrupters. The biological contribution of all the products detected in each sediment extract was compared to the estrogenic activity measured by bioassays. 相似文献
7.
de Farias RF de Souza JM de Melo JV Airoldi C 《Journal of colloid and interface science》1999,212(1):123-129
The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press. 相似文献
8.
Titration microcalorimetry is used to study the influences of iodide, bromide, and chloride counterions on the aggregation of vesicle-forming 1-methyl-4-(2-pentylheptyl)pyridinium halide surfactants. Formation of vesicles by these surfactants was characterised using transmission electron microscopy. When the counterion is changed at 303 K through the series iodide, bromide, to chloride, the critical vesicular concentration (cvc) increases and the enthalpy of vesicle formation changes from exo- to endothermic. With increase in temperature to 333 K, vesicle formation becomes strongly exothermic. Increasing the temperature leads to a decrease in enthalpy and entropy of vesicle formation for all three surfactants. However the standard Gibbs energy for vesicle formation is, perhaps surprisingly, largely unaffected by an increase in temperature, as a consequence of a compensating change in both standard entropy and standard enthalpy of vesicle formation. Interestingly, standard isobaric heat capacities of vesicle formation are negative, large in magnitude but not strikingly dependent on the counterion. We conclude that the driving force for vesicle formation can be understood in terms of overlap of the thermally labile hydrophobic hydration shells of the alkyl chains. Copyright 2000 Academic Press. 相似文献
9.
Olfa Labidi Florence Porcher Rose-Noëlle Vannier 《Journal of solid state chemistry》2008,181(9):2260-2267
Reinvestigation of PbBiOVO4 thermal behaviour revealed a phase transition. As shown by single-crystal X-ray diffraction and high-resolution neutron powder diffraction, α-PbBiOVO4 transforms to β-PbBiOVO4 at 550 °C. At 25 °C, α-PbBiOVO4 is triclinic, S.G. P-1, Z=2, with a=5.6088(3), b=7.1109(3), c=7.2978(3) Å, α=108.957(2), β=111.889(2), and γ=94.833(2)°. Above 550 °C, β-PbBiOVO4 is monoclinic, S.G. C2/m, Z=4, with a=13.61(1), b=5.64(1), c=7.18(1) Å, and β=113.75(1)°. Both structures are built upon (O2Bi2Pb2)∞ chains parallel to the [100] direction in the α polymorph and [001] in the β-polymorph. These chains are undulated in α and linear in β. In both structures, VO4 tetrahedra are organized in two sets of rows parallel to (O2Bi2Pb2)∞ chains, thus building layers of (OBiPb) sandwiched by two layers of VO4 oriented head to tail; VO4 displays different orientations in α- and β-PbBiOVO4. 相似文献
10.
Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14