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排序方式: 共有88条查询结果,搜索用时 140 毫秒
61.
Levillain J Dubant G Abrunhosa I Gulea M Gaumont AC 《Chemical communications (Cambridge, England)》2003,(23):2914-2915
A novel class of chiral ionic liquids derived from amino alcohols is prepared in multi-gram scale. Their potential in chiral recognition is shown in a preliminary example with racemic Mosher's acid salt. 相似文献
62.
The problem of the origin of electrode effects in various electrolytes is studied on the ground of Fourier's equation. Thus the electrolysis time elapsed before the occurrence of an electrode effect is shown to be equal to the calculated time which is the time necessary to bring the temperature of the electrolyte surrounding the electrode up to its boiling point. Then we can conclude in all cases investigated that the electrode effects are induced by a Joule effect heating of the electrolyte. 相似文献
63.
Jocelyne Giraud-Girard Daniel Maynau 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,23(1):91-98
The equilibrium geometries of Na n F n and Na n F n?1 are optimized forn=2, 3, 4 at the SCF level. The Na n F n molecules appear as formed by Na+ and F? ions. The paper studies the localization of the excess electron in the Na n F n?1 molecules. Na n F n?1 is obtained by removing from Na n F n a fluorine atom, and the excess electron takes the place of this lacking center, and allows a weak bond between the neighbouring Na atoms. Secondary minimum geometries, for which the excess electron has no defined place, are also studied. 相似文献
64.
Jocelyne Ethve Philippe Djardin Michel Boissire 《Colloids and surfaces. B, Biointerfaces》2003,28(4):59-293
We present the influence of pH, from pH 4 to 10, with a focus on the neutral range, on the adsorption of lysozyme (isoelectric point pI=11) on a sulphonated membrane and the same membrane pre-treated with poly(ethyleneimine) (PEI). We found a steep increase of the adsorbed amount above pH 6 in phosphate buffer. The adsorbed amount was about twice as low in Tris buffer, around the neutral pH. The difference between the two types of buffer is attributed to their different ionic composition. High interfacial concentration in phosphate buffer is especially linked to the phosphate divalent anions. In the presence of divalent sulphate anions, we measured the same level of interfacial concentration than with phosphate buffer. With the PEI pre-treated membrane, we observed, on the time scale of our experiments (15–20 h), similar adsorbed amounts than on the raw membrane, showing that the PEI layer does not constitute a true barrier to the penetration of lysozyme into the membrane core. However, its presence leads to a slower adsorption rate in a system where convection does not occur through the membrane. 相似文献
65.
Florence Babonneau Christian Bonhomme Christel Gervais Jocelyne Maquet 《Journal of Sol-Gel Science and Technology》2004,31(1-3):9-17
The objective of this paper is to discuss the recent advances in high resolution solid state Nuclear Magnetic Resonance (NMR) to characterise sol-gel derived materials. The first part will be focused on methods to describe M i --O--M j connectivities in sol-gel networks. After a brief review on techniques based on scalar J-coupling, we will focus on the use of 17O solid state NMR experiments. Then in a second part, techniques to probe through-space interactions in hybrid networks will be described, with a particular emphasis on the use of high resolution 1H solid state NMR sequences and related two-dimensional homonuclear or heteronuclear correlations. 相似文献
66.
Azaïs T Bonhomme-Coury L Vaissermann J Bertani P Hirschinger J Maquet J Bonhomme C 《Inorganic chemistry》2002,41(4):981-988
We present the structure and a multinuclear solid-state NMR study of a new cyclic aluminophosphinate. The crystallographic structure of [Al(2)(HC(6)H(5)PO(2))(2)(C(4)H(9)OH)(8)]Cl(4) (compound 1) was obtained at low temperature (a = 11.830(7) A, b = 14.216(6) A, c = 17.790(6) A, beta = 91.25(4) degrees, monoclinic, P21/c, Z = 2). (13)C IRCP (inversion recovery cross polarization) and NQS (non quaternary suppression) NMR experiments allowed the complete assignment of the quaternary carbon atom of the phenyl ring and the precise determination of the isotropic /(1)J(P-C)/ coupling constant. (31)P CP MAS dynamics was carefully studied by varying the contact time. Dipolar oscillations even at slow MAS were observed. Up to 11 kHz, these oscillations were more pronounced, and the P-H distance was easily extracted. (27)Al NMR quadrupolar parameters for 1 were obtained with very good accuracy, and unusual satellite transition splitting was observed. Furthermore, the isotropic lines of the inner and outer transitions were clearly observable, leading to the unambiguous determination of the quadrupolar parameters. 相似文献
67.
Nathalie Lebrun Fabrice Mahe Jocelyne Lamiot Michel Foulon Jean Claude Petit 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1129-1131
The crystal structure of a new high-temperature phase of nitric acid dihydrate, HNO3·2H2O, has been determined at 225 K by single-crystal X-ray diffraction. The H atom of the nitric acid is delocalized to one water molecule, leading to an association of equimolar NO3− and H5O2+ ionic groups. The asymmetric unit contains two molecules of HNO3·2H2O. The two independent molecules are related by a pseudo-twofold c axis, by a translation of 0.54 (approximately ½) along b , with a mean atomic distance difference of 0.3 Å, except for one H atom of the water molecules (1.5 Å), because of their different orientations in the two molecules. The two independent molecules, linked by strong hydrogen bonds, are arranged in layers. These layers are linked by weaker hydrogen bonds oriented approximately along the c axis. A three-dimensional hydrogen-bond network is observed. 相似文献
68.
Irshad Mohammad Lucie Blondeau Jocelyne Leroy Hicham Khodja Magali Gauthier 《Molecules (Basel, Switzerland)》2021,26(18)
Achieving the full potential of magnesium-ion batteries (MIBs) is still a challenge due to the lack of adequate electrodes or electrolytes. Grignard-based electrolytes show excellent Mg plating/stripping, but their incompatibility with oxide cathodes restricts their use. Conventional electrolytes like bis(trifluoromethanesulfonyl)imide ((Mg(TFSI)2) solutions are incompatible with Mg metal, which hinders their application in high-energy Mg batteries. In this regard, alloys can be game changers. The insertion/extraction of Mg2+ in alloys is possible in conventional electrolytes, suggesting the absence of a passivation layer or the formation of a conductive surface layer. Yet, the role and influence of this layer on the alloys performance have been studied only scarcely. To evaluate the reactivity of alloys, we studied InSb as a model material. Ex situ X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy were used to investigate the surface behavior of InSb in both Grignard and conventional Mg(TFSI)2/DME electrolytes. For the Grignard electrolyte, we discovered an intrinsic instability of both solvent and salt against InSb. XPS showed the formation of a thick surface layer consisting of hydrocarbon species and degradation products from the solvent (THF) and salt (C2H5MgCl−(C2H5)2AlCl). On the contrary, this study highlighted the stability of InSb in Mg(TFSI)2 electrolyte. 相似文献
69.
70.
This paper compares the performance on linear systems of equations of three similar adaptive accelerating strategies for restarted GMRES. The underlying idea is to adaptively use spectral information gathered from the Arnoldi process. The first strategy retains approximations to some eigenvectors from the previous restart and adds them to the Krylov subspace. The second strategy also uses approximated eigenvectors to define a preconditioner at each restart. This paper designs a third new strategy which combines elements of both previous approaches. Numerical results show that this new method is both more efficient and more robust. © 1998 John Wiley & Sons, Ltd. 相似文献