全文获取类型
收费全文 | 65篇 |
免费 | 1篇 |
专业分类
化学 | 55篇 |
力学 | 2篇 |
数学 | 6篇 |
物理学 | 3篇 |
出版年
2021年 | 2篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2007年 | 2篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1962年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有66条查询结果,搜索用时 15 毫秒
1.
Manuel Urbano Cuadrado Gonzalo Cerruela García Irene Luque Ruiz Miguel Ángel Gómez-Nieto 《Journal of mathematical chemistry》2006,40(1):15-27
A method for the treatment of long-dimensional chemical data arrays is presented in this work with the aim of maximising classification models. The method is based on the construction of fingerprints and the subsequent generation of a similarity matrix. The similarity calculation has been modified through a scaling process to take into account different significance shown by the variables. The method was applied to spectral measurements of wines and several aspects were studied, namely: threshold considered in the construction of fingerprints and patterns, weighting factor used for scaling, normalisation method, etc. The application of both Principal Components Analysis and Soft-Independent Modelling of Class Analogies to the similarity matrices gave better classifications of the information than those obtained using original data. 相似文献
2.
Study of spectral analytical data using fingerprints and scaled similarity measurements 总被引:1,自引:0,他引:1
Urbano Cuadrado M Luque de Castro MD Gómez-Nieto MA 《Analytical and bioanalytical chemistry》2005,381(4):953-963
A new chemoinformatic model has been developed for enlarging the differences between spectra and applied to differentiation of wines according to the criteria grape origin and variety and ageing process. The model is based on generation of fingerprints from normalised spectra, using empirical parameters and a set of 120 samples. After generation of the fingerprints, similarity matrixes were built on the basis of the Tanimoto similarity index between the fingerprints of the samples. Calculation of the Tanimoto index was modified to adapt the index to the characteristics of the analytical measurements. Thus, scaling factors taking into account pattern fingerprints generated from a group of samples with common characteristics were used. In addition, a modified expression for calculating the Tanimoto index was employed. Principal-components analysis (PCA) and soft independent modelling of class analogy (SIMCA) were applied to the similarity matrixes. The results obtained are discussed as a function of the normalisation method employed, the empirical factor used in generation of the fingerprints, and selection of samples for building the pattern fingerprint, etc. Finally, results from differentiation of wines are compared with those obtained by applying PCA to the unprocessed spectra as stated by the proposed model. 相似文献
3.
J. Losada I. Cuadrado B. González J. Zhang 《Journal of organometallic chemistry》2004,689(17):2799-2807
Cyclosiloxane and silsesquioxane-based ferrocenyl and permethylferrocenyl polymers have been used as mediators in amperometric enzyme electrodes for the detection of glucose. Biosensors have been prepared by electrostatically immobilizing the enzyme glucose oxidase (GOx) on electrodes modified with the polymers. The steady-state amperometric response of the sensors is investigated as a function of the applied potential and substrate concentration. The dependence of the sensors response on the structure of the siloxane-framework and on the presence or not of methyl groups on the ferrocenyl units is discussed. 相似文献
4.
Summary The reactions of MCl4 (M = Ti or V) with R2P(S)P(S)R2 (R = Me or Et) yield hexacoordinate complexes MCl4 · R2P(S)P(S)R2 (M = Ti or V; R = Me or Et), whereas similar reactions with VOCl3 lead to reduction of vanadium and give rise to the vanadium(IV) pentacoordinated complexes: VOCl2-R2P(S)P(S)R2 (R = Me or Et). All the compounds have been characterized by elemental analyses, i.r., visible and e.p.r. spectra, which show thecis-chelate character of these ligands, although in the complexes containing Et4P2S2 the i.r. spectra indicates that thegauche conformation of the ligand is implicated in bonding to the metal. The occupation of the sixth coordination site in pentacoordinate complexes, VOCl2 · R2P(S)P(S)R2, by different donor solvents, has been studied by means of visible and e.p.r. spectra. 相似文献
5.
The reductive electrochemistry of compounds of the type CpFe(CO)2L (Cp = η-C5H5, η-C5Me5; L = SP(S)(OEt)2, SP(S)(OiPr)2) has been examined by polarography, cylic voltammetry and coulometry. The first one-electron reduction step leads to a bond rupture process with formation of a mercury compound, [CpFe(CO)2]2Hg, at a mercury electrode and the corresponding dimer species at a platinum electrode. The second reduction step corresponds to the reduction of the dimer [CpFe(CO)2]2, except in the polarographic reduction of pentamethylcyclopentadienyl compounds. 相似文献
6.
T. R. Cuadrado J. Borrajo R. J. J. Williams 《Journal of Polymer Science.Polymer Physics》1988,26(8):1735-1749
A thermodynamic analysis of interpenetrating polymer networks (IPNs), at any extent of reaction during their synthesis, is presented for both simultaneous and sequential procedures. A model IPN is assumed to be built up by the independent stepwise homopolymerization of two monomers: a tetrafunctional one, A4, and a trifunctional one, A3. No reaction of copolymerization or grafting is allowed between the two types of polymers. For the case of semi-IPNs, A3 is replaced by A2, i.e., a bifunctional monomer leading to a linear polymer. The free energy of mixing is described by a Flory-Huggins lattice model, whereas the elastic contribution is calculated by assuming affine deformation of an ideal elastic network. Results show that a sequential polymerization gives a more incompatible system (i.e., it enters the metastable region at lower conversions) than a simultaneous polymerization starting from the same monomers. In every case, a semi-IPN is shown to be more compatible than an IPN owing to the fact that the average size of the bifunctional monomer increases less with conversion than the size of the trifunctional monomer. When a sequential polymerization begins from a swollen gel at equilibrium, any increase in the extent of reaction of the solvent monomer will lead to its segregation from the swollen gel. The critical Flory-Huggins interaction parameter provides a simple way to ascertain the possibility of phase separation during a simultaneous polymerization. 相似文献
7.
Zusammenfassung Zum Nachweis des Thoriums bewährte sich als Reagens eine wäßrige, perhydrol- und ammomumnitrathaltige Alizarin S-Lösung. Da Alizarin kein spezifisches Reagens für Thorium ist, wird ein Analysengang beschrieben, der sich zur Entfernung störender Substanzen aus Mineralen eignet. Das dabei erhaltene Thoriumnitrat kann am Ringofen quantitativ bestimmt werden.
Wir danken an dieser Stelle dem Conselho Nacional de Pesquisas von Brasilien, der uns die Durchführung dieser Arbeiten ermöglicht hat. 相似文献
Summary Aqueous alizarin S solution along with perliydrol and ammonium nitrate was found suitable for the detection of thorium. Since alizarin is not a specific reagent for thorium, an analytical procedure is described, which is suitable for the removal of interfering substances from minerals. The thorium nitrate obtained in this way can be determined quantitatively on the ring oven.
Résumé On a utilisé pour la recherche du thorium, une solution aqueuse d'alizarine S avec le perhydrol et le nitrate d'ammonium. Comme l'alizarine n'est pas un réactif spécifique du thorium, on a décrit un procédé d'analyse qui permet l'élimination des substances gênantes à partir des minéraux. On peut doser quantitativement le nitrate de thorium alors obtenu, à l'aide du four annulaire.
Wir danken an dieser Stelle dem Conselho Nacional de Pesquisas von Brasilien, der uns die Durchführung dieser Arbeiten ermöglicht hat. 相似文献
8.
Armada MP Losada J Zamora M Alonso B Cuadrado I Casado CM 《Bioelectrochemistry (Amsterdam, Netherlands)》2006,69(1):65-73
The electrochemical characterization of polymethylferrocenyl dendrimers deposited onto a platinum electrode and their applications as hydrogen peroxide and glucose sensor are described. The redox dendrimers consist of flexible poly(propileneimine) dendrimer cores functionalised with octamethylferrocenyl units. Amperometric biosensors for glucose were prepared by immobilization of glucose oxidase onto these modified electrodes. The influence of the dendrimer generation and the thickness of the dendrimer layer, the effect of the substrate concentration, and the interferences and reproducibility on the response of the sensors were investigated. 相似文献
9.
Eulalia Ramírez-Oliva Isabel Cuadrado Carmen M. Casado Beatriz Alonso 《Journal of organometallic chemistry》2006,691(6):1131-1137
A series of multimetallic systems containing silicon-linked cyclopentadienyl dicarbonyl iron moieties including carbosilane dendrimers and cyclic and polymeric siloxanes have been prepared using hydrosilylation reactions. For this purpose the vinyl-substituted silyliron complex (η5-C5H5)Fe(CO)2Si(CH3)2 CHCH2 (1) was prepared by salt elimination reaction between Na[(η5-C5H5)Fe(CO)2] and ClSi(CH3)2CHCH2 and fully characterized. Hydrosilylation reaction of 1 with the appropriate Si-H functionalized molecules in the presence of Karstedt catalyst afforded the novel silyl carbonyl iron-functionalized cyclotetrasiloxane 2, dendrimer 3 and copolymer 4, in which the organometallic units are attached to the silicon-based frameworks through a two-methylene flexible spacer. The electrochemical behaviour of compounds 1-4 has been examined in dichloromethane, tetrahydrofuran and acetonitrile solutions using cyclic voltammetry. 相似文献
10.
J. Fornell A. Concustell S. Suriñach W.H. Li N. Cuadrado A. Gebert M.D. Baró J. Sort 《International Journal of Plasticity》2009
Bulk metallic glass with composition Ti40Zr25Ni8Cu9Be18 exhibits considerably high compressive yield stress, significant plasticity (with a concomitant vein-like fracture morphology) and relatively low density. Yielding and intrinsic plasticity of this alloy are discussed in terms of its thermal and elastic properties. An influence of normal stresses acting on the shear plane is evidenced by: (i) the fracture angle (<45°) and (ii) finite-element simulations of nanoindentation curves, which require the use of a specific yield criterion, sensitive to local normal stresses acting on the shear plane, to properly match the experimental data. The ratio between hardness and compressive yield strength (constraint factor) is analyzed in terms of several models and is best adjusted using a modified expanding cavity model incorporating a pressure-sensitivity index defined by the Drucker–Prager yield criterion. Furthermore, comparative results from compression tests and nanoindentation reveal that deformation also causes strain softening, a phenomenon which is accompanied with the occurrence of serrated plastic flow and results in a so-called indentation size effect (ISE). A new approach to model the ISE of this metallic glass using the free volume concept is presented. 相似文献