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41.
42.
Marzena Ciszak Stefano Euzzor Andrea Geltrude F. Tito Arecchi Riccardo Meucci 《Communications in Nonlinear Science & Numerical Simulation》2013,18(4):938-945
The synchronization in four forced FitzHugh–Nagumo (FHN) systems is studied, both experimentally and by numerical simulations of a model. We show that synchronization may be achieved either by coupling of systems through bidirectional diffusive interactions, by introducing a common noise to all systems or by combining both ingredients, noise and coupling together. Here we consider white and colored noises, showing that the colored noise is more efficient in synchronizing the systems respect to white noise. Moreover, a small addition of common noise allows the synchronization to occur at smaller values of the coupling strength. When the diffusive coupling in the absence of noise is considered, the system undergoes the transition to subthreshold oscillations, giving a spike suppression regime. We show that noise destroys the appearance of this dynamical regime induced by coupling. 相似文献
43.
Fourier-transform infrared spectroscopy (FTIR) shows that during the curing of PMR-15 polyimide, formation of an anhydride intermediate occurs prior to the formation of polyamic acid, suggesting that its origin is the diester diacid starting material, as has recently been proposed by Johnston and coworkers. These results disagree with some previous literature reports that have attributed formation of the anhydride to a degradation pathway of polyamic acid and confirm the validity of a recently published paper by Johnston and coworkers. 相似文献
44.
Favino TF Fronza G Fuganti C Fuganti D Grasselli P Mele A 《The Journal of organic chemistry》1996,61(25):8975-8979
The synthesis of the strong natural roast odorants 1 and 2 is achieved from the C-6 isomeric alcohols 16 and 21 via the acetylenic C-6 and C-7 amines 8 and 9. Key step in the process is the hydrolysis of the N-phenylacetamides 12 and 13 by means of immobilized penicillin acylase, which affords the 1-amino-4,5-diketones 14 and 15, spontaneously ring closing to 1 and 2. These latter compounds form inclusion complexes with beta-cyclodextrin, as demonstrated by NMR measurements in deuterated water and FAB-MS spectra. 相似文献
45.
Tito Lumini David N. Cox Raymond Roulet Gervais Chapuis Francesco Nicolo 《Helvetica chimica acta》1990,73(7):1931-1934
The complex [Ru(η5-C7H11)2H]BF4 (C7H11 = 2,4-dimethylpenta-2,4-dienyl) is highly reactive towards two- and six-electron ligands. e.g. giving with CO complex [RuCO(η4-C7H12)(η5-C7H11)]BF4. The 2,4-dimethylpenta-1,3-diene ligand (C7H12) of the latter complex is readily displaced giving, e.g. with excess cyclohexa-1,3-diene (C6H8) complex [RuCO(η4-C6H8)(η5-C7H11)]BF4. These reactions provide a convenient entry into monopentadienylruthenium chemistry. 相似文献
46.
Multivalent particles competing for binding on the same surface can exhibit switch-like behaviour, depending on the concentration of receptors on the surface. When the receptor concentration is low, energy dominates the free energy of binding, and particles having a small number of strongly-binding ligands preferentially bind to the surface. At higher receptor concentrations, multivalent effects become significant, and entropy dominates the binding free energy; particles having many weakly-binding ligands preferentially bind to the surface. Between these two regimes there is a “switch-point”, at which the surface binds the two species of particles equally strongly. We demonstrate that a simple theory can account for this switch-like behaviour and present numerical calculations that support the theoretical predictions. We argue that binding selectivity based on receptor density, rather than identity, may have practical applications. 相似文献
47.
Daniel-da-Silva AL Lóio R Lopes-da-Silva JA Trindade T Goodfellow BJ Gil AM 《Journal of colloid and interface science》2008,324(1-2):205-211
The influence of magnetite (Fe(3)O(4)) nanoparticles on the rheological properties of kappa-, iota- and lambda-carrageenan gels has been investigated. Small amplitude oscillatory shear measurements were performed to study the effect of the presence of Fe(3)O(4) nanoparticles with particle sizes of ca. 10 nm on the gel properties, as a function of carrageenan type, carrageenan concentration and magnetite load. The formation of Fe(3)O(4) nanoparticles on the presence of biopolymer was observed to promote the gelation process and lead to stronger gels as indicated by an increase in the gel viscoelastic moduli and of the gelation temperature. This effect was more marked for kappa-carrageenan than for iota- and lambda-carrageenan and has been proposed to depend not only on Fe(3)O(4) concentration but also on the concentration of potassium ions. A mechanism based on the combined effect of Fe(3)O(4) nanoparticles and potassium ions was suggested, involving the adsorption of potassium ions on the negatively charged surface of the Fe(3)O(4) nanoparticles, thus leading to an increase of the potassium ion concentration within the "carrageenan cages" containing the magnetite. This would, therefore, promote more extensive biopolymer helical aggregation, thus resulting in the formation of a stronger kappa-carrageenan gel in the presence of Fe(3)O(4), as observed. Since iota- and lambda-carrageenan gels are known to be less sensitive to potassium ions concentration, the effect of precipitating Fe(3)O(4) within these biopolymers is reduced. 相似文献
48.
An amperometric biosensor based on genetically-modified enzymes was used for the in situ detection of trace vapours from a number of explosive compounds. The vapour samples that were generated from a purpose-built vapour generator were collected and pre-concentrated using a trap able to concentrate samples at a rate of 60-fold per minute of sampling. The amperometric biosensor achieved a remarkably low vapour detection limit of 6 parts per trillion from a room temperature sample. The specific activity of the reported enzyme toward a number of explosive compounds was also confirmed using absorbance measurements. 相似文献
49.
Katya Besanon Gbor Laurenczy Tito Lumini Raymond Roulet Giuliana Gervasio 《Helvetica chimica acta》1993,76(8):2926-2935
The monosubstituted [Ir4(CO)11L] clusters (L = P(OPh)3, 1 ; L = P(OMe)3, 2 ; L = P(OCH2)3CEt, 3 ) were obtained in good yields by the reaction of [Ir4(CO)11 I ]? with the corresponding phosphite. In the solid state, cluster 3 has a Cs geometry with all terminal ligands as shown by an X-ray analysis. Three isomers are present in solution: one with terminal ligands ( A ) and two with three edge-bridging CO's and with L in axial ( B ) or radial ( C ) position (see Scheme). The thermodynamic and kinetic parameters of isomerisations B ? A and A ? C were determined by simulation of the variable-temperature 31P-NMR spectra. The three isomers correspond to three minima on the kinetic pathway of CO scrambling, whose relative energies vary independently within a small range (1–9 kJ mol?1 at 298 K). At low temperature, isomer C is always the least stable and is not observed for 1 which bears the most bulky phosphite ligand. The isomerisations are due to two intramolecular merry-go-rounds of CO groups about two unequivalent faces of the unbridged species A . 相似文献