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191.
Summary In the cathodization of palladium, when the final equilibrium concentrationn
f of hydrogen does not exceed the maximum valuen
αmax taken in the α-phase, a temporary formation of β-phase may take place, provided the current density is larger than a limiting
valueJ
m. An expression has been obtained forJ
M which contains all the parameters characterizing the cathodization, as well as the absorption, diffusion and solution of
hydrogen; the same expression contains also an adimensional function of the ratior=n
f/n
αmax, which has been tabulated for a wide range of cathodization processes, and has been approximated, in the whole definition
range, by two elementary functions ofr.
Riassunto Nella catodizzazione del palladio, anche quando la concentrazione atomica finalen f non supera il massimo valoren αmax che la stessa concentrazione può assumere nella fase α, può aver luogo una formazione temporanea di fase β, purché la densità di corrente superi un certo valore limiteJ M. Si è ottenuta un'espressione diJ M la quale contiene i parametri che caratterizzano la catodizzazione, l'assorbimento, la diffusione e la soluzione dell'idrogeno nel palladio; la stessa espressione contiene anche una funzione adimensionale del rapportor=n f /n αmax che è stata calcolata numericamente per un vasto campo di processi di catodizzazione, ed è stata inoltre approssimata, in tutto il suo campo di definizione, per mezzo di due funzioni elementari dir.
Резюме При катодизации палладия, когда конечная равновесная концентрацияn f водорода не превышает максимальной величиныn α max; принятой для α-Фазы, может иметь место упругое образование β-фазы, если плотность тока превышает предельную величинуJ M: Получается выражение дляJ M; которое содержит все параметры, которые характеризуют катодизацию, а также поглощение, диффузию и растворение водорода в палладии. Это выражение содержит также безразмерную функцию отношенияr=n f /n α max ; которая табулируется в широкой области для процесса катодизации и аппроксимируется во всей области определения двуя элементарными функциямиr.相似文献
192.
We prove the existence of a number of smooth periodic motions u
∗ of the classical Newtonian N-body problem which, up to a relabeling of the N particles, are invariant under the rotation group R\mathcal{R} of one of the five Platonic polyhedra. The number N coincides with the order |R||\mathcal{R}| of R\mathcal{R} and the particles have all the same mass. Our approach is variational and u
∗ is a minimizer of the Lagrangian action A\mathcal{A} on a suitable subset K\mathcal{K} of the H
1
T-periodic maps u:ℝ→ℝ3N
. The set K{\mathcal {K}} is a cone and is determined by imposing on u both topological and symmetry constraints which are defined in terms of the rotation group R\mathcal{R}. There exist infinitely many such cones K{\mathcal {K}}, all with the property that A|K{\mathcal {A}}|_{{\mathcal {K}}} is coercive. For a certain number of them, using level estimates and local deformations, we show that minimizers are free
of collisions and therefore classical solutions of the N-body problem with a rich geometric–kinematic structure. 相似文献
193.
Giorgio Fusco 《Journal of Differential Equations》2011,250(7):3230-3279
We consider a regularization for a class of discontinuous differential equations arising in the study of neutral delay differential equations with state dependent delays. For such equations the possible discontinuity in the derivative of the solution at the initial point may propagate along the integration interval giving rise to so-called “breaking points”, where the solution derivative is again discontinuous. Consequently, the problem of continuing the solution in a right neighborhood of a breaking point is equivalent to a Cauchy problem for an ode with a discontinuous right-hand side (see e.g. Bellen et al., 2009 [4]). Therefore a classical solution may cease to exist.The regularization is based on the replacement of the vector-field with its time average over an interval of length ε>0. The regularized solution converges as ε→0+ to the classical Filippov solution (Filippov, 1964, 1988 [13] and [14]). Several properties of the solutions corresponding to small ε>0 are presented. 相似文献
194.
Annese C Fanizza I Calvano CD D'Accolti L Fusco C Curci R Williard PG 《Organic letters》2011,13(19):5096-5099
A synthesis of representative monohydroxy derivatives of valinomycin (VLM) was achieved under mild conditions by direct hydroxylation at the side chains of the macrocyclic substrate using dioxiranes. Results demonstrate that the powerful methyl(trifluoromethyl)dioxirane 1b should be the reagent of choice to carry out these key transformations. Thus, a mixture of compounds derived from the direct dioxirane attack at the β-(CH(3))(2)C-H alkyl chain of one Hyi residue (compound 3a) or of one Val moiety (compounds 3b and 3c) could be obtained. Following convenient mixture separation, each of the new oxyfunctionalized macrocycles became completely characterized. 相似文献
195.
Olga?V.?Stepanenko Alexander?V.?Fonin Olesya?V.?Stepanenko Maria?Staiano Sabato?D’Auria Irina?M.?Kuznetsova Konstantin?K.?TuroverovEmail author 《Journal of fluorescence》2015,25(1):87-94
Changes of the characteristics of intrinsic tryptophan fluorescence of the wild type of D-galactose/D-glucose-binding protein from Escherichia coli (GGBPwt) induced by D-glucose binding were examined by the intrinsic UV-fluorescence of proteins, circular dyhroism in the near-UV region, and acrylamide-induced fluorescence quenching. The analysis of the different characteristics of GGBPwt and its mutant form GGBP-W183A together with the analysis of the microenvironment of tryptophan residues of GGBPwt revealed that Trp 183, which is directly involved in sugar binding, has the least influence on the provoked by D-glucose blue shift and increase in the intensity of protein intrinsic fluorescence in comparison with other tryptophan residues of GGBP. 相似文献
196.
5-Substituted 3,4-diamino-1,2,4-triazoles can be obtained in moderate to good yields in a one-pot reaction starting from a
carboxylic acid and dimethylaminoguanidine monohydrochloride in polyphosphoric acid (PPA) at 120 °C. Several triazoles and
bistriazoles have been prepared in this way, with substituents ranging from alkyl to aryl, including perfluoroaryl or perfluoroalkyl
substituents. The crystal structure analysis of three perfluorinated diaminotriazoles has evidenced a most stable R22 (8) R_{2}^{2} (8) H bonding synthon, involving the amino CNH2 donor and the adjacent nitrogen ring acceptor; additionally, two new synthons consisting of chains of rings have been identified.
The relevance of the short F⋯F intermolecular contacts found in the structures is also discussed. 相似文献
197.
Daniela Guarnieri Angela Guaccio Sabato Fusco Paolo A. Netti 《Journal of nanoparticle research》2011,13(9):4295-4309
The physico-chemical properties of nanoparticles (NPs), such as small dimensions, surface charge and surface functionalization,
control their capability to interact with cells and, in particular, with sub-cellular components. This interaction can be
also influenced by the adsorption of molecules present in biological fluids, like blood, on NP surface. Here, we analysed
the effect of serum proteins on 49 and 100 nm red fluorescent polystyrene NP uptake in porcine aortic endothelial (PAE) cells,
as a model for vascular transport. To this aim, NP uptake kinetic, endocytic pathway and intracellular trafficking were studied
by monitoring NPs inside cells through confocal microscopy and multiple particle tracking (MPT). We demonstrated that NPs
are rapidly internalized by cells in serum-free (SF) medium, according to a saturation kinetic. Conversely, in 10% foetal
bovine serum-enriched (SE) medium, NP uptake rate results drastically reduced. Moreover, NP internalization depends on an
active endocytic mechanism that does not involve clathrin- and caveolae-mediated vesicular transport, in both SE and SF media.
Furthermore, MPT data indicate that NP intracellular trafficking is unaffected by protein presence. Indeed, approximately
50–60% of internalized NPs is characterized by a sub-diffusive behaviour, whereas the remaining fraction shows an active motion.
These findings demonstrate that the unspecific protein adsorption on NP surface can affect cellular uptake in terms of internalization
kinetics, but it is not effective in controlling active and cellular-mediated uptake mechanisms of NPs and their intracellular
routes. 相似文献
198.
Roberto Fusco Luca Longo Luciano Caccianotti Carola Aratari Giuseppe Allegra 《Macromolecular theory and simulations》1993,2(5):685-695
The chain rigidity of poly(p-hydroxybenzoate) was estimated through the theoretical evaluation of its persistence length (Lp). A non-Brownian molecular dynamics (MD) simulation of an isolated chain with 20 monomeric units was performed. The sampled conformational population was analyzed and the orientational correlation function between monomeric units along the chain was calculated. An algorithm based on the worm-like chain model was applied to evaluate the persistence length. The results were compared with those obtained from equilibrium models like the freely-rotating-chain and the rotational-matrix method with fluctuations. Equilibrium models give different results depending on the degree of accuracy used in describing the monomeric unit. The inclusion of thermal fluctuations is crucial to obtain realistic results. These coincide with those given by MD simulation when only nearest-neighbour orientational correlations are taken into account: inclusion of higher-order correlation terms leads to lower values of the persistence length. The origin of this discrepancy was investigated. The MD simulation results are characterized by an overrepresentation of conformations with a short end-to-end distance resulting from an anomalous energy concentration in the first bending mode of the chain. In analogy with previous simulation results from systems characterized by a week coupling amoung their degrees of freedom, failure in the energy equipartition is proposed as a likely explanation of the anomalous dynamical behaviour. 相似文献
199.
Roberto Fusco Luca Longo Francesco Masi Fabio Garbassi 《Macromolecular rapid communications》1997,18(5):433-441
The thermodynamics of the reaction of an ethylene molecule with the Cp2TiCH3Cl/Al(CH3)2Cl system (Cp = η5-C5H5), as a model for olefin polymerization with homogeneous Ziegler-Natta catalysts, was investigated via quantum mechanical DFT calculations. The comparison of the calculated energies for three possible titanium-olefin coordinated intermediates, the ionic complex Cp2TiCH3(C2H4)+/Al(CH3)2Cl, the bimetallic complex Cp2TiCH3(C2H4)δ+ · Al(CH3)2Cl and the olefin-separated ion pair Cp2TiCH/C2H4/Al(CH3)2Cl, shows that the most feasible polymerization mechanism occurs via olefin-separated ion pair. 相似文献