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521.
Carla Bazzicalupi Andrea Bencini Antonio Bianchi Claudia Giorgi Piero Paoletti Barbara Valtancoli Vieri Fusi Enrique Garcia‐Espata Jos M. Llinares 《Journal of heterocyclic chemistry》2001,38(6):1273-1279
Synthesis and characterisation of the new macrocyclic ligands L1‐L4 are reported. The ligands present one or two pentaamine moieties, each containing two piperazine rings, linked by benzene or anthracene spacers. Interaction of L1 with H+, Cu(II), Zn(II), Hg(II), and Pd(II) and of L3 with H+, and Cu(II) has been studied by potentiometric titrations in 0.15 mol dm?3 NaCl aqueous solution at 298.1 ±0.1 K. The thermodynamic data suggest that in the metal complexes only three nitrogen donor atoms bind each metal ion. As a consequence of the low coordination number, these complexes are promising receptors for different molecules. 相似文献
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Monica Mattarozzi Marco Giannetto Andrea Secchi Federica Bianchi 《Journal of chromatography. A》2009,1216(18):3725-3730
A novel solid-phase microextraction coating based on the electropolymerization of a molecular receptor properly functionalized with 2,2′-bithiophene was developed for the determination of environmental pollutants in air and water samples. The 2,2′-bithiophene-based film was electrochemically deposed on the surface of a gold wire using cyclic voltammetry. The fibres showed a porous structure with an average thickness of 12 ± 3 μm (n = 5): a good intra-batch and inter-batch repeatability with RSD lower than 14% was also observed. The selective interactions via hydrogen bonding with organic molecules containing electronegative atoms was proved: LOD values in the low ng/l range allowed the determination of vinyl chloride and chlorobenzenes at trace levels in environmental matrices. 相似文献
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Ignazio Renato Bellobono Riccardo Bianchi Giulia de Martini Paola Maria Tozzi Mauro Luigi Bonardi Flavia Groppi Mauro Rossi 《Journal of Chemometrics》2008,22(7):425-435
Kinetic fitting of substrate disappearance and of total organic carbon (TOC) mineralization of organic micropollutants, in water and air, by photocatalytic membranes immobilizing titanium dioxide, was carried out. A model was used in which mineralization of substrate to CO2 is supposed to occur, with kinetic constant k1, through one single intermediate, mediating the behaviour of all the numerous real intermediates formed in the path to CO2, kinetic constant of formation of the latter being k2. A competitive Langmuirian‐type adsorption of both substrate and ‘intermediate’ was also supposed to be operative, as expressed by pseudo‐thermodynamic constants K1 and K2 respectively, these constants possessing a, partly at least, kinetic significance. Nonlinear models could be fitted to data by using the least‐squares method. The very satisfactory matching is shown for the laboratory‐scale mineralization kinetics of methane, as model molecule of aliphatic contaminants, both in the gas phase and in aqueous solution. Furthermore, in pilot plant experiments, using phenol, as model molecule of aromatics, modelling of quantum yields was carried out, as a function of concentration and of adsorbed radiant power. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or intermediates leading to mineralization, was considered, paralleled by a second competition kinetics due to superoxide anion radical and its conjugate acid, equally leading to mineralization. In this model the contribution of hydroxyl radicals to mineralization decreases with irradiance, while the contribution of superoxide anion radical and its conjugate acid increases. If the regression equations of these two contributions are considered together, in a linear combination, the surface model perfectly fits the experimental data. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
528.
Michele Bianchi Janetti 《Transport in Porous Media》2018,122(3):633-645
This paper deals with the double-constraint methodology for calibration of steady-state groundwater flow models. The methodology is based on updating the hydraulic conductivity of the model domain by comparing the results of two forward groundwater flow models: a model in which known fluxes are specified as boundary conditions and a model in which known heads are specified as boundary conditions. A new zone-integrated double-constraint approach is presented by partitioning the model domain in zones with presumed constant hydraulic conductivity (soft data), and the double-constraint methodology is reformulated accordingly. The feasibility of the method is illustrated by a practical case study involving a numerical steady-state groundwater flow model with about 3 million grid blocks, subdivided into four zones corresponding to the major hydrogeological formations. The results of the zone-integrated double-constraint method for estimating the horizontal and vertical hydraulic conductivities of the zones compare favourably with a classical model calibration based on minimisation of the differences between calculated and measured heads, while the double-constraint method proves to be more robust and computationally less cumbersome. 相似文献
529.
The dual picture of quantum geometry provided by a spin network state is discussed. From this perspective, we introduce a new operator in Loop Quantum Gravity—the length operator. We describe its quantum geometrical meaning and derive some of its properties. In particular we show that the operator has a discrete spectrum and is diagonalized by appropriate superpositions of spin network states. A series of eigenstates and eigenvalues is presented and an explicit check of its semiclassical properties is discussed. 相似文献
530.
Self-locking analysis in closed kinematic chains is sometimes likened to kinematic singularity. Here a novel approach to tackle
self-locking analysis due to joints friction is exploited, that is completely different from the classical kinematic analysis
based on the jacobian conditioning. It is shown that an inverse kinematic singularity always entails a self-locking phenomenon
because of the general increasing of joints reactions and, then, friction forces; hence, a self-locking domain can be always
identified including such a locus. On the other side, this paper is aimed at demonstrating that the aforementioned condition
is not necessary: namely, self-locking may occurs also if the mechanism kinematics is well-conditioned. Then, the theoretical
result is clarified performing the self-locking analysis on a simple crank-slider mechanism. 相似文献