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1.
Sergio Ayala‐Mar Javier Donoso‐Quezada Roberto C. Gallo‐Villanueva Victor H. Perez‐Gonzalez Jos Gonzlez‐Valdez 《Electrophoresis》2019,40(23-24):3036-3049
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed. 相似文献
2.
Non-isothermal short-range-order kinetics of binary alloys as influenced by solute-vacancy complexes
A model describing the roles of bound and unbound vacancies is proposed in order to predict defect decay and short-range-order
kinetics of quenched binary alloys during linear heating experiments. This is an alternative treatment of a previous approach.
The model has been applied to the differential scanning calorimetry (DSC) curves of Cu-5 at.% Zn quenched from different temperatures.
An expression to calculate the activation energy for migration of solute-vacancy complexes was also developed which make use
of DSC trace data. A value of 89.12±0.32 kJ mol-1 was obtained for the above alloy. The relative contribution of bound and unbound vacancies to partition of effective activation
energy corresponding to the ordering process as influenced by quenching temperature was also assessed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
J. Gañán J.F. González C.M. González-García A. Ramiro E. Sabio S. Román 《Applied Surface Science》2006,252(17):5988-5992
In this work the results obtained in the preparation and characterization of carbons made from almond tree pruning by non-catalytic and catalytic gasification (using K and Co) with air are analyzed and discussed. The main aim was to obtain high quality activated carbons at the lowest possible cost. The variables studied have been the temperature (190-260 °C) and the time (1-10 h) in non-catalytic gasification and the influence of the catalyst type (K and Co, 1 wt.% referred to cation, at 190 °C and 1 h) and the time (1-4 h) in catalytic gasification with Co at 190 °C. The air flow rate used in all the series was 167 cm3 min−1. In non-catalytic gasification the reaction normalized rate versus the conversion degree was maintained until a conversion value of 10% for the experiment made at 260 °C since, at lower temperatures, this rate drops quickly for low conversion values. The N2 adsorption isotherms for the carbons of this series resemble type I, although there is an increase of N2 adsorbed volume at relatively high pressures. A temperature rise produced an increase of the carbon porosity and BET specific surface (116-469 m2 g−1). The activation time has a positive effect on the N2 volume adsorbed by the carbons. The isotherms shapes were similar to those previously commented. A concentration equal to 1 wt.% was used to study the influence of the catalyst type. Under the studied experimental conditions, Co drives to a bigger porosity development than K, although with both catalysts a very similar pore size distribution is obtained. The activation time, in the gasifications catalyzed with Co, gives rise to a very important porosity development in the carbons. This produces a strong increase of the carbon specific surface area with very high values in the 4 h experiment, in which a BET specific surface of 959 m2 g−1 was obtained. 相似文献
4.
We study the problem of configuring a fleet, in which vehicles receive information on-line about the demand that they should fulfil while they are on the road. In each district it must be decided the number of vehicles and their capacity. The objective function is to minimise the operational cost subject to constraints for the minimum delivery capacity, the maximum vehicle size and the average waiting time for customers. The last constraint is modelled as a queuing system that is adjusted according to the simulation of the delivery process of a Chilean company that distributes liquefied petroleum gas in portable cylinders. We provide the analytical form of all the components of the model, so it can be solved using a standard non-linear programming package. We show that the fleet may increase its sales by 3% and reduce the waiting time of customers 10% by allowing a set of vehicles to share the buffer of orders rather than having vehicles to exclusively serve smaller sectors. 相似文献
5.
Uranium(VI and IV) and thorium(IV) give cathodic indentations in supporting electrolytes prepared from 0.1M perchloric acid, 0.5 M ammonium thiocyanate and 5·10-3M cupferron (solution A) or from 0.1 M succinic-succinate buffer pH 4, 0.1 M sodium chloride, 10-3M cupferron and 0.05% gelatine (solution B). The uranium indentation on the dE/dt = f(E) curve (Q=0.75 and 0.73) permits its detection at the 3·10-7M level. The thorium indentation (Q=0.78) permits its detection at the 4·10-7M level in solution B. Methods for the elimination of interfering ions for the uranium determination are described. In the determination of thorium, Ga(III), Fe(III), Ti(IV) and U(VI) interfere. 相似文献
6.
Miguel A. Vzquez Segura Josefa Donoso Francisco Muoz INS Fernandez
de
Pirola Francisco Garcia Blanco Gerardo R. Echevarria 《Photochemistry and photobiology》1993,57(Z1):923-928
Abstract— Absorption and fluorescence spectra of 5′-deoxypyridoxal (DPL) in various pure solvents and mixtures were recorded both at room temperature and over the range10–65°C. The areas under the absorption bands were analyzed to obtain the mole fraction (fN, fz) of two tautomers (the zwitterionic, Z, and neutral, N, forms) in the ground state. The following spectral parameters were determined from the fluorescence spectra: Stokes shift (Δv), fluorescence quantum yield of the neutral form (QN), fluorescence ratio of the neutral to the zwitterionic form (øN/øZ) and the rate constant of tautomerization (k1) from Z to N in the excited state. Some of these parameters (fN, Δv, QN, k1) were found to depend on the proton donor character of the solvent, whereas others (øN/øZ) depended on its dipole moment. Thus, the absorption and fluorescence spectra of DPL allow one to obtain information on the polarity and the concentration of –OH groups on its environment. 相似文献
7.
Martinez Alvarez R Herrera Fernandez A Chioua M Ramiro Perez P Villalba Vilchez N Guzman Torres F 《Rapid communications in mass spectrometry : RCM》1999,13(24):2480-2488
Several 5,6-dialkyl-2,4-diarylpyrimidines were prepared and their electron ionization (EI) mass spectra reported. The benzylic cleavage takes place easily together with an important McLafferty rearrangement. The involvement of the nitrogen atom appears to be important in the fragmentation of 5-methyl-substituted pyrimidines. In contrast, the 6-methyl-substituted pyrimidines undergo benzylic cleavage without hydrogen transfer. Thus, the difference in the mass spectrometric behaviour allows the identification of these isomeric compounds which, in contrast, exhibit only small differences in their NMR spectra. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
8.
Summary The ordering behavior of quenched Cu-12 at% Mn was investigated by differential scanning calorimetry (DSC) under increasing temperature conditions. The ordering process can be better explained in terms of a homogeneous short-range-order (SRO) rather than a disperse-short-range-order (DSRO) model as for concentrated Cu-γMn solid solutions. At the employed high quench rates ordering is established in one stage here termed stage 1, assisted by excess vacancies. This stage obeys a first order kinetics law, being the effective activation energy consistent with a weighed average sum of the activation energy for migration of free and bound vacancies. An estimated solute-vacancy binding energy of 15 kJ mol-1 seems quite reasonable for this alloy together with the assessed activation energy for complex migration of 92.6 kJ mol-1. By adopting a first SRO order parameter based in quasi-chemical theory in pair approximation and using boundary values calculated from displayed features of DSC traces, the retained degree of quenched-in order at room temperature was calculated. This procedure also enabled to estimate an ordering energy of -2.7 kJ mol-1. The effect of quenching temperature demonstrate that for smaller vacancy sink densities, the retained degree of order at room temperature goes through a minimum. 相似文献
9.
Bartolom Vilanova Francisco Muoz Josefa Donoso Francisco Garcia-Blanco 《Helvetica chimica acta》1993,76(4):1619-1625
A kinetic study on the alkaline hydrolysis of cephaloridine ( 1 ) at pH 10.5 and 37° was carried out using ion-pair reversed-phase HPLC. The main resulting degradation products, the 7-epimer 2 of 1 , the Δ2-isomer 3 of 1 , and the 3-methylidene compound 4 were identified. The presence of a pyridinio group at C(31) results in a slightly increased formation constant for the 3-methylidene compound 4 and the 7-epimer 2, and introduces a new reaction: the isomerization of the double bond at C(3) in the dihydrothiazine ring to C(2). 相似文献
10.
Ramiro Pino Olivier Bokanowski Eduardo V. Ludeña Roberto López Boada 《Theoretical chemistry accounts》2007,118(3):557-561
Bearing in mind the insight into the Hohenberg–Kohn theorem for Coulomb systems provided recently by Kryachko (Int J Quantum
Chem 103:818, 2005), we present a re-statement of this theorem through an elaboration on Lieb’s proof as well as an extension
of this theorem to finite subspaces.
Contribution to the Serafin Fraga Memorial Issue. 相似文献