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41.
The relative enthalpies of melts in the system KF - K2NbF7 were measured by drop-calorimetry at the temperatures 1058, 1140 and 1208 K as a function of composition. Heat capacities
of melted mixtures and enthalpies of mixing were determined using the experimental data. The molar heat capacity of melts
diverges slightly from additivity. The molar enthalpy of mixing of melts shows small negative deviation from ideality which
decreases with decreasing temperature. The thermal effect at mixing was assigned predominantly to association reactions producing
more complex fluoroniobate anions.
相似文献
42.
C. Sternemann 《高压研究》2016,36(3):275-292
ABSTRACTX-ray Raman scattering spectroscopy is an emerging method in the study of low and intermediate Z elements' core-electron excitations at extreme conditions in order to reveal information on local structure and electronic state of matter in situ. We discuss the capabilities of this method to address questions in Earth materials' science and demonstrate its sensitivity to detect changes in the oxidation state, electronic structure, coordination, and spin state. Examples are presented for the study of the oxygen K-, silicon L- and iron M-edges. We assess the application of both temperature and pressure in such investigations exploiting diamond anvil cells in combination with resistive or laser heating which is required to achieve realistic conditions of the Earth's crust, mantle, and core. 相似文献
43.
M. Bellour A. Knaebel J.P. Munch S.J. Candau 《The European physical journal. E, Soft matter》2000,3(2):111-121
Static and dynamic light scattering and conductivity experiments were carried out on salt-free aqueous micellar solutions
of cetyltrimethylammonium n-hexane sulfonate (CTAC_6SO_3) and cetyltrimethylammonium n-heptane sulfonate (CTAC_7SO_3) as a function of surfactant concentration. This study confirms the analogy between the behavior
in the semi-dilute regime of elongated micellar systems and “classical” polyelectrolyte solutions. Time-resolved scattering
experiments performed after a variation of concentration from about twice the overlap volume fraction to less than half of it revealed the existence of a structural relaxation with a characteristic time of several hours.
Received 21 December 1999 相似文献
44.
A.N. Semenov 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):497-507
Secondary domain superstructures in correlated random block copolymers are considered theoretically using the concept of the
second order parameter related to fluctuations of the local mean block length. It is shown that the size of secondary domains,
, is much larger than the primary domain size, L: , while , where is a small parameter defining the composition asymmetry. Different secondary morphologies are characterized. It is also shown
that separation of the system in two macroscopic phases with different primary morphologies predicted earlier using the free
energy expansion up to ( is the usual order parameter related to local composition) is an artifact of this widely accepted theoretical model.
Received 15 July 1998 and Received in final form 18
January 1999 相似文献
45.
N. Lee D. Thirumalai 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):599-605
The effect of electrostatic interactions on the stretching of DNA is investigated using a simple worm like chain model. In
the limit of small force there are large conformational fluctuations which are treated using a self-consistent variational
approach. For small values of the external force f, we find the extension scales as where is the Debye screening length. In the limit of large force the electrostatic effects can be accounted for within the semiflexible
chain model of DNA by assuming that only small excursions from rod-like conformations are possible. In this regime the extension
approaches the contour length as where f is the magnitude of the external force. The theory is used to analyze experiments that have measured the extension of double-stranded
DNA subject to tension at various salt concentrations. The theory reproduces nearly quantitatively the elastic response of
DNA at small and large values of f and for all concentration of the monovalent counterions. The limitations of the theory are also pointed out.
Received 13 October 1998 and Received in final form 9 June 1999 相似文献
46.
I. Nerád O. Fabrichnaya L. Kosa E. Mikšíková S. Šaušová 《Journal of Thermal Analysis and Calorimetry》1999,56(1):395-400
The thermodynamic data are assessed by using molecular solution model with excess Gibbs energy of mixing expressed by Redlich-Kister
equation with temperature dependent parameters. The optimized data involve phase equilibria, enthalpy and entropy of formation
of crystalline phases, heat capacity (Cp) data of solid and liquid pure components, enthalpy of mixing of liquid pure components, enthalpy and entropy of fusion of
solid phases. Thermodynamic quantities consistent with available experimental phase equilibria and calorimetric measurements
are established for solid phases and liquids in the system CaO·SiO2 (CS)-CaO·Al2O3·2SiO2 (CAS2)-2CaO·Al2O3·SiO2 (C2AS).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
47.
Allowing for flow-dependent slip in the junctions of a temporary junction network, we derive the constitutive equations of temporary slip-link networks. The stress tensor is determined by three material functions, namely, the time-dependent linear-viscoelastic memory function, and two strain-dependent functions describing slip and disentanglement of network strands. Slip and disentanglement are related via a mass balance for network strands.By specifying slip and disentanglement, the constitutive equations of Lodge, Wagner, Doi-Edwards, and Marrucci are shown to be special temporary slip-link constitutive equations. To demonstrate the predictive power of temporary slip-link network theories, we compare predictions and extensional flow data with step change in flow direction.Dedicated to Professor Arthur S. Lodge on the occasion of his 70th birthday and his retirement from the University of Wisconsin. 相似文献
48.
An earlier structural model for binary silicate melts and glasses is extended to MF-BeF2 (M = Li, K) systems. The evaluation of the thermodynamic properties as well as the phase diagrams for the binary LiF-BeF2 system and the integral enthalpy of mixing of the KF-BeF2 system are carried out with this model. This thermodynamic model is based on the assumption that each alkali fluoride produces the depolymerization of BeF2 network with a characteristic free energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analysed and represented with a small number of parameters. The model predicts the chain-length distribution of polymeric ions, even though these are not explicitly treated as structural units of the model. The calculated fluoride polyanion chain-length distribution for the LiF-BeF2 system is in quantitative agreement with the predictions reported in the literature. 相似文献
49.
Bonet Avalos J Johner A Díez-Orrite S 《The European physical journal. E, Soft matter》2006,21(4):305-317
The structure of the layer formed after polymer adsorption onto a spherical particle is numerically studied by means of the
application of the Single-Chain Mean-Field theory. We have determined several overall layer properties including the monomer
volume fraction profiles, the layer thickness, adsorbances related to loops and to tails, as well as the variation of the
crossover distance between loops and tails for different particle radii and fixed polymer length. When the radius of the sphere
is small enough to affect the loop layer, one enters a single-adsorbed-chain regime, characterized by a critical sphere radius.
In this regime, structural changes in the adsorbed layer arise. For such small sphere, the loop layer is confined to a region
whose thickness is of the order of the radius of the adsorbing sphere, and two long tails dominate the outer layer and the
adsorbance due to tails dominates that due to loops. An analysis of the structure of the outer tail layer for this small sphere
case is also presented. 相似文献
50.
Xian Wei Hu Huan Li Bing Liang Gao Jing Jing Liu Zhong Ning Shi Jiang Yu Yu Zhao Wen Wang 《中国化学快报》2012,23(11):1291-1294
A new type of sample cell specially designed for micro-Raman spectra study on volatile melts is described.The cell is made of quartz.The lower section of the cell is circular ring-shaped and the one-end-closed hole in the cell is used for locating the heating body.The tube attached to the cell lid for placing the thermal couple is inserted into the sample,which ensures that the temperature measurement accuracy is good.The cell can be sealed for reducing the effect of the composition change caused by the inhomogeneous volatilization.During the Raman spectra scanning,the laser beam is transmitted into the cell through the side but not the top.Meanwhile,a furnace has been designed to match the cell.The heating body is closely coupled with the sample cell, and there is a hole on the side wall of the furnace for the entrance of the microlens.The assembly has performed well in the tested Raman spectrum measurement of molten NaNO3 at 602℃. 相似文献