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81.
82.
Saunavaara J Jokisaari J 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2006,180(1):58-62
The (129)Xe chemical shift of xenon dissolved in isotropic liquids is very sensitive to solvent density, which in turn is dependent on the sample temperature. Therefore, the (129)Xe chemical shift can be used as the basis of a thermometer for measuring actual sample temperatures in NMR experiments. Good accuracy can be achieved, but the thermometer is particularly useful in monitoring temperature stability. In the present case, carbon tetrachloride (CCl(4)), ethylbromide (C(2)H(5)Br), and deuterated chloroform (CDCl(3)) were chosen as solvents because of their large thermal expansion coefficient. 相似文献
83.
Functional MR imaging (fMRI) has been used in detecting neuronal activation and intrinsic blood flow fluctuations in the brain cortex. This article is aimed for comparing the methods for analyzing the nondeterministic flow fluctuations. Fast Fourier Transformation (FFT), cross correlation (CC), spatial principal component analysis (sPCA), and independent component analysis (sICA) were compared. 15 subjects were imaged at 1.5 T. Three quantitative measures were compared: (1) The number of subjects with identifiable fluctuation, (2) the volume, and (3) mean correlation coefficient (MCC) of the detected voxels. The focusing on cortical structures and the overall usability were qualitatively assessed. sICA was spatially most accurate but time consuming, robust, and detected voxels with high temporal synchrony. The CC and FFT were fast suiting primary screening. The CC detected highest temporal synchrony but the subjective detection for reference vector produced excess variance of the detected volumes. The FFT and sPCA were not spatially accurate and did not detect adequate temporal synchrony of the voxels. 相似文献
84.
Jukka Lempa 《Applied Mathematics and Optimization》2012,65(2):147-173
We present a discrete n-person model of a dynamic strategic market game. We show that for some values of the discount factor the game possesses a
stationary equilibrium where all the players make high bids. Within the class of all the high-bidding strategies we distinguish
between two classes of more and less aggressive ones. We show that the set of discount factors for which these more aggressive
strategies form equilibria shrinks as n goes to infinity. On the other hand, the analogous set for the less aggressive strategies grows to the whole interval (0,1)
as n grows to infinity. Further we analyze the properties of the value function corresponding to these high-bidding equilibria.
We also give some numerical examples contradicting some other properties that seem intuitive. 相似文献
85.
Sami Lipponen Eve Saarikoski Marja Rissanen Jukka Seppälä 《European Polymer Journal》2012,48(8):1439-1445
Cellulose/polyethylene-co-acrylic acid blends (cellulose concentration 0–50 wt.%) was prepared via mixing their alkaline solutions. The formed suspension was precipitated and dried, where after the morphology as well the thermal and mechanical properties of the blends were characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and Dynamic Mechanical Analyses (DMA). In addition, the melt properties of the blend were studied by rotational rheometer following some injection molding trials as well. The polymers were found to be dispersed homogenously in the blend and the crystallization temperature of the PE-co-AA phase was increased ~6 °C due to the nucleation ability of the cellulose phase. The size of the discontinuous cellulose phase was 5 μm at the most while at higher cellulose concentrations (30–50 wt.%) the polymers formed co-continuous morphology in the blend. This change in the morphology was observed also in their melt properties which showed that the blend reached so called percolation point at ~20 wt.% of cellulose. Finally, the blends were found to be injection moldable over the whole composition range, if only the injection molding became more challenging (i.e. higher mold temperatures and longer mold cooling times were required) after the percholation point. 相似文献
86.
We study optimal stopping with exponentially distributed exercise lag. We formalize the problem first in a general Markovian
setting and derive a set of conditions under which the solution exists. In particular, no semicontinuity assumptions of the
payoff function are needed. We analyze also some specific classes of lagged optimal stopping problems with one-dimensional
diffusion dynamics where the solution can be characterized in closed form. Finally, the results are illustrated with an explicit
example. 相似文献
87.
88.
T. Jacob B. Fricke J. Anton S. Varga T. Baştuğ S. Fritzsche W.-D. Sepp 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):257-260
In order to describe processes which are localized on a surface or inside the bulk of a solid, molecular calculations of an
inner cluster may be adequate as long as the effect of the outer environment is taken into account via an embedding-method. Using a relativistic density functional method for the self-consistent cluster calculation we have developed
a new cluster-embedding scheme here. As an example we have studied the adsorption of Al on an Al(100) surface and we get significant
agreement with different methods. This indicates that this embedding-method is reliable enough to simulate an unlimited solid.
Received 29 November 2000 相似文献
89.
90.
J. Rosti L.I. Salminen E.T. Seppälä M.J. Alava K.J. Niskanen 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):259-263
We study the statistics of crack pinning in two dimensions by experiments and simulations of directed polymers in random media.
Mode I tensile tests on paper samples show a delocalization phenomenon as the notch length is varied if the fraction of cracks
pinned to the notch is monitored. This is compared with the behavior of directed polymers in the presence of both an energetically
favorable localized pinning center and bulk disorder. An analysis of the crack interface roughness indicates self-affine behavior
with a roughness exponent ζ in the proximity of the minimum energy surface value 2/3.
Received 4 April 2000 and Received in final form 10 October 2000 相似文献