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91.
It is well known that a crater is formed on the target surface by the irradiation of intense laser pulses in laser ablation. In this work, we report that additional pits are formed on the bottom surface of the ablation crater due to the collapse of a cavitation bubble in liquid-phase laser ablation. We observed the formation of several cavitation-induced pits when the fluence of the laser pulse used for ablation was approximately 5 J/cm2. The number of cavitation-induced pits decreased with the laser fluence, and we observed one or two cavitation-induced pits when the laser fluence was higher than 10 J/cm2. In addition, we examined the influence of the liquid temperature on the formation of cavitation-induced pits. The collapse of the cavitation bubble was not observed when the liquid temperature was close to the boiling temperature, and in this case, we found no cavitation-induced pits on the bottom surface of the ablation crater. This experimental result was discussed by considering the cavitation parameter.  相似文献   
92.
Thermal stability of single-crystalline [ZnO]m[Zn0.7Mg0.3O]n multiple quantum wells (MQWs) grown on a-plane sapphire substrates by plasma-assisted molecular beam epitaxy is reported. X-ray diffraction analysis revealed that these MQWs were grown as designed with a fixed Zn0.7Mg0.3O barrier width of and a series of ZnO well widths of . Cathodoluminescence spectra from these MQWs consisted of two major peaks; one was the emission from the bound excitons in Zn0.7Mg0.3O barrier layers, and the other was that from the confined excitons in ZnO well layers. These structural and optical properties were found to be dramatically changed by the ex situ annealing treatments over 700 °C. These changes were presumably due to the onset of phase separation of the Zn0.7Mg0.3O barrier layers with pronounced Mg diffusion toward the ZnO wells.  相似文献   
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94.
Solvent effects on dynamical and thermal behaviors of ovalbumin (OVA) gels induced by thermal denaturation at high temperature of 160°C were studied from dynamic shear modulus measurement, shear creep and creep recovery measurement, and DSC measurement. Two organic solvents, glycerin (G) and ethylene glycol (EG), and their mixtures with water (W)(G/W and EG/W) were used as solvent for preparation of gels. Stable gels formed in pure glycerin took a fractal structure at OVA concentration C range of 15–45wt% at a temperature specific to respective C, whereas a fractal structure was not observed for gels prepared in EG, G/W, and EG/W. The results were consistent with thermal denaturation behaviors of OVA in these solvents. Morphologies of two gels prepared in water and glycerin were explored using high resolution SEM, which showed that a basic unit responsible for formation of OVA gels was spheres with a diameter ranging from 20 to 40 nm, being much larger than 5.6 nm of the diameter of native OVA, and a fractal structure was related to network formation accompanied by melting of those spheres.Dedicated to Prof. John D. Ferry on the occasion of his 85th birthday.  相似文献   
95.
An attempt to carry out a total synthesis of kulokekahilide-2 (1) by macrolactonization of a seco acid prepared from a suitably protected hexapeptide and a dioxy acid moiety unexpectedly resulted in the formation of the 43-epimer (1a) of the cytotoxic depsipeptide, for which structure 1b has previously been proposed. A second attempt involving macrolactamization of the corresponding amino acid gave the target product, 1b, but the spectral data of the product did not match those of natural 1. Furthermore, neither 1a nor 1b showed any cytotoxicity, from which it is concluded that the structure of natural 1 is incorrect and should be re-examined.  相似文献   
96.
We demonstrate the single mode operation of a broad-area diode laser at 670 nm by means of an external cavity configuration using a diffraction grating. The output power of 150 mW is obtained with a spectral width of 40 MHz.  相似文献   
97.
We develop the formalism to investigate therelation between the evolution of the large-scale(quasi) linear structure and that of the small-scalenonlinear structure in Newtonian cosmology within theLagrangian framework. In doing so, we first derive thestandard Friedmann expansion law using the averagingprocedure over the present horizon scale. Then thelarge-scale (quasi) linear flow is defined by averaging the full trajectory field over a large-scaledomain, but much smaller then the horizon scale. Therest of the full trajectory field is supposed todescribe small-scale nonlinear dynamics. We obtain the evolution equations for the large-scale andsmall-scale part of the trajectory field. These arecoupled each other in most general situations. It isshown that if the shear deformation of fluid elements is ignored in the averaged large-scaledynamics, the small-scale dynamics is described byNewtonian dynamics in an effectiveFriedmann-Robertson-Walker (FRW) background with a localscale factor. The local scale factor is defined by the sum of theglobal scale factor and the expansion deformation of theaveraged large-scale displacement field. This means thatthe evolution of small-scale fluctuations is influenced by the surrounding large-scale structurethrough the modification of FRW scale factor. The effectmight play an important role in the structure formationscenario.  相似文献   
98.
The charge separation occurring in the photosynthetic reaction center is the primary subject in order to understand the whole photosynthetic process. In this article, the electronic structures of the chlorophyll dimer, in which photoexcitation occurs, are investigated by using the ab initio molecular orbital scheme and pseudocharges and dipoles method which takes into account the electrostatic effect of the surrounding proteins, pigments, and aqueous solvent. As a first step, the ionization potentials of BCmp, BCIp, and the dimer of Rhodopseudomonas viridis are computed to study the characteristic of each molecule toward the elucidation of the primary charge separation. It has been found, from the present calculations, that BCmp and BClp constituting the dimer are not equivalent in their electronic ground states, since the electron could be removed more easily from BCmp than from BClp for two reasons: (1) the distorted molecular plane of Cmp, and (2) the effects of the surrounding electrostatic potentials to BCmp and BCIp. This tendency is further strengthened by the polarization of the environment, when, to the ab initio MO calculation, the contribution from the induced dipoles of the neighboring atoms in the proteins and other chromophores is included. From the present application, induced electric dipoles are found to be important to describe the molecular electronic structures affected by proteins. © 1997 John Wiley & Sons, Inc.  相似文献   
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