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121.
Baumgärtner F Sewell RJ Eriksson S Llorente-Garcia I Dingjan J Cotter JP Hinds EA 《Physical review letters》2010,105(24):243003
We investigate the use of a Bose-Einstein condensate trapped on an atom chip for making interferometric measurements of small energy differences. We measure and explain the noise in the energy difference of the split condensates, which derives from statistical noise in the number difference. We also consider systematic errors. A leading effect is the variation of the rf magnetic field in the trap with distance from the wires on the chip surface. This can produce energy differences that are comparable with those due to gravity. 相似文献
122.
123.
Summary Three extensions of the basic PCA and PLS methodologies are described. These extensions are hierarchical, non-linear and batch-based
in nature. The objectives of these methods are to assist in problem understanding and problem solving in very complex (QSAR)
problem formulations. The method extensions are illustrated using two example QSAR data sets containing many X- and Y-variables. 相似文献
124.
Bentley et al. studied the turnover rate in popularity toplists in a ‘random copying’ model of cultural evolution. Based on simulations of a model with population size N, list length ? and invention rate μ, they conjectured a remarkably simple formula for the turnover rate: $\ell \sqrt{\mu}$ . Here we study an overlapping generations version of the random copying model, which can be interpreted as a random walk on the integer partitions of the population size. In this model we show that the conjectured formula, after a slight correction, holds asymptotically. 相似文献
125.
对12C6+ 离子辐照诱变高产阿维链霉菌株ZJAV-Y1-203 和原始菌株ZJAV-A-1 的摇瓶发酵pH 值、菌体浓度、碳源和氮源代谢进行了测定,研究了12C6+ 辐照对阿维链霉菌的代谢效应。在发酵前期(48h),原始菌株发酵液pH 值低于突变菌株;在发酵96~196 h,诱变高产菌株ZJAV-Y1-203 繁殖快,生长旺盛,N的利用率高;菌体浓度大于原始菌株的浓度,且发酵液的pH 稳定,菌体处于代谢相对更稳定期;在发酵144~240 h,诱变高产菌株ZJAV-Y1-203 对糖源消耗低于原始菌株ZJAV-A-1。这些结果表明,12C6+ 离子辐照对阿维链霉菌代谢影响有利于阿维菌素合成。pH value, mycelium concentration, carbon source and nitrogen metabolism in flask fermentation of the mutant high-producing strain ZJAV-Y1-203 and the original strain ZJAV-A1 have been investigated, in order to show the metabolic effect of avermitilis irradiated by ion beam of 12C6. In early stage (48 h) of the fermentation, pH value of the original fermentation was lower than that of the mutant strains. In 96~196 h of fermentation, the nitrogen utilization in the strains ZJAV-Y1-203 was higher than that in the original strains, its reproductive was fast, and its growing was vigorous. The mycelium concentration of ZJAV-Y1-203 was greater than the original strain, and the pH value of fermentation were stable, so its metabolism was relatively more stable. In 144240 h of fermentation, the strain ZJAV-Y1-203 on sugar consumption was less than the original strains. The effect of 12C6 ion irradiation on metabolism of Streptomyces avermitilis is conducive to the synthesis of avermectin. 相似文献
126.
127.
氩、氢混合等离子体处理对GaAs表面性质及发光特性的影响 总被引:1,自引:0,他引:1
介绍了一种氩、氢混合等离子体清洗GaAs基片的实验工艺,深入研究了氩、氢等离子体清洗GaAs表面污染物和氧化层,并活化表面性能的基本原理,同时讨论了气体流量、溅射功率和清洗时间等不同溅射参数对等离子体清洗效果的影响。结果表明,在氩气和氢气流量分别为10 cm3/min和30 cm3/min,溅射功率为20 W,清洗时间为15 min的条件下,GaAs样品的光致发光强度提高达139.12%,样品表面的As-O键和Ga-O键基本消失。 相似文献
128.
润湿特性对超级电容器储能性能有着至关重要的影响。借助分子动力学模拟,本文研究了润湿特性对超级电容器储能动力学行为的影响。以石墨烯和晶体铜作为疏电解液和亲电解液电极材料。结果表明,在充电过程中,亲电解液铜电极呈现出非对称的U型微分电容曲线,负极电容是正极的~5.77倍,不同于经典双电层理论Gouy-Chapman-Stern(对称U型)和疏电解液型。该现象与离子自由能阻力分布密切相关,负极自由能阻力远小于正极(~2倍)和疏电解液电极,进而有利于强化双电层结构对电极电压的响应能力,导致更高微分电容。通过微分离子电荷密度,本文再现了微分电容演变规律,并发现改善润湿性会显著降低双电层厚度。最后,我们指出润湿性直接影响储能微观机理,将电荷储存机制从离子吸附和交换共同主导(疏电解液)转变到离子吸附主导(亲电解液)。本文所得结论揭示了润湿特性对储能动力学行为影响的原子层级机理,对超级电容器材料设计、构筑与润湿特性调控具有重要指导意义。 相似文献
129.
Conventional methods to calculate the thermodynamics of crystals evaluate the harmonic phonon spectra and therefore do not work in frequent and important situations where the crystal structure is unstable in the harmonic approximation, such as the body-centered cubic (bcc) crystal structure when it appears as a high-temperature phase of many metals. A method for calculating temperature dependent phonon spectra self-consistently from first principles has been developed to address this issue. The method combines concepts from Born's interatomic self-consistent phonon approach with first principles calculations of accurate interatomic forces in a supercell. The method has been tested on the high-temperature bcc phase of Ti, Zr, and Hf, as representative examples, and is found to reproduce the observed high-temperature phonon frequencies with good accuracy. 相似文献
130.
We have theoretically studied the possibility to control the equilibrium solubility of dopants in semiconductor alloys, by strategic tuning of the alloy concentration. From the modeled cases of C(0) in Si(x)Ge(1-x), Zn(-) and Cd(-) in Ga(x)In(1-x)P it is seen that under certain conditions the dopant solubility can be orders of magnitude higher in an alloy or multilayer than in either of the elements of the alloy. This is found to be due to the solubility's strong dependence on the lattice constant for size mismatched dopants. The equilibrium doping concentration in alloys or multilayers could therefore be increased significantly. More specifically, Zn- in a Ga(x)In(1-x)P multilayer is found to have a maximum solubility for x = 0.9, which is 5 orders of magnitude larger than that of pure InP. 相似文献