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71.
The nonlinear response of an oscillatory bubble in a complex fluid is studied. The bubble is immersed in a Newtonian liquid, which may have a dilute volume fraction of anisotropic additives such as fibers or few ppm of macromolecules. The constitutive equation for the fluid is based on a Maxwell model with an extensional viscosity for the viscous contribution. The model is considered new in the study of bubble dynamics in complex fluids. The numerical computation solves a system of three first order ordinary differential equations, including the one associated with the solution of the convolution integral, using a fifth order Runge–Kutta scheme with appropriated time steps. Asymptotic solutions of governing equation are developed for small values of the pressure forcing amplitude and for small values of the elastic parameter. A study of the bubble collapse radius is also presented. We compare the results predicted by our model with other model in the literature and a good agreement is observed. The calculated asymptotic solutions are also used to test the results of the numerical simulations. In addition, the orientation of the additives is considered. The angular probability density function is assumed to be a normal distribution. The results show that the model based on the fully aligned additives with the radial direction overestimates the tendency of the additives to stabilize the bubble motion, since the effect of extensional viscosity occurs due to the particle resistance to the movement throughout its longitudinal direction. 相似文献
72.
食品添加剂中某些大量与微量元素的含量与人体的健康越来越受到人们的关注。本文提出用ICP-AES法同时测定钙、钠食品添加剂中多种元素的方法,对基体元素的谱线干扰进行了校正及背景扣除。快速简便,结果满意。 相似文献
73.
This work considers how the ratio signal/noise and the introduction of a cut-off frequency affect the calculus of the thermogenesis. In particular, the validity of the experimental criterion used to calculate this frequency inside the deconvolutive calculus is studied. The deconvolutive efficiency of the universal transference function is also presented comparatively. 相似文献
74.
The solubility of Ag2O was measured for the Na2O–B2O3 and Na2O–B2O3–Al2O3 system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag2O for the Na2O–B2O3 system above the melting point of Ag for the first time. It was found that the addition of Na2O decreases the solubility of Ag2O while the addition of Al2O3 had little effect on the solubility. The effect of Na2O and Al2O3 on the solubility of Ag2O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag2O in Na2O–B2O3–Al2O3 melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver. 相似文献
75.
76.
Hosseln Elsazadeh 《高分子科学》2007,(4):393-397
One of the suitable methods for removing heavy metals from water is by using surface adsorption process. In this paper, the preparation of polypyrrole and its composites as adsorbents are discussed and the capability of separating mercury from water is investigated. The results indicated that the polypyrrole and its composites are able to remove mercury from aqueous media. Furthermore the adsorption percentage is related to the surface morphology, type of additives and its concentration. 相似文献
77.
研究了在烧结NdFeB磁体晶间添加Al、Mg、W、Mo等合金元素对显微组织和磁性能的影响。实验结果表明:低熔点合金元素Al、Mg能显著提高NdFeB磁体的矫顽力,略微降低剩磁,对磁体的热稳定性无影响;高熔点合金元素W、Mo在不降低剩磁的情况下亦能提高磁体的矫顽力,但效果不如Al、Mg明显。显微组织分析表明,在添加低熔点和高熔点合金元素的磁体晶间发现了两种不同的新相。矫顽力的提高可归于晶间新相的出现。进一步分析表明,与传统的合金化相比,对NdFeB磁体晶间区域进行微合金化是改进NdFeB磁体组织与性能的一种更为有效的手段。 相似文献
78.
A. Klisi
ska A. Haras K. Samson M. Witko B. Grzybowska 《Journal of molecular catalysis. A, Chemical》2004,210(1-2):87-92
Effect of additives (A) comprising main group elements (K, P) and transition metals (Ni, Cr, Mo) to VOx/SiO2 catalysts on their catalytic behavior in oxidative dehydrogenation (ODH) of propane are studied. The experimental findings are compared with results of quantum chemical calculations performed for a model O=V---O---V* cluster in which V* atom is replaced by an atom of A. The selectivities to propene found in experiments change on introducing the additives, decreasing in the sequence VK(64)>VCr(38)>VMo=VNi(32)>VP(28)V0(27). Quantum chemical calculations indicate the change in the electron density on the atoms of the active O=V---O groups for the clusters with the additives’ atoms. The extent of the electron transfer from A towards the active group (the increase in the centre basicity) follows the sequence of the decreasing selectivity to propene, confirming the role of acid–base properties in controlling the selectivity in ODH of propane. Results of calculations show also an exceptional behavior of the potassium (the most effective additive for the increase in the selectivity in experiments); in contrast to all other additivies, K transfers electrons towards both V and O atoms in the active group, and does not form a definite O---K bond, but is rather “adsorbed” on the cluster. 相似文献
79.
C. van Schalkwyk H. C. M. Vosloo J. M. Botha 《Journal of molecular catalysis. A, Chemical》2002,190(1-2):185-195
A catalytic system consisting of RuCl3·hydrate, a phosphine and an alkyne were investigated for the metathesis of 1-octene. Hydrogen was used during the reaction to obtain the highest yield of primary metathesis products. The influence of additives (oxygenates) was investigated and the reaction conditions optimized. Metathesis of 1-octene shows the best results at temperatures between 80 and 90 °C if acetic acid or ethanol was used as solvent and a PCy3/Ru molar ratio of 1. It was also found that both internal and terminal alkynes could be used for the in situ activation of the metathesis precursor during metathesis reactions. 相似文献
80.
Christian Leppin Arne Langhoff Oliver Höfft Diethelm Johannsmann 《Electroanalysis》2021,33(12):2529-2538
A fast electrochemical quartz crystal microbalance with dissipation monitoring (EQCM−D) was applied to copper electrodeposition and subsequent stripping. Accumulation brings the frequency noise down to the mHz range, corresponding to 0.1 % of a monolayer. With this precision, the apparent mass transfer rate as determined from the time-derivative of the frequency shift can be directly compared to the current. Small but systematic deviations between the two can be attributed to nanoscale roughness. In the voltage range of underpotential deposition (UPD), the apparent mass transfer rate shows peaks and shoulders. The plating additive benzotriazole (BTA) leaves the magnitude of electrogravimetric signals unchanged, but shifts the UPD onset potential. The additive thiourea (TU) promotes UPD and strongly increases the bandwidth. 相似文献