全文获取类型
收费全文 | 874篇 |
免费 | 27篇 |
国内免费 | 38篇 |
专业分类
化学 | 424篇 |
晶体学 | 3篇 |
力学 | 330篇 |
综合类 | 11篇 |
数学 | 27篇 |
物理学 | 144篇 |
出版年
2023年 | 39篇 |
2022年 | 27篇 |
2021年 | 11篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 22篇 |
2017年 | 27篇 |
2016年 | 20篇 |
2015年 | 42篇 |
2014年 | 32篇 |
2013年 | 49篇 |
2012年 | 29篇 |
2011年 | 47篇 |
2010年 | 40篇 |
2009年 | 59篇 |
2008年 | 42篇 |
2007年 | 54篇 |
2006年 | 45篇 |
2005年 | 43篇 |
2004年 | 26篇 |
2003年 | 41篇 |
2002年 | 24篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 25篇 |
1998年 | 31篇 |
1997年 | 15篇 |
1996年 | 12篇 |
1995年 | 14篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有939条查询结果,搜索用时 15 毫秒
931.
《Particuology》2023
The 440 t/h circulating fluidized bed boiler was numerically simulated by the Computational Particle Fluid Dynamics (CPFD) method. The combustion characteristics of circulating fluidized bed boiler and the effect of secondary air on NO emission were investigated. The full-scale three-dimensional model of a 440 t/h circulating fluidized bed boiler was established. The rationality of the grid was validated by the experimental data of material layer resistance. The accuracy of the simulation was validated by measuring the temperature of each measuring point in the dense phase area. The combustion conditions in the furnace under different setting modes were simulated. The effects of secondary air rates on NO formation in fluidized bed were predicted. The results show that when the secondary air rate increases to 27%, the proper secondary air rate has a positive effect on the inhibition of NO generation, and the proper strengthening of the central air supply will improve the permeability of the secondary air and make the combustion more uniform and stable. When the secondary air rate increases to 33%, excessive improvement of air classification and central air distribution will affect the stability of circulating fluidized bed operation. Therefore, air classification and strengthening of central air supply can be used together to inhibit the generation of NO. 相似文献
932.
《Particuology》2023
The structure of the gas distributor is closely related to the production efficiency of organosilicon monomers. To improve the production efficiency of organosilicon monomers, this study uses Eulerian-Eulerian two fluid model and proposes a design formula for the gas distributor to optimize the gas distributor. It is proposed that the pressure drop of the gas distributor, the velocity nonuniformity coefficient, the relative standard deviation of the solid holdup, and the solid particle dispersion coefficient are used to evaluate the performance of the gas distributor. The results show that the performance of the gas distributor is significantly improved when the opening ratio Φ = 0.53% is optimized to Φ = 0.18%, in which the relative standard deviation of the solid holdup is reduced by 22%, and the solid particle dispersion coefficient is reduced by 40%. On this basis, this article studies the influence of different arrangements of vent holes on gas-solid fluidization characteristics. The results show that the circular arrangement of vent holes is helpful to the mixing of gas and solid. 相似文献
933.
934.
《Particuology》2023
The ultra-low NOx emission requirement (50 mg/m3) brings great challenge to CFB boilers in China. To further tap the NOx abatement potential, full understanding the fundamentals behind CFB boilers is needed. To achieve this, a comprehensive CPFD model is established and verified; gas-solid flow, combustion, and NOx emission behavior in an industrial CFB boiler are elaborated; influences of primary air volume and coal particle size on furnace performance are evaluated. Simulation results indicate that there exists a typical core-annular flow structure in the boiler furnace. Furnace temperature is highest in the bottom dense-phase zone (about 950 °C) and decreases gradually along the furnace height. Oxygen-deficient combustion results in high CO concentration and strong reducing atmosphere in the lower furnace. NOx concentration gradually increases in the bottom furnace, reaches maximum at the elevation of secondary air inlet, and then decreases slightly in the upper furnace. Appropriate decreasing the primary air volume and coal particle size would increase the CO concentration and intensify the in-furnace reducing atmosphere, which favors for NOx reduction and low NOx emission from CFB boilers. 相似文献
935.
《Particuology》2023
In this study, a CFD model coupled with heterogeneous flow structure, mass transfer equations, and chemical reaction kinetics is established to forecast the pyrolusite reduction reaction behavior. Compared with the previous studies which ignore the volume change of solids phase, the influence of volume shrinkage on reaction and flow behavior is explored in this research. Volume shrinkage of pyrolusite is proved to be non-negligible in predicting the conversion rate. The negligence of volume shrinkage leads to the overestimation of conversion rate for its inaccurate estimation of surface area for reaction. Besides, the influence of volume shrinkage on the reaction is found smaller in the scaled-up reactor. 相似文献
936.
《Particuology》2023
In this work, in-situ experimental tests are first performed to investigate the powder spreading process of additive manufacturing, where different kinds of scrapers and spreading speeds are employed. Detailed kinetic behaviours of individual powder particles are discussed by discrete element method simulations. It is found that the decrease of inclination angle of the scraper improves the powder pressure and compaction in the spreading process, leading to a denser powder flow and thus a denser powder bed. The increase of spreading speed also improves the powder pressure and compaction in the spreading process. However, the powder flow becomes looser due to the volume dilation, and thus the quality of the paved powder bed decreases. In industrial applications, if the higher powder spreading speed is employed to improve the processing efficiency, the scraper with a smaller inclination angle can be used to ensure the powder bed quality. 相似文献
937.
《Particuology》2023
Since the carbon dioxide (CO2) capture using solid sorbent is a reversible reaction, the solid sorbent can be regenerated by the desorption process. Therefore, the desorption process is one of the key important processes for the CO2 capture system. Traditionally, most of the literature studies focus on the desorption of solid sorbent under an N2 atmosphere. However, the desorption process of the solid sorbent is inappropriate in the real system because the system will need another process to separate CO2 and nitrogen (N2) after the desorption process. This study focused on the CO2 desorption of potassium carbonate supported on gamma-alumina (K2CO3/γ-Al2O3) in a wet fluidized bed under a steam atmosphere by using the multiphase computational fluid dynamics (CFD) simulation. The effects of water thickness and dry restitution coefficient on CO2 desorption rate were investigated to provide a realistic particle collision behavior and to explore their effects on CO2 desorption phenomena. Moreover, the effect of steam velocity on the hydrodynamic behaviors of fluidization which on CO2 desorption rate was studied. The simulated results demonstrated that all the parameters, water thickness, dry restitution coefficient, and steam velocity had significantly affected system hydrodynamics and CO2 desorption rate in the wet fluidization desorption process. Furthermore, the effect of desorption temperature on CO2 desorption rate was evaluated for finding the appropriate temperature for CO2 desorption process of K2CO3/γ-Al2O3. The results showed that the appropriate desorption temperature for CO2 desorption under steam atmosphere was the temperature over 150 °C. 相似文献
938.
《Particuology》2023
The P1 approximation is a computationally efficient model for thermal radiation. Here, we present a P1 formulation in the context of the combined computational fluid dynamics and discrete element method (CFD-DEM), including closures for dependent scattering and coarse-graining. Using available analytical and semi-analytical solutions, we find agreement for steady-state and transient quantities in size-disperse systems. Heat flux is identified as the most sensitive quantity to predict, displaying unphysical spatial oscillations. These oscillations are due to a temperature slip at the locations of abrupt change in solid fraction. We propose two techniques that mitigate this effect: smoothing of the radiative properties, and pseudo-scattering. Furthermore, using up to a million times enlarged particles, we demonstrate practically limitless compatibility with coarse-graining. Finally, we compare predictions made with our code to experimental data for a pebble bed under vacuum conditions, and in presence of nitrogen. We find that a carefully calibrated simulation can replicate trends observed in experiments, with relative temperature error of less than 10%. 相似文献