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121.
122.
可再生生物质资源的开发与利用能够缓解化石燃料产生的温室气体对环境的负面影响.在生物质燃料制备过程中联产高附加值化学品能大幅提高生物质炼制的经济性.愈创木酚是常见的木质纤维素快速热解产物.本文研究了低温液相氧化愈创木酚制备马来酸,并重点考察了催化剂添加量、pH值、反应时间和反应温度等反应条件的影响.研究发现,在钛硅沸石-过氧化氢碱溶液氧化反应体系中(80℃,pH=13.3),2030mol%的愈创木酚可以选择性转化为马来酸.同时初步探讨了愈创木酚氧化开环转化为马来酸的反应机理.  相似文献   
123.
Nitrogen in biomass is mainly in forms of proteins (amino acids). Glycine, glutamic acid, aspartic acid, leucine, phenylalanine and proline are the major amino acids in agricultural straw. The six amino acids were pyrolyzed individually at 800 °C in a tubular reactor in an argon atmosphere. Each amino acid sample was then pyrolyzed individually with cellulose, hemicellulose or lignin with 1:1 mixing ratio by weight under the same condition. The emissions of HCN and NH3 were detected with a Fourier transform infrared (FTIR) spectrometer. The extent of interaction between the amino acids with cellulose, hemicellulose or lignin was determined by comparing the yields of HCN and NH3 from co-pyrolysis with those from single amino acid pyrolysis under the same condition. The results indicate that the structure of the amino acid has a significant effect on the nitrogen transformation during pyrolysis. The mixtures undergo solid-state decomposition reactions during co-pyrolysis. The extent of interaction between the amino acids with cellulose, hemicellulose or lignin depends on the amino acid types and the components in biomass. Although single proline and leucine form no char, they give a significant amount of nitrogen-containing char when co-pyrolyzed with cellulose, hemicellulose and lignin. HCN and NH3 yields and nitrogen conversion pathway from amino acid pyrolysis are influenced by cellulose, hemicellulose and lignin.  相似文献   
124.
Biomass combustion in pulverized-fuel boilers is a growing way to produce electricity from a renewable source of energy. Slagging and fouling limit however the reliability of the units that were initially designed for coal combustion. Computational Fluid Dynamics (CFD) codes aiming at studying those phenomena include simplified models of biomass particle pyrolysis, of which the pertinence has already been questioned for the typical conditions of interest. A comprehensive model has been developed to investigate pyrolysis of particles in pulverized-fuel boilers, with sizes ranging from 17 μm to 2.5 mm. The detailed model accounts for internal heat conduction, internal gaseous convection, moisture evaporation and particle shrinkage. It includes a competitive, multi-component kinetic scheme, improved for high temperatures. The discrepancy between the simplified models integrated in most CFD applications and the detailed simulations is highlighted. The simplified isothermal models underestimate pyrolysis time for the largest particles. Moreover, such models delay and shorten the volatiles release. The flame lengths, the local temperature fields and the pollutant emissions might be importantly impacted in global combustion simulations. Apparent kinetic parameters have been derived from the detailed simulations. Their use in existing simplified models improves the behavior of the biomass particles during pyrolysis, and offers therefore an efficient alternative to the integration of complex pyrolysis models in CFD codes.  相似文献   
125.
In this paper, activated carbons (ACs) with high specific surface areas were successfully synthesized by simple one-step carbonization-activation from paulownia sawdust biomass, and the effects of the synthetic conditions on their CO2 capture capacity were investigated as well. The results show that, when the mass ratio between activator and biomass is 4, the activation temperature is 700℃ and the activation time is 1 h, as-made AC provides the most micropores for CO2 adsorption. As a consequence, the maximum CO2 uptake of 8.0 mmol/g is obtained at 0 ℃ and 1 bar.  相似文献   
126.
采用双相联系流反应性萃取技术实现常压下小麦秸秆向乙酰丙酸的转化,其中生物质在水相中完成降解,形成乙酰丙酸,而后比水密度大的有机相作为乙酰丙酸的萃取相,把生成的乙酰丙酸萃取到有机相,并经过虹吸到收集瓶中,有机相经蒸馏可反复使用,实现了预处理生物质到乙酰丙酸的高效转化,乙酰丙酸最大的产率为30.66%.  相似文献   
127.
Biomass plays a significant role in replacing fossil resources, and catalytic transformation of platform chemicals to high-value chemicals is an effective approach to maximize the utilization of biomass. Among of which, efficient and durable catalysts are the heart for upgrading of these platform chemicals, and metal–organic frameworks (MOFs)-derived catalysts have attracted much attentions due to their suitable and versatile physicochemical properties. In this work, we present a short review on the applications of MOFs-derived catalysts in upgrading of platform chemicals. The design and synthetic strategies of MOFs-derived catalysts were summarized in detail, and their application in the catalytic upgrading of glycerol, ethanol, furanic compounds, levulinic acid and vanillin were addressed. The final section outlines the potential industrial applications of MOFs-derived catalysts for upgrading platform chemicals.  相似文献   
128.
As the primary component of haze, atmospheric inhalable particulate matters (PM10) are highly detrimental to human health. Biomass combustion is one of China's most pivotal sources to aerosols pollution, inducing non-negligible emissions and uncertain risks. PM10 samples directly from 10 representative biomass fuel combustion sources (2 groups covering the reality widely: straws of rice, wheat, corn, corncob, soybean, peanut, rape, sesame; and branches of pine, peach) were collected using the dilution channel sampler and analyzed for chemical compositions and in vitro cytotoxicity to human lung epithelial cell lines A549. The components of PM10 are dominated by organic carbon (OC), followed by water-soluble K+ and Cl, and rich in metals Fe, Zn, Cr, and Ni. Generally, PM10 emitted from biomass fuel combustions can weaken the antioxidant capacity of cells, and straws emissions, especially rape and peanut straws, show stronger ability to further induce oxidative stress and inflammatory damage than fuelwoods, owing to the key toxic roles of Cr, Ni, and Co. Therefore, reducing the specific source emissions of PM10 from crop straw combustions rich in heavy metals could be an effective oriented strategy to improve environmental air quality and control aerosols pollution precisely for protecting public health.  相似文献   
129.
Dual circulating fluidized bed (DCFB) has emerged as an efficient reactor for biomass gasification due to its unique feature of high gas-solid contact efficiency and separated reactions in two reactors, yet the understanding of complex in-furnace phenomena is still lacking. In this study, biomass gasification in an industrial-scale DCFB system was numerically studied using a multiphase particle-in-cell (MP-PIC) method featuring thermochemical sub-models (e.g., heat transfer, heterogeneous reactions, and homogeneous reactions) under the Eulerian-Lagrangian framework. After model validation, the hydrodynamics and thermochemical characteristics (i.e., pressure, temperature, and species) in the DCFB are comprehensively investigated. The results show that size-/density-induced segregation makes solid fuels concentrate on the bed surface. Interphase momentum exchange leads to the continuous decrease of the gas pressure axially. In the gasifier and combustor, the lower heating value (LHV) of the gas products is 5.56 MJ/Nm3 and 0.2 MJ/Nm3 and the combustible gas concentration (CGC) is 65.5% and 1.86%, respectively. The temperature in the combustor is about 100 K higher than that in the gasifier. A higher solid concentration results in a smaller value of particle heat transfer coefficient (HTC). The HTCs range from 50 to 150 W/(m2 K) for a solid concentration larger than 0.3 in the combustor while the HTCs range from 100 to 200 W/(m2 K) in the gasifier. The Reynolds number of biomass particles is two orders of magnitude larger than that of the sand particle. The numerical results shed light on the reactor design and process optimization of biomass gasification in DCFBs.  相似文献   
130.
《Comptes Rendus Chimie》2016,19(4):441-449
This study proposes a numerical model developed to characterize the chemical composition, heating value and temperature of the syngas produced by a downdraft gasifier fueled with residual biomasses. The process of gasification is essentially described through a global reaction that includes all the gaseous species and the yields of char and tar.The syngas chemical composition has been obtained solving a set of equations that are mass and energy balances, methanation and the water-gas shift reactions, which govern the gasification process. The proposed model was calibrated and validated through the comparison with two sets of experimental data. The comparison between the results of simulation and the experimental data has shown a very good agreement that allows pointing out the capability of the model to characterize the syngas composition and the temperature of the producer gas.Moreover, the performed sensitivity analysis shows the influence of moisture content and equivalent ratio on the chemical composition, equilibrium temperature and heating value of the producer gas.  相似文献   
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