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731.
Abstract The application of high pressures to biomaterials can often result in significant structural modifications and, in some cases, also lead to changes in the rates and the equilibria of any associated biological activities. Pressure-induced changes can conveniently be monitored by molecular spectroscopy. We present here a brief overview of the effects of high pressures on the IR and Raman spectra of biomaterials that have been reported over the past 25 years. Examples of the biomaterials that have been examined are model antithyroid drugs, proteins, amino acids, dental materials, human bones, and bioorganometallic compounds. In addition, some recent investigations on the effect of pressure on microbial activity and the conversion of biomass into molecular hydrogen under supercritical water conditions are discussed. Two typical diamond-anvil cells (DACs), which are used for high-pressure vibrational spectroscopic measurements, are also described here. 相似文献
732.
Synthetic dyes are not uniformly susceptible to degradation in conventional wastewater treatment processes. A number of biotechnological
processes have been suggested as of potential interest in combating these pollutants in an ecofriendly manner. We determined
the optimal parameters necessary for the bacterial consortium SV5 to decolorize Ranocid Fast Blue dye. The best results were
obtained with a 0.1% (w/v) concentration of both starch and yeast extract supplemented in Bushnell Hass Medium under static
conditions at a temperature of 37°C in less than 24 h with an initial dye concentration of 100 ppm. 相似文献
733.
734.
735.
本文基于CFD–DEM方法,将多种传热模型与稠密气固流动与化学反应耦合,对鼓泡流化床内生物质燃烧过程中的传热特性进行了数值模拟研究。结果表明,对于燃料颗粒,反应热占据主导地位,辐射和对流传热同样起到重要作用,导热的影响相对较小。随着燃料挥发分含量的增加,对流传热和颗粒–颗粒导热作用增强,颗粒–壁面导热减弱。床内热点温度由燃料挥发分燃烧引起,从床层表面产生并上升到自由空域。生物质颗粒的温度则随局部颗粒浓度的减小而逐渐增加。
相似文献736.
737.
Wolfgang G. Glasser William E. Kaar Rajesh K. Jain James E. Sealey 《Cellulose (London, England)》2000,7(3):299-317
The isolation of non-cellulosic heteropolysaccharides (HetPS) from barley husks (Hordeum spp.) and yellow poplar wood chips (Liriodendron tulipifera) was accomplished using mild steam explosion followed by extraction with water and ultrafiltration. The generally low yields, low purity, and low degree of polymerization (DP) improved when the HetPS were isolated following either alkali extraction of hammermilled or disk-refined biomass, or from holocellulose preparations generated by the conventional chlorite method or by organosolv delignification. Several purification methods were examined including precipitation using methanol; treatment with hydrogen peroxide (H2O2) or activated carbon (C) followed by precipitation with methanol; and H2O2-treatment followed by ultrafiltration. The isolation protocols were judged based on product yield, xylan content, and DP. The results indicate that, although steam explosion is effective in removing HetPS from the fiber source, virtually none remain in polymeric form. By contrast, alkali extraction succeeds in separating polymeric HetPS from the fiber source; and HetPS purity increases and polydispersity decreases with fiber prehydrolysis and delignification. Significant processing difficulties were attributed to the intimate association of HetPS with lignin which was effectively disrupted by acid-catalyzed pretreatment and treatment with H2O2. Ultrafiltration of H2O2-treated HetPS solutions represents the best procedure for isolating a xylan-rich polymer in high yield, with high DP and with high purity. Aqueous HetPS solutions can be spray- or freeze-dried into powderous products. 相似文献
738.
Selma Zahirović Robert Scharler Pia Kilpinen Ingwald Obernberger 《Combustion Theory and Modelling》2013,17(1):61-87
While reasonably accurate in simulating gas phase combustion in biomass grate furnaces, CFD tools based on simple turbulence–chemistry interaction models and global reaction mechanisms have been shown to lack in reliability regarding the prediction of NOx formation. Coupling detailed NOx reaction kinetics with advanced turbulence–chemistry interaction models is a promising alternative, yet computationally inefficient for engineering purposes. In the present work, a model is proposed to overcome these difficulties. The model is based on the Realizable k–? model for turbulence, Eddy Dissipation Concept for turbulence–chemistry interaction and the HK97 reaction mechanism. The assessment of the sub-models in terms of accuracy and computational effort was carried out on three laboratory-scale turbulent jet flames in comparison with the experimental data. Without taking NOx formation into account, the accuracy of turbulence modelling and turbulence–chemistry interaction modelling was systematically examined on Sandia Flame D and Sandia CO/H2/N2 Flame B to support the choice of the associated models. As revealed by the Large Eddy Simulations of the former flame, the shortcomings of turbulence modelling by the Reynolds averaged Navier–Stokes (RANS) approach considerably influence the prediction of the mixing-dominated combustion process. This reduced the sensitivity of the RANS results to the variations of turbulence–chemistry interaction models and combustion kinetics. Issues related to the NOx formation with a focus on fuel bound nitrogen sources were investigated on a NH3-doped syngas flame. The experimentally observed trend in NOx yield from NH3 was correctly reproduced by HK97, whereas the replacement of its combustion subset by that of a detailed reaction scheme led to a more accurate agreement, but at increased computational costs. Moreover, based on results of simulations with HK97, the main features of the local course of the NOx formation processes were identified by a detailed analysis of the interactions between the nitrogen chemistry and the underlying flow field. 相似文献
739.
740.
燕麦秸秆燃烧灰中矿物质分布及沉积行为 《燃料化学学报》2012,40(11):1310-1316
在自行设计的沉降炉内研究了燕麦秸秆燃烧灰中矿物质分布及沉积行为。采用X射线衍射(XRD)、扫描电镜能谱(SEM/EDS)及电子探针X射线显微(EPMA)对850℃下不同燃烧时间的沉积物进行分析,并结合化学热力学平衡计算,结果表明,燕麦秸秆燃烧的沉积物形成是碱金属挥发黏结作用使大小不同的燃料球团形成,内部伴随着氧化反应从而形成表面孔洞。钾长石是沉积物形成中起黏结和支撑作用的"骨架"的主要组成部分,在燕麦秸秆燃烧初始沉积中有重要作用。K、Al的分布密集而广泛,Na在一定程度上会促进K的活性,表面的部分碱金属逐渐挥发至气相,Fe、Ca、Mg等的相关化合物不断填充沉积物孔隙使其致密、硬化,最终各元素较均匀地分配。 相似文献