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31.
Seidel J Fu D Yang SY Alarcón-Lladó E Wu J Ramesh R Ager JW 《Physical review letters》2011,107(12):126805
We elucidate the mechanism of a newly observed photovoltaic effect which occurs in ferroelectrics with periodic domain structures. Under sufficiently strong illumination, domain walls function as nanoscale generators of the photovoltaic current. The steps in the electrostatic potential function to accumulate electrons and holes on opposite sides of the walls while locally reducing the concentration of the oppositely charged carriers. As a result, the recombination rate adjacent to the walls is reduced, leading to a net diffusion current. In open circuit, photovoltages for periodically ordered domain walls are additive and voltages much larger than the band gap can be generated. The internal quantum efficiency for individual domain walls can be surprisingly high, approaching 10% for above band-gap photons. Although we have found the effect in BiFeO(3) films, it should occur in any system with a similar periodic potential. 相似文献
32.
Zhou Tao Wu Ting Xiang Haonan Li Zhichao Xu Zhongliang Kong Qinghong Zhang Junhao Li Zhi Pan Yetang Wang Deyi 《Journal of Thermal Analysis and Calorimetry》2019,135(4):2117-2124
Journal of Thermal Analysis and Calorimetry - To simultaneously improve flame retardancy and dynamic mechanical properties of epoxy resin (EP) nanocomposites, layered zirconium phenylphosphate... 相似文献
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34.
C/粉煤灰复合吸附材料的制备及表征 总被引:1,自引:0,他引:1
以粉煤灰和蔗糖为原料,浓硫酸为炭化剂,制备了一种新型的C/粉煤灰复合吸附材料。 采用X光电子能谱、红外吸收光谱、场发射扫描电子显微镜、X射线衍射及N2气吸附实验对所制备复合材料进行了表征。 结果表明,粉煤灰表面被类石墨态炭纳米颗粒所包裹,复合材料表面密集分布着大量的介孔,Brunauer-Emmett-Teller(BET)比表面积SBET=5.4 m2/g,并且在该复合材料表面含有丰富的-SO3H、-COOH和-OH等含氧官能团。 考察了所制备的复合材料对典型阳离子型染料亚甲基蓝及重金属离子的吸附能力,结果表明,该复合材料具有优异的吸附性能,其对亚甲基蓝的吸附能力达到活性炭的83.7%,对典型重金属离子的吸附能力优于市售活性炭。 所制备复合材料可作为活性炭的一种替代品,用于水中有机染料和重金属离子的吸附处理。 相似文献
35.
Given the importance of airflow seepage properties to coal self-oxidation in gob, this paper develops a method and self-designed apparatus to assess seepage properties of compacted broken coal. This study mainly focuses on the strain, porosity and permeability evolution under the different conditions of particle size, vertical stress and temperature. The studied results show: (1) The strain, porosity and permeability were enlarged when the particle size increased under the same loading stress. The porosity and permeability reduced when the vertical stress increased. (2) The non-Darcy coefficient was negative in all tests, but the absolute value of the non-Darcy coefficient generally increased when the vertical stress increased. (3) The experiment results indicated that the larger the particle was, the easier to be compacted. The larger the grain diameter was, the lower the porosity and permeability were, which shown that the void volume in broken coal with larger grain diameters could be easily compacted. (4) The permeability was reduced when the temperature increased, which indicated the permeability of the compacted broken coal decreased during low-temperature oxidation in gob. (5) By the effects of stress and the particle size diameter on the porosity and permeability, the vertical stress recovery and generally increase are advantageous to reduce the porosity and permeability in gob. It is favorable to reduce the porosity and permeability and prevent coal self-heating by reducing the degree of fragmentation and percentage of small particles or consolidate the small particles. 相似文献
36.
Zn-Cr整体催化剂中Ce-Zr溶胶涂层的制备、表征及对甲醇自热重整反应的影响 总被引:1,自引:0,他引:1
以溶胶-凝胶法制备出粒子尺度均一的Ce-Zr溶胶. TEM和XRD结果表明, 1073 K焙烧后, Ce-Zr复合氧化物的粒径仍保持在20~50 nm. 将Ce-Zr溶胶作为甲醇自热重整制氢Zn-Cr整体催化剂的涂层,考察了溶胶在涂层多次重复过程中的稳定性和干燥方式对Ce-Zr涂层龟裂程度的影响. 结果表明,对多次使用后的溶胶进行胶溶处理可以有效控制涂层制备过程中胶体粒子的大小; 微波干燥更加有利于蜂窝陶瓷载体各通道中Ce-Zr涂层的均匀干燥; Ce-Zr涂层的引入显著提高了甲醇自热重整Zn-Cr整体催化剂的稳定性,这归因于Ce-Zr涂层提高了催化剂的氧化还原活性,使其能量匹配更好,避免了热点的产生,从而抑制了催化剂的烧结与失活. 相似文献
37.
三维弹性快速多极边界元法 总被引:2,自引:0,他引:2
将静电场多极展开法和广义极小残值法结合于三维弹性问题的边界元法,使其求解的计算量及所需内存量同节点的自由度总数成正比,变革计算结构,加快求解速度以适应大规模数值计算。两者结合的关键点在于边界元法基本解的合理分解,并用广义极小残值法(GMRES)求解方程。轧机支承辊变形场大规模数值算例的总自由度数首次达N=34008并获得成功。清晰地描述了支承辊和工作辊接触区的辊型。 相似文献
38.
The thermal chemistry of perfluoroethyl iodide (C2F5I) adsorbed on Cu(1 1 1) has been investigated by temperature-programmed reaction/desorption (TPR/D), reflection-absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS). I 4d and F 1s XPS spectra show that dissociative adsorption of C2F5I to form the surface-bound perfluroethyl (Cu-C2F5) moieties occurs at very low temperature (T < 90 K), while the C-F bond cleavage in adsorbed perfluroethyl (Cu-C2F5) begins at ca. 300 K. XPS and TPR/D studies further reveal that the reactions of βCF3αCF2(ad) on Cu(1 1 1) are strongly dependent on the surface coverage. At high coverages (?0.16 L exposure), the adsorbed perfluroethyl (Cu-C2F5) evolves, via α-F elimination, into the surface-bound tetrafluoroethylidene moieties (CuCF-CF3) followed by a dimerization step to form octafluoro-2-butene (CF3CFCFCF3) at 315 K as gas product. The surface-bound (Cu-C2F5) decomposes preferentially, at low coverages (?0.04 L), via consecutive α-F abstraction to afford intermediate, trifluoroethylidyne (CuCCF3), resulting in the final coupling reaction to yield hexafluoro-2-butyne (CF3CCCF3) at 425 K. However, at middle coverages (ca. 0.08-0.16 L exposure), the adsorbed perfluroethyl (Cu-C2F5) first experiences an α-F elimination and then prefers to loss the second F from β position to yield the intermediate of Cu-CF2-CFCu (μ-η,η-perfluorovinyl), which may further evolve into hexafluorocyclobutene (CF2CFCFCF2) at 350 K through cyclodimerization reaction. Our results have also shown that the surface reactions to yield the products, CF3CFCFCF3 and CF3CCCF3, obey first-order kinetics, whereas the formation of CF2CFCFCF2 follows second-order kinetics. 相似文献
39.
This paper describes a rapid method for the determination of 14 kinds of sulfonamides (SAs) in wastewater using SPE, and LC-MS/MS with positive ESI (ESI(+)) and selected reaction monitoring (SRM) mode. The SPE was performed on an Oasis hydrophilic-lipophilic-balanced (HLB) cartridge. Chromatographic separation on a C18 column was achieved using a binary eluent containing methanol and water with 0.2% formic acid. Typical recoveries of the analytes ranged from 22.3 to 87.0% at a fortification level of 100 ng/L. The LODs in wastewater except sulfathiazole (3 ng/L) could be detected and quantified at levels as low as 1 ng/L. Finally, the method was applied to water from the municipal outlet and the aquaculture wastewater effluent. Sulfamethazine (SM(2)), sulfamethoxypyridazine (SMP), and sulfamethoxazole (SMZ) were most frequently found in wastewater in a concentration range between 1.2 and 31.7 ng/L. 相似文献
40.