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51.
The Sr(OH)2 and SrCO3 nanostructures were synthesized by reaction of strontium(II) acetate and sodium hydroxide or tetramethylammonium hydroxide (TMAH) via ultrasonic method. Reaction conditions, such as the concentration of the Sr2+ ion, aging time, power of the ultrasonic device and alkali salts show important roles in the size, morphology and growth process of the final products. The pure crystalline SrCO3 were obtained by heating of product at 400 °C. The Sr(OH)2 and SrCO3 nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermal gravimetric (TG), differential thermal analyses (DTA) and the infrared spectroscopy (IR). 相似文献
52.
X-ray powder diffraction patterns of the AgNbO3 have been obtained in a wide temperature range: from room temperature up to 850 K. The type of distortion and the multiplicity of the pseudo-cubic perovskite cell has been determined from the splitting of the main diffraction lines and from analysis of the superlattice peaks. The scheme of oxygen octahedra tilting and the sequence of the distorted pseudocubic cell is: <artwork name="GPHT21121eu1"> 相似文献
53.
基于对熔融碳酸盐体系中电化学还原CO_2所得碳材料(electrolytic-carbon,EC)的形貌、结构、组成的认识,以粉末微电极循环伏安法测试为基础,在稀溶液中对EC的本征电化学行为进行了考察,以揭示这类碳材料的界面电化学特性。实验发现,在典型条件(450°C、4.5 V槽压)下制备的电解碳(450°C-4.5 V-EC)的伏安行为有别于多壁碳纳米管、石墨烯、石墨、乙炔黑等常见碳材料,在负电位区表现出显著的"双电层充放电响应迟滞"现象。通过考察溶液pH值、电位扫描速率、阴阳离子种类对这一现象的影响,发现pH和电解液组成都不影响这一现象的出现;电解液浓度提高和低扫描速率时滞后现象减弱,表明迟滞充放电是这类碳材料的本征特性,与其表面含氧官能团及其对阳离子的特性吸附密切相关。实验进一步研究了不同电解条件下制备的EC所展现的电化学特性吸附及电容性质,发现随着熔盐温度的升高,EC对电解液中阳离子的特性吸附能力降低,而相同温度不同槽压下制备的EC特性吸附能力相近,表现出相似的电容特性,这与EC的含氧量和比表面积有关。电解碳所展现的独特电容特性对其潜在的应用或可提供有价值的线索和指导。 相似文献
54.
总结了高分子材料加工的发展趋势及发展历程,并指出过去很多加工新技术的出现都得益于从自然现象及其他材料行业中获得很好的借鉴,如从蜘蛛吐丝发展出溶液纺丝成型、从玻璃吹制发展出吹塑成型、从金属锻造发展出压延成型及固相拉拔成型等;随后针对生物基可生物降解的立构复合型聚乳酸难以采用传统熔融加工方法成型的问题,借鉴金属粉末冶金加工的思路,提出了一种通过低温烧结制备高性能立构复合型聚乳酸制品的新方法.通过这种加工方法不仅可以有效解决立构复合型聚乳酸在熔融加工过程中熔体稳定性差、易降解的问题,而且可以制得耐热性好、光学透明度高、耐水解降解性佳、综合力学性能优异的高性能聚乳酸制品. 相似文献
55.
Hindered amine light stabilizers are used to protect polymers from heat- and light-induced degradation. In this study the oligomeric stabilizer Tinuvin 622 was analysed in-depth employing high performance liquid chromatography/time of flight mass spectrometry (HPLC/TOF-MS) to differentiate products of different manufacturers in respect of their terminating groups and oligomer length. Additionally, the behaviour of the stabilizer in uncured and cured polyester powder coatings was investigated regarding its interaction with the other coating components and chemical changes during the crosslinking process. The extraction efficiency was determined as a function of oligomer length and coating colour. 相似文献
56.
Lie ZS Pardede M Hedwig R Suliyanti MM Kurniawan KH Munadi Lee YI Kagawa K Hattori I Tjia MO 《Analytical and bioanalytical chemistry》2008,390(7):1781-1787
The applicability of spectrochemical analysis of minute amounts of powder samples was investigated using an ultraviolet Nd-YAG
laser (355 nm) and low-pressure ambient air. A large variety of chemical powder samples of different composition were employed
in the experiment. These included a mixture of copper(II) sulfate pentahydrate, zinc sulfide, and chromium(III) sulfate n-hydrate powders, baby powder, cosmetic powders, gold films, zinc supplement tablet, and muds and soils from different areas.
The powder samples were prepared by pulverizing the original samples to an average size of around 30 μm in order to trap them
in the tiny micro holes created on the surface of the quartz subtarget. It was demonstrated that in all cases studied, good
quality spectra were obtained with low background, free from undesirable contamination by the subtarget elements and featuring
ppm sensitivity. A further measurement revealed a linear calibration curve with zero intercept. These results clearly show
the potential application of this technique for practical qualitative and quantitative spectrochemical analysis of powder
samples in various fields of study and investigation. 相似文献
57.
Y. Leconte M. Leparoux X. Portier N. Herlin-Boime 《Plasma Chemistry and Plasma Processing》2008,28(2):233-248
In the growing field of nanomaterials, SiC nanoparticles arouse interest for numerous applications. The inductively coupled
plasma (ICP) technique allows obtaining large amount of SiC nanopowders from cheap coarse SiC powders. In this paper, the
effects on the SiC structure of the process pressure, the plasma gas composition, and the precursor nature are addressed.
The powders were characterized by X-ray diffraction (XRD), Raman and fourier transform infrared (FT-IR) spectroscopy, scanning
electron microscopy (SEM) and high resolution electron microscopy (HREM), chemical analyses, BET and photon correlation spectroscopy
(PCS) measurements. Whatever the precursor (α- or β-SiC), the nanoparticles were crystallised in the cubic β-SiC phase, with
average sizes in the 20–40 nm range. Few residual grains of precursor were observed, and the decarburization due to the reductive
Ar–H2 plasma lead to the appearance of Si nanograins. The stoichiometry of the final product was found to be controllable by the
process pressure and the addition of methane. 相似文献
58.
Giordano Paniconi Ronald I. Smith Bryan L. Gallagher 《Journal of solid state chemistry》2008,181(1):158-165
Zn3N2 powders were prepared by ammonolysis reactions at 600 °C and examined by thermogravimetric analysis, powder X-ray and neutron diffraction. The powders obtained in this way are unstable in an oxygen atmosphere above 450 °C. In an argon atmosphere, the powders are stable up to their decomposition point at around 700 °C. Structural models obtained from Rietveld refinements against the powder neutron diffraction data indicate that the Zn3N2 powders so-prepared have the anti-bixbyite structure and are almost certainly stoichiometric with no compelling evidence of nitrogen vacancies. Further, no evidence was found for aliovalent oxygen substitution at the nitrogen sites. The calculated bond valence sums imply that Zn3N2 cannot be described as a 100% ionic compound. The structural findings are supported by photoluminescence measurements that reveal a band gap of approximately 0.9 eV. 相似文献
59.
Eu3+-doped Ca2SnO4 (solid solutions of Ca2−xEu2xSn1−xO4, 0?x?0.3) and Eu3+ and Y3+-codoped Ca2SnO4 (Ca1.8Y0.2Eu0.2Sn0.8O4) were prepared by solid-state reaction at 1400 °C in air. Rietveld analysis of the X-ray powder diffraction patterns revealed that Eu3+ replaced Ca2+ and Sn4+ in Eu3+-doped Ca2SnO4, and that Eu3+ replaced Ca2+ and Y3+ replaced Sn4+ in Ca1.8Y0.2Eu0.2Sn0.8O4. Red luminescence at 616 nm due to the electric dipole transition 5Do→7F2 was observed in the photoluminescence (PL) spectra of Ca2−xEu2xSn1−xO4 and Ca1.8Y0.2Eu0.2Sn0.8O4 at room temperature. The maximum PL intensity in the solid solutions of Ca2−xEu2xSn1−xO4 was obtained for x=0.1. The PL intensity of Ca1.8Y0.2Eu0.2Sn0.8O4 was 1.26 times greater than that of Ca2−xEu2xSn1−xO4 with x=0.1. 相似文献
60.
Michal Hušák Alexandr Jegorov Jiří Brus Wouter van Beek Philip Pattison Mogens Christensen Vincent Favre-Nicolin Jaroslav Maixner 《Structural chemistry》2008,19(3):517-525
Metergoline is a dopamine agonist and serotonin antagonist used both in human and veterinary medicine. In addition to the
previously known crystalline form, a new polymorph, which crystallizes from aqueous solution, was found. Since it was initially
impossible to prepare a single crystal of quality suitable for single crystal X-ray diffraction measurements using a conventional
laboratory source, the structure was solved from the powder diffraction data using synchrotron radiation. The structure determination
also included solving the effects of preferred orientation. Characterization was simultaneously done by solid-state NMR spectroscopy.
Finally, a small single crystal suitable for synchrotron diffraction was found after numerous tries. Crystal structure determination
using this single crystal confirmed the powder-based solution. Comparison of information obtained by different experimental
methods (powder diffraction, ssNMR, single crystal diffraction) was made. 相似文献