全文获取类型
收费全文 | 295篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 209篇 |
晶体学 | 2篇 |
力学 | 8篇 |
数学 | 27篇 |
物理学 | 62篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 19篇 |
2012年 | 18篇 |
2011年 | 24篇 |
2010年 | 16篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1977年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有308条查询结果,搜索用时 15 毫秒
51.
Behaviour of pure water and water mixture with benzene or chloroform adsorbed onto ordered mesoporous silicas 总被引:1,自引:0,他引:1
Vladimir M. Gun’ko Vladimir V. Turov Alexander V. Turov Vladimir I. Zarko Vasiliy I. Gerda Victor V. Yanishpolskii Inna S. Berezovska Valentin A. Tertykh 《Central European Journal of Chemistry》2007,5(2):420-454
Structural characteristics of synthesized ordered mesoporous silicas MCM-41, MCM-48 and SBA-15 were studied using XRD, nitrogen
adsorption and FTIR methods. Pure water and mixtures with water/benzene and water/chloroform-d adsorbed onto silicas were studied by 1H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial liquids. Concentrated aqueous suspensions of MCM-48
and SBA-15 were studied by thermally stimulated depolarization current (TSDC) method. Benzene and chloroform-d can displace a portion of water to broad pores from the pore walls and from narrower pores, especially in the case of a large
excess of an organic solvent. This process is accompanied by diminution of both interaction energy of water with an adsorbent
surface and freezing temperature depression of adsorbed water. The effect of nonpolar benzene on pore water is much stronger
than that of weakly polar chloroform-d. Modifications of the Gibbs-Thomson relation to describe the freezing point depression of mixtures of immiscible liquids
confined in pores allow us to determine distribution functions of sizes of structures with unfrozen pore water and benzene.
Former address: Pisarzhevskii Institute of Physical Chemistry, 31 Prospect Nauki, Kiev, Ukraine 相似文献
52.
Young Gun Ko Ung Su Choi Tai Young Kim Dong June Ahn Yong Jin Chun 《Macromolecular rapid communications》2002,23(9):535-539
A new chelating fiber, poly(acrylo‐amidino diethylenediamine), was synthesized based on polyacrylonitrile fibers in diethylenetriamine with the aid of AlCl3. Complex formation with CrO42– was strongly pH‐dependent, as complexes formed only in the presence of NH3+ and NH2+. In the medium pH region, both ionic and hydrogen bonds were formed between poly(acrylo‐amidino diethylenediamine) and the chromate ion, as was confirmed by means of FT‐IR spectroscopy. 相似文献
53.
Jongchul Seo Jongho Jeon Yong Gun Shul Haksoo Han 《Journal of Polymer Science.Polymer Physics》2000,38(21):2714-2720
The water sorption behavior and the activation energy were investigated for various chemical structure polyimide thin films; BPDA‐PDA, BPDA‐ODA, PMDA‐ODA, and 6FDA‐ODA. The activation energy for the water diffusion varied in the range of 5.53 to 9.27kcal/mol, and was in the increasing order: BPDA‐PDA < BPDA‐ODA < PMDA‐ODA < 6FDA‐ODA. BPDA‐PDA and BPDA‐ODA polyimide films showed relatively well‐ordered morphological structure, which results in relatively low diffusion coefficient and high activation energy. It was found that the diffusion coefficient and the activation energy are significantly related to the in‐plane orientation, crystallinity, and packing order in the polyimide thin films. The morphological structure was predominant factors for the water diffusion coefficient and activation energy in the polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2714–2720, 2000 相似文献
54.
Young Gun Ko Ung Su Choi Byeng Gil Ahn Dong June Ahn 《Journal of polymer science. Part A, Polymer chemistry》2000,38(15):2815-2823
High‐performance materials for flameproofing, phosphates (polyphosphate and ammonium phosphate) were synthesized on viscose rayon felt. This surface reaction has the advantage of a nonblooming effect and an application in thermosetting plastics. Metal complexes have the effect of reducing the amount of smoke. Therefore, in the second step, transition‐metal complexes were synthesized on the viscose rayon ammonium phosphate felt. This article focuses on the surface modification of phosphates and metal complexes on viscose rayon. All reactions were confirmed by attenuated total reflectance Fourier transform infrared and time‐of‐flight secondary ion mass spectrometry. As the concentrations of phosphoric acid and urea increased, the peak intensities of ammonium ion groups and phosphate groups greatly increased. The thermal properties of the synthesized materials were studied with thermogravimetric analysis and oxygen index testing. On the basis of the experimental results, the synthesized flame‐retardancy materials showed excellent physicochemical and thermal effects and flame retardancy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2815–2823, 2000 相似文献
55.
56.
Cuong M. Q. Le Hai Ha Pham Thi Xuan Thang Cao Gun‐Do Kim Chul‐Woong Oh Kwon Taek Lim 《Journal of polymer science. Part A, Polymer chemistry》2016,54(23):3741-3750
Redox‐responsive core cross‐linked (CCL) micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) (PEO‐b‐PFMA) block copolymers were prepared by the Diels‐Alder click‐type reaction. First, the PEO‐b‐PFMA amphiphilic block copolymer was synthesized by the reversible addition‐fragmentation chain transfer polymerization. The hydrophobic blocks of PFMA were employed to encapsulate the doxorubicin (DOX) drug, and they were cross‐linked using dithiobismaleimidoethane at 60 °C without any catalyst. Under physiological circumstance, the CCL micelles demonstrated the enhanced structural stability of the micelles, whereas dissociation of the micelles took place rapidly through the breaking of disulfide bonds in the cross‐linking linkages under reduction environment. The core‐cross‐linked micelles showed fine spherical distribution with hydrodynamic diameter of 68 ± 2.9 nm. The in vitro drug release profiles presented a slight release of DOX at pH 7.4, while a significant release of DOX was observed at pH 5.0 in the presence of 1,4‐dithiothreitol. MTT assays demonstrated that the block copolymer did not have any practically cytotoxicity against the normal HEK293 cell line while DOX‐loaded CCL micelles exhibited a high antitumor activity towards HepG2 cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3741–3750 相似文献
57.
The wide tuning characteristics of double-ring coupled lasers with/without an extended waveguide are analyzed and optimized using the scattering matrix formalism. To obtain the optimum design schemes of the tunable laser diodes, the cross coupling ratios of two rings, the tuning enhancement factor, the propagation loss of passive waveguides, the optical gain of an active region, and the back and front-facet reflectivity of the waveguide are taken into account. When the coupling ratio of the ring and input/output waveguides is fixed, the extinction ratio and the linewidth are decreased as the tuning enhancement factor is increased, while the tuning range is increased. 相似文献
58.
G. V. Krylova Yu. I. Gnatyuk N. P. Smirnova A. M. Eremenko V. M. Gun’ko 《Journal of Sol-Gel Science and Technology》2009,50(2):216-228
A variety of Ag nanoparticles/oxide mesoporous films with templated silica, titania, and zirconia was synthesized by sol–gel
method at glass, aluminum, and silicon substrates using metal alkoxides (tetraethoxysilane, titanium tetraisopropoxide, and
zirconium tetrapropoxide) and AgNO3 as precursors of oxide films and Ag nanoparticles, respectively, and Pluronic P123 as a template agent. Oxide films alone
and Ag/oxide composites were characterized using hexane adsorption, X-ray diffraction (XRD), Raman and ultraviolet (UV)/vis
spectroscopies, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The distribution of
Ag nanoparticles within the films, their sizes, intensity, and position of surface plasmon resonance (SPR) absorbance band
at λ = 400 nm, as well as the textural and structural characteristics of whole films depend on treatment temperature, types of
substrates and oxide matrices, oxide crystallization, and Ag content. Ag nanoparticles form preferably on the outer surface
of the films under lower sintering temperatures if the amount of loaded silver is low. Oxide crystallization (e.g., TiO2) promotes silver embedding into the outer film layer. At higher silver content (≥10 at.%) and higher calcination temperature
(873 K), silver nanoparticles could be entrapped more uniformly along the film profile because of more intensive evaporation
of silver droplets from the outer surface of the films on heating. 相似文献
59.
The field of metallurgy has greatly benefited from the development of electron microscopy over the last two decades. Scanning electron microscopy (SEM) has become a powerful tool for the investigation of nano- and microstructures. This article reviews the complete set of tools for crystallographic analysis in the SEM, i.e., electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD), and electron channeling contrast imaging (ECCI). We describe recent relevant developments in electron microscopy, and discuss the state-of-the-art of the techniques and their use for analyses in metallurgy. EBSD orientation measurements provide better angular resolution than spot diffraction in TEM but slightly lower than Kikuchi diffraction in TEM, however, its statistical significance is superior to TEM techniques. Although spatial resolution is slightly lower than in TEM/STEM techniques, EBSD is often a preferred tool for quantitative phase characterization in bulk metals. Moreover, EBSD enables the measurement of lattice strain/rotation at the sub-micron scale, and dislocation density. TKD enables the transmitted electron diffraction analysis of thin-foil specimens. The small interaction volume between the sample and the electron beam enhances considerably the spatial resolution as compared to EBSD, allowing the characterization of ultra-fine-grained metals in the SEM. ECCI is a useful technique to image near-surface lattice defects without the necessity to expose two free surfaces as in TEM. Its relevant contributions to metallography include deformation characterization of metals, including defect visualization, and dislocation density measurements. EBSD and ECCI are mature techniques, still undergoing a continuous expansion in research and industry. Upcoming technical developments in electron sources and optics, as well as detector instrumentation and software, will likely push the border of performance in terms of spatial resolution and acquisition speed. The potential of TKD, combined with EDS, to provide crystallographic, chemical, and morphologic characterizations of nano-structured metals will surely be a valuable asset in metallurgy. 相似文献
60.
N. V. Tepliakov A. S. Baimuratov Yu. K. Gun’ko A. V. Baranov A. V. Fedorov I. D. Rukhlenko 《Optics and Spectroscopy》2017,122(1):64-68
The strength of the enantioselective interaction of chiral semiconductor nanocrystals with circularly polarized light can be varied over a wide range, which finds a series of important applications in modern nanophotonics. As a rule, this interaction is relatively weak, because the dimension of nanocrystals is much smaller than the wavelength of the optical radiation, and the optical activity of nanocrystals is rather low. In this work, we show theoretically that, by applying ion doping, one can significantly enhance the optical activity of nanocrystals and to vary its magnitude over a wide range of values and over a wide range of frequencies. We show that, by precisely arranging impurities inside nanocrystals, one can optimize the rotatory strengths of intraband transitions, making them 100 times stronger than typical rotatory strengths of small chiral molecules. 相似文献