全文获取类型
收费全文 | 1226篇 |
免费 | 50篇 |
国内免费 | 5篇 |
专业分类
化学 | 974篇 |
晶体学 | 10篇 |
力学 | 6篇 |
数学 | 66篇 |
物理学 | 225篇 |
出版年
2023年 | 10篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 24篇 |
2018年 | 15篇 |
2017年 | 19篇 |
2016年 | 26篇 |
2015年 | 25篇 |
2014年 | 33篇 |
2013年 | 78篇 |
2012年 | 64篇 |
2011年 | 97篇 |
2010年 | 44篇 |
2009年 | 38篇 |
2008年 | 88篇 |
2007年 | 76篇 |
2006年 | 72篇 |
2005年 | 77篇 |
2004年 | 78篇 |
2003年 | 70篇 |
2002年 | 74篇 |
2001年 | 14篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1986年 | 3篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1964年 | 3篇 |
1961年 | 2篇 |
排序方式: 共有1281条查询结果,搜索用时 15 毫秒
951.
Various silica nanotubes and nanocapsules have been prepared successfully, possessing unique silica walls of selective H2 permeation and encapsulate group 8-10 metal particles inside and exhibit a marked stabilization effect of H2 and CO over the metals in the network of silica wall and inside nanoscale cavities. 相似文献
952.
Photocatalytic property and electronic structure of triple-layered perovskite tantalates, MCa2Ta3O10 (M = Cs, Na, H, and C6H13NH3) 总被引:2,自引:0,他引:2
Machida M Mitsuyama T Ikeue K Matsushima S Arai M 《The journal of physical chemistry. B》2005,109(16):7801-7806
The Dion-Jacobson series of triple-layered perovskite tantalates (MCa2Ta3O10, M = Cs, Na, H, and C6H13NH3) were synthesized to evaluate their photocatalytic activity for overall water splitting to evolve H2/O2 under UV irradiation. The photocatalytic activity was susceptible to the hydration of interlayer space. The hydrous Na phase exhibited much higher activity (H2: 308 micromol.h(-1)) compared to the anhydrous Cs phase (24 micromol.h(-1)) and the hydrous H phase (22 micromol.h(-1)) in the presence of 0.5 wt % Ni impregnated. H2O/D2O isotopic experiment suggested that the hydrated interlayer plays as an active site for water splitting, where the high mobility of water molecule in the interlayer should correlate with the total photocatalytic activity. The FLAPW electronic structure calculation demonstrated that the terminating oxygen site, O4, which faces to the interlayer space, contributes largely to the top of the valence band. Judging from comparison with the double-layered tantalates, MLaTa2O7, in our previous study, the contribution of terminating oxygen site to the band structure is supposed to depend on the number of perovskite layers. 相似文献
953.
The acyclic asymmetric induction is described which involves heteroconjugate addition of MeLi to α-hydroxy hetero-olefins and concomitant intramolecular silicon-migration to produce α,α-sulfonyl-dianion of the adduct being of utility for the second CC bond formation in one pot. It also contains the first chemical proof of the regiochemical assignment to the hetero-olefins. 相似文献
954.
Masato Kakihana Haruko Ikeuchi Gen P. Satô Koichi Tokuda 《Journal of Electroanalytical Chemistry》1981,117(2):201-211
Stationary electrodes (platinum and glassy carbon) were used for accurate measurement of diffusion coefficients. The theoretical diffusion current-time profile was calculated by digital simulation, by means of which the diffusion coefficient and the product of the charge number of electrode reaction n and the reactant concentration co were determined simultaneously from a single chronoamperogram. The feasibility of the method was demonstrated by measuring the diffusion coefficients of Tl(I) ions. When the nco value agreed with the corresponding known value, the diffusion coefficients were in good agreement with the standard values determined by the thin-walled hanging mercury drop electrode method. The diffusion coefficient of hexacyanoferrate(III) ions in 1 mol dm?3 KCl at, 25°C was also determined. 相似文献
955.
956.
Synthesis of the FGHI ring domain of azaspiracids, the causative agents for a new type of shellfish poisoning, azaspiracid poisoning (AZP), has been achieved. The synthesis features dithiane anion-epoxide coupling for convergent fragment assembly. 相似文献
957.
Ikeda M Nobori T Schmutz M Lehn JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(2):662-668
The bow-shaped molecule 1 bearing a self-complementary DAAD-ADDA (D=donor A=acceptor) hydrogen-bonding array generates, in hydrocarbon solvents, highly ordered supramolecular sheet aggregates that subsequently give rise to gels by formation of an entangled network. The process of hierarchical self-assembly of compound 1 was investigated by the concentration and temperature dependence of UV-visible and (1)H NMR spectra, fluorescence spectra, and electron microscopy data. The temperature dependence of the UV-visible spectra indicates a highly cooperative process for the self-assembly of compound 1 in decaline. The electron micrograph of the decaline solution of compound 1 (1.0 mM) revealed supramolecular sheet aggregates forming an entangled network. The selected area electronic diffraction patterns of the supramolecular sheet aggregates were typical for single crystals, indicative of a highly ordered assembly. The results exemplify the generation, by hierarchical self-assembly, of highly organized supramolecular materials presenting novel collective properties at each level of organization. 相似文献
958.
Jun Segawa Masahiko Kitano Kenji Kazuno Masami Tsuda Ichiro Shirahase Masakuni Ozaki Masato Matsuda Masahiro Kise 《Journal of heterocyclic chemistry》1992,29(5):1117-1123
A series of 8-substituted-7-fluoro-5-oxo-5H-thiazolo[3,2-a]quinoline-4-carboxylic acids was prepared and evaluated for antibacterial activity. These compounds were synthesized from ethyl 2-mercaptoquinoline-3-carboxylates 17 which were obtained from anilines 11 by a route involving an intramolecular cyclization reaction. 相似文献
959.
Masato Shimomura Ryo Miyata Takashi Kuwahara Kenji Oshima Shinnosuke Miyauchi 《European Polymer Journal》2007,43(2):388-394
Glucose oxidase (GOx) was immobilized through amide linkages on the surfaces of the conducting polymer films prepared by electrochemical copolymerization of pyrrole (Py) and 1-(2-carboxyethyl)pyrrole (Py-COOH) for the purpose of fabricating GOx-immobilized electrodes for amperometric sensing of glucose. The conductivity of the copolymer film was in the range 10−8-10−3 S/cm and showed a tendency to decrease with increasing content of Py-COOH units in the copolymer. The amount of immobilized GOx increased significantly with increasing content of Py-COOH units in the copolymer film up to 30%, and showed a tendency to level off when the content of Py-COOH units became larger. The activity of immobilized GOx per area of the copolymer film decreased slightly with increasing content of Py-COOH units in the copolymer. Although the GOx-immobilized copolymer films gave the amperometric response to glucose depending on its concentration, the magnitude of the response to a given concentration was found to decrease with increasing content of Py-COOH units in the copolymer. The variation in the amperometric response was attributed to the difference in conductivity of the copolymer film. The appropriate content of Py-COOH units in the copolymer was considered to be 5% or less for the amperometric sensing of glucose with the GOx-immobilized copolymer film. 相似文献
960.
Hiroyoshi Kamogawa Yoko Takayanagi Masato Nanasawa 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2947-2953
2,4-Dihydroxy-4′-vinylbenzophenone (I) and its 4-alkyl ethers (II), Me, Et, n-Bu, n-Oct, and n-dodecyl, were prepared in three steps by Hoesch synthesis, starting with p-(2-bromoethyl) benzonitrile and resorcinol and its monoalkyl ethers. I and its precursor 2,4-dihydroxy-4′-(2-bromoethyl) benzophenone were also converted into their 4-alkyl ethers with alkyl halides in dimethylformamide (DMF) in the presence of sodium hydrogen carbonate. Copolymerizations of I and II with styrene took place smoothly with satisfactory conversions to yield copolymers with ε-values around 104 L/mol cm?1 per benzophenone unit over the ultraviolet (UV) range of 235–340nm. 相似文献