全文获取类型
收费全文 | 224篇 |
免费 | 16篇 |
专业分类
化学 | 185篇 |
晶体学 | 2篇 |
数学 | 7篇 |
物理学 | 46篇 |
出版年
2024年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 13篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 10篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有240条查询结果,搜索用时 31 毫秒
101.
The synthesis of bioactive oligosaccharides is too tedious to scale up for commercialization. However, structurally simplified glycomimetics are commercializable, if they can be synthesized much more easily than the oligosaccharides while having a comparable bioactivity. In this study, we propose a 2-oxabutane (OB) structure as an imitation of the internal monosaccharide units in oligosaccharides. Two trimannoside and three pentamannoside OB-glycomimics were synthesized in remarkably short steps. Among them, Manα1-OB-2Man 10, a trimannoside mimic, showed eight-fold affinity toward concanavalin A (ConA) relative to methyl mannoside in latex agglutination lectin assay and equilibrium dialysis assay (EDA), while the other mimics showed three- to four-fold affinities. EDA indicated that the bindings between each mimic molecule and a ConA subsite were all in one-to-one stoichiometry and thus these mimics were monovalent ligands, excluding multivalence effect for the high affinities. The strong affinity of 10 could be explained by the occupation of two mannose binding sites of a ConA subsite by its two mannose units. Mimic 10 proved to be even a better ligand for ConA than the natural disaccharide Manα1,2Man, while been much more easy to synthesize, thereby illustrating the potential of the approach here presented. 相似文献
102.
A 3,6-bis(5-amino-2-pyridyl)-1,2,4,5-tetrazine exhibits strong π-π* fluoresce in the presence of zinc ion (Zn(2+)) in aqueous solution, whereas it is not fluorescent in the absence of Zn(2+) as well as in the presence of competing metal ions. 相似文献
103.
Hisatoshi Yuasa 《Journal d'Analyse Mathématique》2013,120(1):333-356
The concept of a uniform set is introduced for an ergodic, measure-preserving transformation on a non-atomic, infinite Lebesgue space. The uniform sets exist inasmuch as they generate the underlying σ-algebra. This leads to the result that every ergodic, measure-preserving transformation on a non-atomic, infinite Lebesgue space is isomorphic to a minimal homeomorphism on a locally compact metric space which admits a unique, up to scaling, invariant Radon measure. 相似文献
104.
Yuki Tsuga Masataka Katou Satoshi Kuwabara Takashi Kanamori Shun‐ichiro Ogura Shigetoshi Okazaki Hiroyuki Ohtani Hideya Yuasa 《化学:亚洲杂志》2019,14(12):2067-2071
While the development of low‐molecular‐weight drugs is saturating, agents for photodynamic therapies (PDTs) may become alternative seeds in pharmaceutical industry. Among them, orally administrative, cancer‐selective, and side effect‐free photosensitizers (PSs) that can be activated by tissue‐penetrative near‐infrared (NIR) lights are strongly demanded. We discovered such a PS from scratch by focusing on a twist‐assisted spin‐orbit charge transfer intersystem crossing (ISC) mechanism in a biphenyl derivative, which was demonstrated by thorough photophysical studies. The unique ISC mechanism enables the PS to be small and slim so as to pass through glucose transporters and exert a PDT effect selectively on a cancer cell line. The smallness will allow for oral administration and fast clearance, which have been agenda of approved PSs with larger molecular weights. We also demonstrated that our PS was able to be activated with an NIR pulse laser through two‐photon excitation. 相似文献
105.
Synthesis of bifunctional terminal octasilicate‐core dendrimer containing fluorocarbon and hydrocarbon chains
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yasuyuki Irie Sota Yuasa Hiroaki Imoto Kensuke Naka 《Journal of polymer science. Part A, Polymer chemistry》2017,55(5):912-918
A bifunctional terminal organic‐inorganic dendrimer with fluorocarbon and hydrocarbon units at its terminal groups was successfully prepared by a hydrosilylation reaction, and a combination of a ring‐opening reaction and condensation reaction of octakis(propenylsuccinicanhydrido)polyhedraloctasilicate (OS‐SA) with 1‐decanol and 1H,1H,2H,2H‐perfluoro‐1‐decanol. The structure of the OS‐core dendrimer bearing the decyl and 1H,1H,2H,2H‐heptadecafluorodecyl groups (OS‐CF) was fully characterized by FT‐IR, NMR spectra, and MALDI TOF MS spectrum. The crystallinity of the fluorinated domains in OS‐CF decreased in comparison with that in I‐CF and the fluorocarbon/hydrocarbon chains form no ordered structure due to suppression of the molecular motion of their branches resulting from the rigid inorganic core. The composite films of PMMA containing OS‐CF were prepared through solution blending of PMMA with various concentrations of OS‐CF (5, 10, and 20 wt %). The refractive index of the neat PMMA film is 1.49, and the refractive indices of the composite films containing OS‐CF decrease linearly with increases in the OS‐CF weight fraction. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 912–918 相似文献
106.
Visible‐Light Sensitization and Photoenergy Storage in Quantum Dot/Polyoxometalate Systems
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Prof. Tetsuya Kida Hiromasa Furuso Kota Kumamoto Azzah Dyah Pramata Prof. Masayoshi Yuasa Prof. Kengo Shimanoe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7462-7469
Recently, the process by which energy is transferred from photoexcited semiconductor nanocrystals, called quantum dots (QDs), to other semiconductors has attracted much attention and has potential application in solar energy conversion (i.e., QD‐sensitized solar cells). Sensitization of wide band gap polyoxometalates (POMs) to visible light by using CuInS2 QDs dispersed in an organic solution is demonstrated herein. Photoluminescence quenching and lifetime studies revealed efficient electron transfer from the CuInS2 QDs to POMs, such as SiW12O40 and W10O32, that were hybridized with a cationic surfactant. CuInS2 QDs function as an antenna that absorbs visible light and supplies electrons to the POMs to enable certain photocatalytic reactions, including noble‐metal‐ion reduction. The photoenergy storage capabilities of the QD‐POM system, in which electrons photogenerated in QDs by visible‐light excitation are trapped and accommodated by POMs to form reduced POM, are also demonstrated. Electrons stored in the POM can be later discharged through reductive reactions, such as oxygen reduction, in the dark. 相似文献
107.
Microcolumn adsorption experiments were conducted to generate breakthrough profiles of dissolved organic matter (DOM) remaining after coagulation treatment of a naturally colored surface water for three coal-based activated carbons (ACs) and four water pH levels. A plug-flow homogeneous surface diffusion model was applied to determine the intraparticle surface diffusivities of the DOM at different AC-pH combinations. It was found that, for all three ACs, the removal of DOM increased as pH decreased and the increasing extent changed with the ACs used. The pH dependency of the column performance seemed to be attributed more apparently to pH's capability in changing the zeta potential of AC particles. In addition, at all pH levels, the column performance varied markedly with the ACs used. Correlation analyses of the accumulated amounts of DOM onto all three ACs with corresponding pore volumes in several divided pore size regions clearly indicated that pores with sizes 30-100 A were more effective in adsorbing organic macromolecules. Furthermore, based on model simulations, the sensitivity of bed performance to equilibrium and kinetic parameters was quantified by conducting variance analyses with a four-way classification method. 相似文献
108.
Fukuyama Y Kubo M Minami H Yuasa H Matsuo A Fujii T Morisaki M Harada K 《Chemical & pharmaceutical bulletin》2005,53(1):72-80
Nine new diterpenes, neovibsanin D (1), 7-epi-neovibsanin D (2), 15-O-methylneovibsanin F (3), 14-epi-15-O-methylneovibsanin F (4), 15-O-methyl-18-oxoneovibsanin F (5), 2-O-methylneovibsanin H (6), 2-O-methylneovibsanin I (7), neovibsanin G (8), and 14-epi-neovibsanin G (9), were isolated from a methanol extract of the leaves of Viburnum awabuki. Their structures were elucidated to be uniquely rearranged vibsane-type diterpenes by spectroscopic analyses and comparison of NMR data with those of previously reported vibsane-type diterpenes. In addition, irradiation of vibsanin B (12) in methanol with a high-pressure Hg lump led to the direct formation of neovibsanins A (14) and B (15). These results gave a clue to understanding of the biogenetic interconversion of 11-membered vibsanins into neovibsanins. 相似文献
109.
The uptake of fractionated [3H]heparin was investigated in rat parenchymal hepatocytes in primary culture. The initial uptake of fractionated [3H]heparin was found to be saturable with the maximum uptake velocity (Vmax) of 10.1 +/- 1.46 pmol/min/mg protein and the Michaelis constant (Km) of 284 +/- 47.9 nM. The effect of alpha-globulin, the major protein binding to fractionated [3H]heparin, on the saturable uptake profile of fractionated [3H]heparin was also investigated. The uptake clearance was reduced, depending on the concentration of fractionated [3H]heparin, by the addition of 1 mg/ml alpha-globulin. We assumed that fractionated 3H-heparin bound to alpha-globulin was not available for uptake and that the reduction in the uptake clearance was solely attributable to the saturable binding of fractionated [3H]heparin to alpha-globulin. The uptake clearance versus concentration profile was analyzed to obtain the dissociation constant (Kd) of 31.8 nM and the capacity (n) of 0.047 for the binding of fractionated [3H]heparin to alpha-globulin. The saturable binding of fractionated [3H]heparin to alpha-globulin was supported by in vitro binding experiments using gel chromatography, in which bound fractionated [3H]heparin decreased with the concentration of fractionated [3H]heparin in the presence of alpha-globulin. In conclusion, the present study demonstrated the saturable uptake of fractionated [3H]heparin by rat parenchymal hepatocytes and the saturable binding of fractionated [3H]heparin to alpha-globulin. The saturable uptake may suggest the involvement of a specific transport system such as receptor-mediated endocytosis. 相似文献
110.
Motokazu Uemura Kazuhiko Take Kazuo Isobe Tatsuya Minami Yuji Hayashi 《Tetrahedron》1985,41(24):5771-5778
(3-Methoxybenzylalcohol)chromium tricarbonyl (10) and (7-methoxy-1-tetralol)chromium tricarbonyl (12) are selectively lithiated at the 4- and 6-positions, respectively, by treatment with n-BuLi-TMEDA. Since the directed lithiation of the corresponding chromium free arenes normally proceeds at the 2-and 8-positions, complementarily substituted arenes can be prepared by using the chromium tricarbonyl complexes. The difierent position of lithiation is explained by the relative configuration of the chromium tricarbonyl group in the (arene)Cr(CO)3 and electrostatic factors. Some anthraquinones, 31,36,42, and 7-hydroxycalamenenes, 43, have been synthesized through the stereo- and regioselective introduction of substituents by means of(η6-arene)chromium tricarbonyl complexes. 相似文献