全文获取类型
收费全文 | 199篇 |
免费 | 8篇 |
专业分类
化学 | 128篇 |
力学 | 4篇 |
数学 | 4篇 |
物理学 | 71篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 8篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 14篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 9篇 |
2006年 | 13篇 |
2005年 | 5篇 |
2004年 | 8篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有207条查询结果,搜索用时 171 毫秒
21.
A series of trinuclear Cu(II)Ln(III)Cu(II) complexes with the bridging ligand 2,6-di(acetoacetyl)pyridine have been prepared by one-pot reaction with Cu(NO(3))(2).3H(2)O and Ln(NO(3))(3).nH(2)O in methanol. X-ray crystallographic studies for all the complexes indicate that two L(2)(-) ligands selectively sandwich two Cu(II) ions with the 1,3-diketonate entities and one Ln(III) ion with the 2,6-acetylpyridine entity to form a trinuclear CuLnCu core bridged by the enolate oxygen atoms. Cryomagnetic properties of the complexes are studied with respect to the electronic structure of the Ln ion. 相似文献
22.
Spectroscopic Properties of Amine‐substituted Analogues of Firefly Luciferin and Oxyluciferin 下载免费PDF全文
Michio Kakiuchi Soichiro Ito Minoru Yamaji Vadim R. Viviani Shojiro Maki Takashi Hirano 《Photochemistry and photobiology》2017,93(2):486-494
Spectroscopic and photophysical properties of firefly luciferin and oxyluciferin analogues with an amine substituent (NH2, NHMe and NMe2) at the C6' position were studied based on absorption and fluorescence measurements. Their π‐electronic properties were investigated by DFT and TD‐DFT calculations. These compounds showed fluorescence solvatochromism with good quantum yields. An increase in the electron‐donating strength of the substituent led to the bathochromic shift of the fluorescence maximum. The fluorescence maxima of the luciferin analogues and the corresponding oxyluciferin analogues in a solvent were well correlated with each other. Based on the obtained data, the polarity of a luciferase active site was explained. As a result, the maximum wavelength of bioluminescence for a luciferin analogue was readily predicted by measuring the photoluminescence of the luciferin analogue in place of that of the corresponding oxyluciferin analogue. 相似文献
23.
Metal-ion complexation of 7-benzylimidazo[1,2-a]pyrazin-3(7H)-one derivative (2) with Li+, Mg2+, Ca2+, Ba2+, Sc3+, and La3+ in acetonitrile resulted in successive modulations of its UV/vis absorption and fluorescence spectroscopic properties. This result indicates that 2 can be used as a colorimetric and fluorometric sensor of the Lewis acidity of a metal ion in aprotic solutions. The hypothesis that the metal-ion complex has a O10(imidazopyrazinone)-metal ion bond was supported by X-ray crystallographic analysis and quantum chemical calculations for a Li+ complex of 7-methylimidazo[1,2-a]pyrazin-3(7H)-one derivative (1). 相似文献
24.
Nitrogen-rich heterocycles, bis(pyrazino[2′,3′:4,5]imidazole)-fused 1,2,5,6-tetrahydro-1,4,5,8,9,10-hexaazaanthracenes (BPI-HAAs) were prepared by conventional Pd(OAc)2/BINAP-catalyzed C-N coupling reactions of 5-aryl-3-bromoaminopyrazines. The BPI-HAA core is a planar structure with aromaticity, and this heterocycle exhibits red fluorescence and moderate electron-accepting characteristics. 相似文献
25.
Shojiro MakiMakiko Okawa Toshimichi MakiiTakashi Hirano Haruki Niwa 《Tetrahedron letters》2003,44(18):3717-3721
A catalyst deposited on a polypropylene sheet having an activity of almost the same level as commercially available Pd black and capable of promoting hydrogenolysis-free hydrogenation was developed. 相似文献
26.
The normal impact of single water drops onto a plane water surface was studied experimentally to reveal the amount of secondary drops produced from the rim of crown-like interfacial structure. Within the experimental ranges tested, the ratio of the total mass of secondary drops to the mass of primary drop was approximately within 0–1 and correlated well as the function of dimensionless parameter K that consisted of the impact Weber number We and the Ohnesorge number Oh (K = We Oh
−0.4). The dependences of the number and the mean diameter of secondary drops on K and dimensionless film thickness were also investigated. 相似文献
27.
Shinnosuke Okawa 《Advances in Mathematics》2011,(5):2869
We show that the bounded derived category of coherent sheaves on a smooth projective curve except the projective line admits no non-trivial semi-orthogonal decompositions. 相似文献
28.
Fluorescence resonance energy transfer by quencher adsorption into hydrogels containing fluorophores
Kaori Okawa Takashi Miyata Tadashi Uragami 《Journal of Polymer Science.Polymer Physics》2006,44(22):3245-3252
We synthesized anionic hydrogels containing fluorophores and investigated the adsorption of a cationic quencher having an amino group into hydrogels by fluorescence resonance energy transfer (FRET). FRET from the fluorophore to the quencher in hydrogels was examined by fluorescence intensity and fluorescence decay using a fluorescence spectrophotometer and femtosecond laser spectroscopy. The fluorescence intensity of the fluorophore‐containing hydrogels decreased rapidly with increasing amounts of adsorbed cationic quencher. The fluorescence emission of the fluorophore in the quencher‐adsorbed hydrogels containing fluorophores decayed more rapidly than that of the original hydrogels. The aforementioned result indicates that the fluorescence of the fluorophore‐containing hydrogels is quenched due to FRET from the fluorophore to the quencher as the cationic quenchers can approach the fluorophores in hydrogels by electrostatic interactions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3245–3252, 2006 相似文献
29.
The idea of twisted reduction of space-time degrees of freedom recently proposed by the present authors is applied to the matrix chiral model. The equivalence of our reduced model and the usual chiral model is established by comparing the Schwinger-Dyson equations and weak coupling expansions and by performing the Monte Carlo simulation. 相似文献
30.
Chang CW Fennimore AM Afanasiev A Okawa D Ikuno T Garcia H Li D Majumdar A Zettl A 《Physical review letters》2006,97(8):085901
We have measured the temperature-dependent thermal conductivity kappa(T) of individual multiwall boron nitride nanotubes using a microfabricated test fixture that allows direct transmission electron microscopy characterization of the tube being measured. kappa(T) is exceptionally sensitive to isotopic substitution, with a 50% enhancement in kappa(T) resulting for boron nitride nanotubes with 99.5% 11B. For isotopically pure boron nitride nanotubes, kappa rivals that of carbon nanotubes of similar diameter. 相似文献