全文获取类型
收费全文 | 263篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 214篇 |
晶体学 | 6篇 |
力学 | 5篇 |
数学 | 16篇 |
物理学 | 33篇 |
出版年
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 30篇 |
2012年 | 14篇 |
2011年 | 11篇 |
2010年 | 11篇 |
2009年 | 11篇 |
2008年 | 17篇 |
2007年 | 9篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 12篇 |
2003年 | 9篇 |
2002年 | 11篇 |
2000年 | 3篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1957年 | 1篇 |
排序方式: 共有274条查询结果,搜索用时 15 毫秒
121.
Hiroyoshi Kamogawa Suguru Amemiya 《Journal of polymer science. Part A, Polymer chemistry》1985,23(9):2413-2423
Copolymers of vinyl viologens such as N-vinylbenzyl-N′-yalkyl and N-(γ-methyacryloyloxy)propyl-N′-propyl-4,4′-bipyridinium dihalides and polar aprotic comonomers such as N-vinyl-2-pyrrolidone (VP) and N,N-dimethylacrylamide (DMA) were prepared by the copolymerizations of vinyl viologens with DMA and the chemical modifications of VP copolymers containing reactive halogens. Copolymers containing various viologen anions such as Br?, BF, SO, and I? were also prepared by the anion exchange of copolymers containing Cl?. The photocolor developments of these aprotic copolymers in the film state were completely reversible and faster than for the corresponding copolymers with protic comonomers such as acrylamide and 2-hydroxyethyl acrylate, all with characteristic absorption spectra attributable to single radical cations. 相似文献
122.
Kadota I Takamura H Sato K Ohno A Matsuda K Yamamoto Y 《Journal of the American Chemical Society》2003,125(1):46-47
The convergent total synthesis of gambierol (1) is described. The octacyclic ether framework of 1 was constructed via the intramolecular allylation of alpha-chloroacetoxy ether followed by ring-closing metathesis. A modified Stille coupling was successfully applied to the synthesis of the triene side chain. 相似文献
123.
Michitaka Kuici Hiroyoshi Nagae Richard J. Cogdell Keizo Shimada Yasushi Koyama 《Photochemistry and photobiology》1994,59(1):116-124
Abstract –The 1Ag?→1Bu+ electronic absorption band and the vibronically coupled, C=C stretching Raman lines in the 1Ag? and 21Ag? states were recorded for spheroidene free in nonpolar and polar solvents as well as for spheroidene bound to the LH1 and LH2 complexes of Rhodobacter sphaeroides 2.4.1. The 1Bu+ energy exhibited a linear dependence on R(n) = (n2 - 1)/(n2+ 2) in both nonpolar and polar solvents; the line for polar solvents had a gentler slope and crossed the line for nonpolar solvents at R(n) = 0.3. The above characteristic of polar solvents was ascribed to the electric field generated by fluctuation of the solvent permanent dipoles; it stabilizes the 1Bu+ energy and reduces the polarizability of the solvent. The vibronically coupled, C=C stretching frequencies in the 1Ag? and 21Ag? states [ν(Ag) and [ν(2Ag)] also showed similar dependence on R(n), which is explained in terms of vibronic coupling among the 1Ag?, 21Ag? and 31Ag? states. The environment of spheroidene in the LH2 and LH1 complexes was assessed on the basis of the 1Bu+ energy and the ν(Ag) and [ν(2Ag) frequencies: Spheroidene in the LH2 complex is located in an environment with high polarizability, while spheroidene in the LH1 complex is located in an environment with lower polarizability. 相似文献
124.
Koshio H Ishihara T Yamada H Hirayama F Matsumoto Y Yanagisawa I 《Chemical & pharmaceutical bulletin》2005,53(4):448-450
A practical and cost-effective procedure has been developed for the synthesis of 7-methyl-2-naphthalenecarbonitrile, the precursor of the anticoagulant agents YM-60828 or YM-96765. This new route generates the key intermediate in only two steps from readily available 3-cyanopropionaldehyde dimethyl acetal and m-tolualdehyde, without requiring chromatographic purification. The synthesis involves condensation of the cyano derivative with the aldehyde and subsequent cyclodehydration. 相似文献
125.
Ferry Iskandar Mikrajuddin Abdullah Hiroyoshi Yoden Kikuo Okuyama 《Journal of Sol-Gel Science and Technology》2004,29(1):41-47
Silica films containing three dimensionally (3D) ordered pores were prepared by a simple dip coating method. A colloidal sol containing silica particles in the nanometer size range and a polystyrene latex (PSL) colloidal sol containing particles of tens of nanometers to one micrometer in size were used as precursors. The pore periodicity, which in turn produces the dielectric periodicity, can be easily altered by changing the size of the PSL beads. Films having a high surface smoothness were obtained by using small silica particles, large PSL particles, and a low withdrawal speed in the dip-coating. When the films were irradiated with a white light source, the reflective spectrum was changed by varying the incident angle, indicating its possible use as a monochromator. The change in the reflective spectrum was explained using effective medium approximation combined with a simple Bragg reflection equation. 相似文献
126.
Kadota I Takamura H Nishii H Yamamoto Y 《Journal of the American Chemical Society》2005,127(25):9246-9250
The convergent total synthesis of brevetoxin B (1) has been achieved. The intramolecular allylation of the O,S-acetal 20, prepared from the alpha-chlorosulfide 17 and the alcohol 5, was carried out using AgOTf as a Lewis acid to give the diene 21, predominantly. Ring-closing metathesis of 21 with the Grubbs catalyst 23 afforded the hexacyclic ether 25 which was converted to the A-G ring segment 2 through several steps. The intramolecular allylation of the alpha-acetoxy ether 42, prepared from 2 and the J-K ring segment 3, followed by ring-closing metathesis provided the polycyclic ether framework 44. A series of reactions of 44, including oxidation of the A ring, deprotection of the silyl ethers, and selective oxidation of the resulting allylic alcohol, furnished 1. 相似文献
127.
Hiroyoshi Kamogawa Masao Kato Hiroko Sugiyama 《Journal of polymer science. Part A, Polymer chemistry》1968,6(11):2967-2991
Photochromic polymers of the azobenzene and thiazine series were synthesized via two routes: (1) synthesis of vinyl photochromic monomers and subsequent polymerization and (2) chemical reactions of the substrate polymers with photochromic components. Polyvinylaminoazobenzenes, polyvinylhydroxyazobenzenes, polyacrylamidomethylaminoazobenzenes, and polyacrylamidomethylthionine were thus prepared and their photochromic behavior investigated. In the case of azobenzene polymers, irradiations from a 100-W projection lamp are enough to induced reversible changes in absorption spectra both in benzene solutions and film states, their absorption maxima being located around 400 mμ in the dark. Better results are obtained for some polymers as compared with the corresponding low molecular weight compounds; in the case of the thionine polymer (absorption maximum, ca. 600 mμ), the presence of ferrous ion remarkably enhances the photosensitivity in aqueous solutions, but incorporation of some polymers containing hydroxyl groups, such as poly(vinyl alcohol), are preferable for film states. 相似文献
128.
Hiroyoshi Kamogawa Hitoshi Koizumi Masato Nanasawa 《Journal of polymer science. Part A, Polymer chemistry》1979,17(1):9-18
Eleven N-substituted carbazoles (CZ) with terminal vinyl groups were synthesized by five sequences of reaction: N-(p-vinylbenzyl)- and N-β-(vinyloxyethyl)CZ by N-alkylations of potassium CZ with corresponding chlorides; N-(β-acryloyloxyethyl)CZ by the esterification of N-(β-hydroxyethyl)CZ with acryloyl chloride; N-acrylamido-or methacryl-amido-methyl CZ from N-hydroxymethyl CZ and acryl- or methacrylamide; N-(3-acryloyl- or methacryloyl-oxy-2-hydroxypropyl)CZ and N-[3-(p- or m-vinylanilino)-2-hydroxypropyl] CZ from N-(2,3-epoxypropyl)CZ and acrylic or methacrylic acid and p- or m-vinylaniline, respectively; and 2-[β-(N-carbazyl)propionyloxy]ethyl acrylate or methacrylate by the Michael addition of CZ to 2-hydroxyethyl acrylate or methacrylate, followed by esterifications. The vinyl polymers with pendant carbazyl groups more or less distant from the polymer backbones, prepared by conventional radical or cationic polymerization procedures, indicated charge-transfer spectra with 2,4,7-trinitrofluorenone (TNF) in tetrahydrofuran (THF) solutions that are spread over most of the visible range. 相似文献
129.
Hiroyoshi Kamogawa Hiroshi Mukai Yoichi Nakajima Masato Nanasawa 《Journal of polymer science. Part A, Polymer chemistry》1982,20(11):3121-3129
Schiff bases of p- and m-aminostyrenes with perfume aldehydes such as citral, cinnamaldehyde, piperonal, vanillin, and ethyl vanillin were synthesized in ethanol in more than 50% yield. Water-soluble copolymers of these Schiff bases with N-vinyl-2-pyrrolidone or with N,N-dimethylacrylamide were obtained. The hydrolytic behavior of Schiff base monomers and copolymers to liberate perfume aldehydes was structure dependent, thereby affording chemical release control. 相似文献
130.
On the basis of the boron-masking strategy, new divalent cross-coupling modules have been designed for the efficient synthesis of boron-substituted oligoarenes. The modules, i.e., monoprotected o-, m-, and p-benzenediboronic acid derivatives, undergo highly selective Suzuki-Miyaura coupling with sp2 iodides, bromides, chlorides, and triflates, affording coupling products in which the protected boronyl groups are left intact. 相似文献