全文获取类型
收费全文 | 933篇 |
免费 | 35篇 |
国内免费 | 4篇 |
专业分类
化学 | 717篇 |
晶体学 | 11篇 |
力学 | 3篇 |
数学 | 87篇 |
物理学 | 154篇 |
出版年
2021年 | 10篇 |
2020年 | 30篇 |
2019年 | 19篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 51篇 |
2011年 | 44篇 |
2010年 | 27篇 |
2009年 | 30篇 |
2008年 | 50篇 |
2007年 | 51篇 |
2006年 | 46篇 |
2005年 | 40篇 |
2004年 | 50篇 |
2003年 | 50篇 |
2002年 | 41篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 9篇 |
1972年 | 4篇 |
1968年 | 6篇 |
1965年 | 4篇 |
排序方式: 共有972条查询结果,搜索用时 15 毫秒
961.
Dr. Jatish Kumar Dr. Takuya Nakashima Dr. Hiroyuki Tsumatori Midori Mori Dr. Masanobu Naito Prof. Tsuyoshi Kawai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14090-14097
Chiral bichromophoric perylene bisimides are demonstrated as active materials of circularly polarized emission. The bichromophoric system exhibited circularly polarized luminescence with dissymmetry factors typical of that of similar organic chiral chromophoric systems in the monomeric state. Variation in solvent composition led to the formation of stably soluble helical aggregates through intermolecular interactions. A large enhancement in the dissymmetry of circularly polarized luminescence was exhibited by the aggregated structures both in the solution and solid states. The sum of excitonic couplings between the individual chromophoric units in the self‐assembled state results in relatively large dissymmetry in the circularly polarized luminescence, thereby giving rise to enhanced dissymmetry factors for the aggregated structures. The spacer between chiral center and chromophoric units played a crucial role in the effective enhancement of chiroptical properties in the self‐assembled structures. These materials might provide opportunities for the design of a new class of functional bichromophoric organic nanoarchitectures that can find potential applications in the field of chiroptical memory and light‐emitting devices based on supramolecular electronics. 相似文献
962.
The absolute configuration of a binaphthyl-azobenzene dyad 2b, which has a chiral axis and a chiral plane, was determined by comparing the experimental circular dichroism (CD) spectra with the theoretical CD spectra calculated by the time-dependent (TD)-DFT method. The CD signals of the trans-azobenzene moiety indicated that the two benzene rings of this moiety are twisted unidirectionally. It is suggested that these dyads with shorter linkers may be suitable for use as chiroptical switches. 相似文献
963.
964.
R. Bevilacqua S. Pomp V.D. Simutkin U. Tippawan P. Andersson J. Blomgren M. ?sterlund M. Hayashi S. Hirayama Y. Naito Y. Watanabe M. Tesinsky F.-R. LeColley N. Marie A. Hjalmarsson A.V. Prokofiev A. Kolozhvari 《Radiation measurements》2010,45(10):1145-1150
We have measured light-ion (p, d, t, 3He and α) production in the interaction of 175 MeV neutrons with iron and bismuth with low-energy thresholds and for a wide angular range (from 20° to 160°, in steps of 20°). Measurements have been performed with the Medley setup, semi-permanently installed at the The Svedberg Laboratory, Uppsala (Sweden), where a quasi-monoenergetic neutron beam is available and well characterized. Medley is a conventional spectrometer system and consists of eight telescopes, each of them composed of two silicon surface barrier detectors, to perform particle identification, and a CsI(Tl) scintillator to fully measure the kinetic energy of the produced light-ions. We report preliminary double-differential cross sections for production of protons, deuterons and tritons in comparison with model calculations using TALYS-1.0 code. These show better agreement for the production of protons, while the theoretical calculations seem to overestimate the experimental production of deuterons and tritons. 相似文献
965.
O. Matsumoto A. Tsukada H. Yamamoto T. Manabe M. Naito 《Physica C: Superconductivity and its Applications》2010,470(20):1029-1032
Recently we have achieved superconductivity in T′-RE2CuO4 (RE = Pr, Nd, Sm, Eu, and Gd), films by metal organic decomposition (MOD). In this article, we first report the cation off-stoichiometry effect, which aims at screening out the possibility of hole doping by cation deficiencies. We also investigated the structure and microstructure of superconducting T′-Nd2CuO4 films synthesized by MOD. This investigation aims at elucidating why MOD-grown Nd2CuO4 films become superconducting whereas our previous Nd2CuO4 films grown by molecular beam epitaxy were not superconducting. 相似文献
966.
Shingo Sato Takeshi Watanabe Hironobu Kumagai Nobuo Kitamura Shigeru Matsuba Toshihiro Kumazawa Jun-Ichi Onodera Masanobu Suzuki 《Journal of heterocyclic chemistry》1999,36(5):1189-1193
Condensation of 2-hydroxyacetophenone with benzaldehyde in the presence of 70% perchloric acid in ethyl orthoformate gave the corresponding 4-ethoxyflavylium perchlorate, which was treated with aqueous ammonia or methylamine solution to afford 1,6,7,8-substituted 2-(3′,4′-substituted-phenyl)-4-quinolone in fair to good yield. 相似文献
967.
Yoshiaki Nishibayashi Izuru Takei Masanobu Hidai 《Angewandte Chemie (International ed. in English)》1999,38(20):3047-3050
The heterolytic cleavage of H 2 is the key to the novel catalytic hydrogenolysis of trimethylsilyl enol ethers catalyzed by [RuCl(η2-H2)(dppe)2]OTf (dppe = 1,2-bis(diphenylphosphanyl)ethane, OTf = trifluoromethanesulfonate), which results in the formation of a ketone and Me3SiH (see scheme). In addition, the stoichiometric, ruthenium-assisted protonation of a prochiral lithium enolate with H2 gave a chiral ketone with high enantioselectivity (up to 75 % ee). 相似文献
968.
969.
Yoshinori Kamiya Yasutoshi Naito Keishin Mizoguchi Katsuhiko Terada Johann Moreau 《Journal of Polymer Science.Polymer Physics》1997,35(7):1049-1053
The Flory–Huggins interaction parameters χ for 23 gases (He, Ne, Ar, Kr, Xe, H2, N2, O2, N2O, CO2, CH4, C2H4, C2H6, C3H6, C3H8, 1,3-C4H6, four C4H8's, n-C4H10, iso-C4H10, and n-C5H12) in five rubbery polymers (1,2-polybutadiene (PB), poly(ethylene-co-vinyl acetate)) (EVAc), polyethylene (PE), polypropylene (PP), and poly(dimethyl siloxane) (PDMS) were determined from either literature data on Henry's law coefficient and partial molar volume or those on sorptive dilation for each polymer/gas system. Values of χ for the gases increased in the order of PDMS < PP ≡ PB < EVAc ≡ PE. Among the gases except He and H2 whose χ values are not reliable, Ne and Xe have respectively the highest and the lowest values of χ for the polyolefins. The χ values of the hydrocarbons were compared together with previously reported χ values of n-alkanes C3-C10. The dependencies of χ upon concentration and temperature were discussed on the basis of the literature data. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1049–1053, 1997 相似文献
970.
Kunio Mochida Shuh-saku Nagano Hiroki Kawata Masanobu Wakasa Hisaharu Hayashi 《应用有机金属化学》1997,11(12):949-955
Upon ultraviolet irradiation of polygermane copolymers of methylphenylgermylene/phenylgermyne units (PhMeGe)n(PhGe)m in air, the germanium–germanium bond in the copolymer film changed into a digermoxane chain. Laser flash photolysis of the copolymer film showed the intermediacy of polygermyl radicals generated by Ge–Ge bond homolysis. The XPS showed the formation of germanium carbide (GeC) and germanium dioxide (GeO2) upon heating the unirradiated and irradiated copolymer (PhMeGe)n(PhGe)m films, respectively. A relatively high-resolution micro- pattern of GeC/GeO2 was obtained by combining the photochemical and thermal properties of the copolymers of methylphenylgermylene/phenylgermyne units. © 1997 John Wiley & Sons, Ltd. 相似文献