全文获取类型
收费全文 | 100239篇 |
免费 | 5458篇 |
国内免费 | 4632篇 |
专业分类
化学 | 57250篇 |
晶体学 | 1335篇 |
力学 | 5593篇 |
综合类 | 322篇 |
数学 | 11903篇 |
物理学 | 33926篇 |
出版年
2023年 | 756篇 |
2022年 | 1764篇 |
2021年 | 2141篇 |
2020年 | 2358篇 |
2019年 | 2540篇 |
2018年 | 2932篇 |
2017年 | 2847篇 |
2016年 | 3533篇 |
2015年 | 2457篇 |
2014年 | 3516篇 |
2013年 | 4999篇 |
2012年 | 5137篇 |
2011年 | 5484篇 |
2010年 | 4306篇 |
2009年 | 4319篇 |
2008年 | 4518篇 |
2007年 | 4243篇 |
2006年 | 3871篇 |
2005年 | 3425篇 |
2004年 | 3079篇 |
2003年 | 2737篇 |
2002年 | 2847篇 |
2001年 | 2559篇 |
2000年 | 1996篇 |
1999年 | 1609篇 |
1998年 | 1540篇 |
1997年 | 1333篇 |
1996年 | 1299篇 |
1995年 | 1083篇 |
1994年 | 1162篇 |
1993年 | 1099篇 |
1992年 | 1064篇 |
1991年 | 1125篇 |
1990年 | 1119篇 |
1989年 | 1040篇 |
1988年 | 918篇 |
1987年 | 915篇 |
1986年 | 882篇 |
1985年 | 922篇 |
1984年 | 917篇 |
1983年 | 825篇 |
1982年 | 800篇 |
1979年 | 802篇 |
1978年 | 813篇 |
1977年 | 809篇 |
1976年 | 919篇 |
1975年 | 812篇 |
1974年 | 844篇 |
1973年 | 848篇 |
1972年 | 753篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
891.
Stolyarov I. P. Gaugash Yu. V. Kryukova G. N. Kochubei D. I. Vargaftik M. N. Moiseev I. I. 《Russian Chemical Bulletin》2004,53(6):1194-1199
The reduction of palladium(ii) carboxylates Pd3(OCOR)6 (R = Me, Et, CHMe2, CMe3) with hydrogen in alcohol solutions containing 1,10-phenanthroline (phen) and subsequent oxidation with oxygen gave new palladium nanoclusters, mainly particles with a nearly spherical metal core and an average size of 18 . Based on elemental analysis, NMR, X-ray photoelectron spectroscopy, and EXAFS, nanoclusters were described by the idealized formula Pd147phen32O60(OCOR)30. The specimens contained up to 25% smaller 55-atomic Pd clusters with a 10 metal core. New nanoclusters catalyze hydrogenation of alkynes and alkenes, reduction of nitriles with formic acid, oxidation of aliphatic and benzylic alcohols, oxidative esterification of ethylene and propylene, and disproportionation of benzyl alcohol into toluene and benzaldehyde. 相似文献
892.
E. M. Suleimenov F. M. Smagulova O. V. Morozova V. A. Raldugin I. Yu. Bagryanskaya Yu. V. Gatilov V. I. Yamovoi S. M. Adekenov 《Chemistry of Natural Compounds》2005,41(6):689-691
The five known lactones matricarin, austricin, canin, and achillin guaianolides and argolide germacranolide and the two flavonoids
eupatilin and its 7-O-methyl ester were isolated for the first time from the aerial part of Artemisia albida Willd. The structure of eupatilin was confirmed by an x-ray structure analysis.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 568–570, November–December, 2005. 相似文献
893.
S. V. Chernov E. E. Shul’ts M. M. Shakirov I. Yu. Bagryanskaya Yu. V. Gatilov G. A. Tolstikov 《Russian Journal of Organic Chemistry》2005,41(4):535-545
Oxidation of lambertianic acid methyl ester and methyl 15,16-epoxy-17-hydroxylabda-13(16)14-dien-18-oate gave 17-nor-8-oxo-, 8,12-epoxy-17-hydroxy-, and 8-formyl-17-norlabdadienoic acid esters which were subjected to reductive amination, and the subsequent intramolecular aminomethylation of 17-nor-8(R)-methylamino- and 17-methylaminolabdadienoates with formaldehyde afforded new polycyclic compounds, furoazocine and furoazonine derivatives.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 4, 2005, pp. 547–556.Original Russian Text Copyright © 2005 by Chernov, Shul’ts, Shakirov, Bagryanskaya, Gatilov, Tolstikov.For communication VIII, see [1]. 相似文献
894.
Yu Gui Gu Xiaolin Zhang Richard F. Clark Stevan W. Djuric Zhenkun Ma 《Tetrahedron letters》2004,45(15):3051-3053
An intramolecular 1,3-dipolar cycloaddition of azomethine ylide, generated in situ via the reaction of C12-glycinate derivative of macrolide with formaldehyde, provided a novel tricyclic macrolide. The high stereoselectivity of this [2+3] reaction was achieved by introducing a suitable directing group at C-6 position of macrolide. 相似文献
895.
896.
N. A. Davidenko Yu. P. Get’manchuk M. A. Zabolotnyi T. G. Zabolotnaya L. P. Linets E. V. Mokrinskaya V. A. Pavlov S. L. Studzinskii N. G. Chuprina 《High Energy Chemistry》2006,40(6):410-416
The effect of doping with CdS nanoparticles of recording medium films for the thermoplastic holographic recording process, which are based on photosemiconductors (oligomers and cooligomers of glycidylcarbazole) and a dielectric (a styrene copolymer with octyl methacrylate) containing a photoconductivity sensitizer, on their photosensitivity was studied. The enhancement of photosensitivity of films by doping with nanoparticles is associated with the appearance of an additional channel for transport of electrons generated from sensitizer molecules. A difference in informational properties between the oligomer and the polymer films was revealed. 相似文献
897.
Aleinikov N. N. Vasil'ev G. K. Kashtanov S. A. Makarov E. F. Chernyshev Yu. A. 《Kinetics and Catalysis》2001,42(2):233-237
The dependence of the rate of a photochemical reaction of XeO4with H2on the concentrations of H2and the diluent gases He and CO2is studied at room temperature. The results are compared with the data for the dark reaction. A mechanism with the elementary energetic branched-chain reaction OH
(v) + XeO4OH
+ O
+ XeO3is proposed to explain the results of the study. 相似文献
898.
899.
900.