全文获取类型
收费全文 | 4430篇 |
免费 | 82篇 |
国内免费 | 22篇 |
专业分类
化学 | 2293篇 |
晶体学 | 47篇 |
力学 | 117篇 |
综合类 | 2篇 |
数学 | 843篇 |
物理学 | 1232篇 |
出版年
2022年 | 81篇 |
2021年 | 96篇 |
2020年 | 96篇 |
2019年 | 111篇 |
2018年 | 110篇 |
2017年 | 108篇 |
2016年 | 199篇 |
2015年 | 131篇 |
2014年 | 191篇 |
2013年 | 287篇 |
2012年 | 254篇 |
2011年 | 263篇 |
2010年 | 198篇 |
2009年 | 202篇 |
2008年 | 257篇 |
2007年 | 230篇 |
2006年 | 175篇 |
2005年 | 162篇 |
2004年 | 123篇 |
2003年 | 107篇 |
2002年 | 134篇 |
2001年 | 58篇 |
2000年 | 67篇 |
1999年 | 43篇 |
1998年 | 33篇 |
1997年 | 34篇 |
1996年 | 45篇 |
1995年 | 37篇 |
1994年 | 29篇 |
1993年 | 32篇 |
1992年 | 36篇 |
1991年 | 27篇 |
1990年 | 36篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 22篇 |
1986年 | 23篇 |
1985年 | 28篇 |
1984年 | 31篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 34篇 |
1977年 | 32篇 |
1976年 | 25篇 |
1975年 | 21篇 |
1970年 | 20篇 |
1969年 | 19篇 |
排序方式: 共有4534条查询结果,搜索用时 0 毫秒
21.
The stoichiometric reactions of trimethylaluminum with 2,6‐(MeOCH2)2C6H3OH (LH) revealed compounds L3Al ( 1 ) and L2AlMe ( 2 ). On the other hand reaction of 1 equiv. of LH with trimethylaluminum did not lead to the formation of complex LAlMe2 ( 3 ), rather 2 together with Me3Al were observed as a result of a disproportionation of 3 . Compounds 1 and 2 were characterized by elemental analysis, 1H and 13C NMR spectroscopy and in the case of 1 by X‐ray diffraction. Derivative 2 underwent transmetalation with Ph3SnOH, giving LSnPh3 ( 4 ) as the result of a migration of ligand L from the aluminum to the tin atom. The identity of 4 was established by elemental analysis, 1H, 13C and 119Sn NMR spectroscopy and 1H, 119Sn HMBC experiments. The system 2 and B(C6F5)3 in a 1:1 molar ratio was shown to be active in the polymerization of propylene oxide and ε‐caprolactone. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
22.
Roman Murawski 《Archive for Mathematical Logic》1988,27(1):21-33
We consider expansions of models of Peano arithmetic to models ofA
2
s
-¦
1
1
+
1
1
–AC which consist of families of sets definable by nonstandard formulas. 相似文献
23.
24.
25.
26.
U. M. Dzhemilev A. G. Ibragimov A. B. Morozov R. R. Muslukhov G. A. Tolstikov 《Russian Chemical Bulletin》1991,40(7):1425-1427
A novel approach was developed for the stereoselective synthesis of trans-3,4-dialkyl-substituted aluminacyclopentanes from -olefins, metallic magnesium, and EtAlCl2 in the presence of catalytic amounts of Cp2ZrCl2. The hydrolysis and deuterolysis products of the 3,4-dialkyl-substituted aluminacyclopentanes obtained are only in the trans configuration.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1607–1609, July, 1991. 相似文献
27.
28.
Umarova N. N. Movchan N. I. Yusupov R. A. Korolev E. A. Morozov V. P. 《Russian Journal of General Chemistry》2003,73(7):999-1004
Ion exchange of silver(I) on thin polycrystalline PbS films in 10-
5-10-
2 M aqueous solutions of AgNO3 at 20-60°C was studied by X-ray fluorescence, atomic-absorption, and X-ray diffraction methods and by transmission electron microscopy. Since, under the given experimental conditions, diffusion of Ag(I) ions in a solid is the limiting stage of the process, the experimental kinetic dependences can be adequately described by the Fick equation for both semi-infinite medium and restricted plane at steady source of a diffusant on the surface. 相似文献
29.
Bombek S Lenarsic R Kocevar M Saint-Jalmes L Desmurs JR Polanc S 《Chemical communications (Cambridge, England)》2002,(14):1494-1495
An electrophilic amination of halogenated phenols with diisopropyl diazenedicarboxylate in the presence of ZrCl4 as a Lewis acid, accompanied by a halogen migration, was demonstrated for the first time; the fluorine, chlorine, bromine, or iodine atom migrated during the amination process under mild reaction conditions. 相似文献
30.