全文获取类型
收费全文 | 950篇 |
免费 | 37篇 |
国内免费 | 4篇 |
专业分类
化学 | 744篇 |
晶体学 | 9篇 |
力学 | 20篇 |
数学 | 46篇 |
物理学 | 172篇 |
出版年
2023年 | 12篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 25篇 |
2015年 | 18篇 |
2014年 | 15篇 |
2013年 | 47篇 |
2012年 | 58篇 |
2011年 | 59篇 |
2010年 | 46篇 |
2009年 | 31篇 |
2008年 | 54篇 |
2007年 | 77篇 |
2006年 | 66篇 |
2005年 | 41篇 |
2004年 | 62篇 |
2003年 | 45篇 |
2002年 | 39篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 15篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 4篇 |
1966年 | 2篇 |
排序方式: 共有991条查询结果,搜索用时 31 毫秒
131.
The electrochemical fluorination of cycloalkyl-substituted acetic and propionic acids were conducted to obtain several kinds of perfluorobicyclic ethers [reaction conditions: Anodic current density: 3.5 A/dm2, Volt: 5~8V, Temp: 5~6 °C] . For example, from cyclopentyl-substituted acetic acids, perfluoro(4-alkyl-2-oxabicyclo[3.3.0]octane)s (I) were formed as the cyclization products in yields of 10~19% together with the corresponding perflouroalkanoyl flourides (II) (Y=3~13%). While, perfluorospiro-ethers were obtained from the fluorination of 3-cycloalkyl-substituted propionic acids. The characterization of these perfluorobicyclic ethers which consists of the reaction with anhydrous aluminum chloride will be reported also. 相似文献
132.
133.
Eiji Horikawa 《Mathematische Annalen》1976,222(3):275-282
134.
135.
Shirakawa E Yamagami T Kimura T Yamaguchi S Hayashi T 《Journal of the American Chemical Society》2005,127(49):17164-17165
Iron and copper complexes cooperatively catalyzed the arylmagnesiation of unfunctionalized alkynes including dialkylacetylenes, where the presence of both iron and copper catalysts is essential for high yields of 2-aryl-1-alkenylmagnesium bromides. 相似文献
136.
Direct beta-glucosidation between benzyl alcohol and D-glucose (5) using the immobilized beta-glucosidase from almonds with the synthetic prepolymer ENTP-4000 gave a benzyl beta-D-glucoside (1) in 53% yield. The coupling of the benzyl beta-D-glucopyranoside congener (8) derived from 1 with phenyl 2,3,4-tri-O-acetyl-1-thio-beta-D-xylopyranoside (9), ethyl 2,3,4-tri-O-acetyl-1-thio-alpha-L-rhamnopyranoside (13), and 2,3,4-tri-O-acetyl-alpha-L-arabinopyranosyl bromide (15) afforded 10, 14, and 16, respectively, as coupled products. Deprotection of 10, 14, and 16 provided the synthetic benzyl beta-D-xylopyranosyl-(1-->6)-beta-D-glucopyranoside (2), benzyl alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside (3), and benzyl alpha-L-arabinopyranosyl-(1-->6)-beta-D-glucopyranoside (4), respectively. 相似文献
137.
Palladium-catalyzed intramolecular cross-coupling reactions between aryl iodides and allyl moieties were successfully demonstrated in the presence of palladium catalyst, tri-o-tolylphosphine, a tertiary amine, and water. Several kinds of trans-2,4-disubstituted 1,2,3,4-tetrahydroquinolines were synthesized in 73-88% yields with excellent diastereoselectivities. This method was further applied to a large variety of substrates to form five-, six-, and seven-membered carbo- and heterocycles in good yields, regardless of the ring-containing atom, via microwave-assisted conditions. 相似文献
138.
Takahashi G Shirakawa E Tsuchimoto T Kawakami Y 《Chemical communications (Cambridge, England)》2005,(11):1459-1461
Alkynes act not as substrates but as co-catalysts in the presence of a nickel catalyst, an organoboronate and an aldehyde to promote the addition reaction between the substrates in combination with H2O. 相似文献
139.
140.
Marek?Fila Michael?Winkler Eiji?YanagidaEmail author 《Journal of Dynamics and Differential Equations》2005,17(2):249-269
We study the behavior of solutions of the Cauchy problem for a diffusion equation with supercritical nonlinearity. It is shown that if two solutions are initially close enough near the spatial infinity, then these solutions approach each other. Under some conditions, we determine the exact convergence rate, which turns out to depend on initial data. 相似文献