全文获取类型
收费全文 | 3570篇 |
免费 | 192篇 |
国内免费 | 96篇 |
专业分类
化学 | 2267篇 |
晶体学 | 53篇 |
力学 | 163篇 |
综合类 | 6篇 |
数学 | 726篇 |
物理学 | 643篇 |
出版年
2024年 | 6篇 |
2023年 | 58篇 |
2022年 | 96篇 |
2021年 | 114篇 |
2020年 | 136篇 |
2019年 | 116篇 |
2018年 | 116篇 |
2017年 | 79篇 |
2016年 | 147篇 |
2015年 | 117篇 |
2014年 | 144篇 |
2013年 | 286篇 |
2012年 | 246篇 |
2011年 | 277篇 |
2010年 | 176篇 |
2009年 | 160篇 |
2008年 | 223篇 |
2007年 | 201篇 |
2006年 | 181篇 |
2005年 | 178篇 |
2004年 | 135篇 |
2003年 | 125篇 |
2002年 | 107篇 |
2001年 | 67篇 |
2000年 | 36篇 |
1999年 | 42篇 |
1998年 | 33篇 |
1997年 | 32篇 |
1996年 | 20篇 |
1995年 | 24篇 |
1994年 | 20篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1940年 | 2篇 |
排序方式: 共有3858条查询结果,搜索用时 46 毫秒
21.
Alex F. Meindertsma Michael M. Pollard Ben L. Feringa Johannes G. de Vries Adriaan J. Minnaard 《Tetrahedron: Asymmetry》2007,18(24):2849-2858
This paper describes the enantioselective hydrogenation of vinylthioethers. We show that thioether derivatives of maleic esters can be hydrogenated with full conversion and up to 60% ee, and that α-thioether cinnamic acids can be hydrogenated in 51% ee with modest conversion. 相似文献
22.
23.
24.
25.
A new class of chiral dienophiles, 5-alkoxy-2(5H)-furanones, has been developed. Both enantiomers of 5-menthyloxy-2(5H)-ftiranone are readily available in enantiomerically pure form, starting from furfural and d- or l-menthol. Excellent diastereoselectivities (d.e. β99%) are obtained in thermal Diels-Alder reactions with several cyclic and acyclic dienes. The use of silyl dienol ethers has resulted in new routes to enantiomerically pure cyclohexanones in a highly regioselective manner. 相似文献
26.
Fabrication of hexaphenylsilole nanowires and their morphology-tunable photoluminescence. 总被引:1,自引:0,他引:1
Liping Heng Jin Zhai Anjun Qin Yuqi Zhang Yongqiang Dong Ben Zhong Tang Lei Jiang 《Chemphyschem》2007,8(10):1513-1518
Immersion of nanoporous alumina membranes into saturated solutions of hexaphenylsilole with subsequent solvent evaporation affords aligned organic nanowires. The luminescent properties of the hexaphenylsilole nanowires can be manipulated by varying their morphologies, which were controlled by changing the channel sizes of the alumina templates. 相似文献
27.
28.
29.
Stols Lucy Kulkarni Gopal Harris Ben G. Donnelly Mark I. 《Applied biochemistry and biotechnology》1997,63(1):153-158
Applied Biochemistry and Biotechnology - The malic enzyme gene ofAscaris suum was cloned into the vector pTRC99a in two forms encoding alternative arnino-termini. The resulting plasmids, pMEAl and... 相似文献
30.
Paul I. Surjasasmita Ben S. Freiser 《Journal of the American Society for Mass Spectrometry》1993,4(2):135-144
In this paper we report an extension of our earlier study on the structure of Alfacetone)2 + Collision-induced dissociation (CID) on MfacetoneXacetone-d6)+ for M = Al, Fe, Co, and Cu yields primarily, if not exclusively, nearly equal amounts of acetone and acetone-d6. Likewise, infrared multiphoton dissociation (IRMPD) at 10.6 μm yields, exclusively, nearly equal losses of the labeled and unlabeled acetones. These results suggest that the two acetone ligands bind in an equivalent fashion. Sc+ was also studied, which proved to be the most interesting. Sc+ reacts with acetone to form primarily ScO+, which undergoes higher order reactions leading to several products including ScO(acetone)2 +. IRMPD on this ion produces ScO(acetone-d6)(CD2CO)+, while its perdeuterated analog also produces ScO(acetone-d6)+ in addition to ScO(acetone-d6(CD2CO)+. The IRMPD results are supplemented by studying the primary and higher order reactions of Sc+ with acetone, as well as the CID of ScO(acetone)2 +. Finally, a qualitative assessment of the infrared photodissociation cross sections is given. It is found that the relative photodissociation cross sections follow the orders Co(acetone-d6)2 + > Co(acetone)(acetone-d6) > Co(acetone)2 + and Co(acetone-d6)+ > Co(acetone)+. 相似文献