全文获取类型
收费全文 | 227篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 148篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 26篇 |
物理学 | 50篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 22篇 |
2012年 | 13篇 |
2011年 | 26篇 |
2010年 | 14篇 |
2009年 | 14篇 |
2008年 | 17篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有236条查询结果,搜索用时 15 毫秒
231.
The mechanism and enantioselectivity of the organocatalytic Diels-Alder reaction were computationally investigated by density functional theory at the B3LYP/6-31G(d) level of theory. The uncatalyzed Diels-Alder reaction was also studied to explore the effect of the organocatalyst on this reaction in terms of energetics, selectivity, and mechanism. The catalyzed reaction showed improved endo/exo selectivity, and the free energy of activation was significantly lowered in the presence of the catalyst. Both uncatalyzed and catalyzed reactions exhibited concerted asynchronous reaction mechanism with the degree of asynchronicity being more evident in the presence of the catalyst. The Corey's experimentally derived predictive selection rules for the outcome of the organocatalytic Diels-Alder reaction were also theoretically analyzed, and an excellent agreement was found between experiment and theory. 相似文献
232.
233.
The crystal synthesis and structure of a new organic monohydrogenmophosphate (3,4‐Cl2‐CH2C6H3NH3)2HPO4·2H2O are reported. This compound crystallizes in the monoclinic P21/n with a = 9.081(7) Å, b = 6.501(5) Å, c = 35.423(12) Å, β = 91.09(5)°, V = 2090.9(2) Å3, and Z = 4. Crystal structure was solved and refined to R = 0.042, using 2543 independent reflections. It can be described by inorganic layers, including the HPO4‐ anions and the H2O molecules, parallel to (a, b) planes and situated at z = 0 and z = 1/2. The interlayer spacing is occupied by the organic molecules which perform different interactions around the 3D network cohesion. A characterization of this compound by solid‐state (13C, 31P) MAS NMR and IR spectroscopies is also reported. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
234.
Ibrahim S. Al Nasr Markus Weise Waleed S. Koko Tariq A. Khan Rainer Schobert Bernhard Biersack 《应用有机金属化学》2023,37(1):e6952
Gold(I) complexes carrying imidazole-2-ylidene ligands and ferrocene substituents were prepared. Their activities against protozoal Leishmania major and Toxoplasma gondii parasites were analyzed. Certain gold(I) complexes with chlorido and 1,1′-bis(triphenylphosphino)ferrocene ligands revealed promising antiparasitic effects. The new chlorido complexes 5b and 5c showed high activities against T. gondii tachyzoites and L. major promastigotes while the new ferrocene-bridged bis-gold(I) complexes 8a and 8b were particularly active against L. major amastigotes and considerably selective as to toxicity results from Vero cells and macrophages. 相似文献
235.
The reaction of 2‐thioxo‐4‐thiazolidinone ( 1a ) with phosphorus ylides 2a and 2b afforded compounds 5 and 6. On the other hand, formylmethylenetriphenylphosphorane (2c) reacts with 1a and its N‐methyl derivative 1b to give the new complicated phosphonium ylides 7a,b, respectively. Reactions of 1b with ylides 2a and 2d gave rise to the olefinic compound 8 and the new phosphorane product 9. Moreover, dialkyl phosphites 3a,b and trialkyl phosphites 4a–c react with 1a to give both the alkylated products 10a–c and the dimeric compounds 11,12. A mechanism is proposed to explain the formation of the new products.© 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 337–341, 1999 相似文献
236.