全文获取类型
收费全文 | 692篇 |
免费 | 192篇 |
国内免费 | 32篇 |
专业分类
化学 | 859篇 |
综合类 | 3篇 |
物理学 | 54篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 21篇 |
2021年 | 25篇 |
2020年 | 66篇 |
2019年 | 42篇 |
2018年 | 28篇 |
2017年 | 25篇 |
2016年 | 62篇 |
2015年 | 75篇 |
2014年 | 48篇 |
2013年 | 47篇 |
2012年 | 56篇 |
2011年 | 55篇 |
2010年 | 34篇 |
2009年 | 27篇 |
2008年 | 41篇 |
2007年 | 53篇 |
2006年 | 38篇 |
2005年 | 38篇 |
2004年 | 23篇 |
2003年 | 32篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 16篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1993年 | 1篇 |
1988年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有916条查询结果,搜索用时 15 毫秒
81.
82.
83.
A novel class of non-classical fullerenes, having pentagon–heptagon pairs, as in azulene, is modeled. The various coverings,
sometimes alternating azulenic and benzenic units, are designed by some new sequences of map operations or generalized operations.
The hypothetical azulenic fullerenes are characterized by PM3 semiempirical data and POAV1 strain energy SE. Their aromaticity
is discussed in the light of several criteria. The HOMA index of aromaticity enabled evaluation of global and local aromaticity
of the designed fullerenes. 相似文献
84.
85.
Venkataramanarao G. Anand Simi K. Pushpan Sundararaman Venkatraman Tavarekere K. Chandrashekar 《Journal of Chemical Sciences》2003,115(5-6):711-720
Expanded porphyrins containing seven pyrrole/heterocyclic rings linked in a cyclic fashion are termed heptaphyrins. The number
ofπ-electrons in heptaphyrins depends on the number ofmeso carbon bridges used to link the heterocyclic rings, accordingly heptaphyrins with 28π-electrons and 30π-electrons are reported to date. Both condensation reactions of the appropriate precursors and acid-catalysed oxidative coupling
reactions have been utilized to synthesise the heptaphyrins. The 30π heptaphyrins exhibit rich structural diversity where some of the heterocyclic rings in the macrocycle undergo a 180° ring
flipping. An overview of the synthetic methods employed for the synthesis of heptaphyrins, their spectroscopic properties,
structural behaviour and aromatic properties are highlighted in this paper.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
86.
为了阐明芳香性及磁性原因,用Aihara提出的TRE概念计算了 ,苯并环丁二烯和戊搭烯等烃的共振能,环共振能和环电流.计算结果表明 因有正共振能具有芳香性并产生反磁性环电流,而苯并环丁二烯和戊塔烯因有负共振能具有反芳香性并产生顺磁性环电流. 相似文献
87.
运用密度泛函理论的两种方法(B3LYP、B3PW91)与二级微扰方法(MP2),对二价负离子全金属团簇Ga42-、In42-的稳定结构、振动频率与电子总能量作了计算.在此基础上,运用B3LYP与HF两种方法,着重对最稳定的正方形结构的Ga42-、In42-团簇的两种磁性质:各向异性磁化率与核独立化学位移进行了研究.计算结果表明,正方形结构Ga42-、In42-团簇具有很强的芳香性.接着对它们进行细致的分子轨道结构分析,揭示了正方形结构Ga42-、In42-团簇具有多重芳香性,一个非局域π分子轨道与两个非局域σ分子轨道对此两种金属团簇的芳香性都起了重要作用. 相似文献
88.
Inside Back Cover: Intermolecular Enantioselective Dearomatization Reaction of β‐Naphthol Using meso‐Aziridine: A Bifunctional In Situ Generated Magnesium Catalyst (Angew. Chem. Int. Ed. 7/2015)
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
89.
Ryo Nozawa Keitaro Yamamoto Prof. Dr. Ji‐Young Shin Prof. Dr. Satoru Hiroto Prof. Dr. Hiroshi Shinokubo 《Angewandte Chemie (International ed. in English)》2015,54(29):8454-8457
Treatment of antiaromatic nickel(II) norcorrole with potassium cyanide provided nickel(II) 3‐cyanonorcorrole with perfect regioselectivity without the help of a catalyst. The reaction of the nickel(II) norcorrole with phenol or thiophenol in the presence of a base also yielded substitution products. The antiaromatic 16π conjugation system in the norcorrole core was preserved in the functionalized products. Introduction of phenylthio groups significantly decreased the HOMO–LUMO gap and enhanced the near IR absorption property. 相似文献
90.
Tetrabenzoperipentacene: Stable Five‐Electron Donating Ability and a Discrete Triple‐Layered β‐Graphite Form in the Solid State
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Akinobu Matsumoto Dr. Mitsuharu Suzuki Dr. Daiki Kuzuhara Dr. Hironobu Hayashi Prof. Dr. Naoki Aratani Prof. Dr. Hiroko Yamada 《Angewandte Chemie (International ed. in English)》2015,54(28):8175-8178
An oxidative ring‐closure reaction of a tetranaphthylpyrene derivative led to the synthesis of a 56 all‐carbon conjugated tetrabenzoperipentacene. In the single‐crystal X‐ray structure, three molecules make a triple‐layered cluster by π‐stacking, wherein each layer rotates by 120°, and is thus considered a petit β‐graphite. As for the optical properties, the Stokes shift is extremely small (10 cm?1), thus indicating its remarkably rigid framework. The tetrabenzoperipentacene exhibits reversible five‐electron oxidation waves in cyclic voltammetry, and is regarded as a counterpart to the fullerene C60 in terms of stable multicharge‐storage nanocarbon materials. 相似文献