全文获取类型
收费全文 | 548篇 |
免费 | 9篇 |
专业分类
化学 | 322篇 |
晶体学 | 3篇 |
力学 | 33篇 |
数学 | 88篇 |
物理学 | 111篇 |
出版年
2022年 | 9篇 |
2021年 | 17篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 5篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 17篇 |
2012年 | 29篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 16篇 |
2008年 | 31篇 |
2007年 | 19篇 |
2006年 | 31篇 |
2005年 | 21篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1971年 | 4篇 |
1966年 | 3篇 |
1919年 | 2篇 |
1906年 | 2篇 |
排序方式: 共有557条查询结果,搜索用时 15 毫秒
111.
112.
Exploiting Synergistic Effects in Organozinc Chemistry for Direct Stereoselective C‐Glycosylation Reactions at Room Temperature
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)
Dr. Alberto Hernán‐Gómez Dr. Samantha A. Orr Dr. Marina Uzelac Dr. Alan R. Kennedy Dr. Santiago Barroso Dr. Xavier Jusseau Dr. Sébastien Lemaire Dr. Vittorio Farina Prof. Eva Hevia 《Angewandte Chemie (International ed. in English)》2018,57(33):10630-10634
Pairing a range of bis(aryl) zinc reagents ZnAr2 with the stronger Lewis acidic [(ZnArF2)] (ArF=C6F5), enables highly stereoselective cross‐coupling between glycosyl bromides and ZnAr2 without the use of a transition metal. Reactions occur at room temperature with excellent levels of stereoselectivity, where ZnArF2 acts as a non‐coupling partner although its presence is crucial for the execution of the C(sp2)–C(sp3) bond formation process. Mechanistic studies have uncovered a unique synergistic partnership between the two zinc reagents, which circumvents the need for transition‐metal catalysis or forcing reaction conditions. Key to the success of the coupling is the avoidance of solvents that act as Lewis bases versus diarylzinc compounds (e.g. THF). 相似文献
113.
Recently the low-energy effective string theory has been used by Gasperini and Veneziano to elaborate a very interesting scenario for the early history of the universe (birth of the universe as quantum scattering). Here we investigate the gauge fixing and the problem of the definition of a global time parameter for the quantum form of the model, and obtain the positive norm Hilbert space of states. 相似文献
114.
α-bromo Michael acceptors undergo ipso-substitution by phenol or benzenethiol in the K2CO3-acetone system, the reaction originating the (Z) isomers, via a stereospecific AdSNE process. 相似文献
115.
Vittorio Lucchini Maurizio Prato Gianfranco Scorrano Paolo Tecilla 《Journal of heterocyclic chemistry》1986,23(4):1135-1139
Substituted 4-benzoyl-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinolines 3 and 6-benzoyl-5,6,6a,7,8,10a-hexahydrophenanthridines 10 are obtained through Lewis acid catalyzed addition of 1-phenyl-2-arylamino-2-methoxyethanones 2 to cyclopentadienes and 1,3-cyclohexadiene respectively. Compounds 3 can be converted to the aromatized analogues by reaction with 2,3-dichloro-5,6-dicyanobenzoquinone in refluxing benzene. Compounds 10 are oxidized by sulfur either in decalin or in quinoline to substituted 6-benzoylphenanthridines. 相似文献
116.
The acetolyses of α-chloro-ketones1a-c,2a-c,9a and11a have been investigated parallely. Several aspects of the mechanisms involved in chlorine normal and cine substitution have been elucidated. Intramolecular trans-acetylation, ultimately leading to fragmentation of acetoxy-ketones3b,4a and4c, have been postulated to account for the formation of thiol ester6, aldehyde5a and ketone5c, respectively. 相似文献
117.
Guido Barone Giuseppina Castronuovo Attilio Cesáro Vittorio Elia 《Journal of solution chemistry》1980,9(11):867-876
The heats of mixing of the aqueous solutions of monomethylurea, monoethylurea, 1,3-dimethylurea, 1,3-diethylurea were determined at 25°C. The excess enthalpies obtained are expressed in virial form, in terms of pair and triplet interaction coefficients. A method previously discussed for predicting the excess enthalpies and the interaction coefficients of ternary solutions has been applied to the alkylureas. The large deviations between the experimental and calculated values, led to the modification of that method, which better accounts for the marked mixed character of these substances. 相似文献
118.
119.
Antonio Qualtieri Giovanni Morello Piernicola Spinicelli Maria T. Todaro Tiziana Stomeo Luigi Martiradonna Milena De Giorni Xavier Quélin Stéphanie Buil Alberto Bramati Jean P. Hermier Roberto Cingolani Massimo De Vittorio 《Superlattices and Microstructures》2010
Direct lithography of resist blends, embedding semiconductor colloidal nanocrystals (NCs) is an innovative way to achieve nanopositioning of NCs in quantum-confined optical resonators. In this work, we show a new appealing approach for the fabrication of single-photon sources operating at room temperature by localizing semiconductor colloidal NCs into vertical planar microcavities with lithographic techniques. 相似文献
120.