全文获取类型
收费全文 | 140篇 |
免费 | 0篇 |
专业分类
化学 | 57篇 |
力学 | 11篇 |
数学 | 29篇 |
物理学 | 43篇 |
出版年
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2016年 | 1篇 |
2014年 | 1篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 10篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1972年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有140条查询结果,搜索用时 0 毫秒
51.
The Zeeman effect on the N.Q.R. of methyl 4-bromobenzoate, 4,4′-dibromodiphenylether, 4,4′-dibromodiphenylsulphide has been studied at 77 K on single crystals, using the ‘geometric method’. The apparatus used in the measurements, which allows one to maintain any temperature between room temperature and 77 K, is described, and the possible significance of the slight variations in the molecular arrangement found in the present measurements and in those performed at room temperature is discussed. 相似文献
52.
Daniela Catarzi Lucia Cecchi Vittoria Colotta Guido Filacchioni Fabrizio Melani 《Journal of heterocyclic chemistry》1992,29(5):1161-1163
The parent 1,2,4-triazolo[1,5-a]quinoxaline was prepared by a few-step reaction from ethyl N1-(2-nitrophenyl)-N3-ethoxalyloxamidrazonate, which afforded the key intermediate diethyl 1-(2-nitrophenyl)-1,2,4-triazole-3,5-dicarboxylate in satisfactory yield. The latter was cyclized, hydrolyzed, decarboxylated, reduced and dehydrogenated to yield the title compound. 相似文献
53.
García Ruano JL Gamboa AE Gutiérrez LG Martín Castro AM Rodríguez Ramos JH Yuste F 《Organic letters》2000,2(6):733-736
A new kind of chiral dienophiles, cyclic vinyl-p-tolylsulfilimines (2a and 2b), were obtained from the corresponding (Z)-sulfinylacrylonitriles with HBF(4) and methanol. The asymmetric Diels-Alder reaction of optically pure 2a with cyclopentadiene under mild thermal or catalyzed conditions afforded only the endo-4a adduct with complete endo and pi-facial selectivities. The ability of the sulfilimine moiety to enhance the dienophilic reactivity of the double bond is similar to that of the sulfinyl group. 相似文献
54.
55.
Comparison of halogen bonding and van der Waals and π–π interactions in 4,5‐dibromo‐2‐hexyloxyphenol
Fabio D. Cukiernik Florencia Cecchi Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(5):o233-o236
The title compound, C12H16BrO2, is an interesting case of a simple organic molecule making use of five different types of intra‐ and intermolecular interactions (viz. conventional and nonconventional hydrogen bonds, and π–π, Br...Br and Br...O contacts), all of them relevant in the molecular and crystal structure geometry. The molecules are strictly planar, with an intramolecular O—H...O hydrogen bond, and associate into two‐dimensional structures parallel to (01) through two different types of halogen bonding. The planar structures, in turn, stack parallel to each other interlinked by C—H...π and π–π contacts. Also discussed are the relevant structural features leading to the rather low melting point of the compound. 相似文献
56.
Antoniotti P Borocci S Bronzolino N Cecchi P Grandinetti F 《The journal of physical chemistry. A》2007,111(40):10144-10151
Noble gas anions of general formula FNgBN- (Ng = He-Xe) have been investigated by MP2, coupled-cluster, and multireference-CI calculations with correlation-consistent basis sets. These species reside in deep wells on the singlet potential energy surface and are thermodynamically stable with respect to the loss of F, F-, BN, and BN-. They are unstable with respect to Ng + FBN-, but at least for Ng = Ar, Kr, and Xe, the involved energy barriers are high enough to suggest their conceivable existence as metastable species. The stability of FNgBN- arises from the strong F--stabilization of the elusive NgBN. The character of the boron-noble gas bond passes from purely ionic for FHeBN- and FNeBN- to covalent for FXeBN-. 相似文献
57.
58.
59.
60.