全文获取类型
收费全文 | 87篇 |
免费 | 2篇 |
专业分类
化学 | 77篇 |
数学 | 1篇 |
物理学 | 11篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 6篇 |
2008年 | 2篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1959年 | 1篇 |
1931年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有89条查询结果,搜索用时 15 毫秒
1.
Dr. Heinz Berner Hellmuth Reinshagen 《Monatshefte für Chemie / Chemical Monthly》1975,106(5):1059-1069
The synthesis of imidazo[4,5-b]pyridines and of [1,2,4]-triazolo[1,5-a]pyridines is described, and their biological activity in relation to the standard antiviral substance, 2-(α-hydroxybenzyl)benzimidazol, is discussed. 相似文献
2.
On treatment with HSO3F in SO2C1F at 0°, 3-hydroxy-2,2-dimethyl-3-phenyl-propionic acid ( 1a ) is transformed into 2-phenyl-3-methyl-2-butenoic acid ( 2a ) (isolated yield: 40–44%). Using monolabelled [3-13C]- 1a ( 1a *) and doubly labelled [1,3-13C2]- 1a ( 1a **), the migration of HOOC (or a mechanistically equivalent group) was proved; a cross experiment established the intramolecular character of the rearrangement. By following the reaction at low temperature in an NMR. spectrometer, the formation of intermediates and side products was demonstrated. 相似文献
3.
A novel type of selfcondensation of some aliphatic and aromatic γ-keto acids (capable of forming γ-lactols) in concentrated sulphuric acid is described. A mechanism for the reaction is proposed, where the key intermediates are the carbonium ion formed by loss of the OH group in the γ-lactols and the α,β-unsaturated γ-lactone with an exocyclic double bond in γ-position formed by loss of one molecule of water from the γ-lactols. The proposal is supported by deuteration experiments. Structure determinations are based on IR, PMR and MS. 相似文献
4.
Heinz Berner Hermann Vyplel Gerhard Schulz Peter Stuchlik 《Monatshefte für Chemie / Chemical Monthly》1983,114(10):1125-1136
The contact of pleuromutilin derivatives with the protein moiety of cytochrome P-450 as well as its orientation towards the heme iron is mainly dependent on the steric environment of the hydrindanone-part of the tricyclus. The apparent affinity between substrate and enzyme, which is correlated with the rate of metabolism can be reduced by inversion of configuration at carbon 6. This inversion is achieved by equilibrating the diastereomeric ketones12 and13 followed by a selective reduction of the keto group at position 7. The 6-methylgroup of14 was assigned α-configuration on the basis of spectroscopic data in comparison to those of the naturally configurated compound14a. 相似文献
5.
Heinz Berner Hermann Vyplel Gerhard Schulz Gernot Fischer 《Monatshefte für Chemie / Chemical Monthly》1985,116(10):1165-1176
2-Hydroxy-19,20-dihydropleuromutilin (10) undergoes a stereospecific ketolisomerisation when treated with base under phase/transfer conditions (11, 12). The subsequent reductive elimination of the 3-acetoxygroup afforded mutilin with a 1,2-transposed ketofunction (13). 相似文献
6.
In HSO3F/SO2ClF the β-hydroxy esters Ph-CHOH-CMe2-COOR ( 1 , R?Me, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8. At ?15°, both 7 and 8 undergo a rearrangement, forming derivatives of Me2C?C(Ph)COOR ( 2 ). By labelling 1 with 13C, singly (13C(3)) and doubly (13C(1,3)), it could be shown that exclusively the ROOC groups undergo a 1,2-shift. Compound 2 is also formed in HSO3F/SO2ClF from the isomeric Me2COH-CHPh-COOR ( 3 ) by elimination, and less easily from the α-hydroxy ester Ph-CMe2-CHOH-COOR (5) via a phenyl 1,2-shift. Another isomer, Ph-C(OH)Me-CHMe-COOR (4) gives products different from 2 . Using more acidic systems containing SbF5, the free carbenium ions 13 (Ph-CH+-CMe2-COOR) can be stabilized; they do not form 2 , possibly because of complexation of the ester group with SbF5. The energy profile and the mechanism of the rearrangement 1 → 2 are discussed. 相似文献
7.
Heinz Berner Gerhard Schulz Gernot Fischer Hellmuth Reinshagen 《Monatshefte für Chemie / Chemical Monthly》1978,109(3):557-566
In order to obtain a better partition of a prodigiosin derivative in biological media, two hydroxy groups were introduced into theansa-part of the molecule. The synthesis of the title compound is described in detail. 相似文献
8.
Temperature sensitive and electric field sensitive hydrogels were prepared for use in modulated drug release systems. Crosslinked poly(N-isopropyl-acrylamide) and its networks, modified with hydrophobic components by copolymerization or by interpenetrating polymer networks (IPNs) formation, were utilized as temperature sensitive hydrogels. Indomethacin (a model solute)-release from polymer matrix and permeation through polymer membrane demonstrated “on-off” regulation with temperature fluctuation. This was the result of polymer surface properties rather than bulk swelling, as temperature was changed past the swelling transition temperature range of the polymer. The on-off regulation in an electric field was also obtained with a positively charged solute (Edrophonium chloride) release in distilled-deionized water from a matrix of crosslinked poly(2-acrylamido-2-methylpropanesulfonic acid-co-butyl methacrylate). This was attributed to the ion exchange between Edrophonium ion and protons produced at the anode. The swelling changes produced by local pH or ionic strength changes affected non-charged solute release. 相似文献
9.
Dr. Heinz Berner Gerhard Schulz Hellmuth Reinshagen 《Monatshefte für Chemie / Chemical Monthly》1977,108(1):233-242
Some syntheses of [9](2,4)pyrrolophane are described. 相似文献
10.
The Diterpene Pleuromutilin(1) reacts with orthoformicacid-trimethylester at room temperature almost quantitatively to give the 11-keto-3-methylester 2 with AB-trans-configuration. This conversion is shown to occur through a 1,5-hydride-shift between C3 and C11. Treatment of 2 with Lewis acid (ZnCl2) initiated a retro-1,5-hydride-shift which resulted in the formation of Pleuromutilin(1). Mechanistic aspects and structure assignments, which are based on chemical and spectroscopic (1H- and 13C-NMR) data are discussed. 相似文献