全文获取类型
收费全文 | 131篇 |
免费 | 8篇 |
专业分类
化学 | 102篇 |
力学 | 1篇 |
数学 | 18篇 |
物理学 | 18篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2002年 | 2篇 |
1999年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有139条查询结果,搜索用时 15 毫秒
31.
K. Bächmann I. Haag U. Sprenger K.-H. Steeg K. Steigerwald B. Bastian A. Röder 《Fresenius' Journal of Analytical Chemistry》1991,340(9):548-552
Summary In this publication the first results of a microanalytical investigation of individual rain droplets are given. Analytical methods for a sampling procedure as well as analysis in the ultra trace level with volumes less than 1 l have been developed. Because of the small volumes chromatographic methods are to be preferred. 相似文献
32.
33.
J. Fiedler L. Frey F. Steigerwald H. Langhoff T. Griegel K. Petkau W. Hammer 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1988,11(2):141-145
Mixtures of rare-gases (Rg) and alkali vapors (A) were excited by helium and argon ions. VUV transitions observed between 131.1 nm and 189.9 nm were ascribed to the decay of (RgA)+ ions where Rg=Kr, Xe and A=Cs, Rb, K, Na, Li. In the (ArA)+ systems (A=Rb, K, Na, Li) transitions appeared between 114.1 nm and 124.7 nm. Since the final state is only weakly bound, the (RgA)+ ions seem to be promising candidates for storage media of VUV lasers. 相似文献
34.
35.
Edgar Mark Erich Zbiral Hannelore H. Brandstetter 《Monatshefte für Chemie / Chemical Monthly》1980,111(1):289-307
Reaction of methyl -D-galactopyranoside (1) with two equivalents oft-butyldimethylchlorosilane yields methyl 2,6-bis-O-(tBDMSi)--D-galactopyranoside (1 b), methyl 3,6-bis-O-(tBDMSi)--D-galactopyranoside (1 c) and methyl 4,6-bis-O-(tBDMSi)--D-galactopyranoside (1 d). Likewise methyl -D-mannopyranoside (6) affords methyl 2,6-bis-O-(tBDMSi)--D-mannopyranoside (6 d) and methyl 3,6-bis-O-(tBDMSi)--D-mannopyranoside (6 b), which can be isomerised withTPP/DEAD to methyl 4,6-bis-O-(tBDMSi)--D-mannopyranoside (6 f). Methyl 6-O-(tBDMSi)--D-galactopyranoside (1 a) and methyl 6-O-(tBDMSi)--D-mannopyranoside (6 a) can be prepared from1 or6 with one equivalent oft-butyldimethylchlorosilane.Without an external nucleophile the sugar derivatives1 a and1 b react withTPP/DEAD to form the 3,4-carbonato--D-galactopyranosides1 h and1 i and the 3,4-carbonato-2-O-ethoxycarbonyl--D-galactoside (1 j). In contrast to the formation of the compound1 i by means ofTPP/DEAD the reaction of1 a withTPP and Di-t-butyl-azodicarboxylate (DTBAD) yields the 2,3-anhydro--D-taloside (4 b) and only a small amount of1 i. The epoxide4 b can be cleaved withp-nitrobenzoylchloride/pyridine to the 3-chloro-3-deoxy-2,6-di-O-p-nitrobenzoyl--D-idoside (5). Reaction of1 c and1 d withTPP/DEAD yields the 2,3-anhydro--D-gulopyranoside (2), which can be transformed with NaN3/NH4Cl to the 2-azido-2-deoxy--D-idopyranoside (3).Likewise6 a and6 d can be converted to the 3,4-anhydro--D-talosides (7 a and7 b). Reaction of7 b or6 d withTPP/DEAD/NH3 leads to 3,4-anhydro-2-azido-2-deoxy--D-galactopyranoside (8) and 3-azido-3-deoxy--D-altropyranoside (10), resp.The epoxide7 b is opened with NaN3/NH4Cl to the 4-azido-4-deoxymannosides (11 a and11 c) and the 3-azido-3-deoxy--D-idopyranoside (12), while the epoxide8 affords the 2,4-di-azido-2,4-dideoxy--D-glucopyranoside (9).Structures were elucidated by1H-NMR-analysis of the corresponding acetates.
H. H. Brandstetter undE. Zbiral, Helv., im Druck. 相似文献
36.
37.
38.
Loo YL Hiszpanski AM Kim B Wei S Chiu CY Steigerwald ML Nuckolls C 《Organic letters》2010,12(21):4840-4843
Fluorinated, contorted hexabenzocoronenes (HBCs) have been synthesized in a facile manner via Suzuki-Miyaura coupling of fluorinated phenyl boronic acids followed by photocyclization and Scholl cyclization. In addition to the molecular conformation observed in previous HBC derivatives, close-contact fluorine-fluorine intramolecular interactions result in a metastable conformation not previously observed. Heating the metastable HBCs above 100 °C irreversibly converts them to the stable conformation, suggesting that the metastable conformation arises from a kinetically arrested state during cyclization. 相似文献
39.
Claudia Bartels Martin Wegrzyn Anne Wiedl Verena Ackermann Hannelore Ehrenreich 《BMC neuroscience》2010,11(1):118
Background
Cognitive deterioration is a core symptom of many neuropsychiatric disorders and target of increasing significance for novel treatment strategies. Hence, its reliable capture in long-term follow-up studies is prerequisite for recording the natural course of diseases and for estimating potential benefits of therapeutic interventions. Since repeated neuropsychological testing is required for respective longitudinal study designs, occurrence, time pattern and magnitude of practice effects on cognition have to be understood first under healthy good-performance conditions to enable design optimization and result interpretation in disease trials. 相似文献40.
Christoph Kratky Hannelore H. Brandstetter Erich Zbiral 《Monatshefte für Chemie / Chemical Monthly》1981,112(10):1105-1111
An X-ray crystal structure analysis of the title compound was carried out at –168°C in order to assign the stereochemistry around the oxirane: C25H49NO8Si2, trigonal, R3,a=25.18(1),c=13.55(1) Å (hexagonal axes),Z=9,d
x
=1.105.The structure was solved with direct methods and refined to anR-factor of 0.086. 相似文献