全文获取类型
收费全文 | 158篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
化学 | 92篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 43篇 |
物理学 | 21篇 |
出版年
2023年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2014年 | 1篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 5篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 9篇 |
2006年 | 1篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 6篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 3篇 |
1967年 | 6篇 |
1966年 | 3篇 |
1965年 | 6篇 |
1964年 | 2篇 |
1963年 | 2篇 |
1962年 | 1篇 |
1960年 | 5篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有161条查询结果,搜索用时 15 毫秒
1.
Reaction diffusion systems on cylindrical domains with terms that vary rapidly and periodically in the unbounded direction can be analyzed by averaging techniques. Here, using iterated normal form transformations and Gevrey regularity of bounded solutions, we prove a result on exponential averaging for such systems, i.e., we show that traveling wave solutions can be described by a spatially homogenous equation and exponentially small remainders. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
Ronny Kleinhempel Gunar Kaune Matthias Herrmann Hartmut Kupfer Walter Hoyer Frank Richter 《Mikrochimica acta》2006,156(1-2):61-67
Indium tin oxide (ITO) thin films were deposited by mid frequency pulsed dual magnetron sputtering using a metallic alloy
target with 10 wt.% tin in an atmosphere of argon and oxygen. The aim of the work was to study the interdependence of structural,
electrical and optical properties of ITO films deposited in the reactive and transition target mode, respectively. The deposition
rate in the transition mode exceeds the deposition rate in the reactive mode by a factor of six, a maximum value of 100 nm·m min−1 could be achieved. This corresponds to a static deposition rate of 200 nm min−1. The lowest electrical resistivity of 1.1·10−3 Ω cm was measured at samples deposited in the high oxygen flow range in the transition mode. The samples show a good transparency
in the visible range corresponding to extinction coefficients being below 10−2. X-ray diffraction was used to characterise crystalline structure as well as film stress. ITO films prepared in the transition
mode show a slightly preferred orientation in (211) direction, whereas films deposited in the reactive mode are strongly (222)
oriented. Compared to undoped In2O3 all samples have an enlarged lattice. The lattice strain perpendicular to the surface is about 0.8% and 2.0% for films grown
in the transition and the reactive mode, respectively. Deposition in the transition mode introduces a biaxial film stress
in the range of −300 MPa, while stress in reactive mode samples is −1500 MPa. 相似文献
3.
4.
5.
Summary On the basis of dihydroresorcinol we prepared 2,2-dimethylchroman-5-ol, 2-prenyl-3-methyl-2-cyclohexen-1-one, 6-methyl-1-tetralone, geranylacetic acid, and 8-rnethyl-8-decenoic acid. 相似文献
6.
V. M. Kopelevich L. N. Bulanova Yu. V. Belousova A. V. Lysenkova V. F. Pozdnev V. I. Gunar 《Chemistry of Natural Compounds》1988,23(4):493-495
The synthesis has been performed of dephosphocoenzyme A, 4,4-di-0-(2,3-9-isopropylideneadenosineuronyl)pantethine, and of 4,4-di(2,3-isopropylideneadenosineuronylamino)-4,4-dideoxypantethine from 2,3-0-isopropylidene adenosineuronic acid, using as condensing agents the tert-butyl dicarbonatepyridine and the N,N-dicyclohexylcarbodiimide-N-hydroxysuccinimide systems, respectively.Vitaminy Scientific-Production Amalgamation, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 587–590, July–August, 1987. 相似文献
7.
The synthesis of - and -N-(4-amino-3, 3-dimethyl-2-hydroxybutyryl)- β-alanine () is described. Compound is an analog of pantothenic acid in which the 4′-hyroxy group is replaced by amino group. The synthetic sequence leading to involved the synthesis L-4-amino-3,3-dimethyl-2-hydroxybutyric acid and its resolution. Coupling of N-benzyloxycarbonyl N-hydroxysuccinimide ester () with β-alanine and followed by removal of the protecting group gave . 相似文献
8.
Sabine Ebeling Dieter Matthies Daniel McCarthy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):265-273
Abstract α-Amidoalkylation of allyttrimethylsilane with methyl-2-chloro-2-(p-chlorobenzoylamino)-ethanoate 1 gave in the presence of Lewis acid racemic methyl-2- (p-chlorobenzoylamino)-4-penteno ate 2. Under the same conditions, vinlytrimethylsilane afforded (±)-trans-2-(p-chlorophenyl)-5,6-dihydro-4-methoxycarbonyl-6-trimethylsilyl-4H-1, 3-oxazine 4 as the major, by n.m.r. data and x-ray crystallography established product. 相似文献
9.
Perkell JS Zandipour M Matthies ML Lane H 《The Journal of the Acoustical Society of America》2002,112(4):1627-1641
This study explores the hypothesis that clear speech is produced with greater "articulatory effort" than normal speech. Kinematic and acoustic data were gathered from seven subjects as they pronounced multiple repetitions of utterances in different speaking conditions, including normal, fast, clear, and slow. Data were analyzed within a framework based on a dynamical model of single-axis frictionless movements, in which peak movement speed is used as a relative measure of articulatory effort (Nelson, 1983). There were differences in peak movement speed, distance and duration among the conditions and among the speakers. Three speakers produced the "clear" condition utterances with movements that had larger distances and durations than those for "normal" utterances. Analyses of the data within a peak speed, distance, duration "performance space" indicated increased effort (reflected in greater peak speed) in the clear condition for the three speakers, in support of the hypothesis. The remaining four speakers used other combinations of parameters to produce the clear condition. The validity of the simple dynamical model for analyzing these complex movements was considered by examining several additional parameters. Some movement characteristics differed from those required for the model-based analysis, presumably because the articulators are complicated structurally and interact with one another mechanically. More refined tests of control strategies for different speaking styles will depend on future analyses of more complicated movements with more realistic models. 相似文献
10.
Conclusions The selective O-alkylation of the Na salts of the 2-methyl- and 2-methylthio-4-hydroxy-6-methyl-pyrimidines with isopropyl iodide in either alcohol or dimethylformamide, and the N-alkylation of the Ag salt of 1-phenyl-6-methyluracil with isopropyl iodide in n-octane, were accomplished.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 404–407, February, 1972.In conclusion the authors express their gratitude to L. A. Nikitina and T. M. Sedletska for making the spectral studies. 相似文献