全文获取类型
收费全文 | 208篇 |
免费 | 4篇 |
专业分类
化学 | 133篇 |
晶体学 | 3篇 |
力学 | 4篇 |
数学 | 12篇 |
物理学 | 60篇 |
出版年
2023年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2015年 | 5篇 |
2013年 | 3篇 |
2012年 | 11篇 |
2011年 | 12篇 |
2010年 | 2篇 |
2009年 | 7篇 |
2008年 | 3篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 8篇 |
2001年 | 8篇 |
1999年 | 11篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1971年 | 6篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1967年 | 4篇 |
1959年 | 4篇 |
1940年 | 2篇 |
1933年 | 2篇 |
1932年 | 1篇 |
1931年 | 1篇 |
1929年 | 1篇 |
1922年 | 1篇 |
1903年 | 1篇 |
1902年 | 1篇 |
排序方式: 共有212条查询结果,搜索用时 687 毫秒
91.
M. Külz A. Kortyna M. Keil B. Schellhaaß K. Bergmann 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,33(2):109-117
The dependence of the Na2 electron impact ionization rate is measured as a function of vibrational excitation in a crossed molecule-electron beamm arrangement at collision energiesE coll ≤ 3 eV above the ionization threshold. Specific vibrational distributions in theX 1∑ g + state with average vibrational energies of 0.17 eV, 0.276 eV, and 0.349 eV, are prepared via Franck-Condon pumping using a narrow-band cw laser. Enhancement of the ionization rate is observed only at impact energies near the ionization threshold where the ionization rate increases linearly as a function of vibrational excitation. Analysis of the experimental data is based on three model calculations. The first of these calculations equates vibrational energy with kinetic energy and agrees well with the experimental data. A second, more refined model allows for differences in state-to-state ionization rates and uses Franck-Condon factors to estimate transition probabilities, but leads to a less favorable agreement. The third one employs a semi-classical formulation of the Franck-Condon principle. It provides the best agreement with the experimental data. In contrast with an earlier study of electron impact ionization of diatomic molecules [20], we find no evidence of dynamical modification of the ionization rate, due to vibrational motion of the nuclei, at the present level of accuracy of our data and analysis. 相似文献
92.
R. Keil 《Fresenius' Journal of Analytical Chemistry》1976,281(2):123-124
Zusammenfassung BrO
4
–
wird in schwach alkalischer Lösung (pH 7–9) bei Siedehitze mit Jodid zu BrO
3
–
reduziert. Ein Arsenitüberschuß wird zugegeben, um die Ausscheidung von Jod in der heißen Lösung zu verhindern. Durch Rücktitration des Arsenits mit einer eingestellten Jodlösung wird der BrO
4
–
-Gehalt bestimmt.Das gesamte BrO
3
–
in der Lösung wird anschließend nach ansäuern und Zusatz von KJ mit Thiosulfat titriert. Aus den beiden Titrationen läßt sich der ursprüngliche Gehalt an Bromat in der Probe ermitteln. Die Bestimmungen sind einfach und sehr genau. Es wird auch eine Methode zur direkten Analyse von BrO
3
–
neben BrO
4
–
angegeben.Für die Überprüfung des Manuskriptes möchte ich den Herren Dr. P. Baertschi und O. Antonsen herzlich danken. 相似文献
93.
H. -H. Schröder U. Zimmermann K. -H. Keil G. Zäpfel A. Jaeger Egon F. Kasper W. P. Schmidt P. Stahlknecht 《Mathematical Methods of Operations Research》1977,21(3):152-156
Ohne Zusammenfassung 相似文献
94.
R. Keil 《Analytical and bioanalytical chemistry》1973,262(4):273-275
The selectivity of the spectrophotometric determination of beryllium by thorin has been essentially improved by simply masking the other cations with large quantities of EDTA and ammonium citrate. Over 60 cations and 20 anions, which have been investigated, do not disturb the determination in a wide range. The relative standard deviation is about ± 1%. 相似文献
95.
96.
97.
An athermal arrayed-waveguide grating (AWG) multiplexer relying on an all-polymer approach is reported. By properly adjusting
the positive coefficient of thermal expansion of the polymer substrate and the negative thermo-optic coefficient of the polymer
waveguide, athermal and polarisation-independent AWG devices are demonstrated.
Received: 21 May 2001 / Revised version: 26 July 2001 / Published online: 2 November 2001 相似文献
98.
G. Hansen Carl Zeiss R. Ramb O. Schließmann K. Zänker F. H. Emery H. S. Booth A. de Gramont A. R. Striganow E. Brand F. Twyman E. Harvey K. A. Ssuchenko G. S. Landsberg S. L. Mandelstam S. W. Tuljankin W. F. Smirnow W. W. Zeiden S. A. Alexandrow S. M. Raisski H. B. Vincent R. A. Sawyer G. Scheibe A. Schöntag E. Lay A. Keil H. Martin und L. Wwedjenski 《Fresenius' Journal of Analytical Chemistry》1938,114(1-2):43-55
Ohne Zusammenfassung 相似文献
99.
Dr. Heinz Mustroph Dr. Knut Reiner Dr. Bianca Senns Dr. Jürgen Mistol Dr. Steffen Ernst Dr. Dietmar Keil Dr. Lothar Hennig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(26):8140-8149
Two series of new merocyanine dyes have been synthesised and the dependence of their electronic structure on substituents and solvents has been studied by NMR spectroscopy, by using both the NMR 13C chemical shifts between adjacent C atoms in the polymethine chain and the 3J(H,H) coupling constants for trans‐vicinal protons. The widely used valence bond (VB) model based on two contributing structures cannot account theoretically for the observed alternating π‐electron density in the polymethine chain. In addition, the prediction of zero‐π‐bond order alternation (or zero‐bond length alternation) by this model is also incorrect. However, the results are consistent with the predictions of a qualitative VB model which considers the resonance of a positive charge throughout the whole polymethine chain. Based on this model and the Franck‐Condon principle the effect of substituents and solvents on the fine structure of the electronic spectra of these dyes can be explained as vibronic transitions from the vibrational state v=0 to v′, where v is the vibrational quantum number of the totally symmetric C?C valence vibration of the polymethine chain in the electronic ground state and v′ is that in the electronic excited state. In contrast, neither the effects of substituents or solvents on the electronic structure of merocyanines and their electronic spectra can be accounted for by the simple two state VB model. 相似文献
100.
Zeuner JM Rechtsman MC Keil R Dreisow F Tünnermann A Nolte S Szameit A 《Optics letters》2012,37(4):533-535
We report on the experimental demonstration of negative coupling constants between defect guides in a waveguide lattice. We find that coupling can only be negative if the defects are negative and an odd number of lattice sites is between the defect guides. 相似文献