全文获取类型
收费全文 | 210篇 |
免费 | 4篇 |
专业分类
化学 | 138篇 |
力学 | 4篇 |
数学 | 10篇 |
物理学 | 62篇 |
出版年
2023年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2015年 | 5篇 |
2013年 | 3篇 |
2012年 | 10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 | 5篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 9篇 |
1989年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3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214条查询结果,搜索用时 15 毫秒
91.
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
92.
93.
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
94.
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
95.
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
96.
Dreisow F Heinrich M Keil R Tünnermann A Nolte S Longhi S Szameit A 《Physical review letters》2010,105(14):143902
We present the first experimental realization of an optical analog for relativistic quantum mechanics by simulating the Zitterbewegung (trembling motion) of a free Dirac electron in an optical superlattice. Our photonic setting enables a direct visualization of Zitterbewegung as a spatial oscillatory motion of an optical beam. Direct measurements of the wave packet expectation values in superlattices with tuned miniband gaps clearly show the transition from weak-relativistic to relativistic and far-relativistic regimes. 相似文献
97.
We present an O(n
4
)-time and O(n
2
)-space algorithm that computes a subgraph of the minimum weight triangulation (MWT) of a general point set. The algorithm works by finding a collection of edges guaranteed to be in any locally minimal triangulation. We call this subgraph the LMT-skeleton. We also give a variant called the modified
LMT-skeleton that is both a more complete subgraph of the MWT and is faster to compute requiring only O(n
2
) time and O(n) space in the expected case for uniform distributions. Several experimental implementations of both approaches have shown
that for moderate-sized point sets (up to 350 points^1) the skeletons are connected, enabling an efficient completion of the exact MWT. We are thus able to compute the MWT of substantially larger random point sets than have previously been computed.
^1Though in this paper we summarize some empirical findings for input sets of up to 350 points, a variant of the algorithm has
been implemented and tested on up to 40,000 points producing connected subgraphs [2].
Received May 29, 1996, and in revised form January 10, 1997. 相似文献
98.
Dr. Yunus Zorlu Connor Brown Dr. Claudia Keil Dr. M. Menaf Ayhan Prof. Dr. Hajo Haase Dr. Richard B. Thompson Dr. Imre Lengyel Dr. Gündoğ Yücesan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11129-11134
Herein, we report the third generation of fluorescent probes (arylphosphonic acids) to target calcifications, particularly hydroxyapatite (HAP). In this study, we use highly conjugated porphyrin-based arylphosphonic acids and their diesters, namely 5,10,15,20-tetrakis[m-(diethoxyphosphoryl)phenyl]porphyrin ( m -H8TPPA-OEt8 ) and 5,10,15,20-tetrakis [m-phenylphosphonic acid]porphyrin ( m -H8TPPA ), in comparison with their positional isomers 5,10,15,20-tetrakis[p-(diisopropoxyphosphoryl)phenyl]porphyrin ( p -H8TPPA-iPr8 ) and 5,10,15,20-tetrakis [p-phenylphosphonic acid]porphyrin ( p -H8TPPA ), which have phosphonic acid units bonded to sp2 carbon atoms of the fluorescent core. The conjugation of the fluorescent core is thus extended to the (HAP) through sp2-bonded −PO3H2 units, which generates increased fluorescence upon HAP binding. The resulting fluorescent probes are highly sensitive towards the HAP in rat bone sections. The designed probes are readily taken up by cells. Due to the lower reported toxicity of ( p -H8TPPA ), these probes could find applications in monitoring bone resorption or adsorption, or imaging vascular or soft tissue calcifications for breast cancer diagnosis etc. 相似文献
99.
Experimental Techniques - 相似文献
100.
Dreisow F Wang G Heinrich M Keil R Tünnermann A Nolte S Szameit A 《Optics letters》2011,36(20):3963-3965
We report on the experimental observation of Bloch oscillations of an optical wave packet in a lattice with second-order coupling. To this end, we employ zigzag waveguide arrays, in which the second-order coupling can be precisely tuned. 相似文献