全文获取类型
收费全文 | 795篇 |
免费 | 32篇 |
国内免费 | 9篇 |
专业分类
化学 | 587篇 |
晶体学 | 5篇 |
力学 | 10篇 |
数学 | 37篇 |
物理学 | 197篇 |
出版年
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 19篇 |
2014年 | 16篇 |
2013年 | 38篇 |
2012年 | 29篇 |
2011年 | 41篇 |
2010年 | 31篇 |
2009年 | 29篇 |
2008年 | 37篇 |
2007年 | 36篇 |
2006年 | 35篇 |
2005年 | 43篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 20篇 |
2001年 | 17篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1993年 | 23篇 |
1992年 | 7篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1978年 | 9篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1939年 | 5篇 |
1936年 | 5篇 |
1935年 | 5篇 |
1933年 | 4篇 |
1909年 | 5篇 |
排序方式: 共有836条查询结果,搜索用时 31 毫秒
1.
2.
Jürgen Kurths M. Carmen Romano Marco Thiel Grigory V. Osipov Mikhail V. Ivanchenko István Z. Kiss John L. Hudson 《Nonlinear dynamics》2006,44(1-4):135-149
We present two different approaches to detect and quantify phase synchronization in the case of coupled non-phase coherent
oscillators. The first one is based on the general idea of curvature of an arbitrary curve. The second one is based on recurrences
of the trajectory in phase space. We illustrate both methods in the paradigmatic example of the R?ssler system in the funnel
regime. We show that the second method is applicable even in the case of noisy data. Furthermore, we extend the second approach
to the application of chains of coupled systems, which allows us to detect easily clusters of synchronized oscillators. In
order to illustrate the applicability of this approach, we show the results of the algorithm applied to experimental data
from a population of 64 electrochemical oscillators. 相似文献
3.
P. K. Kashkarov B. V. Kamenev M. G. Lisachenko O. A. Shalygina V. Yu. Timoshenk M. Schmidt J. Heitmann M. Zacharias 《Physics of the Solid State》2004,46(1):104-108
The photoluminescence spectra and kinetics of both erbium-doped and undoped multilayer structures of quasi-ordered silicon
nanocrystals in a silicon dioxide matrix were studied. It was shown that the optical excitation energy of silicon nanocrystals
2–3 nm in size can be practically completely transferred to Er3+ ions in the oxide surrounding the nanocrystals, with its subsequent radiation at 1.5 μm. Possible reasons for the high excitation
efficiency of the Er3+ ions are discussed, and the conclusion is drawn that the F?rster mechanism is dominant in the energy transfer processes occurring
in these structures.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 105–109.
Original Russian Text Copyright ? 2004 by Kashkarov, Kamenev, Lisachenko, Shalygina, Timoshenko, Schmidt, Heitmann, Zacharias. 相似文献
4.
H. Zacharias 《Applied Physics A: Materials Science & Processing》1988,47(1):37-54
In this article the application of tunable dye lasers to desorption phenomena is illuminated. These lasers provide radiation continuously tunable from 105 nm in the vacuum ultraviolet to about 10 m in the mid-IR. By employing either laser induced fluorescence (LIF) or resonance enhanced multiphoton ionization (REMPI) spectroscopy almost all diatomic and many polyatomic molecules can be probed with the sensitivity required to detect desorbing molecules under UHV conditions. The spectral resolution of the lasers is sufficiently high that rotational state selectivity is achieved. Recent developments permit in addition the velocity distributions of molecules to be determined with internal quantum state resolution. Therefore very detailed information about the molecular dynamics has been obtained. In most experiments so far reactive recombinations off surfaces have been investigated. In this paper special emphasis will be given to the recombination of hydrogen on copper and palladium surfaces. For these systems very detailed data about the internal state populations at various surface temperatures have been obtained. The rotational cooling previously observed in molecular beam scattering has also been established for desorption. Strong vibrational excitation has been observed, which in the case of desorption from copper may be associated with the recombination dynamics, whereas for desorption of D2 from Pd(100) a molecular precursor state might be responsible. By measuring the velocity distribution in each quantum state, the complete energetics of the desorbing molecules has been determined. Some first experiments on laser induced desorption with state selective detection of the desorbing molecules will also be discussed. Finally, making use of the polarization analysis of the signal, alignment effects in the desorption can be observed, permitting observation of molecular dynamics with a magnifying glass.Heisenberg fellow of the Deutsche Forschungsgemeinschaft 相似文献
5.
6.
The thermal decompositions of-AlF3 · 3H2O, AlF3 · 3.5H2O, AlF3 · 1.5H2O,-AlF3 and hydroxyfluorides of aluminium were investigated. The literature data were complemented with X-ray results. The first stages of decomposition are described. The AlF3 hydrates and hydroxyfluorides were used as model systems in order to interpret the thermal behaviour of -AlF3 in more detail.
Zusammenfassung Die thermische Zersetzung von-AlF3 · 3H2O, AlF3 · 3,5H2O, AlF3 · 1,5H2O,-AlF3 und Hydroxyfluoriden des Aluminiums wurden untersucht und die in der Literatur beschriebenen Ergebnisse durch Röntgenuntersuchungen ergänzt. Die ersten Phasen der Zersetzung werden beschrieben. Die AlF3-Hydrate und Hydroxyfluoride des Aluminiums können als Modellsystem genutzt werden, um das thermische Verhalten von -AlF3 detailliert zu beschreiben.
-AlF3 · 2, AlF3 · 3,52, AlF3 · 1,52,-AlF3 . . . - lF3.相似文献
7.
U. Robra H. Zacharias K. H. Welge 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1990,16(3):175-188
The dynamics of the photodissociation of NO2 into NO(X 2ΠΩ″, ν″=0,J″)+O(3 P 0,1,2) is investigated near the thermodynamic threshold. Cooling the internal degrees of freedom by a supersonic beam expansion provides a nearly complete quantum state selection prior to the predissociation. Measurements of the wavelength dependent dissociation yield into specific product quantum states are reported. At certain wavelengths Λ″ doublet resolved rotational population distributions of the fragments are obtained. Up to an excess energy ofE exc=121 cm?1 about 42% of this energy is partitioned into the rotation of the NO molecules, and correspondingly 58% into the translational degree of freedom. The role of electronic and total parity is discussed. 相似文献
8.
Galvanic cells of the type (C+Cl2)(NaCl(s))(MCl2(s))(C+Cl2) give e. m. f. 's above 280°, which are due to the formation of ternary chlorides NanMCln+2. By the change in slope of continuously measured e.m.f.vs. T curves, the temperatures of solid-state reactions in systems NaCl-MCl2 can be found. This method was applied for the systems of NaCl with NiCl2, CoCl2 and CdCl2, and for KCl-NiCl2. With the exception of the system NaCl-NiCl2, all phase diagrams must be corrected.
This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. 相似文献
Zusammenfassung Mit galvanischen Zellen des Typs (C+Cl2)/NaCl(s)/MCl2(s)/(C+Cl2) lassen sich oberhalb 280° EMK's messen, die auf der Bildung ternärer Chloride NanMCln+2 beruhen. Durch die Änderung der Steigung kontinuierlich gemessener EMK- gegen T-Kurven lassen sich in Systemen NaCl/MCl2 die Temperaturen von Festkörperreaktionen nachweisen. Diese Methode wurde auf die Systeme des NaCl mit NiCl2, CoCl2 und CdCl2 sowie auf das System KCl-NiCl2 angewendet. Alle Phasendiagramme, mit Ausnahme des Systems NaCl-NiCl2, mußten auf Grund dieser Messungen revidiert werden.
(C+Cl2)/NaCl./MCl2./(C +Cl2) 280 °C . . , NanMCln+2. . . , NaCl-MCl2. NaCl NiCl2, CoCl2, CdCl2 KCl-NiCl2. NaCl-NiCl2,ce .
This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. 相似文献
9.
10.
P L Davis E Kanal G N Farnum D H Van Thiel S M Iwatsuki 《Magnetic resonance imaging》1987,5(5):407-411
We report a case of a 55-year-old woman with polycystic liver disease that we examined with magnetic resonance (MR) imaging, CT and ultrasound. The MR images demonstrated varying intensities in the cyst contents which we believe is due to different degrees and age of hemorrhage. Such variability among the cysts was not seen on the CT or ultrasound images. 相似文献