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1.
2.
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
3.
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
4.
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
5.
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
6.
Korupoju SR Mangayarkarasi N Zacharias PS Mizuthani J Nishihara H 《Inorganic chemistry》2002,41(16):4099-4101
New homo trinuclear Zn(II) complexes [Zn(3)L(1)(micro-OAc)](ClO(4))(2).3CHCl(3).H(2)O, 1, and [Zn(3)L(1)(micro-OAc)].ClO(4).PF(6).5CH(3)OH.H(2)O, 2, and hetero trinuclear complex [Zn(2)CuL(1)(micro-OAc)](ClO(4))(2).3CHCl(3).H(2)O,3, of optically active hexaaza triphenolic macrocycle H(3)L(1) were synthesized and crystallographically characterized. The cation [Zn(3)L(1)(micro-OAc)](+) structure of 1 and 2 closely resembles the trinuclear Zn(II) active site of P1 nuclease. The distorted tetrahedral geometry of Zn3 was successfully reproduced at Cu1 in complex 3. The complexes 2 and 3 cleave CT DNA at 37 and 50 degrees C. 相似文献
7.
Rapid approximate calculation of water binding free energies in the whole hydration domain of (bio)macromolecules 下载免费PDF全文
The evaluation of water binding free energies around solute molecules is important for the thermodynamic characterization of hydration or association processes. Here, a rapid approximate method to estimate water binding free energies around (bio)macromolecules from a single molecular dynamics simulation is presented. The basic idea is that endpoint free‐energy calculation methods are applied and the endpoint quantities are monitored on a three‐dimensional grid around the solute. Thus, a gridded map of water binding free energies around the solute is obtained, that is, from a single short simulation, a map of favorable and unfavorable water binding sites can be constructed. Among the employed free‐energy calculation methods, approaches involving endpoint information pertaining to actual thermodynamic integration calculations or endpoint information as exploited in the linear interaction energy method were examined. The accuracy of the approximate approaches was evaluated on the hydration of a cage‐like molecule representing either a nonpolar, polar, or charged water binding site and on α‐ and β‐cyclodextrin molecules. Among the tested approaches, the linear interaction energy method is considered the most viable approach. Applying the linear interaction energy method on the grid around the solute, a semi‐quantitative thermodynamic characterization of hydration around the whole solute is obtained. Disadvantages are the approximate nature of the method and a limited flexibility of the solute. © 2016 Wiley Periodicals, Inc. 相似文献
8.
Jan-Niklas Dienemann Shu-Yu Chen Manuel Hitzenberger Montana L. Sievert Stephan M. Hacker Sean T. Prigge Martin Zacharias Michael Groll Stephan A. Sieber 《Angewandte Chemie (International ed. in English)》2023,62(31):e202304533
The development of novel anti-infectives requires unprecedented strategies targeting pathways which are solely present in pathogens but absent in humans. Following this principle, we developed inhibitors of lipoic acid ( LA ) salvage, a crucial pathway for the survival of LA auxotrophic bacteria and parasites but non-essential in human cells. An LA -based probe was selectively transferred onto substrate proteins via lipoate protein ligase (LPL) in intact cells, and their binding sites were determined by mass spectrometry. Probe labeling served as a proxy of LPL activity, enabling in situ screenings for cell-permeable LPL inhibitors. Profiling a focused compound library revealed two substrate analogs ( LAMe and C3 ) as inhibitors, which were further validated by binding studies and co-crystallography. Importantly, LAMe exhibited low toxicity in human cells and achieved killing of Plasmodium falciparum in erythrocytes with an EC50 value of 15 μM, making it the most effective LPL inhibitor reported to date. 相似文献
9.
Navamoney Arulsamy Chepuri R. K. Rao Panthappally S. Zacharias 《Transition Metal Chemistry》1991,16(6):606-609
Summary Condensations of Cu(L-ser)2 and Cu(L-thr)2 (where L-ser=L-serinato anion and L-thr=L-threoninato anion) with formaldehyde at pH 4.5 yield two new optically active products:bis[L-(oxazolidine-4-carboxylato)]-copper(II) monohydrate (1) andbis[L-(N-hydroxymethyl-5-methyloxazolidine-4-carboxylato)]copper(II) dihydrate (2), respectively. Cu(D-ser)2 and Cu(D-thr)2 also undergo similar reactions. The new products are different from the products obtained from Cu(DL-ser)2 and Cu(DL-thr)2, and a mechanism has been suggested to explain the stereospecificity of these conversions. Condensation of Cu(L-ser)2 with formaldehyde and ammonia at pH 4.5 yields the new product, [3N,7N-(1,3,5,7-tetraazabicyclo-[3.3.1]nonyl)di(hydroxymethyl)-acetato]copper(II), (3). The compexes have been characterized by analytical and by i.r. electronic and c.d. spectral data. Complexes (1) and (2) undergo a reversible CuII/CuI redox process in aqueous media at –0.18 Vversus s.c.e.; complex (3) exhibits irreversible CuII/CuI reduction at –0.49 V confirming the presence of a rigid pentamethylenediaza-bridged ligand system. 相似文献
10.
S.V. Filseth H. Zacharias J. Danon R. Wallenstein K.H. Welge 《Chemical physics letters》1978,58(1):140-144
Production of CH(X2Π) in a low pressure H/O/C2H2 flame has been observed by laser excited fluorescence in the 0, 0 band of the A2 Δ ← X2Π system at 431 nm. Laser excitation spectra have been recorded of the P, Q, and R branches with a bandwidth of 0.03 nm and of the head of the Q branch with a bandwidth of 0.0009 nm. Values of the spin—orbit and spin—rotation coupling constants in the A2Δ state have been obtained. 相似文献