全文获取类型
收费全文 | 261篇 |
免费 | 5篇 |
专业分类
化学 | 122篇 |
晶体学 | 5篇 |
力学 | 7篇 |
数学 | 38篇 |
物理学 | 94篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 10篇 |
2011年 | 6篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 5篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1891年 | 2篇 |
1878年 | 2篇 |
1868年 | 2篇 |
排序方式: 共有266条查询结果,搜索用时 187 毫秒
51.
52.
53.
We investigate quantum Brownian motion sustained transport in both, adiabatically rocked ratchet systems and quantum stochastic resonance (QSR). Above a characteristic crossover temperature T(0) tunneling events are rare; yet they can considerably enhance the quantum-noise-driven particle current and the amplification of signal output in comparison to their classical counterparts. Below T(0) tunneling prevails, thus yielding characteristic novel quantum transport phenomena. For example, upon approaching T=0 the quantum current in Brownian motors exhibits a tunneling-induced reversal, and tends to a finite limit, while the classical result approaches zero without such a change of sign. As a consequence, similar current inversions generated by quantum effects follow upon variation of the particle mass or of its friction coefficient. Likewise, in this latter regime of very low temperatures the tunneling dynamics becomes increasingly coherent, thus suppressing the semiclassically predicted QSR. Moreover, nonadiabatic driving may cause driving-induced coherences and quantized resonant transitions with no classical analog. (c) 1998 American Institute of Physics. 相似文献
54.
Eberhard Reimann Rainer Hertel Jürgen Krauss 《Monatshefte für Chemie / Chemical Monthly》2008,139(6):673-684
Alkylation of Reissert compounds derived from 3-methylisoquinolines with several 2-cyanobenzylbromides followed by hydrolytic cleavage provided the corresponding 1-benzyl-3-methylisoquinolines. Treatment of the latter with methylmagnesiumiodide caused cyclization to the title compounds rather than formation of 2-acetylbenzylisoquinolines. 相似文献
55.
Maite Nößler René Jäger David Hunger Dr. Marc Reimann Tobias Bens Dr. Nicolás I. Neuman Dr. Arijit Singha Hazari Prof. Dr. Martin Kaupp Prof. Dr. Joris van Slageren Prof. Dr. Biprajit Sarkar 《欧洲无机化学杂志》2023,26(19):e202300091
Due to their ability to form stable molecular complexes that have tailor-made properties, terpyridine ligands are of great interest in chemistry and material science. In this regard, we prepared two terpyridine ligands with two different fluorinated phenyl rings on the backbone. The corresponding CoII and FeII complexes were synthesized and characterized by single-crystal X-ray structural analysis, electrochemistry and temperature-dependent SQUID magnetometry. Single crystal X-ray diffraction analyses at 100 K of these complexes revealed Co−N and Fe−N bond lengths that are typical of low spin CoII and FeII centers. The metal centers are coordinated in an octahedral fashion and the fluorinated phenyl rings on the backbone are twisted out of the plane of the terpyridine unit. The complexes were investigated with cyclic voltammetry and UV/Vis-NIR spectroelectrochemistry. All complexes show a reversible oxidation and several reduction processes. Temperature dependent SQUID magnetometry revealed a gradual thermal SCO behavior in two of the complexes, while EPR spectroscopy provided further insights on the electronic structure of the metal complexes, as well as site of reduction. 相似文献
56.
Gerald Senarclens de Grancy Marc Reimann 《Central European Journal of Operations Research》2016,24(1):29-48
This paper systematically compares an ant colony optimization (ACO) and a greedy randomized adaptive search procedure (GRASP) metaheuristic. Both are used to solve the vehicle routing problem with time windows and multiple service workers. In order to keep the results comparable, the same route construction heuristic and local search procedures are used. It is shown that ACO clearly outperforms GRASP in the problem under study. Additionally, new globally best results for the used benchmark problems are presented. 相似文献
57.
Karolina Haberska Cristina Vaz-Domínguez Antonio L. De Lacey Marius Dagys Curt T. Reimann Sergey Shleev 《Bioelectrochemistry (Amsterdam, Netherlands)》2009,76(1-2):34
In an effort to find conditions favouring bioelectrocatalytic reduction of oxygen by surface-immobilised human ceruloplasmin (Cp), direct electron transfer (DET) reactions between Cp and an extended range of surfaces were considered. Exploiting advances in surface nanotechnology, bare and carbon-nanotube-modified spectrographic graphite electrodes as well as bare, thiol- and gold-nanoparticle-modified gold electrodes were considered, and ellipsometry provided clues as to the amount and form of adsorbed Cp. DET was studied under different conditions by cyclic voltammetry and chronoamperometry. Two Faradaic processes with midpoint potentials of about 400 mV and 700 mV vs. NHE, corresponding to the redox transformation of copper sites of Cp, were clearly observed. In spite of the significant amount of Cp adsorbed on the electrode surfaces, as well as the quite fast DET reactions between the redox enzyme and electrodes, bioelectrocatalytic reduction of oxygen by immobilised Cp was never registered. The bioelectrocatalytic inertness of this complex multi-functional redox enzyme interacting with a variety of surfaces might be associated with a very complex mechanism of intramolecular electron transfer involving a kinetic trapping behaviour. 相似文献
58.
M. Manninen M. Koskinen S.M. Reimann B. Mottelson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):381-385
Exact many-body methods as well as current-spin-density functional theory are used to study the magnetism and electron localization
in two-dimensional quantum dots and quasi-one-dimensional quantum rings. Predictions of broken-symmetry solutions within the
density functional model are confirmed by exact configuration interaction (CI) calculations: In a quantum ring the electrons
localize to form an antiferromagnetic chain which can be described with a simple model Hamiltonian. In a quantum dot the magnetic
field localizes the electrons as predicted with the density functional approach.
Received 5 December 2000 相似文献
59.
Nilvebrant Nils-Olof Reimann Anders Larsson Simona Jönsson Leif J. 《Applied biochemistry and biotechnology》2001,91(1-9):35-49
Lignocellulose hydrolysates contain fermentation inhibitors causing decreased ethanol production. The inhibitors include phenolic
compounds, furan aldehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior
to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of
three different resins were examined: an anion exchanger, a cation exchanger, and a resin without charged groups (XAD8). A
dilute acid hydrolysate of spruce was treated with the resins at pH 5.5 and 10.0 prior to ethanolic fermentation with Saccharomyces cerevisiae. In addition to the experiments with hydrolysate, the effect of the resins on selected model compounds, three phenolics (vanillin,
guaiacol, and coniferyl aldehyde) and two furan aldehydes (furfural and hydroxymethyl furfural), was determined. The cation
exchanger increased ethanol production, but to a lesser extent than XAD-8, which in turn was less effective than the an ion
exchanger. Treatment at pH 10.0 was more effective than at pH 5.5. At pH 10.0, the anion exchanger efficiently removed both
anionic and uncharged inhibitors, the latter by hydrophobic interactions. The importance of hydrophobic interactions was further
indicated by a substantial decrease in the concentration of model compounds, such as guaiacol and furfural, after treatment
with XAD-8. 相似文献
60.
T. Shih K. Reimann M. Woerner T. Elsaesser I. Waldmüller A. Knorr R. Hey K.H. Ploog 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):262
Radiative coupling of resonantly excited intersubband transitions in GaAs/AlGaAs multiple quantum wells can have a strong impact on the coherent nonlinear optical response, as is shown by phase and amplitude resolved propagation studies of ultrashort electric field transients. Upon increasing the driving field amplitude, strong radiative coupling leads to a pronounced self-induced absorption, followed by a bleaching due to the onset of delayed Rabi oscillations. A many-particle theory including light propagation effects accounts fully for the experimental results. 相似文献