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221.
Luminescent [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O), which forms from aqueous solutions of [(NH(3))(4)Pt]Cl(2) and K[Au(CN)(2)], crystallizes with extended chains of the two ions with multiple close Pt...Au (3.2804(4) and 3.2794(4) A) and Au...Au (3.2902(5), 3.3312(5), and 3.1902(4) A) contacts. Nonluminescent [(NH(3))(4)Pt][Ag(CN)(2)](2).1.4(H(2)O) is isostructural with [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O). Treatment of [(NH(3))(6)Ni]Cl(2) with K[Au(CN)(2)] forms [(NH(3))(2)Ni][Au(CN)(2)](2) in which the [Au(CN)(2)](-) ions function as nitrile ligands toward nickel, which assumes a six-coordinate structure with trans NH(3) ligands. The [Au(CN)(2)](-) ions self-associate into linear columns with close Au...Au contacts of 3.0830(5) A, and pairs of gold ions in these chains make additional but longer (3.4246(5) A) contacts with other gold ions. 相似文献
222.
Three cyclodextrine derivatives (6A,6D-di-O-(prop-2-one-1,3-dienyl)-alpha-cyclodextrin (1), 6-O-(prop-2-one-1-yl)-alpha-cyclodextrin (2) and 6A,6D-di-O-(prop-2-one-1,3-dienyl)-beta-cyclodextrin (3)) were synthesised and investigated as epoxidation catalysts. The three compounds were synthesised from the corresponding perbenzylated cyclodextrins which were mono- or didebenzylated in the 6-position using Sina?'s method. Reaction with NaH and methallyl chloride in the case of 2, or methallyl dichloride in the case of 1 and 3, followed by dihydroxylation, periodate cleavage and protection group removal gave the target compounds. All three compounds catalysed, in the presence of oxone, the epoxidation of a series of alkenes. Epoxidation was compared to the reaction catalysed by simple ketones and inhibition was studied. 相似文献
223.
Torben Stender 《Linear algebra and its applications》2007,426(1):53-70
Rotation numbers and chain rotation numbers may be interpreted as a generalization of the imaginary parts for matrices. In dimension two they measure how the solutions of a linear autonomous differential equation rotate in the phase space, and they reduce to the imaginary parts of the eigenvalues of the system’s matrix. In higher dimensions they measure how a two-frame of vectors rotate under the induced flow in the plane which is spanned by the frame. For their calculation, only special sets in the oriented Grassmann manifold of planes are relevant, and to each of these sets corresponds a compact interval of chain rotation numbers. In this paper we will determine these relevant sets and calculate the corresponding sets of chain rotation numbers. 相似文献
224.
Wolfgang Dahmen Torben Klint Karsten Urban 《Foundations of Computational Mathematics》2008,3(2):135-143
We consider fictitious domain-Lagrange multiplier formulations for variational problems in the space H(curl:
Ω{\bf)} derived from Maxwell's equations. Boundary conditions and the divergence constraint are imposed weakly by using Lagrange
multipliers. Both the time dependent and time harmonic formulations of the Maxwell's equations are considered, and we derive
well-posed formulations for both cases. The variational problem that arises can be discretized by functions that do not satisfy
an a-priori divergence constraint. 相似文献
225.
Dr. Sarah Puhl Dr. Torben Steenbock Prof. Dr. Carmen Herrmann Prof. Dr. Jürgen Heck 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2428-2434
Pinching molecules via chemical strain suggests intuitive consequences, such as compression at the pinched site and clothespin-like opening of other parts of the structure. If this opening affects two spin centers, it should result in reduced communication between them. We show that for naphthalene-bridged biscobaltocenes with competing through-space and through-bond pathways, the consequences of pinching are far less intuitive: despite the known dominance of through-space interactions, the bridge plays a much larger role for exchange spin coupling than previously assumed. Based on a combination of chemical synthesis, structural, magnetic, and redox characterization, and a newly developed theoretical pathway analysis, we can suggest a comprehensive explanation for this non-intuitive behavior. These results are of interest for molecular spintronics, as naphthalene-linked cobaltocenes can form wires on surfaces for potential spin-only information transfer. 相似文献
226.
Torben Jasper-Tönnies Dr. Manuel Gruber Dr. Sandra Ulrich Prof. Dr. Rainer Herges Prof. Dr. Richard Berndt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7074-7083
The competition between honeycomb and hexagonal tiling of molecular units can lead to large honeycomb superstructures on surfaces. Such superstructures exhibit pores that may be used as 2D templates for functional guest molecules. Honeycomb superstructures of molecules that comprise a C3 symmetric platform on Au(111) and Ag(111) surfaces are presented. The superstructures cover nearly mesoscopic areas with unit cells containing up to 3000 molecules, more than an order of magnitude larger than previously reported. The unit cell size may be controlled by the coverage. A fairly general model was developed to describe the energetics of honeycomb superstructures built from C3 symmetric units. Based on three parameters that characterize two competing bonding arrangements, the model is consistent with the present experimental data and also reproduces various published results. The model identifies the relevant driving force, mostly related to geometric aspects, of the pattern formation. 相似文献
227.
Torben Tiedemann Tammo Francksen Uwe Latacz-Lohmann 《Central European Journal of Operations Research》2011,19(4):571-587
This article presents a novel model for evaluating the performance of field players in football. Based upon Data Envelopment
Analysis (DEA), we employ a non-concave metafrontier approach that permits estimation of players’ efficiency scores under
consideration of their playing positions. The model is applied to a data set of Germany’s premier league football players
covering the playing seasons 2002/03 to 2008/09. The results reveal a clear positive relationship between a team’s average
player efficiency score and its rank in the league table at the end of the season. In addition, the metafrontier approach
is used to identify a footballer’s optimal playing position in the team and to quantify the performance increase from moving
to that position. 相似文献
228.
Adam Sobkowiak Jonas Ångström Thomas Kollin Nielsen Yngve Cerenius Torben R. Jensen Martin Sahlberg 《Applied Physics A: Materials Science & Processing》2011,104(1):235-238
A new hydrogen absorbing material has been discovered, ScNiAl, which can store 1.5 wt.% hydrogen reversibly. In this compound,
hydrogen absorption is a two-step process; solid solution of hydrogen at temperatures below 180°C and decomposition into ScH2 and NiAl at higher temperatures. Detailed analysis of the hydrogen absorption/desorption has been performed using in situ
synchrotron radiation powder X-ray diffraction and thermal desorption spectroscopy. The apparent activation energy for hydrogen
desorption was determined to be 182 kJ/mol and the material is stable during cycling. 相似文献
229.
Carlo G. Zambonin Antonella Aresta Torben Nilsson 《International journal of environmental analytical chemistry》2013,93(10):651-657
Solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was optimized for the analysis of hexachlorocyclohexanes, DDD, DDE, DDT and other organochlorine pesticides in aqueous samples. Higher extraction efficiency was observed with the SPME fibre coated with 100 µm polydimethylsiloxane than with the fibres coated with 85 µm polyacrylate or 65 µm polydimethylsiloxane/divinylbenzene. Equilibration times were longer than 60 min, except for the hexachlorocyclohexanes, in spite of rapid stirring of the sample. However, precise quantitative analysis could be performed also under non-equilibrium conditions: i.e. repeatability standard deviations below 20%. Salt addition had a positive effect on the response for the hexachlorocyclohexanes, whereas the extraction of the other analytes was affected negatively. The pH of the sample solution did not influence the extraction efficiency. The desorption was performed for 5 min at 275°C directly in the GC injector. At shorter desorption times or lower temperatures a significant carry-over was observed for the heavier analytes. Generally, detection limits in the ng/L range were obtainable. 相似文献
230.
Chilla G Kipp T Menke T Heitmann D Nikolic M Frömsdorf A Kornowski A Förster S Weller H 《Physical review letters》2008,100(5):057403
We report on the direct observation of confined acoustic phonons in the photoluminescence spectra of single CdSe-CdS-ZnS nanocrystals, whose ligands were exchanged to poly(ethylene oxide) (PEO) before they were embedded in a PEO matrix. Modeling a nanocrystal as an elastic sphere, the confined acoustic modes can be assigned to purely radial vibrations: the breathing mode and its two first radial harmonics. In addition to acoustic modes, we also observe longitudinal optical modes of the core material and, remarkably, also of both shell materials. 相似文献