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排序方式: 共有109条查询结果,搜索用时 250 毫秒
1.
A palladium-carbene catalyzed Sonogashira coupling of unactivated alkyl bromides with alkyl substituted alkynes is reported. For the first time, unactivated secondary alkyl halides were successfully employed in Sonogashira reactions. 相似文献
2.
Dipl. Chem. Keven Muller Dr. Yu Sun Andreas Heimermann Fabian Menges Gereon Niedner‐Schatteburg Christoph van Wüllen Prof. Dr. Werner R. Thiel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7825-7834
Pyridinylazolato (N–N′) ruthenium(II) complexes of the type [(N–N′)RuCl(PMe3)3] have been obtained in high yields by treating the corresponding functionalised azolylpyridines with [RuCl2(PMe3)4] in the presence of a base. 15N NMR spectroscopy was used to elucidate the electronic influence of the substituents attached to the azolyl ring. The findings are in agreement with slight differences in the bond lengths of the ruthenium complexes. Furthermore, the electronic nature of the azolate moiety modulates the catalytic activity of the ruthenium complexes in the hydrogenation of carbon dioxide under supercritical conditions and in the transfer hydrogenation of acetophenone. DFT calculations were performed to shed light on the mechanism of the hydrogenation of carbon dioxide and to clarify the impact of the electronic nature of the pyridinylazolate ligands. 相似文献
3.
Dipl.‐Chem. Steffen Styra Dr. Sandra González‐Gallardo Dr. Felix Armbruster Dr. Pascual Oña‐Burgos Dipl.‐Chem. Eric Moos Dr. Matthias Vonderach Priv.‐Doz. Dr. Patrick Weis Priv.‐Doz. Dr. Oliver Hampe Dipl.‐Chem. Anneken Grün Dipl.‐Chem. Yvonne Schmitt Prof. Dr. Markus Gerhards Dipl.‐Chem. Fabian Menges Dipl.‐Chem. Maximilian Gaffga Prof. Dr. Gereon Niedner‐Schatteburg Prof. Dr. Frank Breher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8436-8446
A series of bimetallic silyl halido cuprates consisting of the new tripodal silicon‐based metalloligand [κ3N‐Si(3,5‐Me2pz)3Mo(CO)3]? is presented (pz=pyrazolyl). This metalloligand is straightforwardly accessible by reacting the ambidentate ligand tris(3,5‐dimethylpyrazolyl)silanide ({Si(3,5‐Me2pz)3}?) with [Mo(CO)3(η6‐toluene)]. The compound features a fac‐coordinated tripodal chelating ligand and an outward pointing, “free” pyramidal silyl donor, which is easily accessible for a secondary coordination to other metal centers. Several bimetallic silyl halido cuprates of the general formula [CuX{μ‐κ1Si:κ3N‐Si(3,5‐Me2pz)3Mo(CO)3}]? (X=Cl, Br, I) have been synthesized. The electronic and structural properties of these complexes were probed in detail by X‐ray diffraction analysis, electrospray mass spectrometry, infrared‐induced multiphoton dissociation studies, cyclic voltammetry, spectroelectrochemistry, gas‐phase photoelectron spectroscopy, as well as UV/Vis and fluorescence spectroscopy. The heterobimetallic complexes contain linear two‐coordinate copper(I) entities with the shortest silicon–copper distances reported so far. Oxidation of the anionic complexes in methylene chloride and acetonitrile solutions at ${E{{0\hfill \atop 1/2\hfill}}}$ =?0.60 and ?0.44 V (vs. ferrocene/ferrocenium (Fc/Fc+)), respectively, shows substantial reversibility. Based on various results obtained from different characterization methods, as well as density functional theory calculations, these oxidation events were attributed to the Mo0/MoI redox couple. 相似文献
4.
Ren‐Qi Wang Katharina Druckenmüller Gereon Elbers Klaus Guenther Jean‐Philippe Croué 《Journal of mass spectrometry : JMS》2014,49(2):154-160
The composition and physiochemical properties of aquatic‐phase natural organic matter (NOM) are most important problems for both environmental studies and water industry. Laser desorption/ionization (LDI) mass spectrometry facilitated successful examinations of NOM, as humic and fulvic acids in NOM are readily ionized by the nitrogen laser. In this study, hydrophobic NOMs (HPO NOMs) from river, reservoir and waste water were characterized by this technique. The effect of analytical variables like concentration, solvent composition and laser energy was investigated. The exact masses of small molecular NOM moieties in the range of 200–1200 m/z were determined in reflectron mode. In addition, spectra of post‐source‐decay experiments in this range showed that some compounds from different natural NOMs had the same fragmental ions. In the large mass range of 1200–15 000 Da, macromolecules and their aggregates were found in HPO NOMs from natural waters. Highly humic HPO exhibited mass peaks larger than 8000 Da. On the other hand, the waste water and reservoir water mainly had relatively smaller molecules of about 2000 Da. The LDI‐MS measurements indicated that highly humic river waters were able to form large aggregates and membrane foulants, while the HPO NOMs from waste water and reservoir water were unlikely to form large aggregates. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
Glorius F Altenhoff G Goddard R Lehmann C 《Chemical communications (Cambridge, England)》2002,(22):2704-2705
Enantiomerically pure imidazolium triflates can be readily prepared from bioxazolines and oxazolineimines; deprotonation of imidazolium triflate 2 gives a chiral N-heterocyclic carbene that can act as a ligand in a catalytically active palladium complex. 相似文献
6.
R. A. Ritchie D. W. von Oertzen N. J. Davidson R. M. Quick H. G. Miller 《Zeitschrift fur Physik C Particles and Fields》1992,55(2):347-351
Hadron gas models have proved successful in predicting particle production in relativistic nucleus-nucleus collisions. The extension of these models to the smaller systems formed in proton-nucleus collisions requires that the finite size of the system be considered. We study two features introduced by the finite size: the need to conserve strangeness and baryon number exactly by performing calculations in the canonical ensemble, and the inclusion of a finite size geometrical correction term in the single particle density of states. We find significant differences between the grand canonical and canonical ensembles and a strong dependence on the baryon number of the system. 相似文献
7.
Characteristic data of the frequency-modulated simultaneous multielement atomic absorption spectrometry (FREMSAAS) using electrothermal atomizer with deuterium background correction, have been determined. The data obtained have been processed by using several statistical tests recommended for quality control purposes. The instrumentation has been presented as well as procedures of separating elements into measure groups and fixing of variable conditions. Detection limits, characteristic masses and working ranges have been given for the eleven elements examined. The data have been in good agreement to results obtained with conventional one-channel AAS instruments. The eleven elements have been simultaneously determined in a standard reference material (SRM) and all results are compatible with a 95% certainty with the certified values. FREMSAAS has been applied to a real sample.Dedicated to Professor Dr. Dieter-Klockow on the occasion of his 60th birthday 相似文献
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10.
Scanning optical coherence tomography (OCT) is limited in sensitivity and resolution by the restricted focal depth of the confocal detection scheme. Holoscopy, a combination of holography and Fourier-domain full-field OCT, is proposed as a way to detect photons from all depths of a sample volume simultaneously with uniform sensitivity and lateral resolution, even at high NAs. By using the scalar diffraction theory, as frequently applied in digital holographic imaging, we fully reconstruct the object field with depth-invariant imaging quality. In vivo imaging of human skin is demonstrated with an image quality comparable to conventionally scanned OCT. 相似文献