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41.
Jens Rudlof Niklas Aders Dr. Jan-Hendrik Lamm Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Norbert W. Mitzel 《ChemistryOpen》2021,10(10):1020-1027
Starting from 1,2-diethynylbenzene, a series of bidentate Lewis acids was prepared by means of hydrometalations, in particular hydrosilylation, hydroboration, hydroalumination and terminal metalation based on group 13 and 14 elements. In the case of terminal alkyne metalation, the Lewis-acidic gallium function was introduced using triethylgallium under alkane elimination. A total of six different Lewis acids based on a semiflexible organic scaffold were prepared, bearing −SiClMe2, −SiCl2Me, −SiCl3, −B(C6F5)2, −AlBis2 (Bis=bis(trimethylsilyl)methyl) and −GaEt2 as the corresponding functional units. In all cases, the Lewis acid functionalisation was carried out twice and the products were obtained in good to excellent yields. In the case of the twofold gallium Lewis acid, a different structural motif in the form of a polymer-like chain was observed in the solid state. All new bidentate Lewis acids were characterised by multinuclear NMR spectroscopy, CHN analysis and X-ray diffraction experiments. 相似文献
42.
In this study, microcapsules were prepared by solvent evaporation technique using ethyl cellulose component as wall and essential oil as core material. The synthesis of microcapsules was carried out using different oil masses. The analysis of the microcapsules was carried out using field emission scanning electron microscope (FE-SEM) and UV spectrophotometric analysis using absorption spectrophotometer. The obtained results confirm the regular spherical shape and size of the synthesized microcapsules. The qualitative and quantitative spectrophotometric analysis of the microencapsulated immortelle oil was measured at the wavelength of 265 nm. The calibration diagram was used to calculate the unknown concentrations of the microencapsulated oil. The obtained results confirm the application of the presented method as relevant for the possible determination of microencapsulated oil on textile materials. 相似文献
43.
Giraud N Blackledge M Böckmann A Emsley L 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,184(1):51-61
The effect of nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion. 相似文献
44.
Xianwen Lou Sandra M. C. Schoenmakers Joost L. J. van Dongen Miguel Garcia-Iglesias Nicolás M. Casellas Marcos Fernández-Castaño Romera Rint P. Sijbesma E. W. Meijer Anja R. A. Palmans 《Journal of polymer science. Part A, Polymer chemistry》2021,59(12):1151-1161
A comprehensive understanding of the structure, self-assembly mechanism, and dynamics of one-dimensional supramolecular polymers in water is essential for their application as biomaterials. Although a plethora of techniques are available to study the first two properties, there is a paucity in possibilities to study dynamic exchange of monomers between supramolecular polymers in solution. We recently introduced hydrogen/deuterium exchange mass spectrometry (HDX-MS) to characterize the dynamic nature of synthetic supramolecular polymers with only a minimal perturbation of the chemical structure. To further expand the application of this powerful technique some essential experimental aspects have been reaffirmed and the technique has been applied to a diverse library of assemblies. HDX-MS is widely applicable if there are exchangeable hydrogen atoms protected from direct contact with the solvent and if the monomer concentration is sufficiently high to ensure the presence of supramolecular polymers during dilution. In addition, we demonstrate that the kinetic behavior as probed by HDX-MS is influenced by the internal order within the supramolecular polymers and by the self-assembly mechanism. 相似文献
45.
Dr. Dennis Rottschäfer Beate Neumann Dr. Hans-Georg Stammler Dr. Tetiana Sergeieva Dr. Diego M. Andrada Dr. Rajendra S. Ghadwal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(9):3055-3064
Herein, we report the first 1,4-diphosphinine-1,4-diide compound [(ADCPh)P]2 ( 5-Ph ) (ADCPh=PhC{(NDipp)C}2; Dipp=2,6-iPr2C6H3) derived from an anionic dicarbene (ADCPh) as a red crystalline solid. Compound 5-Ph containing a 16π-electron planar fused-tricyclic ring system was obtained by the 4e reduction of [(ADCPh)PCl2]2 ( 4-Ph ) with Mg (or KC8) in a quantitative yield. Experimental and computational results imply that the central 8π-electrons C4P2 ring of 5-Ph , which is fused between two 6π-electrons C3N2 aromatic rings, is antiaromatic. Thus, each of the phosphorus atoms of 5-Ph has two electron-lone-pairs, one in a p-type orbital is in conjugation with the C=C bonds of the C4P2 ring, while the second resides in a σ-symmetric orbital. This can be shown with the gold complex [(ADCPh)P(AuCl)2]2 ( 6-Ph ) obtained by reacting 5-Ph with (Me2S)AuCl. A mixture of 5-Ph and 4-Ph undergoes comproportionation in the presence of MgCl2 to form the intermediate oxidation state compound [(ADCAr)P]2(MgCl4) ( 7-Ph ), which is an aromatic species. 相似文献
46.
Natalia Tiessen Dr. Nico Schwarze Mira Keßler Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Berthold Hoge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(43):11041-11044
While alkyl-substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C2F5)3]−, which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron-withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C2F5)3O]−. In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C2F5)3OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C2F5)3SiOSi(C2F5)3. Deprotonation of Si(C2F5)3OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C2F5)3O}2]2−, implies Lewis amphoteric character of the monomeric [Si(C2F5)3O]− anion. 相似文献
47.
Harry Biller Swantje Lerch Katharina Tölke Dr. Hans-Georg Stammler Prof. Dr. Berthold Hoge Prof. Dr. Thomas Strassner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(53):13325-13329
We synthesized new imidazolium-based tunable aryl alkyl ionic liquids (TAAILs) with the weakly coordinating tetrakis(pentafluoroethyl)gallate anion, [Ga(C2F5)4]−. Phenyl and phenyl derivatives (2-Me, 4-OMe, 2,4-F) were combined with varying alkyl chain lengths at the imidazolium core leading to TAAILs, which were investigated with regard to their viscosity, conductivity, and electrochemical window and compared to EMIM and BMIM standard cations. Remarkable low viscosities of 29 cP at 25 °C for [BMIM][Ga(C2F5)4] were achieved. However, the EMIM and BMIM gallates show electrochemical instability, releasing pentafluoroethane at a voltage of 1.5 V. The 2-Me-substituted gallate-TAAILs slowly decompose over several weeks, whereas all other gallate-TAAILs showed no decomposition at all. With electrochemical windows of up to 5.15 V and low viscosities in a range of 66–162 cP, the gallate-TAAILs are promising candidates as electrolytes in electrochemical applications. 相似文献
48.
Mechanism of Host–Guest Complex Formation and Identification of Intermediates through NMR Titration and Diffusion NMR Spectroscopy
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M. Sc. Jan‐Hendrik Lamm B. Sc. Philipp Niermeier Dr. Andreas Mix Dr. Jasmin Chmiel Beate Neumann Dr. Hans‐Georg Stammler Prof. Dr. Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2014,53(30):7938-7942
The formation of host–guest (H‐G) complexes between 1,8‐bis[(diethylgallanyl)ethynyl]anthracene (H) and the N‐heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host–guest structures in solution were compared with those of tailor‐made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host–guest species and equilibria. With increasing concentrations of the pyridine guest, the equilibrium H2?H2κ1‐G1?HG2 is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H2→H1κ2‐G1?HG2 is observed (the formation of a 1:1 aggregate is the second step). 相似文献
49.
50.
Anja Müller Katia Sparnacci Wolfgang E.S. Unger Sven Tougaard 《Surface and interface analysis : SIA》2020,52(11):770-777
Most real core-shell nanoparticle (CSNP) samples deviate from an ideal core-shell structure potentially having significant impact on the particle properties. An ideal structure displays a spherical core fully encapsulated by a shell of homogeneous thickness, and all particles in the sample exhibit the same shell thickness. Therefore, analytical techniques are required that can identify and characterize such deviations. This study demonstrates that by analysis of the inelastic background in X-ray photoelectron spectroscopy (XPS) survey spectra, the following types of deviations can be identified and quantified: the nonuniformity of the shell thickness within a nanoparticle sample and the incomplete encapsulation of the cores by the shell material. Furthermore, CSNP shell thicknesses and relative coverages can be obtained. These results allow for a quick and straightforward comparison between several batches of a specific CSNP, different coating approaches, and so forth. The presented XPS methodology requires a submonolayer distribution of CSNPs on a substrate. Poly(tetrafluoroethylene)-poly(methyl methacrylate) and poly(tetrafluoroethylene)-polystyrene polymer CSNPs serve as model systems to demonstrate the applicability of the approach. 相似文献