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31.
32.
Bigmore HR Zuideveld MA Kowalczyk RM Cowley AR Kranenburg M McInnes EJ Mountford P 《Inorganic chemistry》2006,45(16):6411-6423
One-pot reactions of V(NMe2)4 with a range of primary alkyl- and arylamines RNH2 and Me3SiCl afforded the corresponding five-coordinate vanadium(4+) imido compounds V(NR)Cl2(NHMe2)2 [R = 2,6-C6H3(i)Pr2 (1a, previously reported), 2-C6H4(t)Bu (1b), 2-C6H4CF3 (1c), (t)Bu (1d), Ad (Ad = adamantyl, 1e)]. The crystal structures of 1b (two diamorphic forms) and 1c featured N-H...Cl hydrogen-bonded chains. Reaction of 1a-e with the neutral face-capping, N3 donor ligands TACN (TACN = 1,4,7-trimethyltriazacyclononane) or TPM [TPM = tris(3,5-dimethylpyrazolyl)methane] gave the corresponding six-coordinate complexes V(NR)(TACN)Cl2 (2a-e) and V(NR)(TPM)Cl2 (3a-e). The X-ray structures of 2b, 2c, 2d, 3b, 3c, and 3e were determined. When activated with methylaluminoxane, certain of the complexes V(NR)(TPM)Cl2 (3) formed moderately active ethylene polymerization catalysts, whereas none of the compounds V(NR)(TACN)Cl2 (2) were active. 相似文献
33.
Dialkyl [2-hydroxy-5-(phenylazo)benzyl]phosphonates were prepared by a convenient procedure in good yield from Mannich base and trialkyl phosphite in benzene with the elimination of ammonium or morpholinium cation. 2-[(Dialkylamino)methyl]-4-(phenylazo)phenol methiodide is a new reagent in the Michaelis-Arbuzov reaction. 相似文献
34.
A short-term aerobic stabilization of digested waste in the final methane phase was studied. The effect of aeration rate on the reduction of leachate parameters and on the rate of CO2 production and O2 assimilation was investigated. Experimental simulation of aerobic landfill stabilization was carried out using lysimeters. When testing the effect of aeration rate on the reduction of leachate indices (BOD5, COD, N-NH4+), it was reported that the most significant reduction was obtained at the highest rate of aeration and the smallest reduction of leachate indices was attained not at the lowest but at medium aeration rates. Both the rate of CO2 production and the O2 assimilation reached their highest values in the lysimeters aerated at a high rate of aeration. The proposed mathematical model which consists of a system of five differential equations describing CO2 production, O2 assimilation and the changes of organic carbon content in the leachate correspond well with the experimental data. 相似文献
35.
Agnieszka Lacz Barbara Bak Radoslaw Lach 《Journal of Thermal Analysis and Calorimetry》2018,133(1):107-114
Nb-doped BaWO4 with the assumed formula BaW1?xNbxO4?δ (x = 0, 0.005, 0.01, 0.02 and 0.05) were prepared by solid-state reaction method. Crystal structure and phase composition were determined by X-ray diffraction method. Scanning electron microscopy (SEM) coupled with energy-dispersive spectrometry (EDS) was used to describe microstructure and chemical composition of synthesised materials. It was found that solubility limit of niobium in the BaWO4 structure is the range 0.5–1 mol%, as formation of second phase—Ba5Nb4O15—was observed for samples with higher dopant content. For evaluation of the chemical stability of synthesized materials, the comparative CO2/H2O exposure test was performed. Samples were exposed to carbon dioxide- and water vapour-rich atmosphere (7% CO2 in air, 100% RH) at 298 K for 700 h. During this exposition, the chemical reactions between the samples and the surrounding gaseous atmosphere resulting in formation of barium hydroxide and/or barium carbonate can process. Thermogravimetry (TG) method was used for chemical stability evaluation. The comparison of samples before and after the CO2/H2O exposure test was performed. To support the interpretation of TG results, the analysis of gaseous products evolved during thermal treatment of the samples was done using mass spectrometer. The effect of dopant on the BaWO4 chemical stability improvement was observed. In order to determine the electrical properties of obtained materials, the DC resistance measurements in synthetic air atmosphere were taken. It was shown that niobium doping and the presence of second phase—Ba5Nb4O15—leads to an increase in the total conductivity of synthesised materials. 相似文献
36.
Multiple Binding Sites Contribute to the Mechanism of Mixed Agonistic and Positive Allosteric Modulators of the Cannabinoid CB1 Receptor 下载免费PDF全文
Dr. Noureldin Saleh Dr. Oliver Hucke Gert Kramer Esther Schmidt Dr. Florian Montel Dr. Radoslaw Lipinski Prof. Dr. Boris Ferger Prof. Dr. Timothy Clark Prof. Dr. Peter W. Hildebrand Dr. Christofer S. Tautermann 《Angewandte Chemie (International ed. in English)》2018,57(10):2580-2585
The cannabinoid CB1 receptor (CB1R) is an abundant metabotropic G‐protein‐coupled receptor that has been difficult to address therapeutically because of CNS side effects exerted by orthosteric drug candidates. Recent efforts have focused on developing allosteric modulators that target CB1R. Compounds from the recently discovered class of mixed agonistic and positive allosteric modulators (Ago‐PAMs) based on 2‐phenylindoles have shown promising functional and binding properties as CB1R ligands. Here, we identify binding modes of both the CP 55,940 agonist and GAT228, a 2‐phenylindole allosteric modulator, by using our metadynamics simulation protocol, and quantify their affinity and cooperativity by atomistic simulations. We demonstrate the involvement of multiple adjunct binding sites in the Ago‐PAM characteristics of the 2‐phenylindole modulators and explain their ability to compete with orthosteric agonists at higher concentrations. We validate these results experimentally by showing the contribution of multiple sites on the allosteric binding of ZCZ011, another homologous member of the class, together with the orthosteric agonist. 相似文献
37.
Kowalczyk RM Schleicher E Bittl R Weber S 《Journal of the American Chemical Society》2004,126(36):11393-11399
The photogenerated triplet states of riboflavin and flavin mononucleotide (FMN) have been examined by time-resolved electron paramagnetic resonance (EPR) spectroscopy at low temperature (T = 80 K). Because of the high time resolution of the utilized EPR instrumentation, the triplets are for the first time observed in the nonequilibrated electron-spin polarized state and not in their equilibrated forms with the population of the triplet sublevels governed by Boltzmann distribution. The electron-spin polarization pattern directly reflects the anisotropy of the intersystem crossing from the excited singlet-state precursor. Spectral analysis of the resulting enhanced absorptive and emissive EPR signals yields the zero-field splitting parameters, |D| and |E|, and the zero-field populations of the triplet at high accuracy. These parameters are sensitive probes for the protonation state of the flavin's isoalloxazine ring, as becomes evident by a comparison of the spectra recorded at different pH values of the solvent. The three protonation states of the flavins can furthermore be distinguished by the kinetics of the transient EPR signals, which are dominated by spin-lattice relaxation. The fastest decays are observed for the protonated FMN and riboflavin triplets, followed by the deprotonated flavin triplets. Slow decays are measured for the triplet states of neutral FMN and riboflavin. Because proton transfer is found to be slow on the time scale of spin-polarized triplet detection by transient EPR, the pH-dependent spin-relaxation and zero-field splitting parameters offer a novel approach to probe the protonation state of flavins in their singlet ground state through the characterization of their triplet-state properties. 相似文献
38.
The investigation of the intermolecular composition distribution of an ethylene/1-hexene copolymers using DSC method has been
carried out. The known methods: step crystallization (SC) and successive self-nucleation/annealing (SSA) have been adapted
for this purpose, and particularly, the optimal condition of the process have been chosen to enable the best fractional crystallization
of the copolymer. The method has been applied for fractionation of two ethylene/1-hexenecopolymers synthesized with supported
vanadium and zirconocene catalysts and having similar concentrations of 1-hexene. Although metallocene catalysts are known
from their more homogeneous structure of active sites in comparison to multi-site Ziegler–Natta catalysts, the copolymers
obtained over both catalytic systems gave DSC curves resolved into several peaks but with different melting points. Using
the Thomson–Gibbs equation, comparable average lamellar thickness of the separated peaks has been calculated. The amounts
of copolymer fraction with defined lamellar thickness have been determined. It was obtained that the copolymer produced from
the metallocene system contains a thinner and more homogeneous lamella thickness than that obtained with Ziegler–Natta vanadium
catalyst supported on the same carrier.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
39.