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Reduction of phenyl-substituted pyridinium methoiodides with sodium borohydride in water afforded besides the desired tetrahydropyridines substantial amounts of amine-borane complexes. Reduction in methanol afforded tetrahydropyridines in high yield, with almost no amine-boranes formed. 相似文献
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Elwira Chrobak Ewa Michalik Joachim Kusz Maria Nowak Stanisaw Boryczka 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(9):847-851
The lupane triterpenoid betulonic aldehyde [also known as betulonal; systematic name: lup‐20(29)‐en‐28‐al‐3‐one, C30H46O2] is a product of betulin oxidation. Crystals were obtained from hexane [form (I)] and dimethyl sulfoxide [form (II)] solutions. Forms (I) and (II) are both orthorhombic. The molecular geometric parameters in the two forms are similar, but the structures are different with respect to the crystal packing. Polymorph (I) contains two independent molecules in the asymmetric unit, while polymorph (II) contains only one molecule, which has a disordered aldehyde group [the disorder ratio is 0.769 (4):0.231 (4)]. In each molecule, the six‐membered rings have chair conformations, whereas the cyclopentane ring in each molecule adopts an envelope conformation. All the rings in the lupane nucleus are trans‐fused. The extended structures of both polymorphs are stabilized by weak intermolecular C—H...O and van der Waals interactions. Weak intramolecular C—H...O interactions are also observed. 相似文献
46.
Christoph Peschel Stefan van Wickeren Yves Preibisch Verena Naber Denis Werner Lars Frankenstein Dr. Fabian Horsthemke Prof. Dr. Urs Peuker Prof. Dr. Martin Winter Dr. Sascha Nowak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(22):e202200485
Herein we report on an analytical study of dry-shredded lithium-ion battery (LIB) materials with unknown composition. Samples from an industrial recycling process were analyzed concerning the elemental composition and (organic) compound speciation. Deep understanding of the base material for LIB recycling was obtained by identification and analysis of transition metal stoichiometry, current collector metals, base electrolyte and electrolyte additive residues, aging marker molecules and polymer binder fingerprints. For reversed engineering purposes, the main electrode and electrolyte chemistries were traced back to pristine materials. Furthermore, possible lifetime application and accompanied aging was evaluated based on target analysis on characteristic molecules described in literature. With this, the reported analytics provided precious information for value estimation of the undefined spent batteries and enabled tailored recycling process deliberations. The comprehensive feedstock characterization shown in this work paves the way for targeted process control in LIB recycling processes. 相似文献
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Sebastian Wöllner Timothy Nowak Dr. Gui-Rong Zhang Dr. Nils Rockstroh Dr. Hanadi Ghanem Prof. Dr. Stefan Rosiwal Prof. Dr. Angelika Brückner Prof. Dr. Bastian J. M. Etzold 《ChemistryOpen》2021,10(5):600-606
Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) offers a renewable approach to produce the value-added platform chemical 2,5-furandicarboxylic acid (FDCA). The key for the economic viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a high-performing catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of free-standing Cu-foam, and CuCoO modified with NaPO2H2 and Ni, which were immobilized on boron-doped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed. 相似文献
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Neshev DN Sukhorukov AA Dreischuh A Fischer R Ha S Bolger J Bui L Krolikowski W Eggleton BJ Mitchell A Austin MW Kivshar YS 《Physical review letters》2007,99(12):123901
We present the first observation of spatiospectral control and localization of supercontinuum light through the nonlinear interaction of spectral components in extended periodic structures. We use an array of optical waveguides in a LiNbO3 crystal and employ the interplay between diffraction and nonlinearity to dynamically control the output spectrum of the supercontinuum radiation. This effect presents an efficient scheme for optically tunable spectral filtering of supercontinua. 相似文献
49.
The present Letter demonstrates a pop-in event that is caused by a nanoindentation-induced phase transformation in GaAs, and not accompanied by any dislocation nucleation. Our computer simulations reveal the appearance of the new phase, documented by the structural correlation functions and visualization of the atomic positions. This challenges the orthodox view that the initial pop-in event reflects nucleation of dislocations or their movement, and has a bearing on materials where dislocation activity is not present. 相似文献
50.
Chemical Probing of the Human Sirtuin 5 Active Site Reveals Its Substrate Acyl Specificity and Peptide‐Based Inhibitors
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Claudia Roessler Theresa Nowak Martin Pannek Dr. Melanie Gertz Giang T. T. Nguyen Michael Scharfe Dr. Ilona Born Prof. Dr. Wolfgang Sippl Prof. Dr. Clemens Steegborn Prof. Dr. Mike Schutkowski 《Angewandte Chemie (International ed. in English)》2014,53(40):10728-10732
Sirtuins are NAD+‐dependent deacetylases acting as sensors in metabolic pathways and stress response. In mammals there are seven isoforms. The mitochondrial sirtuin 5 is a weak deacetylase but a very efficient demalonylase and desuccinylase; however, its substrate acyl specificity has not been systematically analyzed. Herein, we investigated a carbamoyl phosphate synthetase 1 derived peptide substrate and modified the lysine side chain systematically to determine the acyl specificity of Sirt5. From that point we designed six potent peptide‐based inhibitors that interact with the NAD+ binding pocket. To characterize the interaction details causing the different substrate and inhibition properties we report several X‐ray crystal structures of Sirt5 complexed with these peptides. Our results reveal the Sirt5 acyl selectivity and its molecular basis and enable the design of inhibitors for Sirt5. 相似文献