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991.
Christophe Chendo Dao Le Trang N. T. Phan Didier Gigmes Laurence Charles 《Journal of polymer science. Part A, Polymer chemistry》2016,54(20):3388-3397
An analytical workflow involving high resolution mass analysis, collision‐induced dissociation and ion mobility was implemented to structurally characterize polymeric by‐products detected in lieu of intact species when performing matrix‐assisted laser desorption/ionization (MALDI) of polystyrenes with fragile end groups. Studied samples were prepared by atom transfer radical polymerization, reversible addition–fragmentation transfer polymerization and nitroxide‐mediated polymerization. Spectral resolution enabled by orthogonal injection of MALDI ions into a reflectron time‐of‐flight mass analyzer allowed a thorough inventory of species, including some with the same nominal m/z value but different elemental composition. Individual end‐group mass determination was achieved in MS/MS experiments, implementing an additional separative dimension based on ion mobility prior to CID to assist precursor ion selection in case of interferences. Besides validating commonly reported polystyrene chains terminated with either endo‐ or exo‐double bond, this multidimensional approach permitted to show that initiating moiety could also be affected by the MALDI process. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3388–3397 相似文献
992.
993.
Mitsuhiko Miyazaki Ryuhei Ohara Kota Daigoku Kenro Hashimoto Jonathan R. Woodward Claude Dedonder Christophe Jouvet Masaaki Fujii 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(50):15304-15308
Hydrogen‐release by photoexcitation, excited‐state‐hydrogen‐transfer (ESHT), is one of the important photochemical processes that occur in aromatic acids and is responsible for photoprotection of biomolecules. The mechanism is described by conversion of the initial state to a charge‐separated state along the O(N)‐H bond elongation, leading to dissociation. Thus ESHT is not a simple H‐atom transfer in which a proton and a 1s electron move together. Here we show that the electron‐transfer and the proton‐motion are decoupled in gas‐phase ESHT. We monitor electron and proton transfer independently by picosecond time‐resolved near‐infrared and infrared spectroscopy for isolated phenol–(ammonia)5, a benchmark molecular cluster. Electron transfer from phenol to ammonia occurred in less than 3 picoseconds, while the overall H‐atom transfer took 15 picoseconds. The observed electron‐proton decoupling will allow for a deeper understanding and control of of photochemistry in biomolecules. 相似文献
994.
Cline Taglang Luis Miguel Martínez‐Prieto Iker delRosal Laurent Maron Romuald Poteau Karine Philippot Bruno Chaudret Serge Perato Anaïs SamLone Cline Puente Christophe Dugave Bernard Rousseau Grgory Pieters 《Angewandte Chemie (International ed. in English)》2015,54(36):10474-10477
The activation of C H bonds has revolutionized modern synthetic chemistry. However, no general strategy for enantiospecific C H activation has been developed to date. We herein report an enantiospecific C H activation reaction followed by deuterium incorporation at stereogenic centers. Mechanistic studies suggest that the selectivity for the α‐position of the directing heteroatom results from a four‐membered dimetallacycle as the key intermediate. This work paves the way to novel molecular chemistry on nanoparticles. 相似文献
995.
996.
997.
Comprehensive Two-dimensional Gas Chromatography for Analysis of the Volatile Compounds and Fishy Odor Off-flavors from Heated Rapeseed Oil 总被引:1,自引:0,他引:1
998.
Origin of the Enantioselectivity in Organocatalytic Michael Additions of β‐Ketoamides to α,β‐Unsaturated Carbonyls: A Combined Experimental,Spectroscopic and Theoretical Study 下载免费PDF全文
Dr. Adrien Quintard Dr. Diana Cheshmedzhieva Dr. Maria del Mar Sanchez Duque Dr. Anouk Gaudel‐Siri Dr. Jean‐Valère Naubron Dr. Yves Génisson Dr. Jean‐Christophe Plaquevent Dr. Xavier Bugaut Prof. Jean Rodriguez Prof. Thierry Constantieux 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):778-790
The organocatalytic enantioselective conjugate addition of secondary β‐ketoamides to α,β‐unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto’s thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99 % ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst. 相似文献
999.
A Tris(triazolate) Ligand for a Highly Active and Magnetically Recoverable Palladium Catalyst of Selective Alcohol Oxidation Using Air at Atmospheric Pressure 下载免费PDF全文
Dr. Dong Wang Christophe Deraedt Dr. Lionel Salmon Christine Labrugère Laetitia Etienne Dr. Jaime Ruiz Prof. Didier Astruc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6501-6510
High efficiency and selectivity, easy magnetic recovery and recycling, and use of air as the oxidant at atmospheric pressure are major objectives for oxidation catalysis in terms of sustainable and green processes. A tris(triazolyl) ligand, so far only used in copper‐catalyzed alkyne azide cycloadditions, was found to be extremely efficient in SiO2/γ‐Fe2O3‐immobilized palladium complexes. It was characterized by inductively coupled plasma (ICP) analysis, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy‐dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectra (XPS) and found to fulfill the combined conditions for the selective oxidation of alcohols to aldehydes and ketones. 相似文献
1000.
Evaluation of a combined glycomics and glycoproteomics approach for studying the major glycoproteins present in biofluids: Application to cerebrospinal fluid 下载免费PDF全文