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941.
Diego Dusso Cristina Ramirez Alejandro Parise P. Lanza D. Mariano Vera Carlos Chesta E. Laura Moyano Novruz G. Akhmedov 《Magnetic resonance in chemistry : MRC》2019,57(7):423-454
A free-catalyst microwave-assisted cyanation of brominated Tröger's base derivatives ( 2a - f ) is reported. The procedure is simple, efficient, and clean affording the nitrile compounds ( 3a - e, I ) in very good yields. Complete assignment of 1H and 13C chemical shifts of 2a - f, I and 3a - d, I was achieved using gradient selected 1D nuclear magnetic resonance (NMR) techniques (1D zTOCSY, PSYCHE, DPFGSE NOE, and DEPT), homonuclear 2D NMR techniques (gCOSY and zTOCSY), and heteronuclear 2D NMR techniques (gHSQCAD/or pure-shift gHSQCAD, gHMBCAD, bsHSQCNOESY, and gHSQCAD-TOCSY) with adiabatic pulses. Determination of the long-range proton–proton coupling constants nJHH (n = 4, 5, 6) was accomplished by simultaneous irradiation of two protons at appropriate power levels. In turn, determined coupling constants were tested by an iterative simulation program by calculating the 1H NMR spectrum and comparing it to the experimental spectrum. The excitation-sculptured indirect-detection experiment (EXSIDE) and 1H-15N CIGARAD-HMBC (constant time inverse-detection gradient accordion rescaled heteronuclear multiple bond correlation) were applied for determination of long-range carbon–proton coupling constants nJCH (n = 2, 3, and 4) and for assignment of 15N chemical shift at natural abundance, respectively. DFT/B3LYP optimization studies were performed in order to determine the geometry of 2c using 6-31G(d,p), 6-311G(d,p), and 6–311 + G(d,p) basis sets. For calculation of 1H and 13C chemical shifts, nJHH (n = 2, 3, 4, 5, and 6), and nJCH (n = 1, 2, 3, and 4) coupling constants, the GIAO method was employed at the B3LYP/6-31G(d,p), B3LYP/6-31+G(d,p), B3LYP/6-311+G(d,p), B3LYP/6-311++G(2d,2p), B3LYP/cc-pVTZ), and B3LYP/aug-cc-pVTZ) levels of theory. For the first time, a stereochemical dependence magnitude of the long-range nJHH (n = 4, 5, and 6) and nJCH (n = 1, 2, 3, 4, and 5) have been found in bromo-substituted analogues of Tröger's bases. 相似文献
942.
Garín Carolina León Alejandro Pacheco Mónica Riveros Gonzalo 《Journal of Solid State Electrochemistry》2019,23(11):3099-3106
Journal of Solid State Electrochemistry - This work presents a theoretical-experimental study on electronic transfer mechanism on crystal silicon surface modified with redox molecules derived from... 相似文献
943.
Dr. Rossella Greco Estefania Tiburcio-Fortes Dr. Antonio Fernandez Dr. Carlo Marini Dr. Alejandro Vidal-Moya Dr. Judit Oliver-Meseguer Prof. Donatella Armentano Prof. Emilio Pardo Dr. Jesús Ferrando-Soria Dr. Antonio Leyva-Pérez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202103781
Extremely high electrophilic metal complexes, composed by a metal cation and very electron poor σ-donor ancillary ligands, are expected to be privileged catalysts for oxidation reactions in organic chemistry. However, their low lifetime prevents any use in catalysis. Here we show the synthesis of fluorinated pyridine-Pd2+ coordinate cages within the channels of an anionic tridimensional metal-organic framework (MOF), and their use as efficient metal catalysts for the aerobic oxidation of aliphatic alcohols to carboxylic acids without any additive. Mechanistic studies strongly support that the MOF-stabilized coordination cage with perfluorinated ligands unleashes the full electrophilic potential of Pd2+ to dehydrogenate primary alcohols, without any base, and also to activate O2 for the radical oxidation to the aldehyde intermediate. This study opens the door to design catalytic perfluorinated complexes for challenging organic transformations, where an extremely high electrophilic metal site is required. 相似文献
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Luis Leyva-Parra Luz Diego Diego Inostroza Dr. Osvaldo Yañez Rodolfo Pumachagua-Huertas Dr. Jorge Barroso Dr. Alejandro Vásquez-Espinal Prof. Gabriel Merino Prof. William Tiznado 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(67):16701-16706
After exploring the potential energy surfaces of MmCE2p (E=S−Te, M=Li−Cs, m=2, 3 and p=m-2) and MnCE3q (E=S−Te, M=Li−Cs, n=1, 2, q=n-2) combinations, we introduce 38 new global minima containing a planar hypercoordinate carbon atom (24 with a planar tetracoordinate carbon and 14 with a planar pentacoordinate carbon). These exotic clusters result from the decoration of V-shaped CE22− and Y-shaped CE32− dianions, respectively, with alkali counterions. All these 38 systems fulfill the geometrical and electronic criteria to be considered as true planar hypercoordinate carbon systems. Chemical bonding analyses indicate that carbon is covalently bonded to chalcogens and ionically connected to alkali metals. 相似文献
946.
Dr. Alejandro Criado Dr. Michele Melchionna Dr. Silvia Marchesan Prof. Maurizio Prato 《Angewandte Chemie (International ed. in English)》2015,54(37):10734-10750
The utilization of grown or deposited graphene on solid substrates offers key benefits for functionalization processes, but especially to attain structures with a high level of control for electronics and “smart” materials. In this review, we will initially focus on the nature and properties of graphene on substrates, based on the method of preparation. We will then analyze the most relevant literature on the functionalization of graphene on substrates. In particular, we will comparatively discuss radical reactions, cycloadditions, halogenations, hydrogenations, and oxidations. We will especially address the question of how the reactivity of graphene is affected by its morphology (i.e., number of layers, defects, substrate, curvature, etc.). 相似文献
947.
Alejandro V. Funes Dr. Luca Carrella Prof. Dr. Eva Rentschler Prof. Dr. Pablo Alborés 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14308-14318
We have prepared and structurally characterized a new member of the butterfly‐like {CoIII2DyIII2} single‐molecule magnets (SMMs) through further CoIII decoration, with the formula [CoIII4DyIII2(OH)2(teaH)2(tea)2(Piv)6] (teaH3=triethanolamine; Piv=trimethylacetate or pivalate). Direct current (DC) susceptibility and magnetization measurements were performed allowing the extraction of possible crystal‐field parameters. A simple electrostatic modeling shows reasonable agreement with experimental data. Alternating current (AC) susceptibility measurements under a zero DC field and under small applied fields were performed at different frequencies (i.e., 10–1500 Hz) and at low temperatures (i.e., 2–10 K). Multiple magnetization relaxation pathways are observed. Comparison with previously reported {CoIII2DyIII2} complex measurements allows an overall discussion about the origin of the dynamic behavior and its relationship with crystal‐field split ground multiplet sublevels. 相似文献
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