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751.
Henrik v. Wachenfeldt Philipp Röse Filip Paulsen Dr. Nagarajan Loganathan Dr. Daniel Strand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7982-7988
Multicomponent reactions are attractive for assembling functionalized heterocyclic compounds. To this end, an efficient gold‐catalyzed three‐component domino reaction to form oxazoles directly from imines, alkynes, and acid chlorides is presented. The reaction proceeds in a single synthetic step by using a gold(III)–N,N′‐ethylenebis(salicylimine) (salen) catalyst to give trisubstituted oxazoles in up to 96 % yield. The substrate scope, a mechanistic study exploring the role of the gold catalyst, and the synthetic applications of the oxazole products are discussed. 相似文献
752.
Reported is the synthesis of azo mutual prodrugs of the nonsteroidal anti-inflammatory agents (NSAIDs) 4-aminophenylacetic acid (4-APAA) or 5-aminosalicylic acid (5-ASA) with peptides, including an antibiotic peptide temporin analogue modified at the amino terminal by an α-aminoisobutyric acid (Aib) residue. These prodrugs are designed for colonic delivery of two agents to treat infection and inflammation by the bacterial pathogen Clostridium difficile . 相似文献
753.
Florent M Kaminker I Nagarajan V Goldfarb D 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,210(2):192-199
Nitroxide spin probe electron paramagnetic resonance (EPR) has proven to be a very successful method to probe local polarity and solvent hydrogen bonding properties at the molecular level. The g(xx) and the (14)N hyperfine A(zz) principal values are the EPR parameters of the nitroxide spin probe that are sensitive to these properties and are therefore monitored experimentally. Recently, the (14)N quadrupole interaction of nitroxides has been shown to be also highly sensitive to polarity and H-bonding (A. Savitsky et al., J. Phys. Chem. B 112 (2008) 9079). High-field electron spin echo envelope modulation (ESEEM) was used successfully to determine the P(xx) and P(yy) principal components of the (14)N quadrupole tensor. The P(zz) value was calculated from the traceless character of the quadrupole tensor. We introduce here high-field (W-band, 95 GHz, 3.5 T) electron-electron double resonance (ELDOR)-detected NMR as a method to obtain the (14)N P(zz) value directly, together with A(zz). This is complemented by W-band hyperfine sublevel correlation (HYSCORE) measurements carried out along the g(xx) direction to determine the principal P(xx) and P(yy) components. Through measurements of TEMPOL dissolved in solvents of different polarities, we show that A(zz) increases, while |P(zz)| decreases with polarity, as predicted by Savitsky et al. 相似文献
754.
A. R Choudhury K. Nagarajan T. N. Guru Row 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o644-o647
The crystal structures of 1‐(4‐fluorophenyl)‐2‐phenyl‐4,5,6,7‐tetrahydro‐1H‐indole, C20H18FN, and 1‐(4‐fluorophenyl)‐6,6‐dimethyl‐2‐phenyl‐4,5,6,7‐tetrahydro‐1H‐indole, C22H22FN, have been determined in order to study the role of `organic fluorine' in crystal engineering. These molecules pack in the crystal structure via different types of molecular motifs utilizing weak C—H⋯F and C—H⋯π interactions. 相似文献
755.
Nagarajan Vembu Maruthai Nallu Semih Durmus Matthew Panzner Jered Garrison Wiley J. Youngs 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(4):o248-o251
The structures of the title compounds, C12H8N2O7S and C12H8ClNO5S, contain weak C—H⋯O interactions creating layers of molecules which, taking the conformation of the molecules into account, are arranged in an ABAB sequence. Both structures can be designated, therefore, as ordered racemates of rotameric species. 相似文献
756.
Using the density functional theory (DFT) method, the electronic and mechanical properties of perovskites FeBO3 (B = Ti, Mn, Cr) nanostructures were studied in the pressure range of 0–100 GPa. The band structure studies show the change in the band structure upon substitution of different B cation in FeBO3 perovskite structure. The density of states spectrum gives the perception of change in the electronic properties of FeBO3 with the substitution of B cation. The bulk, shear and Young's moduli were calculated and an increase in the moduli is noticed. Moreover, the hardness increases under high pressure. The high-pressure studies of FeBO3 perovskite nanostructures are explored at atomistic level. The findings show that ductility and hardness of FeBO3 get increased upon an increase in the applied pressure. The substitution of Ti, Mn and Cr on FeBO3 shows a significant change in the electronic and mechanical properties. 相似文献
757.
Soundappan Nagarajan Kalathur Sabdham Vangepuram Srinivasan 《Macromolecular rapid communications》1996,17(4):261-267
Novel block copolymers of poly(ethylene glycol) (PEG) with acrylamide (AAm) and methacrylic acid (MAA) were synthesized using a redox system consisting of ceric ions and PEG in aqueous acidic medium. The molecular weight of PEG in the redox system was varied to obtain a series of block copolymers with differing molecular weights of PEG segment. The polymerization proceeded via macroradical generation, which was substantiated by ESR spectroscopy. This macroradical acted as a redox macroinitiator for the block copolymerization of the vinyl monomers. The formation of the block copolymers was confirmed by fractional precipitation technique. 相似文献
758.
759.
Dr. Tulasi Prapakaran Dr. C. I. Sathish Prof. Jiabao Yi Prof. Ajayan Vinu Prof. Ramaswamy Murugavel 《欧洲无机化学杂志》2023,26(17):e202300071
Starting from sterically encumbered 2,6-di-tert-butylphenyl phosphate (dtbppH2) and co-ligand 3,5-dimethyl pyrazole (dmpz), it is possible to isolate either mono-, di- or tetranuclear copper phosphates by varying the copper source and making attendant changes in the reaction conditions. For example, reaction of copper nitrate with dtbppH2 and dmpz at 60 °C leads to the isolation of the mononuclear copper phosphate [Cu(dtbppH)2(dmpz)(MeOH)2] ( 1 ) as the only product. However, the use of copper acetate in place of copper nitrate and conducting the reaction at the room temperature leads to the formation of both dinuclear [Cu(dtbpp)(dmpz)2]2 ( 2 ) and tetranuclear [Cu2(dtbpp)(dmpz)2(OAc)(MeO)]2 ( 3 ) from the same reaction mixture. Compounds 2 and 3 could be isolated in pure form through fractional crystallization. Copper phosphates 1 – 3 have been characterized by both analytical and spectroscopic methods including EPR and magnetic measurements. The molecular structures of all three compounds were established through single crystal diffraction studies. Dc magnetic measurements indicate antiferromagnetic interactions between the metal centres in all the compounds. 相似文献
760.
Generally well-annealed alkali halide crystals exhibit three lifetime components. τ1 arises due to annihilation with anion and τ2 due to Bloch Ps. The origin of τ3 is not well understood. Positron lifetime and etching techniques have been performed on solid solutions of KCl100−xBrx with mole % of x = 0.0, 15, 30, 37, 50, 70, and 100. The positron lifetime spectra have been analysed to resolve into three components. The positron capture rate K3 for the longest lived component and the dislocation density shows a non-linear variation with composition. The positron capture rate varies linearly with the dislocation density of the samples. The origin of τ3 is identified as due to positronium formation in the dislocations present in the samples. The trapping probability per dislocation has been estimated to be 2.2 × 10−12/s. 相似文献