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41.
In order to analyse metal complexation with polyfunctional phenolic compounds as ligand models of natural substances, a detailed examination is described for five simple binary complexes and three ternary mixed ligand complexes at 25°C (μ = 0.1 M NaClO4). The ligands are tyrosine, 4,5-dihydroxy-1,3-benzene disulfonic acid, disodium salt (tiron), 3,4-dihydroxycinnamic acid (caffeic acid), 3,4,5-trihydroxy-1 -cyclohexene-1 -carboxylic acid (shikimic acid) and 1,3,4,5-tetrahydroxycyclohexanecarboxylic acid 3-(3,4-dihydroxycinnamate) (chlorogenic acid). The ternary systems are Cu(II)/HqA/tiron, where HqA is tyrosine, caffeic or chlorogenic acids. Potentiometric data were used successively to evaluate the protonation of each individual ligand, to detect simple and mixed complexes (including protonated species) and to determine their stability constants (a set of 33 values of constants with several original data is provided). The calculated distribution (speciation) of each species as a function of pH is indicated. Mixed coordination enhances the stability of complexes and the stabilization is expressed in terms of various parameters. The results emphasize that mixed ligand complex formation is essential to studies of multiple equilibria. 相似文献
42.
Perturbative solution of the RPA equation. An application to the calculation of rotational strengths
The RPA equation is solved by perturbation in Møller-Plesset (MP) and Epstein-Nesbet (EN) partitions, which are first compared on a specific example. To still accelerate the faster one (EN), a third scheme is proposed, which involves preliminary diagonalization within a limited subset
, followed by usual EN perturbation between
and the rest of the whole configuration space. Criteria for the choice of
are given. 相似文献
43.
Roger Azria Yvonnick Le Coat Jean-Pierre Ziesel Jean-Pierre Guillotin Brahim Mharzi Michel Tronc 《Chemical physics letters》1994,220(6):417-422
Absolute kinetic energy distributions and yields associated with ground state 3P and excited state 1D oxygen atoms have been obtained for O− anion electron stimulated desorption from condensed O2 in the electron energy range 6–15 eV. The observed yields are understood as resulting essentially from dissociative electron attachment reactions via the two lowest 2Σ+g O−2 resonance states through adiabatic and non-adiabatic transitions to the limits O−(2P) + O(3P) and O−(2P) + O(1D). The kinetic energy distributions show the prominent role of electron multiple collision processes and post-dissociation interactions of the O− anions in the condensed phase. 相似文献
44.
Zusammenfassung Eine Methode der Identifizierung von Alkyl- und Arylgruppen organischer Sulfide wurde ausgearbeitet, die die Spaltung dieser Stoffe mit Raney-Nickel zur gaschromatographischen Bestimmung der dabei entstandenen Kohlenwasserstoffe ausnützt.
Die Autoren danken den Kollegen Dr.M. Veea, Ing.J. Petránek und Ing.J. Gaspari für die Überlassung von Proben organischer Sulfide. 相似文献
Summary A method was developed for identifying alkyl- and aryl groups of organic sulfides. The method employs the cleavage of these materials with Raney nickel for the gas chromatographic determination of the resulting hydrocarbons.
Résumé On a mis au point une méthode d'identification des groupes alkylés et arylés des sulfures organiques exploitant la dissociation de ceux-ci par le nickel Raney pour le dosage par chromatographic en phase gazeuse des carbures d'hydrogène qui se forment.
Die Autoren danken den Kollegen Dr.M. Veea, Ing.J. Petránek und Ing.J. Gaspari für die Überlassung von Proben organischer Sulfide. 相似文献
45.
Malassene R Vanquelef E Toupet L Hurvois JP Moinet C 《Organic & biomolecular chemistry》2003,1(3):547-551
The anodic cyanation of methanolic solutions of the 2-alkyl-N-phenylpiperidines 6b-d was performed in a flow cell equipped with a graphite felt anode. The reaction led to the formation of the 2-cyano-6-alkyl-N-phenylpiperidines 2b-d and proceeded with a high degree of regioselectivity. The 1H NMR spectra of the aminonitriles 2b-d showed an epimeric mixture at C-6. The major isomer has a trans configuration in which the cyano group is axial and the alkyl substituent is equatorial. Conversely, electrochemical oxidation of the 4-methyl-6-pentyl-N-phenylpiperidine 6e afforded the trisubstituted aminonitrile 2e as a single diastereomer (> 98% de). The 4-cyanobutyl side chain was incorporated in a two-step procedure to yield dinitrile 4e. This latter compound was directly converted into spiropiperidine 5e by using the Thorpe-Ziegler annulation procedure. The overall sequence (4 steps, 43%) allows the construction of the basic carbon framework of perhydrohistrionicotoxin. 相似文献
46.
Muriel Lepère Ghislain Blanquet Jacques Walrand Jean-Pierre Bouanich 《Journal of Molecular Spectroscopy》1996,180(2):218-226
Infrared absolute line intensities of the ν6band of CH3F have been measured around 8.5 μm using a diode-laser spectrometer. These line strengths were obtained by the equivalent width method and, for 13 lines, by fitting a Rautian profile to the measured shape of the lines. From these results, we have deduced the vibrational band strength to beS0v= 9.66 ± 0.13 cm−2atm−1at 296 K and the first Herman–Wallis factors. 相似文献
47.
Delangle P Dutasta JP Van Oostenryck L Tinant B Declercq JP 《The Journal of organic chemistry》1996,61(25):8904-8914
The semirigid phosphonamide ligands 1-5 have been synthesized from the macrocyclic precursors 6-9 by reaction with 1,3-propanediol ditosylate or 1,2-dichloroethane. For the thiophosphoryl compounds 1 and 2, and the phosphoryl derivative 5, the reactions were carried out in biphasic aqueous NaOH solutions. The phosphoryl derivatives 3 and 4 were better obtained from NaH in anhydrous tetrahydrofuran. The conformations of the hosts in solution were deduced from low-temperature NMR and NOE difference experiments. Conformational equilibria between exo and endo forms are observed for the 18-membered macrocycles 1 and 3. The exo conformer predominates in solution for the 21-membered macrocycle 2, whereas 4 exists as rapidly exchanging conformers. The X-ray crystal structures of macrocycles 1, 2, and 5 have been determined as well as the complexes 1.Hg(SCN)(2) and 5.LiNO(3). In the Hg(2+) complex the metal ion is located out of the macrocyclic cavity and is coordinated to the thiophosphoryl unit. In 5.LiNO(3)()()the Li(+) cation is located inside the macrocyclic cavity and is coordinated to a tetrahedral array of oxygen donors. Free energies of complexation (DeltaG degrees ) of the phosphorylated ligands 3-5 with alkali metal and ammonium cations were determined in CHCl(3) saturated with H(2)O by picrate extraction experiments. The -DeltaG degrees values are greatest for 4 complexing K(+) and NH(4)(+) (7.3 and 8.0 kcal/mol, respectively). The relationships between structure and binding are discussed. 相似文献
48.
M. Niaz Khan Jean-Pierre Fleury Philippe Baumlin Christian Hubschwerlen 《Tetrahedron》1985,41(22):5341-5345
Amides or vinylogous amides react with tosyl chloride-pyridine to form activated intermediates which condense with Fischer's base or their vinylogs to give carbocyanine structures. Under the same conditions formylated Fischer's base reacts with vinylogous Fischer's bases to give trinuclear carbocyanines in good yields. Their structure and the limitations of this route are discussed. 相似文献
49.
Meyer F Demeshko S Leibeling G Kersting B Kaifer E Pritzkow H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(5):1518-1526
Pyrazolate-based dinucleating ligands with thioether-containing chelate arms have been used for the synthesis of a family of novel tetranuclear nickel(II) complexes [L2Ni4(N3)3(O2CR)](ClO4)2 that incorporate three azido bridges and one carboxylate (R = Me, Ph). Molecular structures have been elucidated by X-ray crystallography in four cases, revealing Ni4 cores with a unique topology in which two of the azido ligands adopt an unusual mu3-1,1,3 bridging mode. The compounds were further characterized by mass spectrometry, IR spectroscopy, and variable-temperature magnetic susceptibility measurements. Magnetic data analyses indicate a combination of significant intramolecular ferromagnetic and antiferromagnetic exchange interactions that give rise to an overall S(T) = 0 ground state. The sign and the magnitude of the individual couplings have been rationalized in the framework of the common magnetostructural correlations for end-to-end and end-on azido linkages, suggesting that these correlations also remain valid for the respective fragments of multiply bridging mu3-1,1,3 azido ligands. 相似文献
50.
Yolande MespliÉ Michel Bergon Jean-Pierre Calmon 《Journal of heterocyclic chemistry》1984,21(4):985-993
The alkaline hydrolysis of propargyl 3-chlorocarbanilates was investigated kinetically using uv spectropotometry. The cyclization to 4-methoylene-2-oxazolisinones proceeds via the numcleophilic attack of the substrate anion concomitantly with that of the hydroxide ion on the triple bond. The nucleophilic attack leads directly to the heterocycle whereas the hydroxide ion attack gives rise to a ketocarbamate which is then cyclized to the oxazolidione. 相似文献