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11.
To investigate the influence of the anisotropic part of the potential, exact quantum mechanical calculations have been performed of the differential co 相似文献
12.
Regioselectivite de la reaction des dialkyl cuprates de magnesium sur des aldehydes α,β-ethyleniques
Monique Bourgain-Commerçon Jean-Pierre Foulon Jean François Normant 《Journal of organometallic chemistry》1982,228(3):321-326
Various magnesium organocuprates give conjugative addition products with α,β-ethylenic aldehydes, and even with acrolein. The enolates may be trapped with bromine or trimethylsilyl chloride. 相似文献
13.
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
14.
Rudolph Willem Ann Delmotte Inge De Borger Monique Biesemans Marcel Gielen Franois Kayser Edward R. T. Tiekink 《Journal of organometallic chemistry》1994,480(1-2):255-259
The synthesis of (Z)-2-methyl-3-triphenylstannyl-3-pentene-2-ol and its characterization by an X-ray diffraction study and multinuclear NMR are reported. The tin atom exhibits a distorted tetrahedral SnC4 geometry with the four Sn---C bond distances experimentally equivalent. The slight distortion from the ideal tetrahedral geometry is because of the presence of a weak intramolecular HO → Sn interaction of 3.012(3) Å which produces a loose four-membered ring. The title compound was characterized in solution by 1H, 13C and 119Sn NMR, and the persistence of the weak intramolecular HO → Sn coordination in solution was revealed by 13C and 119Sn secondary isotope multiplet of partially labelled entities (SIMPLE-NMR) experiments. 相似文献
15.
Fangzin Fu Hongyu Li Dongsheng Zhu Qunxin Fang Huade Pan Edward R. T. Tiekink Franois Kayser Monique Biesemans Ingrid Verbruggen Rudolph Willem Marcel Gielen 《Journal of organometallic chemistry》1995,490(1-2):163-171
The synthesis and characterization by 1H, 13C, 119Sn NMR and 119Sn Mössbauer spectroscopy of (Z)-1-[2-(triphenylstannyl)vinyl]-1-cycloheptanol,
(1), and (Z)-1-[2-tri-p-tolylstannyl)vinyl-1-cycloheptanol,
(2), are described, together with their halodemetallation by I2, Br2 and ICIl to yield derivatives of the types
(Ar = phenyl or p-tolyl, N = 1, 2; X = I, Br, Cl, respectively). The solid-state structures of four compounds have been determined by X-ray diffraction analysis. In the crystals of
(1) and
(2) the Sn atom has a tetrahedral geometry distorted towards trigonal bipyramid as a consequence of a close intramolecular contact with the hydroxyl O(1) atom of 2.742(3) Å and 2.768(3) Å, respectively. A trigonal bipyramidal geometry is found in
(12) and
(4), in which significant Sn---O(1) interactions are noted [2.437(8) Å and 2.407(8) Å, respectively]. 相似文献
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16.
In order to identify possible signatures of the most typical structures adopted by guanine-rich oligonucleotides, we submitted them to the crossed fire of circular dichroism (CD) and electrophoresis. These signatures show up in the circular dichroism spectra even when simultaneously present within the same molecule. Guanine-rich oligonucleotides, when structured, manifest themselves by CD contributions around 260 or 295 nm. For instance, positive bands at 264 nm and 295 nm, respectively, signal the parallel and antiparallel guanine quartets, while a positive band around 261 nm may indicate the presence of a (parallel?) Hoogsteen duplex. A positive band at 264 nm may also reflect the presence of rigidly and unusually oriented GpT and TpG steps within loops. The signatures are additive with those of other structural features of the same molecule, such as hairpins or Watson-Crick duplexes, whose bands are observed at 280 nm. 相似文献
17.
den Brok MW Nuijen B Miranda E Floriano P Munt S Manzanares I Beijnen JH 《Journal of chromatography. A》2003,1020(2):251-258
ES-285 x HCl [(2S,3R)-2-amino-3-octadecanol hydrochloride] is a novel investigational anticancer agent, which has shown in vitro and in vivo cytotoxic activity against various tumor cell lines with selectivity for certain solid tumors. The pharmaceutical development of ES-285 x HCl warranted the availability of an assay for the quantification and purity determination of ES-285 x HCl active pharmaceutical ingredient (API) and its pharmaceutical dosage form. A liquid chromatographic method (LC) comprising of derivatisation of ES-285 x HCl with phenylisothiocyanate and UV-detection was developed. The method was found to be linear, precise and accurate. The assay also proved selectivity as determined by analysing ES-285 x HCl in combination with 15 analogues and in combination with hydroxypropyl-beta-cyclodextrin, the excipient used in the lyophilised pharmaceutical dosage form. Stress testing showed that the degradation products were separated from the parent compound, confirming its stability indicating capacity. The method was found robust as determined with design of experiments (DoE), which made it possible to predict system suitability responses in worst case experimental conditions and to define criteria for system suitability testing. 相似文献
18.
Cyrille Ceugniet Ltitia Lepetit Nancy Lauth De Viguerie Henry Jammes Nicole Peyrot Monique Rivire 《Journal of chromatography. A》1998,810(1-2):237-240
A high-performance liquid chromatographic (HPLC) procedure was developed to allow the rapid separation, in a single run, of a mixture of the main retinal isomers (all-trans, 13-cis, 9-cis), all-trans-retinol, and of the two major photooxygenated photoproducts (5,8-peroxyretinal and 5,6-epoxyretinal). The mixture was separated by HPLC on an octadecyl (ODS) column with 16% (v/v) diethyl ether in hexane as mobile phase and anthracene as the internal standard. A commercial type cosmetic formulation containing 0.05% all-trans-retinal was analyzed successfully for this analyte. 相似文献
19.
Excess enthalpies and excess volumes were determined at 298.15 K for: dimethoxymethane+heptane, diethoxymethane+heptane, 1,1-dimethoxyethane+heptane, 1,1-diethoxyethane+heptane, 2,2-dimethoxypropane+heptane and 1,1-diethoxypropane+heptane. 相似文献
20.
Biesemans M Martins JC Jurkschat K Pieper N Seemeyer S Willem R 《Magnetic resonance in chemistry : MRC》2004,42(9):776-780
It is demonstrated that long-range nJ(1H,117Sn) coupling constants down to 0.3 Hz, can be accurately quantified from non-linear fitting of the sine modulation of the associated 1H-117Sn correlation cross-peak intensities sampled as a function of the heteronuclear antiphase coherence preparation time in the 1H-117Sn J-HMQC pulse sequence. The contribution of additional, undesired modulations is illustrated and assessed using the product operator formalism, and is traced back to contributions that arise from miss-setting of the wandering 180 degrees pulse angle in the constant time period. The power of the method and its use in the characterization of weak intramolecular donor-acceptor interactions are illustrated by the determination of long-range nJ(1H,117Sn) coupling constants of bis[3-(dimethylamino)propyl]tin derivatives, [Me2N(CH2)3]2SnR2 (', R = Me; 3, R = Ph; 4, R = t-Bu). By comparing these with the values found for the corresponding bis(4-methylpentyl)tin derivatives, [Me2CH(CH2)3]2SnR2 (2', R = Me; 3', R = Ph), which lack such interactions, the use of long-range coupling constants to detect intramolecular donor-acceptor interactions is evaluated. It is concluded that nJ(1H,117Sn) couplings up to six bonds through an organic carbon chain can be quantified, whether donor-acceptor interactions are present or not. Furthermore, evidence is presented that, when two scalar coupling pathways co-exist, the pathway involving an intramolecular donor-acceptor interaction can have opposite sign, thus decreasing the overall coupling constant to a value smaller than that actually measured in the absence of a donor-acceptor interaction, where only one coupling pathway is active. There is nevertheless clear numerical value discrimination in the series of compounds investigated between long-range couplings in derivatives without weak intramolecular donor-acceptor interactions and those where such interactions can exist. 相似文献