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71.
Duroure L Jousseaume T Aráoz R Barré E Retailleau P Chabaud L Molgó J Guillou C 《Organic & biomolecular chemistry》2011,9(23):8112-8118
Simple models of the spiroimine core of (-)-gymnodimine A have been synthesized in racemic and optically active forms. The quaternary carbon of the racemic spiroimines was created by Michael addition of a β-ketoester to acrolein, whereas the asymmetric allylic alkylation of the same β-ketoester was used to access the spiroimines in an enantioselective fashion. Both racemic and enantio-enriched mixtures were tested for their biological activities on Xenopus oocytes either expressing (human α4β2) or having incorporated (Torpedoα1(2)βγδ) nicotinic acetylcholine receptors (nAChRs). These spiroimine analogs of (-)-gymnodimine A inhibited acetylcholine-evoked nicotinic currents, but were less active than the phycotoxin. Our results reveal that the 6,6-spiroimine moiety is important for the blockade of nAChRs and support the hypothesis that it is one of the pharmacophores of this group of toxins. 相似文献
72.
Stephen R. Wasserman Jordi Benach John W. Koss Laura L. Morisco 《Synchrotron Radiation News》2015,28(6):4-9
On May 11 and 12, 2000, the Stanford Synchrotron Radiation Laboratory, as it was then known, hosted a “Workshop on Techniques for Automated Mounting, Viewing and Centering Pre-Cooled Protein Crystals” [1, 2]. The 12 presentations during the meeting all focused on the impact that automation could have on the performance of synchrotron beamlines and thus on research in structural biology. Two principal themes ran through the workshop: (1) robotics to mount crystals on a diffractometer; and (2) methods to place a crystal in the X-ray beam. Five conceptual and prototype robotic systems for automated mounting were described—the original ACTOR from Abbott Laboratories, later modified and marketed by Rigaku/MSC, and the systems which in final form become the ALS [3], EMBL/ESRF SC3 [4], APS/SBC [5], and SSRL SAM robots [6]. By December of that year, the ACTOR had been installed for testing at Sector 32 of the Advanced Photon Source (Figure 1). Within three years, by the end of 2003, several of these robots, plus the commercial MARcsc from MAR Research, had been deployed to handle frozen protein crystals at beamlines for macromolecular crystallography (MX). Currently, at least 13 distinct robot types, not including variants of the ALS automounter, are employed at synchrotron beamlines to transfer crystals from storage to beam position. 相似文献
73.
Paital AR Mitra T Ray D Wong WT Ribas-Ariño J Novoa JJ Ribas J Aromí G 《Chemical communications (Cambridge, England)》2005,(41):5172-5174
Based on a combined theoretical-experimental study, we propose that substituted m-phenylene ligands (m-N-Phi-N) can act as tuneable strong ferromagnetic couplers connecting Cu(II) ions; a new complex presenting that bridge with J close to +15 cm(-1) has been suggested and synthesized. 相似文献
74.
Jordi Contreras J. Idris Jones 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):67-68
Abstract Various sulfides are easily oxidized selectively to the corresponding sulfoxides in quantitative yields by iodosylarene (ArIO) catalyzed by metalloporphyrin (TPPM(III)Cl (M [dbnd] Fe, Mn)). The oxidation system is demonstrated to be a possible model for monooxygenase in the study of the stereochemistry of these sulfoxides. Metalloporphyrin-iodosylarene can initially equilibrate with the oxometalloporphyrin (TPPM(V)=O·Cl) formed in situ. The initial process may involve one-electron transfer from the sulfide to the intermediate oxometalloporphyrin followed by coupling of two resulting charged products, and/or nucleophilic attack of sulfide on oxometalloporphyrin oxygen. The overall reactions are depicted by paths with different electron demands from the results of Hammett plots. 相似文献
75.
Density functional calculations on XYYX and X2YY isomers of the X2Y2 species (X: H, Li, Na, F, Cl, Br, I; Y: O, S, Se, Te) show that the XYYX isomers are more stable than the X2YY forms except for X = F and Y = S and Te, for which the F2SS and F2TeTe isomers are slightly more stable. 相似文献
76.
γ-Carboxylation of β-diketones, 1, can be improved using samples containing 100% of ketoenol tautomers, 3, prepared by mild hydrolysis of the corresponding copper(II) complexes 2. Cyclization of the so formed 4-alkyl-3,5-dioxohexanoic acids, 4, affords 5-alkyl-4-hydroxy-6-methyl-2-pyrones, 5. 相似文献
77.
Basabe-Desmonts L Beld J Zimmerman RS Hernando J Mela P García Parajó MF van Hulst NF van den Berg A Reinhoudt DN Crego-Calama M 《Journal of the American Chemical Society》2004,126(23):7293-7299
Self-assembled monolayers (SAMs) on glass were used as a platform to sequentially deposit fluorophores and small molecules for ion sensing. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on small molecules. The resulting libraries are easily measured and show varied responses to a series of both cations and anions. This technology is transferable from the macro- to the microscale both via microcontact printing (microCP), where the fluorophore is printed onto a glass surface, and via direct attachment of the fluorophore to microchannel walls. The ease of miniaturization of this technology may make the generation of a wide variety of simple yet efficient microarrays possible. 相似文献
78.
A method for the identification of double bond locations in polyunsaturated long chain alkenones adapted to nanogram amounts
as currently analyzed by gas chromatography coupled to mass spectrometry (GC-MS) has been developed. The method is based on
interpretation of the electron impact mass spectra of the imino derivatives of the carbonyl groups using either cyclopentyl
or phenyl substitutents. Other complementary derivatization methods such as elaidization and hydrogenation have also been
used for structural characterization of these compounds. This application has led to the identification of a novel homologous
series of di-, tri-, and tetraunsaturated ketones with carbon number chain lengths between 37 and 40 in coastal hypersaline
sediments. The novel series identified shows a distribution in which the double bond position between different homologs is
established by reference to the distance from the carbonyl group whereas the previously known alkenones were constituted by
unsaturated homologs with double bonds located at defined distances of the terminal methyl. This difference points out to
a dissimilar, but still unknown, biogenic precursor of these novel alkenones. 相似文献
79.
Near Infrared Chemical Imaging (NIR-CI) is demonstrating an increasing interest in pharmaceutical research since it meets the challenging analytical needs of pharmaceutical quality and may serve as a versatile adjunct to conventional NIR spectroscopy in many fields.The direct analysis of samples by using hyperspectral imaging techniques, which provide a NIR spectrum in each pixel of the image, generates a big amount of information from one sample. Focusing the interest in pharmaceutical research, several chemometric algorithms are demonstrating their usefulness extracting the relevant information (i.e. quantitative determination of the component in one sample) in tablets with only one sample and without damaging it.In this work, a quantitative method to analyze different commercial Acetylsalicylic acid tablets is proposed by using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) method to the hyperspectral image and without any previous calibration model. For this purpose, a large concentration range of active pharmaceutical ingredient (ASA, Acetylsalicylic acid in this work), between 82% and 12%, was covered depending on the manufacturer. MCR-ALS allowed obtaining a concentration maps for acetylsalicylic acid and therefore, consequent analysis of the ASA distribution in the tablet was developed by using the histograms of the distribution of concentration.Results certified the good distribution of ASA despite the different origins of the tablets. Moreover, the obtained values of concentration showed a very good concordance with the nominal value of ASA. As a matter of fact, the quality of the results demonstrated the useful of encompassing NIR-CI techniques with MCR-ALS and, consequently, the well development on the production of Acetylsalicylic acid tablets. 相似文献
80.
A practical and efficient three-step sequence for the deamination of α-aminoesters is reported. This method is based on the NaBH4-mediated selective reduction of α-diazoesters to α-hydrazonoesters and has been successfully applied to the deamination of several representative α-aminoesters including some l-cysteine ethyl ester derivatives, key intermediates in the synthesis of a series of CysLT1 antagonists. 相似文献