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601.
Dr. Shobhan Mondal Ester Maria Di Tommaso Prof. Berit Olofsson 《Angewandte Chemie (International ed. in English)》2023,62(8):e202216296
Efficient protocols for accessing iodo-substituted diaryl and aryl(vinyl) sulfides have been developed using iodonium salts as reactive electrophilic arylation and vinylation reagents. The reactions take place under transition-metal-free conditions, employing odorless and convenient sulfur reagents. A wide variety of functional groups are tolerated in the S-diarylation, enabling the regioselective late-stage application of several heterocycles and drug molecules under mild reaction conditions. A novel S-difunctionalization pathway was discovered using vinyliodonium salts, which proceeds under additive-free reaction conditions and grants excellent stereoselectivity in the synthesis of aryl(vinyl) sulfides. A one-pot strategy combining transition-metal-free diarylation and subsequent reduction provided facile access to electron-rich thioanilines and a direct synthesis of a potential drug candidate derivative. The retained iodo group allows a wide array of further synthetic transformations. Mechanistic insights were elucidated by isolating the key intermediate, and the relevant energy profile was substantiated by DFT calculations. 相似文献
602.
603.
We prove a discrete version of the Stam inequality for randomvariables taking values on a finite group. 相似文献
604.
Reineri F Viale A Ellena S Alberti D Boi T Giovenzana GB Gobetto R Premkumar SS Aime S 《Journal of the American Chemical Society》2012,134(27):11146-11152
(15)N-Propargylcholine has been synthesized and hydrogenated with para-H(2). Through the application of a field cycling procedure, parahydrogen spin order is transferred to the (15)N resonance. Among the different isomers formed upon hydrogenation of (15)N-propargylcholine, only the nontransposed derivative contributes to the observed N-15 enhanced emission signal. The parahydrogen-induced polarization factor is about 3000. The precise identification of the isomer responsible for the observed (15)N enhancement has been attained through a retro-INEPT ((15)N-(1)H) experiment. T(1) of the hyperpolarized (15)N resonance has been estimated to be ca. 150 s, i.e., similar to that reported for the parent propargylcholine (144 s). Experimental results are accompanied by theoretical calculations that stress the role of scalar coupling constants (J(HN) and J(HH)) and of the field dependence in the formation of the observed (15)N polarized signal. Insights into the good cellular uptake of the compound have been gained. 相似文献
605.
Tommaso Crisenza Hans‐Jürgen Butt Kaloian Koynov Roberto Simonutti 《Macromolecular rapid communications》2012,33(2):114-119
Blends of chlorinated polyethylene and nylon‐6/‐6,6/‐12 terpolyamide were prepared. The ratio of the two components was systematically varied within the blends. The mechanical behavior of the samples was analyzed with tensile tests and dynamical mechanical analysis showing that, for several ratios, materials with improved mechanical properties typical of thermoplastic elastomers were obtained. In such a mechanical regime, a co‐continuous phase‐separated morphology was clearly evidenced at the microscopic scale by 3D laser scanning confocal fluorescent microscopy (LSCFM). At blend compositions where plastic tensile behavior is observed, LSCFM reveals dispersed spheres of one component in the other. 相似文献
606.
A simple two-step procedure yielding peracetylated furanoses directly from free aldoses was implemented. Key steps of the method are (i) highly selective formation of per-O-(tert-butyldimethylsilyl)furanoses and (ii) their clean conversion into acetyl ones without isomerization. This approach was easily applied to galactose and structurally related carbohydrates such as arabinose, fucose, methyl galacturonate and N-acetylgalactosamine to give the corresponding peracetylated targets. The success of this procedure relied on the control of at least three parameters: (i) the tautomeric equilibrium of the starting unprotected oses, (ii) the steric hindrance of both targeted furanoses and silylating agent, and finally, (iii) the reactivity of each soft nucleophile during the protecting group interconversion. 相似文献
607.
Poli T Chiantore O Giovagnoli A Piccirillo A 《Analytical and bioanalytical chemistry》2012,402(9):2977-2984
The study of polished cross sections is a well-assessed and practical method to investigate the stratigraphy of paintings
and multilayer polychromies on works of art, in general. Analyses on cross sections allow us to characterize, at once, all
the layers in the stratigraphy, giving information about the artists technique, the number of layers and their composition
and sometimes about the conservation history of the artefact. In this paper, the application of an imaging detector focal
plane array (FPA) coupled to an infrared (IR) microscope has been studied, focusing on the characteristics and potential of
the different working methodologies (attenuated total reflectance (ATR) and total reflection). FPA detector coupled with ATR
crystal can “localize” IR information coming from a 30 × 30μm sample area, in a 64 × 64 dot matrix detector. In particular,
an innovative analysis methodology has been tested for the total reflectance measurements in order to obtain maximum information
with single measurements. Micro-infrared total reflection measurements have been carried out in an extended IR range (from
1,000 to 5,266 cm−1) exploiting the broad spectral response of mercury cadmium telluride detector in order to include overtones and combination
bands from near-infrared spectral range without any modification of the standard mid-infrared micro-FT instrumentation. The
potentialities of this new approach have been successfully transferred in the imaging/mapping investigations with a minimal
tuning of the apparatus. Results obtained on a polished cross section coming from a modern painting and on a micro-sample
of a wood polychromy from an undated historic polyptic are shown for demonstration. 相似文献
608.
The liquid-phase Knoevenagel condensation between benzaldehyde and ethyl cyanoacetate catalyzed by aminopropyl-modified silica has been investigated using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. The aim of the work was to demonstrate the different levels of information on the reaction mechanism that can be achieved by operating the spectroscopic cell in the absence and in the presence of a solvent, in flow-through and stop-flow modes and in combination with concentration modulation spectroscopy. The reaction mechanism involves the formation of an imine intermediate whose existence has been verified in situ by combining in one experiment continuous and stop-flow operations. Identical information has been gained more elegantly using concentration modulation spectroscopy, which additionally provided information on the possible origin of the solvent effect observed in the Knoevenagel reaction. Faster production and consumption of the imine intermediate was observed in cyclohexane solvent than in toluene. Identification of other species evolving on the catalyst surface and monitoring of the effluents of the spectroscopic cell provided some insight in possible catalyst deactivation. 相似文献
609.
Mecca T Consoli GM Geraci C La Spina R Cunsolo F 《Organic & biomolecular chemistry》2006,4(20):3763-3768
A mutual induced fit mechanism is responsible for the exceptional complexation performances exhibited by calix[8]arene polycations towards heparin. The recognition process was studied in comparison with two other heparin antagonists: protamine and polylysine. The arrangement of multiple functional groups on the flexible macrocyclic scaffold of calix[8]arene, with respect to the conformationally rigid protamine and low ordered polylysine, allowed a mutual adaptability between calixarene polycations and heparin, significantly enhancing the recognition performances. Fluorescence, NMR titration, and activated partial thromboplastin time (aPTT) experiments confirmed that these calixarene derivatives have a very high specificity and affinity towards heparin neutralization as in aqueous solution as in blood. Analogous results were obtained with low molecular weight heparin (LMWH) whose effect protamine is unable to completely reverse. 相似文献
610.
[structure: see text] A convergent and rapid stereoselective synthesis of (-)-spongidepsin has been achieved from the Roche ester in 14 steps with an overall yield of 13%. 相似文献