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151.
Commercially available pyridine ligands can significantly enhance the rate, yield, substrate scope, and site selectivity of arene C-H olefination (Fujiwara-Moritani) reactions. The use of a 1:1 ratio of Pd/pyridine proved critical to maximize reaction rates and yields. 相似文献
152.
The palladium-catalyzed C-H fluorination of 8-methylquinoline derivatives with nucleophilic fluoride is reported. This transformation involves the use of AgF as the fluoride source in combination with a hypervalent iodine oxidant. Both the scope and mechanism of the reaction are discussed. 相似文献
153.
Chiu M Jaun B Beels MT Biaggio I Gisselbrecht JP Boudon C Schweizer WB Kivala M Diederich F 《Organic letters》2012,14(1):54-57
A formal [2 + 2] cycloaddition-cycloreversion (CA-CR) between N,N'-dicyanoquinone diimides (DCNQIs) and electron-rich alkynes was explored, providing a new class of π-conjugated donor-acceptor chromophores. These DCNQI adducts exist in the solid state as single diastereoisomers, but as two interconverting diastereoisomers in solution. Solid- and solution-state evidence for intramolecular charge transfer (CT) was obtained; additionally, the DCNQI adducts exhibit positive solvatochromism and significant solution-state third-order polarizabilities. 相似文献
154.
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157.
Priestman MA Shell TA Sun L Lee HM Lawrence DS 《Angewandte Chemie (International ed. in English)》2012,51(31):7684-7687
Falling apart, on cue: Signaling pathways often display a profound spatiotemporal component that is best studied using light-activatable reagents. Three separate photolabile moieties that can be distinguished based upon their response to three distinct wavelengths (360, 440, and 560?nm) have been synthesized and evaluated. This tri-color system is also applied to imaging in microwells and HeLa cells (see picture). 相似文献
158.
Racowski JM Gary JB Sanford MS 《Angewandte Chemie (International ed. in English)》2012,51(14):3414-3417
Pd(IV) -fluoride complexes, some of which are remarkably insensitive to water, have been synthesized and used in the title reaction, which proceeds with high selectivity to give the product of the C(sp(3) )?F coupling (see scheme, TfO=trifluoromethanesulfonate). Preliminary mechanistic studies implicate a pathway involving dissociation of pyridine followed by direct C?F coupling at the Pd center. 相似文献
159.
Zha Y Disabb-Miller ML Johnson ZD Hickner MA Tew GN 《Journal of the American Chemical Society》2012,134(10):4493-4496
Here we present the first metal-cation-based anion exchange membranes (AEMs), which were synthesized by copolymerization and cross-linking of a norbornene monomer functionalized with a water-soluble bis(terpyridine)ruthenium(II) complex and dicyclopentadiene. Each ruthenium complex has two associated counteranions, unlike most ammonium- and phosphonium-based membranes with single cation-anion pairs. The resulting AEMs show anion conductivities and mechanical properties comparable to those of traditional quaternary-ammonium-based AEMs as well as good alkaline stability and methanol tolerance. These results suggest that metal-cation-based polymers hold promise as a new class of materials for anion-conducting applications. 相似文献
160.
Zagdoun A Casano G Ouari O Lapadula G Rossini AJ Lelli M Baffert M Gajan D Veyre L Maas WE Rosay M Weber RT Thieuleux C Coperet C Lesage A Tordo P Emsley L 《Journal of the American Chemical Society》2012,134(4):2284-2291
A new nitroxide-based biradical having a long electron spin-lattice relaxation time (T(1e)) has been developed as an exogenous polarization source for DNP solid-state NMR experiments. The performance of this new biradical is demonstrated on hybrid silica-based mesostructured materials impregnated with 1,1,2,2-tetrachloroethane radical containing solutions, as well as in frozen bulk solutions, yielding DNP enhancement factors (ε) of over 100 at a magnetic field of 9.4 T and sample temperatures of ~100 K. The effects of radical concentration on the DNP enhancement factors and on the overall sensitivity enhancements (Σ(?)) are reported. The relatively high DNP efficiency of the biradical is attributed to an increased T(1e), which enables more effective saturation of the electron resonance. This new biradical is shown to outperform the polarizing agents used so far in DNP surface-enhanced NMR spectroscopy of materials, yielding a 113-fold increase in overall sensitivity for silicon-29 CPMAS spectra as compared to conventional NMR experiments at room temperature. This results in a reduction in experimental times by a factor >12,700, making the acquisition of (13)C and (15)N one- and two-dimensional NMR spectra at natural isotopic abundance rapid (hours). It has been used here to monitor a series of chemical reactions carried out on the surface functionalities of a hybrid organic-silica material. 相似文献