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排序方式: 共有235条查询结果,搜索用时 31 毫秒
41.
Manal Diab Ana Mateo Joumada El Cheikh Zeinab El Hajj Mohamed Haouas Alireza Ranjbari Vincent Gurineau David Touboul Nathalie Leclerc Emmanuel Cadot Daoud Naoufal Carles Bo Sbastien Floquet 《Molecules (Basel, Switzerland)》2022,27(22)
Herein we report the synthesis of a new class of compounds associating Keggin and Dawson-type Polyoxometalates (POMs) with a derivative of the anionic decahydro-closo-decaborate cluster [B10H10]2− through aminopropylsilyl ligand (APTES) acting as both a linker and a spacer between the two negatively charged species. Three new adducts were isolated and fully characterized by various NMR techniques and MALDI-TOF mass spectrometry, notably revealing the isolation of an unprecedented monofunctionalized SiW10 derivative stabilized through intramolecular H-H dihydrogen contacts. DFT as well as electrochemical studies allowed studying the electronic effect of grafting the decaborate cluster on the POM moiety and its consequences on the hydrogen evolution reaction (HER) properties. 相似文献
42.
43.
Mustapha Khelladi Nicolas Leclerc Denis Jacquemin Antoinette De Nicola Gilles Ulrich 《Tetrahedron letters》2018,59(10):878-881
New symmetrical and non-symmetrical benzoBODIPYs have been synthesized from diketones. For the two series the 3 and 5 positions have been substituted by different aromatic rings and onto benzo sub-units different groups have been introduced. The methodology of diketones self-condensation provides symmetrical dyes. By cross-condensation reaction, these positions can be differentiated and specific functions connected to the desired positions. These molecules have been fully characterized and their optical properties analyzed by both experimental and theoretical means. They are red to NIR emitters with a range of emission from 679 to 780?nm in CH2Cl2. They show maxima of absorption between 651?nm and 732?nm, strong ε of around 100,000?M?1?cm?1 and quite good quantum yields from 16% to 75%. The thienyl moiety on α-positions of the nitrogens generates the highest red shifts. Meanwhile dimethylamino groups in the same positions bring, besides chemical properties, proton sensitive dyes. The bromine atom onto the dibenzo sub-units exhibits good reactivity through Sonogashira coupling reactions. This approach provides multifunctional red to NIR dyes with endless possibilities of combination of chemical properties. 相似文献
44.
Alain Lascoux Bernard Leclerc Jean-Yves Thibon 《Communications in Mathematical Physics》1996,181(1):205-263
We present a fast algorithm for computing the global crystal basis of the basic
-module. This algorithm is based on combinatorial techniques which have been developed for dealing with modular representations of symmetric groups, and more generally with representations of Hecke algebras of typeA at roots of unity. We conjecture that, upon specializationq1, our algorithm computes the decomposition matrices of all Hecke algebras at an
th root of 1.Partially supported by PRC Math-Info and EEC grant n0 ERBCHRXCT930400. 相似文献
45.
Daniel Michaud Rmi Leclerc ric Proulx 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1575-1581
Laser-Induced Breakdown Spectroscopy (LIBS) was applied to the analysis of iron ore concentrates. The objective was to determine the influence of particle size and mineral phase on the LIBS signal. The LIBS spectra of hematite and magnetite ore concentrates were qualitatively indistinguishable from each other but magnetite yielded systematically less than hematite. This behavior could be set into an empirical equation to correct the iron peak intensities according to the level of magnetite in the analyzed sample. Similarly, an increase of the LIBS signal was observed as the particle size of the ore samples decreased. Again, an equation could be written down to correct the intensity of either iron or silicon in response to a variation of the average particle size of the ore concentrate. Using these corrections, proper response of the silicon signal against the concentration of silica in the samples was restored. The observed dependence of the strength of the iron signal upon the mineral phase is attributed to oxidation of magnetite into hematite. 相似文献
46.
Boussie TR Diamond GM Goh C Hall KA LaPointe AM Leclerc M Lund C Murphy V Shoemaker JA Tracht U Turner H Zhang J Uno T Rosen RK Stevens JC 《Journal of the American Chemical Society》2003,125(14):4306-4317
For the first time, new catalysts for olefin polymerization have been discovered through the application of fully integrated high-throughput primary and secondary screening techniques supported by rapid polymer characterization methods. Microscale 1-octene primary screening polymerization experiments combining arrays of ligands with reactive metal complexes M(CH(2)Ph)(4) (M = Zr, Hf) and multiple activation conditions represent a new high-throughput technique for discovering novel group (IV) polymerization catalysts. The primary screening methods described here have been validated using a commercially relevant polyolefin catalyst, and implemented rapidly to discover the new amide-ether based hafnium catalyst [eta(2)-(N,O)[bond](2-MeO[bond]C(6)H(4))(2,4,6-Me(3)C(6)H(2))N]Hf(CH(2)Ph)(3) (1), which is capable of polymerizing 1-octene to high conversion. The molecular structure of 1 has been determined by X-ray diffraction. Larger scale secondary screening experiments performed on a focused 96-member amine-ether library demonstrated the versatile high temperature ethylene-1-octene copolymerization capabilities of this catalyst class, and led to significant performance improvements over the initial primary screening discovery. Conventional one gallon batch reactor copolymerizations performed using selected amide-ether hafnium compounds confirmed the performance features of this new catalyst class, serving to fully validate the experimental results from the high-throughput approaches described herein. 相似文献
47.
Barbara Heyberger Najib Belmekki Valrie Conraud Pierre‐Alexandre Glaude Ren Fournet Frdrique Battin‐Leclerc 《国际化学动力学杂志》2002,34(12):666-677
If the mechanism of formation of alkenes, the main primary products of the combustion of alkanes above 1000 K, is now well understood, their ways of degradation have been much less studied. Following a previous modeling of the oxidation of propene in a static and a jet‐stirred reactors by using an automatically generated mechanism, the present paper shows new validations of the same mechanism for ignition delays in a shock tube. It also describes the extension of the rules used for the automatic generation to the case of 1‐butene. The predictions of the mechanism produced for the oxidation of 1‐butene are compared successfully with two sets of experimental results: the first obtained in a jet‐stirred reactor between 900 and 1200 K; the second being new measurements of ignitions delays behind reflected shock waves for temperatures from 1200 up to 1670 K, pressures from 6.6 to 8.9 atm, equivalence ratios from 0.5 to 2, and with argon as bath gas. Flux and sensitivity analyses show that the role of termination reactions involving the very abundant allylic radicals is less important for 1‐butene than for propene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 666–677, 2002 相似文献
48.
J. M. Kolthoff E. A. Pearson H. F. Bradley E. J. A. H. Verzijl St. Urbasch J. Guéron N. H. Furman N. Joassard E. Leclerc A. Hecquet C. E. P. Jeffreys E. H. Swift und H. G. Isbell 《Fresenius' Journal of Analytical Chemistry》1934,97(1-2):36-44
Ohne ZusammenfassungChemikerfachausschuß der Gesellschaft Deutscher Metallhütten- und Bergleute 相似文献
49.
By assuming simplified hypotheses which result from the molecular analysis of Doi-Edwards, it is possible to propose rheological methods for characterizing molar weight distribution of entangled polymeric liquids. The generalized exponential distribution is especially concerned. Theoretical expressions of rheological parameters are derived, and their numerical values are calculated in special cases. A numerical method of discrimination and identification of these special distributions is proposed. 相似文献
50.
Palladium-catalyzed tandem multifunctional reactions leading to the synthesis of substituted biaryl molecules have been developed including tandem Heck-direct arylation and tandem-sequential Heck-direct arylation-hydrogenation. These reactions occur in good yield and have been employed in the synthesis of a cytotoxic biaryl compound. 相似文献