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41.
Oxidation by sodium perborate of selected alcohols and unsaturated compounds to ketones and acids was achieved at 60–80°C in the presence of catalytic amounts of chromium(VI) oxide and methyltridecylammonium chloride. 相似文献
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43.
The stability of finite amplitude roll waves that may develop at a liquid free surface in inclined open channels of arbitrary cross-section is studied. In the framework of shallow water theory with turbulent friction the modulation equations for wave series are derived and a nonlinear stability criterion is obtained. To cite this article: A. Boudlal, V.Yu. Liapidevskii, C. R. Mecanique 330 (2002) 291–295. 相似文献
44.
Energy levels, transition probabilities and effective collision strengths for the 1s2 2s2 2p6 3s2 3p6 3d10, and the 1s2 2s2 2p6 3s2 3p6 3d9 4l (l=s, p, d, and f) states of nickel-like Eu are used in the determination of the reduced population for 55 fine structure levels over a wide range of electron densities (from 10+20 to 4×10+22 cm−3) and at various electron plasma temperatures.The gain coefficients for those transitions with positive population inversion factor are determined and plotted against the electron density. 相似文献
45.
Abdelaziz Kacha My Hassan Hbid Rafael Bravo de la Parra 《Nonlinear Analysis: Real World Applications》2009,10(3):1662-1678
In this paper, we propose a mathematical model to study a bacteria–fish system, based upon the interactions between Clostridium botulinum and tilapia, Oerochromis mossambicus. The fish population is divided into susceptible and infected, and the infected fish population is considered structured by the level of infection. The model is thus a system with the infected fish equation being an evolution equation, while those corresponding to the susceptible fish and bacteria in water are ordinary differential equations. The model is firstly transformed into a system with distributed delay for susceptible fish and bacteria and, further, under some assumptions, into a system with discrete delay. The study of this system gives us some results concerning the existence, uniqueness, positivity and boundedness of solutions; we also discuss the existence and stability of its equilibrium points, including conditions for the appearance of Hopf bifurcation. The theoretical results are illustrated by some numerical simulations. 相似文献
46.
Important aspects of the electrochemical reduction of a series of substituted arene sulfenyl chlorides are investigated. A striking change is observed in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the arene sulfenyl chloride. With p-substituted phenyl chlorides a "sticky" dissociative ET mechanism takes place where a concerted ET mechanism leads to the formation of a radical/anion cluster before decomposition. With o-nitropheyl sulfenyl substituted chlorides a stepwise mechanism is observed where through space S...O interactions play an important role stabilizing both the neutral molecules and their reduced forms. Disulfides are generated through a nucleophilic reaction of the two-electron reduction produced anion (arenethiolate) on the parent molecule. The dissociative electron transfer theory, as well as its extension to the case of strong in-cage interactions between the produced fragments, along with the gas phase chemical quantum calculations results helped rationalize both the observed change in the ET mechanism and the occurrence of the "sticky dissociative" ET mechanism. The radical/anion pair interactions have been determined both in solution as well as in gas phase. This study shows that despite the low magnitude of in-cage interactions in acetonitrile as compared to in the gas phase, their existence strongly affects the kinetics of the involved reactions. It also shows that, as expected, these interactions are reinforced by the existence of strong electron-withdrawing substituents. 相似文献
47.
Laurence Oswald Dr. Abdelaziz Al Ouahabi Prof. Dr. Laurence Charles Dr. Jean‐François Lutz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3462-3469
Soluble polystyrene supports with optimal molecular structures for iterative phosphoramidite chemistry were prepared by atom‐transfer radical polymerization (ATRP) and subsequent chain‐end modification steps. The controlled radical polymerization of styrene was first performed in the presence of an 9‐fluorenylmethoxycarbonyl (Fmoc)‐protected amino‐functional ATRP initiator. Soluble supports of different molecular weight were prepared. Size‐exclusion chromatography and NMR analysis indicated formation of well‐defined polymers with controlled chain lengths and narrow dispersity. After synthesis, the bromo ω end group of the ATRP polymer was removed by dehalogenation in the presence of tributyltin hydride, and the Fmoc protecting group of the α moiety was subsequently cleaved with piperidine. The resulting α‐primary amine was afterwards treated with a linker containing a carboxyl group, a cleavable ester site, and a dimethoxytrityl‐protected hydroxyl group to afford ideal soluble supports for phosphoramidite chemistry. NMR analysis indicated that these chain‐end modifications were quantitative. The supports were tested for the synthesis of a non‐natural sequence‐defined oligophosphates. High‐resolution ESI‐MS analysis of the cleaved oligomers indicated formation of uniform species, and thus confirmed the efficiency of the ATRP‐made soluble polymer supports. In addition, the synthesis of a thymidine‐loaded soluble support was achieved. 相似文献
48.
α-Halo hydroxamic acids were used in the synthesis of N-methoxyindolinones, symmetric and dissymmetric N-methoxymaleimides in good yields. The hydrolysis of N-methoxymaleimides constitues a new and good route to maleic anhydrides. 相似文献
49.
50.
Catalin Florin Petre Abdelaaziz Azizi Caroline Olsen Abdelaziz Baçaoui Faïçal Larachi 《Journal of separation science》2008,31(22):3902-3910
A capillary electrophoretic protocol for the separation and quantification of the most important species potentially liberated during the cyanidation of gold sulfide‐rich ores was accomplished in this study. The separation of 11 ions: S2O32–, Cu(CN)32–, Fe(CN)64–, Fe(CN)63–, SCN–, Au(CN)2–, Ag(CN)2–, SO42–, OCN–, SO32–, and HS– was achieved using an indirect UV detection method. The robustness of the analytical protocol was tested by analyzing ions speciation during the cyanidation of two gold sulfide‐rich ores. The 1‐h cyanidation of the two ores released up to six complexes into solution: S2O32–, Cu(CN)32–, SCN–, Fe(CN)64–, OCN–, and SO42–. The mineralogy of the ore was found to influence directly the nature and the amount of the dissolved species. Conserving the cyanidation solution for 72 h after sampling resulted in 96% total sulfur recovery. These results allow us to conclude that the analytical protocol developed in this study can become very useful for the optimization of precious‐metals cyanidation plants. 相似文献