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41.
The oxidation of hydrazoic acid in perchloric acid in the absence of added chloride under pseudo first-order conditions ([HN3] » [AuCl 4 ? ]) is first order in [Au(III)]. Michaelis–Menten type of dependence (linear plots of k obs ?1 vs [HN3]?1) is observed with respect to [HN3]. The k obs is independent of ionic strength and the plot between k obs ?1 and [H+] is linear. The inner-sphere mechanism is consistent with the formation of an axial complex (K = 25 dm3 mol?1) between AuCl3(HO)? ion and HN3 prior to its rate determining decomposition (k = 0.0182 s?1). It is inferred that the free radicals N 3 ? do not oxidise Au(II). The reaction becomes outer-sphere in the presence of added Cl? ions which are inferred to form a cage around the hydronium ion surrounding the AuCl 4 ? ions. The penetration of N 3 ? through the cage is rate controlling and within the cage, the electron transfer from N 3 ? ion to AuCl 4 ? is fast. The value of the rate determining constant k 2 is 0.547 dm3 mol?1 s?1 and the equilibrium constant K Cl for the cage formation is 5 dm3 mol?1 at 25 °C. It is calculated that the minimum HN3 concentration required before the reaction exhibits zero-order dependence in HN3 is 0.31 mol dm?3 when [H+] = 0.18 mol dm?3 at 25 °C. 相似文献
42.
Vimal D Pacheco AB Iyengar SS Stevens PS 《The journal of physical chemistry. A》2008,112(31):7227-7237
The rate constants for the reaction of the OH radical with 1,3-butadiene and its deuterated isotopomer has been measured at 1-6 Torr total pressure over the temperature range of 263-423 K using the discharge flow system coupled with resonance fluorescence/laser-induced fluorescence detection of OH. The measured rate constants for the OH + 1,3-butadiene and OH + 1,3-butadiene- d 6 reactions at room temperature were found to be (6.98 +/- 0.28) x 10 (-11) and (6.94 +/- 0.38) x 10 (-11) cm (3) molecule (-1) s (-1), respectively, in good agreement with previous measurements at higher pressures. An Arrhenius expression for this reaction was determined to be k 1 (II)( T) = (7.23 +/- 1.2) x10 (-11)exp[(664 +/- 49)/ T] cm (3) molecule (-1) s (-1) at 263-423 K. The reaction was found to be independent of pressure between 1 and 6 Torr and over the temperature range of 262- 423 K, in contrast to previous results for the OH + isoprene reaction under similar conditions. To help interpret these results, ab initio molecular dynamics results are presented where the intramolecular energy redistribution is analyzed for the product adducts formed in the OH + isoprene and OH + butadiene reactions. 相似文献
43.
Han X Balakrishnan VK Buncel E 《Langmuir : the ACS journal of surfaces and colloids》2007,23(12):6519-6525
The effect of varying surfactant chain length (C12, C14, C16, C18) on the alkaline hydrolysis of the organophosphorus pesticide fenitrothion was determined for the following series of inert counterion cationic surfactants: dodecyltrimethylammonium bromide (DTABr), tetradecyltrimethylammonium bromide (TTABr), hexadecyltrimethylammonium bromide (CTABr), and octadecyltrimethylammonium bromide (OTABr). Plots of kobs versus [surfactant] at constant [KOH] showed saturation behavior at low total [Br-], and (constrained) S-shaped curvature was observed at high total [Br-]. kobs values increased with increasing surfactant chain length but decreased with added KBr. For systems exhibiting saturation behavior, further analysis of the results using the PPIE treatment as modified to account for HO-/Br- exchange allowed the evaluation of substrate binding constants, KS, and micellar rate constants, k2m. The binding constants increased with chain length (hydrophobicity), but ionic strength had no effect on KS. Meanwhile, because of the increased KS values as the surfactant chain length increased, the rate enhancements observed for fenitrothion degradation correspondingly increased. However, rate enhancements decreased with ionic strength because reactive counterions could not compete against the bromide anion for micellar binding sites. Low k2m/k2w ratios revealed that the observed rate enhancements were due to the so-called concentration effect rather than true catalysis. Finally, where the PPIE model failed (displaying S-shaped curvature), our results support the intervention of sphere-to-rod transitions that are favored at high ionic strength (>0.01 M Br-) and lower temperatures as the cause of the S-shaped curvature. 相似文献
44.
Nilesh D. Parmar Sanjay D. Hadiyal Vimal H. Kapupara Jaydeep N. Lalpara Hitendra S. Joshi 《Journal of heterocyclic chemistry》2021,58(7):1437-1445
We report here the synthesis of different substituted tetrahydropyridopyrazine derivatives. This approach of synthesis has been designed in a way that in first simple chloro-amine coupling as an alternative of Buchwald coupling followed by heterogeneous hydrogenation of nitro to give amine and further cyclization of this amine with carboxylic acid was accomplished in a single process with the help of continuous flow hydrogenation reactor. This processing was a generation of hydrogen (in situ) by electrolysis of water molecule and using a pre-packed cartridge of a palladium catalyst. In a further step, LAH was used to reduce lactam to a yielding product as tetrahydropyridopyrazine (TPP) scaffold. Final adducts were obtained using substituted benzoyl and sulfonyl derivatives. 相似文献
45.
Vimal Singh 《Nonlinear Analysis: Real World Applications》2013,14(3):1503-1510
A novel criterion for the elimination of overflow oscillations in 2-D state-space digital filters described by the Roesser model employing two’s complement overflow arithmetic is presented. The criterion takes the form of linear matrix inequality (LMI) and, hence, is computationally tractable. The criterion is a generalization and improvement over an earlier criterion. An example shows the effectiveness of the new criterion. 相似文献
46.
Vimal Singh 《Journal of Difference Equations and Applications》2013,19(9):1281-1290
A new sufficient condition in the form of a state-space criterion for global asymptotic stability of direct-form digital filters utilizing single saturation nonlinearity is presented. An alternative sufficient condition in the form of a matrix frequency-domain inequality is also presented. Examples show the effectiveness of the present criteria. 相似文献
47.
Vimal Singh 《Physics letters. A》2008,372(19):3537-3538
It is pointed out that an unnatural assumption is made in the following Letter [Z. Mao, H. Zhao, Phys. Lett. A 364 (1) (2007) 38]. Therefore, the results of the Letter are not relevant to the real Cohen-Grossberg neural network model. 相似文献
48.
Cover Picture: Short Chemoenzymatic Total Synthesis of ent‐Hydromorphone: An Oxidative Dearomatization/Intramolecular [4+2] Cycloaddition/Amination Sequence (Angew. Chem. Int. Ed. 17/2014)
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Vimal Varghese Prof. Tomas Hudlicky 《Angewandte Chemie (International ed. in English)》2014,53(17):4251-4251
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50.
Methylindium(III) dithiolate complexes of the general formulae [Me2In(S∩S)] ( 1 ) and [MeIn(S∩S)2] ( 2 ) [S∩S = (EtO)2PS2?, (PriO)2PS2?, Et2NCS2?, , O(CH2CH2)2NCS2?, EtOCS2? and PriOCS2?] have been isolated conveniently by the reaction of Me3In·OEt2 with In(S∩S)3 ( 3 ) in an appropriate stoichiometry. Both 1 and 2 have been characterized by indium analysis, IR, NMR (1H, 13C{1H} and 31P{H}) and mass spectral data. NMR data of 3 are also included for comparison. The Me–In and S∩S resonances are sensitive to the number of methyl groups attached to indium metal. The mass spectral data indicate that these complexes are monomeric in nature. The thermal behavior of a few complexes has been investigated. The xanthate and dithiocarbamate complexes on pyrolysis under dynamic vacuum or flowing nitrogen atmosphere gave either In2S3 or a mixture of InS, In2S3 and In6S7, which were characterized using EDAX and powder XRD. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献