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71.
Bazilevsky AV Kornev KG Rozhkov AN Neimark AV 《Journal of colloid and interface science》2003,262(1):16-24
We have developed a new technique to monitor spontaneous adsorption of fluids by porous substrates. The method is based on an optical electronic measuring system providing millisecond resolution. The method capabilities are demonstrated with the example of the absorption of millimeter-size droplets of water and aqueous solutions of polyethylene oxide and polyacrylamide by capillaries. It is shown that polymer additives even in a small amount reduce significantly the rate of adsorption. We have introduced a generalized Lucas-Washburn equation to account for the fluid elasticity. This equation is shown to explain the observed kinetics quantitatively without invoking adjustable parameters. We have derived a modified Bosanquet equation for the initial velocity of penetration, which accounts for the fluid elasticity. This simple formula gives a reasonable estimate of the rate of absorption of small droplets. We report visualization experiments on absorption of water and polymer solutions by sugar cubes as an example of porous substrates. Although the kinetics of droplet adsorption by porous substrates is similar to the kinetics of droplet adsorption by capillaries, the interpretation of experimental data is more complex and requires a plausible hydrodynamic model for lateral spreading in pores. 相似文献
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73.
Nataliya V. Slovesnova Artem S. Minin Anna V. Belousova Aleksey A. Ustyugov Kirill D. Chaprov Alexey P. Krinochkin Maria I. Valieva Yaroslav K. Shtaitz Ekaterina S. Starnovskaya Igor L. Nikonov Anton N. Tsmokalyuk Grigory A. Kim Sougata Santra Dmitry S. Kopchuk Emiliya V. Nosova Grigory V. Zyryanov 《Molecules (Basel, Switzerland)》2022,27(23)
Linked to Alzheimer’s disease (AD), amyloids and tau-protein are known to contain a large number of cysteine (Cys) residues. In addition, certain levels of some common biogenic thiols (cysteine (Cys), homocysteine (Hcy), glutathione (GSH), etc.) in biological fluids are closely related to AD as well as other diseases. Therefore, probes with a selective interaction with the above-mentioned thiols can be used for the monitoring and visualizing changes of (bio)thiols in the biological fluids as well as in the brain of animal models of Alzheimer’s disease. In this study, new Eu(III), Tb(III), Gd(III) and Sm(III) complexes of 2,2′-bipyridine ligands containing TEMPO fragments as receptor units for (bio)thiols are reported. The presence of free radical fragments of the ligand in the complexes was proved by using the electronic paramagnetic resonance (EPR) method. Among all the complexes, the Eu(III) complex turned out to be the most promising one as luminescence- and spin-probe for the detection of biogenic thiols. The EPR and fluorescent titration methods showed the interaction of the resulting complex with free Cys and GSH in solution. To study the practical applicability of the probes for the monitoring of AD in-vivo, by using the above-mentioned Eu(III)-based probe, the staining of the brain of mice with amyloidosis and Vero cell cultures supplemented with the cysteine-enriched medium was studied as well as the fluorescence titration of Bovine Serum Albumin, BSA (as the model for the thiol moieties containing protein), was carried out. Based on the results of fluorescence titration, the formation of a non-covalent inclusion complex between the above-mentioned Eu(III) complex and BSA was suggested. 相似文献
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75.
Received December 12, 2000 / Published online: June 1, 2001 相似文献
76.
Aleksey E. Koklin Nataliia A. Bobrova Tatiana V. Bogdan Igor I. Mishanin Viktor I. Bogdan 《Molecules (Basel, Switzerland)》2022,27(5)
Hydrogenation of phenol in aqueous solutions on Pt-Ni/SiO2, Pt-Ni-Cr/Al2O3, Pt/C, and Ru/C catalysts was studied at temperatures of 150–250 °C and pressures of 40–80 bar. The possibility of hydrogenation of hydrolysis lignin in an aqueous medium in the presence of a Ru/C catalyst is shown. The conversion of hydrolysis lignin and water-soluble sodium lignosulfonate occurs with the formation of a complex mixture of monomeric products: a number of phenols, products of their catalytic hydrogenation (cyclohexanol and cyclohexanone), and hydrogenolysis products (cyclic and aliphatic C2–C7 hydrocarbons). 相似文献
77.
Aleksey E. Kuznetsov Yurii V. Geletii Craig L. Hill Keiji Morokuma Djamaladdin G. Musaev 《Theoretical chemistry accounts》2011,130(2-3):197-207
The mechanism of reaction of the di-Ru-substituted polyoxometalate, {??-[(H2O)RuIII(??-OH)2RuIII(H2O)][X n+W10O36]}(8?n)?, I_X, with O2, i.e. I_X?+?O2????{??-[(·O)RuIV(??-OH)2RuIV(O·)][X n+W10O36]}(8?n)??+?2H2O, (1), was studied at the B3LYP density functional and self-consistent reaction field IEF-PCM (in aqueous solution) levels of theory. The effect of the nature of heteroatom X (where X?=?Si, P and, S) on the calculated energies and mechanism of the reaction (1) was elucidated. It was shown that the nature of X only slightly affects the reactivity of I_X with O2, which is a 4-electron oxidation process. The overall reaction (1): (a) proceeds with moderate energy barriers for all studied X??s [the calculated rate-determining barriers are X?=?Si (18.7?kcal/mol)?<?S (20.6?kcal/mol)?<?P (27.2?kcal/mol) in water, and X?=?S (18.7?kcal/mol)?<?P (21.4?kcal/mol)?<?Si (23.1?kcal/mol) in the gas phase] and (b) is exothermic [by X?=?Si [28.7 (22.1) kcal/mol]?>?P [21.4 (9.8) kcal/mol]?>?S [12.3 (5.0) kcal/mol]. The resulting $ \left\{ {\gamma - \left[ {\left( {^{ \cdot } {\text{O}}} \right) {\text{Ru}}^{\text{IV}} \left( {\mu - {\text{OH}}} \right)_{2} {\text{Ru}}^{\text{IV}} \left( {{\text{O}}^{ \cdot } } \right)} \right]\left[ {{\text{X}}^{{{\text{n}} + }} {\text{W}}_{10} {\text{O}}_{36} } \right]} \right\}^{{\left( {8 - {\text{n}}} \right) - }} $ , VI_X, complex was found to have two RuIV?=?O· units, rather than RuV?=?O units. The ??reverse?? reaction, i.e., water oxidation by VI_X is an endothermic process and unlikely to occur for X?=?Si and P, while it could occur for X?=?S under specific conditions. The lack of reactivity of VI_X biradical toward the water molecule leads to the formation of the stable [{Ru 4 IV O4(OH)2(H2O)4}[(??-XW10O36]2}m? dimer. This conclusion is consistent with our experimental findings; previously we prepared the $ \left[ {\left\{ {{\text{Ru}}_{4}^{\text{IV}} {\text{O}}_{4} ({\text{OH}})_{2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{4} } \right\}} \right[\left( {\gamma - {\text{XW}}_{10} {\text{O}}_{36} } \right]_{2} \}^{{{\text{m}} - }} $ dimers for X?=?Si (m?=?10) [Geletii et al. in Angew Chem Int Ed 47:3896?C3899, 2008 and J Am Chem Soc 131:17360?C17370, 2009] and P (m?=?8) [Besson et al. in Chem Comm 46:2784?C2786, 2010] and showed them to be very stable and efficient catalysts for the oxidation of water to O2. 相似文献
78.
Fukin Georgy K. Samsonov Maxim A. Kalistratova Olga S. Gushchin Aleksey V. 《Structural chemistry》2016,27(1):357-365
Structural Chemistry - The molecular structure and charge density distribution in the crystals of triphenylantimony bis[(2E)-3-phenylprop-2-enoate] [Ph3Sb(O2CCH=CHPh)2] and triphenylantimony... 相似文献
79.
Aleksey B. Ryabitskii Julia L. Bricks Aleksey D. Kachkovskii Vladimir V. Kurdyukov 《Journal of Molecular Structure》2012
A systematic investigation of the conformational structure was performed for the series of symmetrical and unsymmetrical mono-, tri-, pentamethine cyanines, and styryl dyes bearing 2-azaazulenium terminal group. The rotation energy barriers of terminal groups were determined via the dynamic variable temperature NMR experiments. The conformational transformation energy was calculated by quantum chemical methods (B3LYP and M05-2X) both for the cases of considering the solvent influence and not tacking it into account. Based on the comparison of theoretical and experimental data, relative electron-donating abilities and geometrical features of the heterocyclic terminal groups in 2-azaazulenium dyes were estimated. The arrangement of certain heterocyclic nuclei in order of basicity by considering the results of the dynamic NMR investigations was proposed. Influence of the conjugated chain length and the solvent nature on the conformational lability of the investigated dye molecules was discussed. 相似文献
80.