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991.
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993.
Cp2TiCl2-LiAlH4体系的研究——芳香族二元醇、二元酮及其它有机官能团的还原 总被引:2,自引:1,他引:1
本文报道了Cp2TjCl2-LiAlH4体系对芳香族二元醇、二元酮及其它有机官能团的还原作用,发现对于不同的芳香族二元醇、二元酮等,其还原反应产物的组成不同。 相似文献
994.
Kazuhiko Suga 《Flow, Turbulence and Combustion》2016,96(3):717-756
To understand turbulence over porous media, a series of PIV measurements were carried out in porous-walled channel flows. The porous walls were made of three types of foamed ceramics which had the same porosity but different permeability. For turbulence inside porous media, LES studies of fully developed flows in three different model porous media were performed. Referring to these databases, a multi-scale k ? ε four equation eddy viscosity model for turbulence around and/or inside porous media was developed. Through the comparison to the experimental results, the proposed model was validated with satisfactory accuracy. 相似文献
995.
Shinji Tanaka Yumiko Nakajima Atsuko Ogawa Takashi Kuragano Yoshihiro Kon Masanori Tamura Kazuhiko Sato Christophe Copret 《Chemical science》2022,13(16):4490
Polymer-supported catalysts have been of great interest in organic syntheses, but have suffered from the difficulty in obtaining direct structural information regarding the catalyst species embedded in the polymer due to the limitations of most analytical methods. Here, we show that dynamic nuclear polarization (DNP)-enhanced solid-state NMR is ideally positioned to characterize the ubiquitous cross-linked polystyrene (PS)-supported catalysts, thus enabling molecular-level understanding and rational development. Ammonium-based catalysts, which show excellent catalytic activity and reusability for the transesterification of methyl esters with glycidol, giving glycidyl esters in high yields, were successfully characterized by DNP 15N NMR spectroscopy at 15N natural abundance. DNP 15N NMR shows in particular that the decomposition of quaternary alkylammonium moieties to tertiary amines was completely suppressed during the catalytic reaction. Furthermore, the dilute ring-opened product derived from glycidol and NO3− was directly characterized by DNP 15N CPMAS and 1H–15N and 1H–13C HETCOR NMR using a 15N enriched (NO3) sample, supporting the view that the transesterification mechanism involves an alkoxide anion derived from an epoxide and NO3−. In addition, the detailed analysis of a used catalyst indicated that the adsorption of products on the cationic center is the major deactivation step in this catalysis.We demonstrated that DNP-enhanced NMR spectroscopy enables the direct and detailed characterization of polymer-supported alkylammonium catalysts. 相似文献
996.
Takashi Ohta Takeo Kajishima Kazuhiko Mizobata Kazuki Nakamura 《Flow, Turbulence and Combustion》2012,89(3):435-448
To investigate the effect of density variation on turbulent heat transfer prediction, we perform a direct numerical simulation (DNS) of turbulent flow in a horizontal channel with varying wall temperature using a new method dealing with the effect of density variation. As a result, asymmetric profiles are observed in turbulence statistics. This tendency cannot be reproduced by the Boussinesq approximation, which is based on the constant-density formulation. A quadrant analysis of the turbulent shear stress finds that the density variation affects ejection events in the vicinity of the walls. It is also revealed that the variable viscosity and thermal conductivity change the dynamic and thermodynamic balances of the flow. 相似文献
997.
Wenzhi Hu Paul R. Haddad Helmy Cook Hiroaki Yamamoto Kyioshi Hasebe Kazuhiko Tanaka James S. Fritz 《Journal of chromatography. A》2001,920(1-2):95-100
This paper describes an electrostatic ion chromatographic system in which the separation selectivity for inorganic anions, especially for sulfate and phosphate, could be manipulated by altering the molar ratio of the zwitterionic and cationic surfactants in the column coating solution used to prepare the stationary phase. The zwitterionic surfactant used for this study was 3-(N,N-dimethyltetradecylammonio)propanesulfonate (Zwittergent-3-14) and the cationic surfactant was tetradecyltrimethylammonium (TTA). Using a reversed-phase C18 column (250×4.6 mm I.D.) coated with 10/10 (mM/mM) of TTA/Zwittergent-3-14 mixed micelles as the stationary phase and either NaHCO3 or Na2CO3 aqueous solution as the eluent, together with suppressed conductivity detection, baseline separation of seven model inorganic anions was obtained. The elution order for those anions was found to be F−42−−42−2−
−3−. Under the same conditions but using 1/10 (mM/mM) of TTA/Zwittergent-3-14 mixed micelles as the column coating solution, the elution order for these model ions was F−42−42−−2−
−3−. The early elution of phosphate and sulfate is a unique attribute of this system. Detection limits for F−, HPO42−, Cl−, SO42−, NO2−, Br− and NO3− (S/N=3, sample injection volume 100 μl) were 0.11, 0.12, 0.12, 0.18, 0.49, 0.49, 0.52 μM, respectively. 相似文献
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1000.
Kazuhiko Hashimoto Jun Yasuda Masaki Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》1999,37(7):909-915
The potassium t‐butoxide‐catalyzed ring‐opening polymerization of 3,3‐dimethyl‐ and 4,4‐dimethyl‐2‐azetidinone proceeds quantitatively in a mixture of N,N‐dimethylacetamide and 5–10 wt % of lithium chloride at 25°C to give the corresponding monodisperse polyamides. The addition of methyl α‐D ‐glucoside into the living polyamide system gives a novel polyamide linked with the glucose moiety at one chain end. A new graft copolymer composed of a water soluble polysaccharide (dextran) backbone and many monodisperse polyamide branches was also prepared by a similar coupling method. The difference in acidity among the lactam monomers, the corresponding polyamides, and the alcohols was essential for the attainment of such a proton transfer‐controlled system composed of the living polymerization and the subsequent coupling reaction. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 909–915, 1999 相似文献