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101.
3-Cyano-7-diethylamino-N-ethoxycarbonyl-iminocoumarin reacted with different hydrazines as N-nucleophiles to afford, in one step, a new series of 2-N-substituted 3-triazolonyl-iminocoumarins in good yields. In two cases, N-unsubstituted derivatives were also obtained. The structures of all the products obtained were confirmed by infrared, 1H NMR, 13C NMR, and elemental analysis. The optical properties of three of these compounds in dichloromethane and ethanol were reported. 相似文献
102.
103.
Mohamed Amine Aounallah Imen Ben Slimene-Debez Kais Djebali Dorra Gharbi Majdi Hammami Sana Azaiez Ferid Limam Olfa Tabbene 《Applied biochemistry and biotechnology》2017,181(2):650-666
A strain producing chitinase, isolated from potato stem tissue, was identified as Bacillus licheniformis by biochemical properties and 16S RNA sequence analysis. Statistical experimental designs were used to optimize nine independent variables for chitinase production by B. licheniformis AT6 strain in submerged fermentation. Using Plackett–Burman design, (NH4)2SO4, MgSO4.7H2O, colloidal chitin, MnCl2 2H2O, and temperature were found to influence chitinase production significantly. According to Box–Behnken response surface methodology, the optimal fermentation conditions allowing maximum chitinase production were (in gram per liter): (NH4)2SO4, 7; K2HPO4, 1; NaCl, 1; MgSO4.7H2O, 0.1; yeast extract, 0.5; colloidal chitin, 7.5; MnCl2.2H2O, 0.2; temperature 35 °C; pH medium 7. The optimization strategy led to a 10-fold increase in chitinase activity (505.26 ± 22.223 mU/mL versus 50.35 ± 19.62 mU/mL for control basal medium). A major protein band with a molecular weight of 61.9 kDa corresponding to chitinase activity was clearly detected under optimized conditions. Chitinase activity produced in optimized medium mainly releases N-acetyl glucosamine (GlcNAc) monomer from colloidal chitin. This enzyme also acts as an exochitinase with β-N-acetylglucosaminidase. These results suggest that B. licheniformis AT6 secreting exochitinase is highly efficient in GlcNAc production which could in turn be envisaged as a therapeutic agent or as a conservator against the alteration of several ailments. 相似文献
104.
105.
Guillaume Freychet Mireille Maret Marta Fernandez-Regulez Raluca Tiron Ahmed Gharbi Celia Nicolet Patrice Gergaud 《Journal of polymer science. Part A, Polymer chemistry》2020,58(15):2041-2050
The morphologies of poly(lactide)-block-poly(dimethylsiloxane)-block-polylactide (PLA-b-PDMS-b-PLA) triblock copolymer films were studied using a combination of grazing-incidence small-angle X-ray scattering, X-ray reflectivity and scanning electron microscopy. This block copolymer is characterized by a high Flory–Huggins interaction parameter which leads to the self-assembly of periodic high-resolution nanodomains. In this article, we performed a detailed analysis of GISAXS patterns, in the frame of the Distorted Wave Born Approximation, in order to determine the morphology of blocks and their spatial arrangement. For a low volume fraction of PLA (17%), a three-dimensional hexagonal lattice of PLA spherical blocks is revealed, while, for a PLA fraction twice larger, in-plane (parallel) PLA lying cylinders adopt a two-dimensional centered rectangular lattice. Moreover, the in-depth electron density profile of the polymer film for the cylindrical morphology was extracted from the XRR data, revealing the presence of interfacial layers at the top surface and at the interface with the Si substrate. 相似文献
106.
Chiheb Chaker Walid El Gharbi Annie Simon Mario Maglione 《Journal of Physics and Chemistry of Solids》2011,72(10):1140-1146
Na1−xLixNbO3 ceramics with composition 0.05≤x≤0.30 were prepared by solid-state reaction method and sintered in the temperature range 1100-1150 °C. These ceramics were characterised by X-ray diffraction as well as dielectric permittivity measurements and Raman spectroscopy. Dielectric properties of ceramics belonging to the whole composition domain were investigated in a broad range of temperatures from 300 to 750 K and frequencies from 0.1 to 200 kHz. The Rietveld refinement powder X-ray diffraction analysis showed that these ceramics have a single phase of perovskite structure with orthorhombic symmetry for x≤0.15 and two phases coexistence of rhombohedral and orthorhombic above x=0.20. The evolution of the permittivity as a function of temperature and frequency showed that these ceramics Na1−xLixNbO3 with composition 0.05≤x≤0.15 present the classical ferroelectric character and the phase transition temperature TC increases as x content increases. The polarisation state was checked by pyroelectric and piezoelectric measurements. For x=0.05, the piezoelectric coefficient d31 is of 2pC/N. The evolution of the Raman spectra was studied as a function of temperatures and compositions. The results of the Raman spectroscopy study confirm our dielectric measurements, and they indicate clearly the transition from the polar ferroelectric phase to the non-polar paraelectric one. 相似文献
107.
The reaction of carbonylative addition of alkyl alkynes to aniline derivatives has been successfully achieved by a catalytic system formed of Pd(OAc)2 and a suitable bidentate phosphine ligand. The reaction led mainly to gem‐α,β‐unsaturated amides ( 3 ) with Pd(OAc)2/1,3‐bis(diphenylphosphino)propane/p‐toluenesulfonic acid/CO as the catalytic system. However, the reaction catalyzed by Pd(OAc)2/1,4‐bis(diphenylphosphino)butane/H2/CO in CH2Cl2 as a solvent affords trans‐α,β‐unsaturated amides ( 4 ) as the major product. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
108.
N. Ghaouar A. Aschi L. Belbahri S. Trabelsi A. Gharbi 《Physica B: Condensed Matter》2009,404(21):4246-4252
The behaviour of cellulase enzymes in phosphate saline buffer has been studied over a wide range of temperatures and enzyme concentrations by using viscosity measurements. To characterize the conformation change of cellulase versus temperature and chemical denaturants, such as guanidinium chloride (GdmCl) and urea, the information about the intrinsic viscosity and the hydrodynamic radius are necessary. The dependence of the intrinsic viscosity and the hydrodynamic radius in its random coil conformation on temperature and denaturant concentration were studied. Our results and discussions are limited to the dilute regime of concentration because of abnormalities in conformation observed in the very dilute regime due to the presence of capillary absorption effects. 相似文献
109.
Using a light scattering technique at a fixed temperature, we have investigated viscoelastic behaviour exhibited by the ferroelectric smectic phase (SmC*) of C8tolane in a homeotropic orientation. Experiments were performed in backward and forward scattering geometries that allowed us to deduce separately orientational diffusivities k3/η and k+/η corresponding to the Goldstone mode. The k3/η value measured in the SmC* phase is about 100 times higher than in the SmCA* phase exhibited by the same liquid crystal compound. The factor 100 may be attributed in great part to the molecular arrangement mode in adjacent smectic layers. However k+/η measured in the SmC* phase is in the same order of magnitude as those measured previously in SmCA* phases. 相似文献
110.
Sylvain Gaillard Caroline J. Ross Vincent Armbruster Mark A. Hill David L. Stevens Tijani Gharbi Michel Fromm 《Radiation measurements》2005,40(2-6):279-282
In radiobiology, low doses of high-LET radiation correspond to a few particle traversals through the cell population. Therefore, for studies on cell monolayers irradiated with a low dose of -particles, it is extremely useful if the number and position of particle traversals can be determined. In this study we describe a new method, based on UV-curing, to obtain a thick CR-39 grafted onto a thick PolyEthylene Terephtalate (PET). This thin double polymeric layer, used as a dish base, has a regular and reproducible detector thickness which can be traversed by 3.5 MeV -particles, with a sufficient residual energy to traverse mammalian cells attached to the base. The recording properties of a PET-CR-39 dish, together with a demonstration of its use for radiobiological experiments, are presented. This new tool allows the precise determination of single-track impact parameters at a sub-cellular level. 相似文献