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排序方式: 共有101条查询结果,搜索用时 15 毫秒
1.
Madhuri Manpadi 《Tetrahedron letters》2005,46(26):4433-4437
Various substituted arylcuprates undergo stereocontrolled additions to a d-mannitol-derived γ-alkoxy-α,β-enoate with exclusive anti-selectivity. The method is well suited for the preparation of a broad range of biologically active Amaryllidaceae alkaloids and their aromatic analogues. A model accounting for the stereochemical outcome of this process is presented. 相似文献
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3.
M. Penchal Reddy W. Madhuri K. Sadhana I. G. Kim K. N. Hui K. S. Hui K. V. Siva Kumar R. Ramakrishna Reddy 《Journal of Sol-Gel Science and Technology》2014,70(3):400-404
Magnetic nickel ferrite (NiFe2O4) was prepared by sol–gel process and calcined in the 2.45 GHz singlemode microwave furnace to synthesize nickel nanopowder. The sol–gel method was used for the processing of the NiFe2O4 powder because of its potential for making fine, pure and homogeneous powders. Sol–gel is a chemical method that has the possibility of synthesizing a reproducible material. Microwave energy is used for the calcining of this powder and the sintering of the NiFe2O4 samples. Its use for calcination has the advantage of reducing the total processing time and the soak temperature. In addition to the above combination of sol–gel and microwave processing yields to nanoscale particles and a more uniform distribution of their sizes. X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and vibrating sample magnetometer were carried out to investigate structural, elemental, morphological and magnetic aspects of NiFe2O4. The results showed that the mean size and the saturation magnetization of the NiFe2O4 nanoparticles are about 30 nm and 55.27 emu/g, respectively. This method could be used as an alternative to other chemical methods in order to obtain NiFe2O4 nanoparticles. 相似文献
4.
The synthesis of C1-C12 and C13-C22 fragments of (−)-callystatin A is accomplished employing desymmetrization strategy for the creation of five chiral centres of the polypropionate fragment and application of cross-metathesis (CM) reaction for the first time for this molecule. 相似文献
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The present work describes an exciting method for the selective and sensitive determination of calcitonin in human blood serum samples. Adopting the surface molecular imprinting technique, a calcitonin-imprinted polymer was prepared on the surface of the zinc oxide nanostructure. Firstly, a biocompatible tyrosine derivative as a monomer was grafted onto the surface of zinc oxide nanostructure followed by their polymerization on vinyl functionalized electrode surface by activator regenerated by electron transfer–atom transfer radical polymerization (ARGET–ATRP) technique. Such sensor can predict the small change in the concentration of calcitonin in the human body and it may also consider to be as cost-effective, renewable, disposable, and reliable for clinical studies having no such cross-reactivity and matrix effect from real samples. The morphologies and properties of the proposed sensor were characterized by scanning electron microscopy, cyclic voltammetry, difference pulse voltammetry and chronocoulometry. The linear working range was found to be 9.99 ng L−1 to 7.919 mg L−1 and the detection limit as low as 3.09 ± 0.01 ng L−1 (standard deviation for three replicate measurements) (S/N = 3). 相似文献
7.
Madhuri Mukhopadhyay Debi Banerjee Aleksander Koll Aleksander Filarowski Samaresh Mukherjee 《Chemical physics letters》2006,420(4-6):316-320
The effect of neutral, cationic and anionic micellar environments on the ground and excited state proton transfer reactions of salicylidine-3,4,7-methyl amine (SMA) in water has been studied by steady state and time resolved fluorescence spectroscopy. In the ground state, the formation of the primary form of SMA is enhanced at the expense of the zwitterionic species due to micellization. In the excited state, anion formation decreases both in the presence of Triton-X and cetyl trimethyl ammonium bromide (CTAB). However, in the presence of sodium dodecyl sulphate (SDS), the anionic emission increases after reaching a certain micellar concentration. The lifetime of the anion is significantly reduced in CTAB compared to that in the bulk water and also in the presence of Triton-X. It is proposed that the destabilization and modification of SMA anion occurs due to the different electrostatic environments produced by micellization. 相似文献
8.
Summary The formation of near square planar mixed ligand CuII complexes with diethyldithiocarbamate (dtc) as one of the ligands and 8-hydroxyquinolinate (Hy) or salicylaldehydate (Sal) as the second ligand by exchange reactions, has been detected by e.p.r. spectroscopy. The concentrations of the mixed ligand complexes in the reaction mixtures are small compared to those of the reactants. Six different tests were used to identify the m1=3/2,63Cu hyperfine transition of the near square planar complexes, based upon the relative concentrations of the different CuII species in the reaction mixture, ligand hyperfine structures, the minium linewidths observed in a temperature dependent study and the isotropic g0 estimated from the e.p.r. spectra in solution. 相似文献
9.
A.G. Page S.V. Godbole K.H. Madraswala Madhuri J. Kulkarni Vanita S. Mallapurkar B.D. Joshi 《Spectrochimica Acta Part B: Atomic Spectroscopy》1984,39(4):551-557
Feasibility studies have been carried out on the use of a graphite electrode assembly for the introduction of U3O8 solid samples into a continuously running low-powered argon inductively coupled plasma for the assay of trace metallic elements in uranium. The d.c. arc carrier distillation procedure has been adopted here for the selective volatilisation of analyte elements from the refractory matrix by injecting analyte vapours into the central zone of the plasma using Scribner-Mullin electrodes covered with a graphite lid having a central opening. The experimental parameters have been optimised for the direct determination of B, Be, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Na, Ni and Pb in U3O8 powders. The analytical performance of the method has been checked by analysing spiked U3O8 samples and is seen to be comparable to or better than d.c. arc methods for these analytes. These results indicate that the carrier-distillation-ICP combination shows promise as a sensitive and precise method for analysis of trace metallic elements in a refractory matrix with a complex spectrum. 相似文献
10.
O.M. Hussain K. Srinivasa Rao K.V. Madhuri C.V. Ramana B.S. Naidu S. Pai J. John R. Pinto 《Applied Physics A: Materials Science & Processing》2002,75(3):417-422
Molybdenum trioxide thin films were prepared by reactive pulsed laser deposition on Corning 7059 glass substrates. The influence
of oxygen partial pressure and deposition temperature on the structure, surface morphology and optical properties of these
films was studied to understand the growth mechanism of MoO3 thin films. The films formed at 473 K in an oxygen partial pressure of 100 mTorr exhibited predominantly a (0k0) orientation,
corresponding to an orthorhombic layered structure of α-MoO3. The evaluated optical band gap of the films was 3.24 eV. The crystallite size increased with increase of deposition temperature.
The films formed at an oxygen partial pressure of pO2=100 mTorr and at a deposition temperature greater than 700 K exhibited both (0k0) and (0kl) orientations, representing α-β
mixed phases of MoO3. The films formed at an oxygen partial pressure less than 100 mTorr were found to be sub-stoichiometric with α-β mixed phases.
The investigation revealed the growth of polycrystalline and single-phase orthorhombic-layered-structure α-MoO3 thin films with composition nearly approaching the nominal stoichiometry at moderate substrate temperatures in an oxygen
partial pressure of 100 mTorr.
Received: 9 April 2001 / Accepted: 6 August 2001 / Published online: 17 October 2001 相似文献