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61.
62.
A 109Cd radioisotope-induced energy-dispersive X-ray fluorescence (EDXRF) study has been performed on samples of cauliflower consisting
of the flower, the leaves and the associated root soil. The cauliflowers were collected from farms near the main dumping site
of municipal solid waste in the city of Kolkata, India and also from uncontaminated farms about 50 km away from the city.
A unified calibration approach was undertaken for the elemental analysis of the samples of widely varying matrices. The present
study suggests that the elemental concentrations in the root soils and leaves of the samples vary from farm to farm, whereby
the concentrations of Cu, Zn and Pb in root soils of MSW-contaminated farms are higher by almost an order of magnitude compared
to uncontaminated farms. But, the most notable feature of this study is the strikingly similar elemental concentrations in
the edible flower part of all samples irrespective of the type of soil. 相似文献
63.
Since its discovery 5-fluorouracil 1(1,5-FU), an important anticancer drug, has been the subject of study for the preparation of some suitable derivatives2 which may have better therapeutic efficacy. These are prepared through silylation method3, mercuri salt method4 and direct alkylation method5 of 5-FU. It was reported5 that the direct alkylation of 5-FU with saturated and allylic type halides under controlled conditions occur at N3 (3-) and N1 (1-) position respectively in contrast to alkylation of uracil where N1 alkylated products are obtained in both cases. The position of alkylation in 5-FU was determined, with analogy from uracil6, by the bathochromic shift in UV from the neutral pH to alkaline pH of the 3-substituted product compared to no such shift of the 1-substituted product. 相似文献
64.
65.
A new iridoid, shanzhiol (1), was isolated from the aerial parts of Mussaenda roxburghii. The structure was established by spectroscopic (including 2D NMR) and chemical methods. Shanzhiol (1) showed mild antibacterial activity against both Staphylococcus aureus and Escherichia coli with a MIC of 100 microg/mL by the broth dilution method. 相似文献
66.
Jang YJ Syu SE Jhang YW Lee YT Lee CJ Chen KW Das U Lin W 《Molecules (Basel, Switzerland)》2012,17(3):2529-2541
A new highly efficient three-component reaction of alkyl acrylate, aldehyde and dialkyl malonate using ethyl diphenylphosphine as organocatalyst has been described. Various highly functional compounds bearing hydroxyl groups and the ester functions can be easily prepared in moderate to good yields according to our one-step procedure. The reactions are believed to proceed via Morita-Baylis-Hillman reactions of alkyl acrylate and aldehydes, followed by the Michael addition reactions of dialkyl malonates. Our reactions indicated that the intermediate species formed in the phosphine-catalyzed MBH reaction are an effective organic base to catalyze the Michael addition reactions of dialkyl malonates to the preformed MBH adducts. 相似文献
67.
Polycarbonate—a thermostable polymer is activated by a simple and rapid method using a photolinker, 1-fluoro-2-nitro-4-azidobenzene (FNAB) for covalent immobilization of a biomolecule. Horseradish peroxidase (HRP) is used as a model enzyme to check the efficacy of the activated surface. HRP is immobilized on the activated polycarbonate surface without addition of any reagent or catalyst and is found to give 2-2.5-fold increase in absorbance with the substrate as compared to the directly adsorbed enzyme. Photochemical attachment of FNAB to the PC surface is confirmed by X-ray photoelectron spectroscopy (XPS), which shows the presence of nitrogen and fluorine in the ratio of 2:1 in the activated polycarbonate. Disappearance of fluorine peak in the XP spectra of PC bound enzyme further confirms the covalent binding of HRP, through displacement of fluorine moiety of the activated PC by the amino group of the protein. Optimized concentration of the photolinker is found as 6 μmol of FNAB per well and time of photo irradiation is 8 min for activation of a PCR polycarbonate plate. PC bound HRP has shown enhanced thermal and storage stability. Kinetic studies of the immobilized HRP shows improved catalytic activity. The potential application of activated polycarbonate surface includes immobilization of biomolecules for biosensors, immunoassays, and protein and DNA micro-arrays. Due to the stability of the polycarbonate at high temperature, the activated polycarbonate has an advantage for immobilization of thermostable biomolecule such as thermostable enzyme for reaction at elevated temperature. 相似文献
68.
Utpal Nundy 《Pramana》2010,75(5):895-899
13.9 μm radiation from the 1000-0110 transition can be obtained from a CO2 laser by saturating the 0001-1000, 10.6 μm transition with an internally generated q-switched pulse or by the application of an external 10.6 μm pulse. Because
of Fermi resonance between the symmetric stretch and the bending modes, decay of population from the 1000 level is fast, and such lasers operate at low power and energies. A theoretical model was developed to study such lasers.
The results of the calculations indicate that a large-aperture E-beam-sustained discharge is effective for excitation of the
cryogenically cooled gain medium, which uses He rich mixture at low pressure. The system is scalable and capable of generating
large powers and energies. 相似文献
69.
Jitesh R. Bhatt Bipin R. Desai Ernest Ma G. Rajasekaran Utpal Sarkar 《Physics letters. [Part B]》2010
We propose a new solution to the origin of dark energy. We suggest that it was created dynamically from the condensate of a singlet neutrino at a late epoch of the early Universe through its effective self-interaction. This singlet neutrino is also the Dirac partner of one of the three observed neutrinos, hence dark energy is related to neutrino mass. The onset of this condensate formation in the early Universe is also related to matter density and offers an explanation of the coincidence problem of why dark energy (70%) and total matter (30%) are comparable at the present time. We demonstrate this idea in a model of neutrino mass with (right-handed) singlet neutrinos and a singlet scalar. 相似文献
70.
To connect the scalar field (acceleron) responsible for dark energy to neutrinos, the usual strategy is to add unnaturally light neutral singlet fermions (right-handed neutrinos) to the Standard Model. A better choice is actually a Higgs triplet, through the coupling of the acceleron to the trilinear Higgs triplet–double–doublet interaction. This hypothesis predicts an easily observable doubly-charged Higgs boson at the forthcoming Large Hadron Collider (LHC). 相似文献