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1.
Carlo Carlini Valentina De Luise Anna Maria Raspolli Galletti Glauco Sbrana 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):200-206
Novel catalytic systems, prepared in situ by the oxidative addition of 8‐hydroxyquinoline ligands to bis(1,5‐cyclooctadiene)nickel(0) and activated by methylaluminoxane, were studied in ethylene polymerization. When 8‐hydroxyquinoline was employed, only oligomeric products were obtained. On the contrary, 5,7‐dinitro‐8‐hydroxyquinoline gave linear polyethylene (PE), but with a modest activity. For the catalyst based on 5‐nitro‐8‐hydroxyquinoline, the productivity was largely dependent on the content of free trimethylaluminum (TMA) present in the commercial aluminoxane. The progressive optimization of the TMA/oligomeric methylaluminoxane ratio increased the productivity, which reached 700 kg of PE/(mol of Ni × h), by an order of magnitude. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 200–206, 2006 相似文献
2.
Luise Unger 《manuscripta mathematica》1986,57(1):1-31
Let
be the path algebra for some representation-infinite quiver
over some field k. There exists a bound
such that mI is faithful for all indecomposable injective
-modules I and all
, and such that there exists an indecomposable injective
-module J satisfying that
J is not faithful, denotes the Auslander-Reiten-translation. Let m() be the maximum of the
taken over all possible orientations of the underlying graph . In this article we determine the bounds m() for representation-infinite quivers
for which is a tree. 相似文献
3.
Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II) and zinc(II) are determined in environmental matrices. The voltammetric measurements were carried out using a conventional three-electrode cell and the ammonia-ammonium chloride buffer pH 9.3 as supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials Estuarine Sediment BCR-CRM 277 and River Sediment BCR-CRM 320. The precision, expressed as relative standard deviation (s(r)), and the accuracy, expressed as relative error, were, in all cases, less than 5%; the detection limits, for each element and in the experimental conditions employed, were around 10(-9) M. The standard addition technique significantly improved the resolution of the voltammetric method, even in the case of very high metal concentration ratios. 相似文献
4.
Analytical characterization of bioactive fluoropolymer ultra-thin coatings modified by copper nanoparticles 总被引:5,自引:0,他引:5
Cioffi N Ditaranto N Torsi L Picca RA Sabbatini L Valentini A Novello L Tantillo G Bleve-Zacheo T Zambonin PG 《Analytical and bioanalytical chemistry》2005,381(3):607-616
Copper–fluoropolymer (Cu-CFx) nano-composite films are deposited by dual ion-beam sputtering. The extensive analytical characterization of these layers reveals that inorganic nanoparticles composed of Cu(II) species are evenly dispersed in a branched fluoropolymer matrix. In particular, X-ray photoelectron spectroscopy has been employed to study the surface chemical composition of the material and to assess how it changes on increasing the copper loading in the composite. Transmission electron microscopy reveals that the copper nanoclusters have a mean diameter of 2–3 nm and are homogeneously in-plane distributed in the composite films. Electrothermal atomic absorption spectroscopy has been used to study the kinetics of copper release in the solutions employed for the biological tests. The Cu-CFx layers are employed as bioactive coatings capable of inhibiting the growth of target microorganisms such as Saccharomyces cerevisiae, Escherichia coli, Staphylococcus aureus, and Lysteria. The results of the analytical characterization enable a strict correlation to be established among the chemical composition of the material surface, the concentration of copper dissolved in the microorganisms broths, and the bioactivity of the nano-structured layer. 相似文献
5.
In previous works, it has been shown that a standard ultraviolet-visible detection system can be used for quantitative analysis of heterogeneous systems (dispersed supermicron particles) in field-flow fractionation (FFF) by single peak area measurements. Such an analysis method was shown to require either experimental measurements (standardless analysis) or an accurate model (absolute analysis) to determine the extinction efficiency of the particulate samples. In this work, an experimental design to assess absolute analysis in FFF through prediction of particles' optical extinction is presented. Prediction derives from the semiempirical approach by van de Hulst and Walstra. Special emphasis is given to the restriction of the experimental domain of instrumental conditions within which absolute analysis is allowed. Validation by statistical analysis and a practical application to real sample recovery studies are also given. 相似文献
6.
Krauth-Siegel RL Bauer H Schirmer RH 《Angewandte Chemie (International ed. in English)》2005,44(5):690-715
Parasitic diseases such as sleeping sickness, Chagas' heart disease, and malaria are major health problems in poverty-stricken areas. Antiparasitic drugs that are not only active but also affordable and readily available are urgently required. One approach to finding new drugs and rediscovering old ones is based on enzyme inhibitors that paralyze antioxidant systems in the pathogens. These antioxidant ensembles are essential to the parasites as they are attacked in the human host by strong oxidants such as peroxynitrite, hypochlorite, and H2O2. The pathogen-protecting system consists of some 20 thiol and dithiol proteins, which buffer the intraparasitic redox milieu at a potential of -250 mV. In trypanosomes and leishmania the network is centered around the unique dithiol trypanothione (N1,N8-bis(glutathionyl)spermidine). In contrast, malaria parasites have a more conservative dual antioxidative system based on glutathione and thioredoxin. Inhibitors of antioxidant enzymes such as trypanothione reductase are, indeed, parasiticidal but they can also delay or prevent resistance against a number of other antiparasitic drugs. 相似文献
7.
Luise Oemisch Kai-Uwe Goss Satoshi Endo 《Analytical and bioanalytical chemistry》2013,405(8):2567-2574
Experimental determination of oil-water partition coefficients often poses difficulties associated with emulsion formation. The aim of this work was to find an appropriate technique for determination of oil–water partition coefficients of polar, nonvolatile compounds. Two different methods were tested. The first method used a “silicone membrane equilibrator.” For the second method, solid-phase microextraction (SPME) fibers with a polyacrylate (PA) coating were used as a passive sampler. With both methods, oil–water partition coefficients for 14 compounds with polar functional groups were determined at 37 °C with good repeatability (standard deviation 0.11 log units or lower). The partition coefficients determined with the silicone membrane equilibrator method ranged from 0.50 to 3.49 log units. The oil–water partition coefficients obtained with the PA-SPME passive sampling approach were significantly higher than those obtained with the silicone membrane equilibrator method for nine of 14 compounds. The differences were up to 0.39 log units (i.e., a factor of 2.5). Additional experiments suggested that this difference occurred because the sorption properties of the PA fibers used were influenced by the surrounding phase, e.g., through swelling of the polymer phase. Therefore, the SPME passive sampling method using PA fibers seems to be less reliable, whereas the silicone membrane equilibrator method was found to be a convenient technique for the determination of oil–water partitioning. 相似文献
8.
I. Farella A. Valentini N. Cioffi L. Torsi 《Applied Physics A: Materials Science & Processing》2005,80(4):791-795
The morphological (TEM) and chemical (XPS, ARXPS) characterizations of fluoropolymer films modified with palladium particles (CFx(Pd)) are reported in this article. The films, which have different levels of metal content, have been deposited by ion beam co-sputtering a Teflon target and a palladium one. Composite films with a thickness of a few nanometers have also been deposited and analyzed. For all degrees of thickness, the analyses show the fluoropolymer nature of the hosting material, the nanoscopic character of metal domains, and their uniform distribution in the polymer matrix. The likely application of this ion sputter-deposited material in the sensor field has also been preliminary tested. PACS 81.05.Qk; 82.35.Np; 81.15.Cd; 79.60.Fr; 07.07.Df 相似文献
9.
Anna Luise Grab Dirk Hose Patrick Horn Elisabetta Ada Cavalcanti-Adam Anja Seckinger Martin Müller 《Particle & Particle Systems Characterization》2021,38(3):2000263
In the malignant plasma cell disease multiple myeloma (MM), bone lesions and resulting fractures caused by MM cell (MMC) accumulation represent a major cause of morbidity and mortality. Despite recent advantages in systemic treatment, residual MMCs remain, especially in bone lesions. Therefore an interfacial delivery system for local treatment of MM and induced bone disease based on polyelectrolyte complex nanoparticles (PEC NP) loaded with bone morphogenetic protein 6 (BMP-6) inducing de-novo bone formation and MMC apoptosis is presented herein. BMP-6 loaded PEC NP are fabricated by defined mixing bio-related cationic and anionic polysaccharides and BMP-6 according to molar ratio of BMP-6/PEC-NP of 1/3. BMP-6/PEC NP bound to a model substrate releases 10% BMP-6 sustainably within two weeks as accessed by infrared spectroscopy. BMP-6 loaded PEC NP adheres to cell membranes of MMCs and MSCs and activated phosphorylation of Smad 1/5. Osteogenic differentiation (ALP-concentration) is enhanced in MSCs (p < 0.05). All patient samples (10/10) of MMCs show significant induction of apoptosis (median 84%, p < 0.05). Finally, BMP-6/PEC NP are successfully integrated in a commercial hyaluronic acid based hydrogel material revealing MMC death as principal proof for the local treatment of MM induced bone lesions. 相似文献
10.
Experimental study on the retention of silica particles in gravitational field-flow fractionation effects of the mobile phase composition 总被引:3,自引:0,他引:3
Pierluigi Reschiglian Dora Melucci Giancarlo Torsi 《Journal of chromatography. A》1996,740(2):245-252
Effects of mobile phase composition can play an effective role in modulating the retention of particles in gravitational field-flow fractionation (GFFF), the simplest and cheapest among field-flow fractionation (FFF) techniques. In the framework of an optimized procedure for the GFFF characterization of particulate systems, an experimental approach to the effects of the mobile phase composition on the retention of silica particles retention is presented. The role of the ionic strength and the presence of surfactant are emphasized, with special regards to the shape of the particles. Moreover, the first experimental evidence of potential-barrier GFFF is reported. 相似文献