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71.
A conformational energy analysis of the isolated chain of syndiotactic poly(m-methylstyrene) under the constraint of a crystalline field is reported. Two different minimum energy conformations having similar energy have been found; the trans-planar conformation with tcm symmetry and the two-fold helical conformation with s(2/1)2 symmetry, according with the observed polymorphic behavior of this polymer. The calculated chain axes are in agreement with the experimental axes of 5.1 and 7.9 Å found for the different polymorphic forms of syndiotactic poly(m-methylstyrene). However, only a metastable disordered modification (form III) having chains in trans-planar conformation has been described. This indicates that, even though the trans-planar conformation is, in the isolated chain as stable as the helical conformation, the packing of the chains in helical conformation is probably more efficient than that of the trans-planar chains. 相似文献
72.
73.
Dr. Riccardo Martini Dr. Francesca Esposito Dr. Angela Corona Dr. Roberto Ferrarese Dr. Elisa Rita Ceresola Dr. Laura Visconti Dr. Cristina Tintori Dr. Alessandro Barbieri Dr. Andrea Calcaterra Dr. Valentina Iovine Dr. Filippo Canducci Prof. Enzo Tramontano Prof. Maurizio Botta 《Chembiochem : a European journal of chemical biology》2017,18(4):374-377
74.
Metal speciation and pH effect on Pb,Cu, Zn and Cd biosorption onto Sphaerotilus natans: Langmuir-type empirical model 总被引:13,自引:0,他引:13
Biosorption data of lead, copper, zinc and cadmium onto Sphaerotilus natans at different equilibrium pH (3-5 units) were here reported and analysed. Experimental results outlined the positive effect of pH increase on pollutant uptake and also the biomass affinity series (Pb > Cu > Zn > Cd) reflecting the hydrolytic properties of metals. An original empirical model was proposed to represent the effect of pH on heavy metal biosorption inserting q(max) vs. pH empirical functions into the classical Langmuir isotherm. 相似文献
75.
New derivatives of N-benzo[d]isothiazol-3-yl-benzamidine 6 a were synthesized as nonacidic anti-inflammatory/antidegenerative agents. We investigated the influence of the amidines 6 a-j on the production of NO, PGE(2), MMP-3, COX-2, ROS, and GAGs, key molecules involved in cartilage destruction in osteoarthritic diseases. The antidegenerative properties of the novel designed derivatives 6 b-j were improved with respect to N-benzo[d]isothiazol-3-yl-benzamidine 6 a. All of the compounds 6 a-j promoted the reduction of most of the IL-1beta-induced harmful effects. Derivatives 6 d, 6 h, and 6 j were the most potent of all the tested compounds, particularly in the human chondrocyte culture model. 相似文献
76.
The metabolic syndrome (also referred to as syndrome X or the insulin resistance syndrome) has emerged as an important cluster of risk factors for atherosclerotic disease. Patients with the syndrome also are at increased risk for developing type 2 diabetes mellitus. Common features are central (abdominal) obesity, insulin resistance, hypertension, and dyslipidemia. Weight reduction deserves first priority in individuals with abdominal obesity and the metabolic syndrome. Both weight reduction and maintenance of a lower weight are best achieved by a combination of reduced caloric intake and increased physical activity. Dietary patterns close to the Mediterranean diet and rich in fruit and vegetables, and high in monounsaturated fats are negatively associated with features of the metabolic syndrome. Some recent studies dealing specifically with the effect of interventions on the resolution of the metabolic syndrome have demonstrated a 25% net reduction in the prevalence of the syndrome following lifestyle changes mainly based on nutritional recommendations. Similar rates of resolution have been obtained with drugs, such as rosiglitazone and rimonabant. The favourable benefit/hazard ratio makes Mediterranean-style diets particularly promising to reduce the cardiovascular burden associated with the metabolic syndrome. 相似文献
77.
M. Dionigi R. Sorrentino L. Tarricone A. Esposito 《International Journal of Numerical Modelling》1997,10(6):315-328
A strategy is proposed to enhance the performance of some numerical methods used in the solution of electromagnetic problems. The strategy can be extended to any numerical method based on the partitioning of the spatial domain into elementary cells. Two different implementations of the strategy are compared: modified-reversed Cuthill-McKee and tabu search. While the former is well known, the latter is here applied for the first time to such problems. Their application is shown in conjunction with three different numerical methods: mode matching of complex MW circuits, finite difference solution of PDE and FEM analysis of microstrip lines. The efficiency and versatility of the approach is proved for each of the three numerical methods, reaching a reduction in the working times of up to 20 times. © 1997 John Wiley & Sons, Ltd. 相似文献
78.
Roberto Andreozzi Tullia Aquila Vincenzo Esposito Roberto Sanchirico 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1997,69(3):297-300
The thermal decomposition of 2-nitrobenzoic acid is investigated by means of adiabatic and quasi-isothermal calorimetry. The decomposition process develops according to zero order kinetics which gives substantial support to the intervention of vapour-phase reaction. The apparent activation energy of 144·8 kJ mol−1 is evaluated. Chemical analysis gives support to the proposal of reliable reaction mechanisms. © 1997 SCI. 相似文献
79.
Tomaselli S Esposito V Vangone P van Nuland NA Bonvin AM Guerrini R Tancredi T Temussi PA Picone D 《Chembiochem : a European journal of chemical biology》2006,7(2):257-267
Current views of the role of beta-amyloid (Abeta) peptide fibrils range from regarding them as the cause of Alzheimer's pathology to having a protective function. In the last few years, it has also been suggested that soluble oligomers might be the most important toxic species. In all cases, the study of the conformational properties of Abeta peptides in soluble form constitutes a basic approach to the design of molecules with "antiamyloid" activity. We have experimentally investigated the conformational path that can lead the Abeta-(1-42) peptide from the native state, which is represented by an alpha helix embedded in the membrane, to the final state in the amyloid fibrils, which is characterized by beta-sheet structures. The conformational steps were monitored by using CD and NMR spectroscopy in media of varying polarities. This was achieved by changing the composition of water and hexafluoroisopropanol (HFIP). In the presence of HFIP, beta conformations can be observed in solutions that have very high water content (up to 99 % water; v/v). These can be turned back to alpha helices simply by adding the appropriate amount of HFIP. The transition of Abeta-(1-42) from alpha to beta conformations occurs when the amount of water is higher than 80 % (v/v). The NMR structure solved in HFIP/H2O with high water content showed that, on going from very apolar to polar environments, the long N-terminal helix is essentially retained, whereas the shorter C-terminal helix is lost. The complete conformational path was investigated in detail with the aid of molecular-dynamics simulations in explicit solvent, which led to the localization of residues that might seed beta conformations. The structures obtained might help to find regions that are more affected by environmental conditions in vivo. This could in turn aid the design of molecules able to inhibit fibril deposition or revert oligomerization processes. 相似文献
80.
Esposito A Mezzogiorno A Sannino A De Rosa A Menditti D Esposito V Ambrosio L 《Journal of materials science. Materials in medicine》2006,17(12):1365-1372
A wide number of gastro-intestinal disorders are associated with structural alterations of this district leading to an impaired
gastrointestinal function. The study of cell material interactions represents one of the major issues for the development
of tissue engineering purposes. Benzyl esters of hyaluronic acid are promising materials because they exhibit good tissue
compatibility and are available in various configurations. In this work they have been studied for the possible application
of intestinal cell growth and functioning.
The preliminary investigation on the morphologic and biochemistry data obtained by monitoring the growth and differentiation
of intestinal epithelial cells on two hyaluronic acid benzyl esters is reported. Two types of materials structures were studied:
a three dimensional matrix and a macroporous flat sheet membrane. Caco-2 cell line was used: these cells undergo spontaneous
enterocytic differentiation after several days in culture. The differentiation status of these cells grown on different materials
was used as a parameter of biocompatibility and cell functioning. The status of cell growth and differentiation was monitored
by studying cell morphology using scanning electron microscopy. The results obtained were confirmed by biochemical determinations.
Although both the configurations of the two polymers exhibited good compatibility with respect to intestinal cells, only the
flat sheet membrane proved to induce cell differentiation, leading us to the conclusion that it is a promising substrate for
the proposed application. 相似文献