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21.
The pesticide concentration levels flowing into paddy fields and surrounding lagoons of the Rhône river delta were investigated over a period of 6 months in 2004. Water samples were collected at the outlets of the major ditches and in the lagoons in order to study the seasonal variation in pesticide concentrations and the spatial contamination profile. Twenty four pesticides were monitored, mainly herbicides and insecticides. Rice pesticides accounted for 90% of the detection rates while the pesticides transported by the Rhône river water dissolved phase only accounted for 10%. Pretilachlor, oxadiazon, MCPA and bentazone herbicides were found at the highest frequencies into the effluent waters of ditches with maximum concentration levels of 1.2, 0.8, 2.5 and 1.6 μg/L, respectively. Only one insecticide, tebufenozide, was sporadically detected at a maximum concentration level of 0.12 μg/L. There were two main peaks of contamination. The first one in April corresponded to the use of pre-emergence herbicides (oxadiazon and pretilachlor) and the second one in June was related to the post-emergence herbicides (MCPA and bentazone). These concentration peaks were well correlated with the pesticide application period time and rapid pesticide transfer (1–2 weeks) from fields to lagoons were observed. Increased loads of the pre-emergence herbicides were induced by the specific management of paddy fields which includes water emptying of fields before and after rice seeding. Pesticide dissipation into the lagoons occurred very quickly and the duration of the exposure of non-target aquatic organisms to high pesticide concentrations (in total a few μg/L level) was no longer than 2 weeks. According to the physico-chemical properties of the chemicals, contrasting results were observed when studying the spatial variation in pesticide concentrations through the lagoons. The concentrations of bentazone and MCPA, two substances with high phototransformation abilities, quickly decreased between the ditches and the lagoons while the oxadiazon and pretilachlor concentrations were more homogeneous. 相似文献
22.
Eva Monroy Fabien Guillot Sylvain Leconte Laurent Nevou Laetitia Doyennette Maria Tchernycheva Francois H. Julien Esther Baumann Fabrizio R. Giorgetta Daniel Hofstetter 《Journal of Materials Science: Materials in Electronics》2008,19(8-9):821-827
In this work, we summarize the latest progress in intersubband devices based on GaN/AlN nanostructures for operation in the near-infrared. We first discuss the growth and characterization of ultra-thin GaN/AlN quantum well and quantum dot superlattices by plasma-assisted molecular-beam epitaxy. Then, we present the performance of nitride-based infrared photodetectors and electro-optical modulators operating at 1.55 μm. Finally, we discuss the progress towards intersubband light emitters, including the first experimental observation of intersubband photoluminescence in nitride nanostructures. 相似文献
23.
Mostepha R. Khouadjia El-Ghazali Talbi Laetitia Jourdan Briseida Sarasola Enrique Alba 《The Journal of supercomputing》2013,63(3):836-853
In dynamic optimization problems, changes occur over time. These changes could be related to the optimization objective, the problem instance, or involve problem constraints. In most cases, they are seen as an ordered sequence of sub-problems or environments that must be solved during a certain time interval. The usual approaches tend to solve each sub-problem when a change happens, dealing always with one single environment at each time instant. In this paper, we propose a multi-environmental cooperative model for parallel meta-heuristics to tackle dynamic optimization problems. It consists in dealing with different environments at the same time, using different algorithms that exchange information coming from these environments. A parallel multi-swarm approach is presented for solving the Dynamic Vehicle Routing Problem. The effectiveness of the proposed approach is tested on a well-known set of benchmarks, and compared with other meta-heuristics from the literature. Experimental results show that our multi-environmental approach outperforms conventional meta-heuristics on this problem. 相似文献
24.
Laetitia Martinie 《Cement and Concrete Research》2010,40(2):226-234
25.
Rym Boukhicha Laetitia Vincent Charles Renard Cyrille Gardès Vy Yam Frédéric Fossard Gilles PatriarcheFauzia Jabeen Daniel Bouchier 《Thin solid films》2012,520(8):3304-3308
Si nanowires were grown on (111) substrates by ultra high vacuum chemical vapor deposition using the Au-catalyzed vapor-liquid-solid (VLS) technique. Depending on the growth temperature, the nanowires can be straight in the <111> direction or kinked towards <112>. We present a transmission electron microscopy investigation of the <112> Si nanowires. Results exhibit the relationship between the morphology of nanowires and the distribution of gold on sidewalls bounding the nanowires. The distribution of Au nanoclusters is used as a probe to investigate the growth mechanisms of the VLS process. Our observations are consistent with the model of nucleation and step flow related to the oscillatory behavior of the catalyst droplet. 相似文献
26.
We investigated CdSe-sensitized TiO(2) solar cells by means of electrodeposition under galvanostatic control. The electrodeposition of CdSe within the mesoporous film of TiO(2) gives rise to a uniform, thickness controlled, conformal layer of nanostructured CdSe particles intimately wrapping the anatase TiO(2) nanoparticles. This technique has the advantage of providing not only a fast method for sensitization (?5?min) but also being easily scalable to the sensitization of large-area panels. XRD together with SAED analysis highlight that the deposit of CdSe is exclusively constituted of the hexagonal polymorph. In addition, hierarchical growth has also been shown, starting from the formation of a TiO(2)-CdSe core-shell structure followed by the growth of an assembly of CdSe nanoparticles resembling cauliflowers. This assembly exhibits at its core a mosaic texture with crystallites of about 3?nm in size, in contrast to a shell composed of well-crystallized single crystals between 5 and 10?nm in size. Preliminary results on the photovoltaic performance of such a nanostructured composite of TiO(2) and CdSe show 0.8% power conversion efficiency under A.M.1.5?G conditions-100?mW?cm(-2) in association with a new regenerative redox couple based on cobalt(+III/+II) polypyridil complex (V(oc )?=?485?mV, J(sc )?=?4.26?mA cm (-2), ff=0.37). 相似文献
27.
Elias J Gizowska M Brodard P Widmer R Dehazan Y Graule T Michler J Philippe L 《Nanotechnology》2012,23(25):255705
Here, an easy and effective electrochemical route towards the synthesis of gold thin films with well-controlled roughness, morphology and crystallographic orientation is reported. To control these different factors, the applied potential during deposition played a major role. A tentative nucleation and growth mechanism is demonstrated by means of electrochemical characterizations and a formation mechanism is proposed. Interestingly, the differences in geometry and orientation of the different gold deposits have shown a clear correlation with the electrocatalytical activity in the case of oxygen sensing. In addition, not only the electrocatalytical activity but also the surface-enhanced Raman scattering of the gold deposits have been found to depend both on the roughness and on the size of the surface nanostructures, allowing a fine tuning by controlling these two parameters during deposition. 相似文献
28.
A new experimental approach for the characterization of the diametrical elastic modulus of individual nanowires is proposed by implementing a micro/nanoscale diametrical compression test geometry, using a flat punch indenter. A 250 nm diameter single crystal silicon nanowire is compressed inside of a scanning electron microscope. Since silicon is highly anisotropic, the wire crystal orientation in the compression axis is determined by electron backscatter diffraction. In order to analyze the load-displacement compression data, a two-dimensional analytical closed-form solution based on a classical contact model is proposed. The results of the analytical model are compared with those of finite element simulations and to the experimental diametrical compression results and show good agreement. 相似文献
29.
Jamil Elias Laetitia Philippe Johann Michler Claude Lévy-Clément 《Electrochimica acta》2011,56(26):9532
Thin films composed of ZnO nanowires (NWs) hierarchically organized with an urchin-like 3D morphology were obtained by combining the electrochemical deposition and sphere lithography methods. Deposited on a transparent conductive oxide substrate (TCO), a monolayer of carboxylate modified polystyrene spheres organized with a hexagonal closed-packed structure played the role of a template. The spheres were activated in a solution of zinc chloride by the formation of bonds between the carboxylate terminals and the Zn2+ ions and were used as a template for the electrodeposition of vertically aligned ZnO NWs around them. Without this treatment, ZnO NWs were deposited only on the TCO substrate between the PS spheres. To reach a density of nanowires high enough to obtain the urchin morphology, the concentration of ZnCl2 had to be at least equal to 2 M. It was also found, as soon as small grains of ZnO started to be electrodeposited on the polystyrene spheres that the spheres were no longer close packed. The space created between them increased with the increase in the number of small ZnO grains and the increase in their length, allowing the further growth of the nanowires between the spheres. As a result the initial round shape of the spheres was modified and the urchin-like ZnO exhibited an ellipsoidal shape. 相似文献
30.
Etienne Buscail Guillaume Le Cosquer Fabian Gross Marine Lebrin Laetitia Bugarel Cline Deraison Nathalie Vergnolle Barbara Bournet Cyrielle Gilletta Louis Buscail 《International journal of molecular sciences》2021,22(18)
Between 20 to 25% of Crohn’s disease (CD) patients suffer from perianal fistulas, a marker of disease severity. Seton drainage combined with anti-TNFα can result in closure of the fistula in 70 to 75% of patients. For the remaining 25% of patients there is room for in situ injection of autologous or allogenic mesenchymal stem cells such as adipose-derived stem/stromal cells (ADSCs). ADSCs exert their effects on tissues and effector cells through paracrine phenomena, including the secretome and extracellular vesicles. They display anti-inflammatory, anti-apoptotic, pro-angiogenic, proliferative, and immunomodulatory properties, and a homing within the damaged tissue. They also have immuno-evasive properties allowing a clinical allogeneic approach. Numerous clinical trials have been conducted that demonstrate a complete cure rate of anoperineal fistulas in CD ranging from 46 to 90% of cases after in situ injection of autologous or allogenic ADSCs. A pivotal phase III-controlled trial using allogenic ADSCs (Alofisel®) demonstrated that prolonged clinical and radiological remission can be obtained in nearly 60% of cases with a good safety profile. Future studies should be conducted for a better knowledge of the local effect of ADSCs as well as for a standardization in terms of the number of injections and associated procedures. 相似文献