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81.
Sombel Diaham François Saysouk Marie‐Laure Locatelli Boubakeur Belkerk Yves Scudeller Rodica Chiriac François Toche Vincent Salles 《应用聚合物科学杂志》2015,132(34)
The thermal conductivity of polyimide/boron nitride (PI/BN) nanocomposite thin films has been studied for two sizes of BN nanofillers (40 and 120 nm) and for a wide range of content. A strong influence of BN particle size on the thermal conduction of PI has been identified. In the case of the largest nanoparticles (hexagonal‐BN), the thermal conductivity of PI/h‐BN (120 nm) increases from 0.21 W/mK (neat PI) up to 0.56 W/mK for 29.2 vol %. For the smaller nanoparticles (wurtzite‐BN), PI/w‐BN (40 nm), we observed two different behaviors. First, we see a decrease until 0.12 W/mK for 20 vol % before increasing for higher filler content. The initial phenomenon can be explained by the Kapitza theory describing the presence of an interfacial thermal resistance barrier between the nanoparticles and the polymer matrix. This is induced by the reduction in size of the nanoparticles. Modeling of the experimental results allowed us to determine the Kapitza radius aK for both PI/h‐BN and PI/w‐BN nanocomposites. Values of aK of 7 nm and >500 nm have been obtained for PI/h‐BN and PI/w‐BN nanocomposite films, respectively. The value obtained matches the Kapitza theory, particularly for PI/w‐BN, for which the thermal conductivity is expected to decrease compared to that of neat PI. The present work shows that it seems difficult to enhance the thermal conductivity of PI films with BN nanoparticles with a diameter <100 nm due to the presence of high interfacial thermal resistance at the BN/PI interfaces. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42461. 相似文献
82.
Matrix‐assisted laser desorption/ionization mass spectrometry and Raman spectroscopy: An interesting complementary approach for lipid detection in biological tissues
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83.
Laure Monnereau Laetitia Urbanczyk Jean-Michel Thomassin Michaël Alexandre Christine Jérôme Isabelle Huynen Christian Bailly Christophe Detrembleur 《Polymer》2014
Supercritical carbon dioxide readily induced foaming of various polymers. In that context, supercritical CO2 was applied to carbon nanotubes based polycarbonate nanocomposites to ensure their foaming. Surprisingly, efficient foaming only occurs when low pressure is applied while at high pressure, no expansion of the samples was observed. This is related to the ability of supercritical carbon dioxide to induce crystallization of amorphous polycarbonate. Moreover, this behaviour is amplified by the presence of carbon nanotubes that act as nucleating agents for crystals birth. The thermal behaviour of the composites was analysed by DSC and DMA and was related to the foaming observations. The uniformity of the cellular structure was analysed by scanning electron microscopy (SEM). By saturating the polycarbonate nanocomposites reinforced with 1 wt% of MWNTs at 100 bar and 100 °C during 16 h, microcellular foams were generated, with a density of 0.62, a cell size ranging from 0.6 to 4 μm, and a cellular density of 4.1 × 1011 cells cm−3. The high ability of these polymeric foams to absorb electromagnetic radiation was demonstrated at low MWNT content as the result of the high affinity of the polycarbonate matrix for MWNTs, and therefore to the good MWNTs dispersion. 相似文献
84.
Alex Bauer Chaojie Song Rob Hui Laure Chevallier Jacques Rozière 《Electrochimica acta》2010,55(28):8365-8370
The electrochemical stability of Pt deposited on mesoporous carbon, which was either applied in its unmodified state or coated with 20 wt% TiO2, was investigated by cyclic voltammetry in N2 purged 0.5 M sulfuric acid. XRD analysis revealed that TiO2 was present in the anatase phase. The mean Pt particle diameter was ∼6 and ∼4 nm for mesoporous carbon with and without TiO2, respectively. Pt supported on TiO2 modified substrates was more stable than Pt supported on conventional mesoporous carbon when subjected to 1000 cycles in the potential range from 0.05 to 1.25 V vs. RHE. This was evident from the observation that the support with TiO2 retained ∼53% of the electrochemically active surface area relative to the state observed after 100 cycles, whereas ∼33% of the active area remained in the case without TiO2. The oxygen reduction mass activity was identical for both fresh samples (i.e., ). After 1000 cycles the mass activity decreased to for the case without TiO2, whereas with TiO2 the deactivation was minor; i.e., the mass activity after 1000 cycles was . 相似文献
85.
86.
Alice Louise Woguia Judith Laure Ngondi Thaddée Boudjeko Christophe Rihouey Enyong Julius Oben 《Food science and biotechnology》2012,21(6):1715-1721
Two different mucilages were extracted from dika nut (Irvingia gabonensis) kernels and nkui (Trimphetta cordifolia) stem barks and the hypolipidemic and antioxidant effects were studied on Triton WR-1339 induced hyperlipidemic rats. The GC analysis revealed that, dika nut mucilage is an arabinogalactan type while nkui is a rhamnogalacturonane type. The mucilage of nkui (200 mg/kg) showed the greatest hypolipidemic effect (p<0.05). An oxidative stress marker analysis suggested that the level of malonyl dialdehyde was significantly decreased in serum by the 2 mucilages (p<0.05). There was also a significant decrease in hydroperoxide level for the tested fibers. Moreover, nkui mucilage gave the highest levels in liver homogenate and in the hemolysate and tissues (p<0.05). The results suggest that the hypolidemic effect of mucilages varies with their chemical nature. They would be effective in the prevention of increase of serum lipid levels, in the reduction of lipid peroxidation and in the improvement of antioxidant status. 相似文献
87.
Ulrike Groenhagen Rita Baumgartner Aurélien Bailly Amber Gardiner Leo Eberl Stefan Schulz Laure Weisskopf 《Journal of chemical ecology》2013,39(7):892-906
Increasing evidence indicates that volatile compounds emitted by bacteria can influence the growth of other organisms. In this study, the volatiles produced by three different strains of Burkholderia ambifaria were analysed and their effects on the growth of plants and fungi, as well as on the antibiotic resistance of target bacteria, were assessed. Burkholderia ambifaria emitted highly bioactive volatiles independently of the strain origin (clinical environment, rhizosphere of pea, roots of maize). These volatile blends induced significant biomass increase in the model plant Arabidopsis thaliana as well as growth inhibition of two phytopathogenic fungi (Rhizoctonia solani and Alternaria alternata). In Escherichia coli exposed to the volatiles of B. ambifaria, resistance to the aminoglycoside antibiotics gentamicin and kanamycin was found to be increased. The volatile blends of the three strains were similar, and dimethyl disulfide was the most abundant compound. Sulfur compounds, ketones, and aromatic compounds were major groups in all three volatile profiles. When applied as pure substance, dimethyl disulfide led to increased plant biomass, as did acetophenone and 3-hexanone. Significant fungal growth reduction was observed with high concentrations of dimethyl di- and trisulfide, 4-octanone, S-methyl methanethiosulphonate, 1-phenylpropan-1-one, and 2-undecanone, while dimethyl trisulfide, 1-methylthio-3-pentanone, and o-aminoacetophenone increased resistance of E. coli to aminoglycosides. Comparison of the volatile profile produced by an engineered mutant impaired in quorum-sensing (QS) signalling with the corresponding wild-type led to the conclusion that QS is not involved in the regulation of volatile production in B. ambifaria LMG strain 19182. 相似文献
88.
Ling Ding Zhenbin Lyu Beatrice Louis Aura Tintaru Erik Laurini Domenico Marson Mengjie Zhang Wanxuan Shao Yifan Jiang Ahlem Bouhlel Laure Balasse Philippe Garrigue Eric Mas Suzanne Giorgio Juan Iovanna Yuanyu Huang Sabrina Pricl Benjamin Guillet Ling Peng 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(37)
Bioimaging has revolutionized medicine by providing accurate information for disease diagnosis and treatment. Nanotechnology‐based bioimaging is expected to further improve imaging sensitivity and specificity. In this context, supramolecular nanosystems based on self‐assembly of amphiphilic dendrimers for single photon emission computed tomography (SPECT) bioimaging are developed. These dendrimers bear multiple In3+ radionuclides at their terminals as SPECT reporters. By replacing the macrocyclic 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid cage with the smaller 1,4,7‐triazacyclononane‐1,4,7‐triacetic acid scaffold as the In3+ chelator, the corresponding dendrimer exhibits neutral In3+‐complex terminals in place of negatively charged In3+‐complex terminals. This negative‐to‐neutral surface charge alteration completely reverses the zeta‐potential of the nanosystems from negative to positive. As a consequence, the resulting SPECT nanoprobe generates a highly sought‐after biodistribution profile accompanied by a drastically reduced uptake in liver, leading to significantly improved tumor imaging. This finding contrasts with current literature reporting that positively charged nanoparticles have preferential accumulation in the liver. As such, this study provides new perspectives for improving the biodistribution of positively charged nanosystems for biomedical applications. 相似文献
89.
Laure Gonnord Nicolas Halbwachs Pascal Raymond 《Electronic Notes in Theoretical Computer Science》2006,153(4):3-22
The goal of this paper is to translate (fragments of) the quantified discrete duration calculus QDDC, proposed by P. Pandya, into symbolic acceptors with counters. Acceptors are written in the synchronous programming language Lustre, in order to allow available symbolic verification tools (model-checkers, abstract interpreters) to be applied to properties expressed in QDDC. We show that important constructs of QDDC need non-deterministic acceptors, in order to be translated with a bounded number of counters, and an expressive fragment of the logic is identified and translated. Then, we consider a more restricted fragment, which only needs deterministic acceptors. 相似文献
90.
Xavier Aguilar Michael Schliephake Olav Vahtras Judit Gimenez Erwin Laure 《Future Generation Computer Systems》2013,29(8):2197-2204
Dalton is a molecular electronic structure program featuring common methods of computational chemistry that are based on pure quantum mechanics (QM) as well as hybrid quantum mechanics/molecular mechanics (QM/MM). It is specialized and has a leading position in calculation of molecular properties with a large world-wide user community (over 2000 licenses issued). In this paper, we present a performance characterization and optimization of Dalton. We also propose a solution to avoid the master/worker design of Dalton to become a performance bottleneck for larger process numbers. With these improvements we obtain speedups of 4x, increasing the parallel efficiency of the code and being able to run in it in a much bigger number of cores. 相似文献