全文获取类型
收费全文 | 1226篇 |
免费 | 91篇 |
专业分类
电工技术 | 17篇 |
综合类 | 5篇 |
化学工业 | 361篇 |
金属工艺 | 20篇 |
机械仪表 | 18篇 |
建筑科学 | 53篇 |
矿业工程 | 1篇 |
能源动力 | 33篇 |
轻工业 | 188篇 |
水利工程 | 13篇 |
石油天然气 | 3篇 |
无线电 | 74篇 |
一般工业技术 | 197篇 |
冶金工业 | 122篇 |
原子能技术 | 9篇 |
自动化技术 | 203篇 |
出版年
2024年 | 3篇 |
2023年 | 17篇 |
2022年 | 40篇 |
2021年 | 56篇 |
2020年 | 41篇 |
2019年 | 40篇 |
2018年 | 32篇 |
2017年 | 46篇 |
2016年 | 39篇 |
2015年 | 49篇 |
2014年 | 48篇 |
2013年 | 76篇 |
2012年 | 67篇 |
2011年 | 91篇 |
2010年 | 63篇 |
2009年 | 70篇 |
2008年 | 46篇 |
2007年 | 43篇 |
2006年 | 35篇 |
2005年 | 32篇 |
2004年 | 28篇 |
2003年 | 21篇 |
2002年 | 20篇 |
2001年 | 22篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 34篇 |
1997年 | 24篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 16篇 |
1992年 | 9篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
排序方式: 共有1317条查询结果,搜索用时 312 毫秒
41.
Smart metal sheets by direct functional integration of piezoceramic fibers in microformed structures
A. Schubert V. Wittstock H.-J. Koriath S. F. Jahn S. Peter B. Müller M. Müller 《Microsystem Technologies》2014,20(6):1131-1140
Microassembly of piezoceramic fibers in micro cavities at the surface of sheet metal is a novel approach for high volume production of smart adaptronic structural metal parts. In this paper a technology, manufacturing processes and characterization results of metal sheets with an active piezo-metal substructure based on directly integrated piezoceramic fibers are described. The processes include micro-milling of cavities in sheet metal, precision grinding of piezoceramic fibers, PECVD insulating layers with high dielectric strength, microassembly and force-locked joining by forming. In experiments, measurements of the surface roughness and geometric parameters of the piezoceramic fibers and micro cavities were performed. Further, the electrical properties of the insulation coatings were measured. The sensor function of the piezo-metal substructure was proven by a mechanical excitation resulting in a proportional measured sensor signal. 相似文献
42.
Electrically insulating polymeric nanocomposites with enhanced thermal conductivity by visible‐light curing of epoxy–boron nitride nanotube formulations 下载免费PDF全文
Marco Sangermano Nicolò Razza Gabriele Graham Irati Barandiaran Galder Kortaberria 《Polymer International》2017,66(12):1935-1939
Epoxy–boron nitride nanotube (BNNT) composites were prepared using visible light through a radical‐induced cationic polymerization method activated by camphorquinone. The fully cured films showed an enhancement of glass transition temperature in the presence of the filler. Electrical characterization showed a slight dielectric constant decrease with BNNT content. Finally, thermal conductivity measured using nano‐flash analysis showed a linear increase in the thermal conductivity of the materials with increasing BNNT content in the photocurable formulations. © 2017 Society of Chemical Industry 相似文献
43.
44.
45.
Cold forming generally allows the fast generation of parts with very low tolerances. In addition, mechanical properties are improved, if work hardening materials are used. Transferring the cold forming process to micro range leads to a decrease in the maximum achievable upset ratio so that the forming process becomes inefficient. Therefore, a laser-based free form heading process has been developed to generate preforms which can be calibrated in a secondary cold forming step. The achievable upset ratios reach values of several hundreds instead of 2.1 which is common for single step mechanical upsetting. In this article, heat losses arising in the material accumulation process using laser-based free form heading are analyzed and discussed. For this purpose, the process is modeled within the framework of continuum mechanics and simulated by a finite element method. By using a numerical approach, a systematic study on heat losses is performed in order to identify the influence of radiation, heat transfer due to convection and thermal conduction during laser irradiation time. The simulation results, which are validated with experimental data, show that the radiation is the most important mechanism reducing the efficiency of the accumulation process. 相似文献
46.
Markus F. Weber Gabriele Poxleitner Elke Hebisch Erwin Frey Madeleine Opitz 《Journal of the Royal Society Interface》2014,11(96)
Dispersal of species is a fundamental ecological process in the evolution and maintenance of biodiversity. Limited control over ecological parameters has hindered progress in understanding of what enables species to colonize new areas, as well as the importance of interspecies interactions. Such control is necessary to construct reliable mathematical models of ecosystems. In our work, we studied dispersal in the context of bacterial range expansions and identified the major determinants of species coexistence for a bacterial model system of three Escherichia coli strains (toxin-producing, sensitive and resistant). Genetic engineering allowed us to tune strain growth rates and to design different ecological scenarios (cyclic and hierarchical). We found that coexistence of all strains depended on three strongly interdependent factors: composition of inoculum, relative strain growth rates and effective toxin range. Robust agreement between our experiments and a thoroughly calibrated computational model enabled us to extrapolate these intricate interdependencies in terms of phenomenological biodiversity laws. Our mathematical analysis also suggested that cyclic dominance between strains is not a prerequisite for coexistence in competitive range expansions. Instead, robust three-strain coexistence required a balance between growth rates and either a reduced initial ratio of the toxin-producing strain, or a sufficiently short toxin range. 相似文献
47.
Sheldon M. Wiederhorn Theo Fett Gabriele Rizzi Michael J. Hoffmann Jean-Pierre Guin 《Metallurgical and Materials Transactions A》2013,44(3):1164-1174
When a crack forms in silica glass, the surrounding environment flows into the crack opening, and water from the environment reacts with the glass to promote crack growth. A chemical reaction between water and the strained crack-tip bonds is commonly regarded as the cause of subcritical crack growth in glass. In silica glass, water can also have a secondary effect on crack growth. By penetrating into the glass, water generates a zone of swelling and, hence, creates a compression zone around the crack tip and on the newly formed fracture surfaces. This zone of compression acts as a fracture mechanics shield to the stresses at the crack tip, modifying both the strength and subcritical crack growth resistance of the glass. Water penetration is especially apparent in silica glass because of its low density and the fact that it contains no modifier ions. Using diffusion data from the literature, we show that the diffusion of water into silica glass can explain several significant experimental observations that have been reported on silica glass, including (1) the strengthening of silica glass by soaking the glass in water at elevated temperatures, (2) the observation of permanent crack face displacements near the crack tip of a silica specimen that had been soaked in water under load, and (3) the observation of high concentrations of water close to the fracture surfaces that had been formed in water. These effects are consistent with a model suggesting that crack growth in silica glass is modified by a physical swelling of the glass around the crack tip. An implication of water-induced swelling during fracture is that silica glass is more resistant to crack growth than it would be if swelling did not occur. 相似文献
48.
49.
50.
Annalisa Marcuzzi Elisa Piscianz Marina Zweyer Roberta Bortul Claudia Loganes Martina Girardelli Gabriele Baj Lorenzo Monasta Claudio Celeghini 《International journal of molecular sciences》2016,17(3)
Deregulation of the cholesterol pathway is an anomaly observed in human diseases, many of which have in common neurological involvement and unknown pathogenesis. In this study we have used Mevalonate Kinase Deficiency (MKD) as a disease-model in order to investigate the link between the deregulation of the mevalonate pathway and the consequent neurodegeneration. The blocking of the mevalonate pathway in a neuronal cell line (Daoy), using statins or mevalonate, induced an increase in the expression of the inflammasome gene (NLRP3) and programmed cell death related to mitochondrial dysfunction. The morphology of the mitochondria changed, clearly showing the damage induced by oxidative stress and the decreased membrane potential associated with the alterations of the mitochondrial function. The co-administration of geranylgeraniol (GGOH) reduced the inflammatory marker and the damage of the mitochondria, maintaining its shape and components. Our data allow us to speculate about the mechanism by which isoprenoids are able to rescue the inflammatory marker in neuronal cells, independently from the block of the mevalonate pathway, and about the fact that cell death is mitochondria-related. 相似文献