首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1747篇
  免费   116篇
  国内免费   1篇
电工技术   12篇
化学工业   422篇
金属工艺   36篇
机械仪表   30篇
建筑科学   66篇
矿业工程   2篇
能源动力   53篇
轻工业   148篇
水利工程   7篇
石油天然气   3篇
无线电   209篇
一般工业技术   354篇
冶金工业   94篇
原子能技术   25篇
自动化技术   403篇
  2023年   21篇
  2022年   35篇
  2021年   37篇
  2020年   50篇
  2019年   51篇
  2018年   57篇
  2017年   65篇
  2016年   66篇
  2015年   53篇
  2014年   63篇
  2013年   125篇
  2012年   111篇
  2011年   151篇
  2010年   99篇
  2009年   101篇
  2008年   111篇
  2007年   87篇
  2006年   87篇
  2005年   72篇
  2004年   58篇
  2003年   48篇
  2002年   39篇
  2001年   15篇
  2000年   15篇
  1999年   25篇
  1998年   25篇
  1997年   35篇
  1996年   22篇
  1995年   16篇
  1994年   18篇
  1993年   18篇
  1992年   11篇
  1991年   8篇
  1990年   9篇
  1989年   5篇
  1988年   7篇
  1987年   4篇
  1986年   4篇
  1985年   4篇
  1984年   7篇
  1983年   5篇
  1982年   5篇
  1977年   5篇
  1976年   4篇
  1975年   3篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1967年   1篇
  1954年   1篇
排序方式: 共有1864条查询结果,搜索用时 234 毫秒
81.
82.
In this paper, we propose a method for real-time horizon tracking (i.e., separation line between the sky and the sea) in a maritime operations context. We present the fusion of an image processing algorithm with the data obtained from the inertial measurement unit (IMU). The initial aim is to filter out environmental conditions using inertial information in order to combine a video stream with onboard electronic charts. This is achieved by the detection of the horizon with an image processing algorithm in an area defined by the IMU. We then present an evaluation of the algorithm with regard to the rate of detection of the horizon and the impact of the image resolution on the computational time. The purpose of developing this method is to create an augmented reality maritime operations application. We combine the video stream with electronic charts in a single display. We use the position of the horizon in the image to split the display into different areas. Then, we use transparency to display the video, the electronic charts or both.  相似文献   
83.
The purpose of this work was to study the role of cesium in sodium‐based geopolymer and its thermal stability for nuclear waste management. A series of mixed sodium and cesium geopolymer samples (Na1?x Cs x )2O·Al2O3·SiO2·12H2O (referred to as (Na1? x Cs x )‐GP, where x = 0, 0.08, 0.15, 0.42, 1) have been prepared. All geopolymer samples were heated at 1100°C for 24 h. Pollucite (CsAlSi2O6) and feldspathoid (CsAlSiO4) were crystallized from Cs‐GP. Nepheline (NaAlSiO4) and a small amount of crystallized silica were obtained from Na‐GP. The other geopolymers (Na1? x Cs x )‐GP (x = 0.08, 0.15, 0.42) led to pollucite and nepheline main phases. Amorphous silica phase was observed in all the geopolymer samples with various amounts. Phase quantification and scanning electron microscope revealed that higher Cs concentrations in Na‐GP tend to decrease the amorphous phase while improving pollucite and nepheline phase quantification. The amorphous geopolymers have also been studied by pair distribution function analysis. Tetrahedral chains formed by T–O bonding (with T = Si, Al) were shown to be more tighten around Cs+ than around Na+. It led to shorter Cs–T bond than Na–T bond matching the higher solvation property of Na+. Furthermore, thermal study analysis pointed out the fact that geopolymer samples (Na1? x Cs x )‐GP, can be considered as solid solutions.  相似文献   
84.
Ammonium pentaborate (APB) was used to modify urea formaldehyde (UF) resins, in which the formaldehyde to urea molar ratio was set at 1.80, 1.50, 1.25, and 1.05. Some specific properties, including gel time, free formaldehyde content in UF, bond strength, and formaldehyde emission levels from plywood were evaluated. The result showed that APB increased the gel time length, but also decreased free formaldehyde content and emission levels, which was reduced mostly by 79.0% and 81.4%, respectively. The result of bond strength indicated that APB was proper to modify high F/U molar ratio of UF resin regardless of the loading level, but a recommended loading level should be considered to relevantly lower the F/U molar ratio of UF. The suggested loading level of APB to UF is 8.0% to 6.0%, 6.0%, and 4.0% to UF resin with F/U molar ratio of 1.8, 1.5, and 1.25 separately.  相似文献   
85.
In this work, a new, universal method is described that uses the photopatterning of liquid crystals, which is accurately translated into a controlled, intricately wrinkled metal surface. Remarkably, the patterns have an oscillation in amplitude of the wrinkles. This rapid method allows generation of intricate multidomain patterns and continuous circular structures, including azimuthal, radial, and even higher complexity arrangements as examples. These wrinkled gold surfaces are also strikingly visual, which is interesting for applications ranging from diffractive elements to fine jewelry.  相似文献   
86.
An economic and environment friendly process was adapted to synthesize new dielectric composite materials. Using ethylene vinyl acetate (EVA)/vinyl ester of versatic acid (VeoVa) terpolymer as an aqueous emulsion provides a homogenous dispersion of BaTiO3 (BT) particles, due to the high viscosity and polarity of the vinyl resin (VR). Composites films were obtained from these dispersions by water evaporation. The evolution of the dielectric properties as a function of the BaTiO3 content, was correctly fitted by a Maxwell‐Garnett model. This fitting of the experimental curve shows a good dispersion of filler in the vinyl resin and the particles separation by a layer of resin as expected for the preparation method used in this study. The VR/BT composites show good synergy between the dielectric properties of the different phases of the composites due to the formation of macrodipoles and to the strong interactions between polar EVA/VeoVa groups and the BaTiO3 particles surface. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44333.  相似文献   
87.
Varying the formulation and processing conditions of polymer blends allows the design of materials with a large range of morphologies. Active materials embedding active compounds in a devoted phase are promising applications of such blends, offering possible various transport properties. In this study, 13 poly(butylene succinate‐co‐butylene adipate) (PBSA)/polyethylene oxide (PEO) blends were extruded in a slit die. Their morphologies were characterized by water extraction (selective PEO dissolution), FTIR spectroscopy, and differential scanning calorimetry. Transport properties were assessed by water vapor permeation and fluorescein release as model migrant. Indeed, the desorption in water of fluorescein (previously entrapped in PEO) was monitored to preliminary investigate the release properties of these materials: two morphologies were obtained (i) pseudo multilayer films made of PEO‐rich layer/PBSA‐rich layer/PEO‐rich layer and (ii) PEO nodules dispersed in the PBSA‐rich matrix for the highest PBSA contents. The first systems were erodible ones with an uncontrolled fast delivery by PEO dissolution whereas the second ones showed a controlled release by permeation through the PBSA matrix from PEO nodules. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42874.  相似文献   
88.
89.
The continuous use of chemical dyes in various industries, and their discharge into industrial effluents, results in severe problems to human life and water pollution. Laccases have the ability to decolorize dyes and toxic chemicals in industrial effluents as green biocatalysts. Their possible industrial applications have been limited by poor reusability, low stability, and loss of free laccase action. In this research, laccase was immobilized on zeolitic imidazolate framework coated multi-walled carbon nanotubes (Laccase@ZIF-8@MWCNTs) via metal affinity adsorption to develop an easy separable and stable enzyme. The optimum reaction conditions for immobilized laccase are at a pH of 3.0 and a temperature of 60?℃. The immobilized laccase was enhanced in storage and thermal stability. The results indicated that Laccase@ZIF-8@MWCNTs still maintained 68% of its original activity after 10 times of repeated use. Most importantly, the biocatalytic system was applied for decolorization of different dyes (20?mg·L?1) without a mediator, and up to 97.4% for Eriochrome black T and 95.6% Acid red 88 was achieved in 25 min. Biocatalysts with these properties may be used in a variety of environmental and industrial applications.  相似文献   
90.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号