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   265篇
  免费   4篇
电工技术   3篇
化学工业   60篇
金属工艺   11篇
机械仪表   16篇
建筑科学   2篇
能源动力   5篇
轻工业   36篇
水利工程   3篇
石油天然气   1篇
无线电   29篇
一般工业技术   76篇
冶金工业   7篇
自动化技术   20篇
  2023年   9篇
  2022年   11篇
  2021年   11篇
  2020年   12篇
  2019年   10篇
  2018年   16篇
  2017年   10篇
  2016年   11篇
  2015年   6篇
  2014年   11篇
  2013年   18篇
  2012年   13篇
  2011年   23篇
  2010年   6篇
  2009年   15篇
  2008年   20篇
  2007年   7篇
  2006年   8篇
  2005年   3篇
  2004年   5篇
  2003年   2篇
  2002年   5篇
  2001年   2篇
  2000年   4篇
  1999年   2篇
  1998年   4篇
  1997年   2篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1989年   3篇
  1987年   3篇
  1986年   5篇
  1985年   1篇
  1980年   1篇
  1976年   1篇
  1974年   2篇
  1971年   1篇
排序方式: 共有269条查询结果,搜索用时 15 毫秒
1.
Wireless Personal Communications - Despite its various benefits, the Mobile Ad-hoc Network (MANET) has a number of obstacles due to its mobility, unstable topology, energy efficiency, and other...  相似文献   
2.
3.
TiO2 nanoparticles decorated nitrogen (N) doped helical carbon nanofiber (CNF)-carbon nanotube (CNT) hybrid material is prepared by low-cost electrospinning technique followed by hydrothermal method. Morphological investigations establish helical structure of CNFs with hierarchical growth of CNTs around CNFs. The hybrid material shows a high specific surface area of 295.17 m2 g?1 with nanoporous structure. X-ray photoelectron spectroscopic studies establish Ti–O–C/Ti–C bond mediated charge transfer channel between TiO2 nanoparticles and carbon structures with the success of N doping in CNFs. The electrospun hybrid material delivered high reversible charge capacities of 316 mAh g?1 (100th cycle) and 244 mAh g?1 (100th cycle) at a current density of 75 mA g?1 and 186 mA g?1 respectively. The charge capacities obtained for different applied current densities are higher than the conventional graphitic microporous microbeads anode. Results indicate that the hybrid material reported here shows high performance compare to graphite for LIBs.  相似文献   
4.
5.
Multimedia Tools and Applications - The quality and quantity of agricultural products are significantly affected by plant diseases. The plant diseases could be mitigated if identified at an early...  相似文献   
6.
This paper elucidates Common Mode Voltage (CMV) reduction in transformerless 3-phase 3-level Coupled Inductor Neutral Point (CI-NPC) Clamped Inverter with Hybrid Energy System. The three dimensional Space Vector Pulse Width Modulation (3D-SVPWM) with Nearest State Vector (NSV) is implemented to reduce the CMV by proper selection of medium, large and small vectors in 3D cubic space region. This NSV scheme in addition to CMV reduction, reduces the capacitor voltage balancing issues and minimizes switching losses. The proposed control provides full utilization of dc link voltage with reduced harmonics. This 3-level CI-NPC inverter is energized by hybrid energy source which includes photovoltaic system and wind energy system. The results obtained for the proposed scheme through simulation and experimental setup is compared with the conventional 2D-SVPWM and 3D-SVPWM scheme. From the compared results it is evident that the proposed scheme reduces CMV to a larger extent than 2D and 3D-SVPWM control. The simulation and experimental results are verified using matlab-simulink and FPGA-Spartan-6 controller respectively.  相似文献   
7.
8.
Nano-Micro Letters - Magnesia (MgO) nanoparticles were produced from magnesite ore (MgCO3) using ball mill. The crystalline size, morphology and specific SSA were characterized by X-ray diffraction...  相似文献   
9.
Organic solar cells have been significantly attracted due to the need to develop an inexpensive clean and sustainable renewable energy source. We report on the fabrication of poly [N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]/[6, 6]-phenyl-C71-butyric acid methyl ester blend active layer using airbrush spray-coating method in mixed solvents. Optical absorption of the active layers was analyzed using UV–visible spectral studies in the wavelength range from 300 to 800 nm. The surface morphology of the active layers deposited with different parameters (spraying time and substrate-nozzle distance) was examined using atomic force microscopy. The current density–voltage (JV) characteristics of photovoltaic cells were measured under the illumination of simulated solar light with 100 mW cm?2 (AM 1.5G) by an Oriel 1000 W solar simulator. The power conversion efficiency of the solar cell is more than 5 %.  相似文献   
10.
Machining chips of commercially pure Ti (ASTM grade 2) were consolidated into full density by equal channel angular pressing (ECAP) with an average grain size as low as 0.8 μm, yield strength up to 650 MPa, and ductility of ~16%. Effect of recycling condition on the microstructure and mechanical properties were investigated in terms of ECAP temperature, number of passes and chemical composition. Using electron backscatter diffraction it is evident that continuous dynamic recrystallization (however, which is purely a phenomenological terminology) plays a significant role in grain (with misorientation ≥15°) formation, whilst benefitting from high stacking fault energy, this continuous conversion of subgrain (<15°) into grain can be essentially considered as an extended recovery with a substantial presence of low angle grain boundaries in the recycled Ti. The Hall–Petch relationship is adapted to explain the strengthening of the recycled Ti. Additionally, using scanning electron microscopy fractography, the ductility was analyzed by a modified Griffith criterion. Last, superior energy efficiency of ECAP reduces environmental impact when comparing to conventional melting/casting. ECAP develops an innovative solid-state process for improving the recycling value of waste Ti.  相似文献   
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