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   182篇
  免费   10篇
  国内免费   1篇
电工技术   4篇
化学工业   43篇
金属工艺   4篇
机械仪表   4篇
建筑科学   6篇
能源动力   23篇
轻工业   4篇
无线电   20篇
一般工业技术   37篇
冶金工业   8篇
原子能技术   1篇
自动化技术   39篇
  2024年   3篇
  2023年   3篇
  2022年   9篇
  2021年   8篇
  2020年   4篇
  2019年   4篇
  2018年   8篇
  2017年   6篇
  2016年   9篇
  2015年   8篇
  2014年   11篇
  2013年   16篇
  2012年   8篇
  2011年   19篇
  2010年   12篇
  2009年   10篇
  2008年   6篇
  2007年   8篇
  2006年   7篇
  2005年   1篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1985年   2篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1971年   1篇
  1968年   1篇
排序方式: 共有193条查询结果,搜索用时 15 毫秒
41.
42.
The focus of this paper is to demonstrate the close links between the airline and the manufacturing industry in so far as some of their decision support problems are concerned. We show that the yield management (YM) problem for the airline characterized by perishable and limited resources has counterparts in manufacturing and retail although with some variations. In the process of establishing similarities we highlight the importance of the concept of value of assets/resources, known as bid price in the airline terminology, that ties the two together. Several examples of its calculations and uses are provided. We believe that this new paradigm will open up new avenues for profits for manufacturers in the new era of e-commerce where the businesses shall have to be increasingly customer centric including pricing functions.  相似文献   
43.
Microsystem Technologies - The non-planar 3D structure of multi-gate FinFETs makes them able to be scaled down to 20 nm and beyond and also have greater performance. But any variation of...  相似文献   
44.
In this article, the authors proposed an eight‐element linear array of fractal antennas for dedicated short range communication (DSRC; 5.9 GHz) service band. The single element of the array is a newly proposed fractal antenna whose radiating patch is derived from the Fibonacci series with the incorporation of Koch snowflake, and it poses a 2D quadrantal symmetry. The gain of the structure is improved by down shifting the radiating patch with respect to its ground plane. The feed network of the array is designed in such a manner to make the structure compact as well as to use the advantage of array mutual coupling for improving the array radiation pattern. The fabricated single element gives 7.54 dB gain and 128 MHz bandwidth with a radiation efficiency of η = 85.11%. The prototype array gives 15.18 dB gain with 105 MHz bandwidth and radiation efficiency of η = 72.12%. The measured cross‐polarization of single element and the array along the direction of the main beam are less than ?80 dB and ?60 dB, respectively, in both the xz‐ and yz‐plane. Both single element and the array are capable of satisfying the bandwidth requirements for DSRC applications.  相似文献   
45.
Recently, high-efficiency video coding (HEVC) has been developed as a new video coding standard focusing on the coding of ultrahigh definition videos as high-resolution and high-quality videos are getting more popular. However, one of the most important challenges in this new standard is its encoding time complexity. Due to this it is quite difficult to implement the HEVC encoder as a real-time system. In this paper, we have addressed this problem in a new way. Generally, for a natural video sequence good amount of coding blocks are “skip” in nature, which need not be transmitted and can be generated in the decoder side using the reference pictures. In this paper, we propose an early skip detection technique for the HEVC. Our proposed method is based on identifying the motionless and homogeneous regions in a video sequence. Moreover, a novel entropy difference-based calculation is proposed in this paper which can predict the skip coding blocks more accurately in a natural video sequence. The experimental result shows our proposed technique can achieve more than 30 % encoding time reduction than the conventional HEVC encoder with negligible degradation in video quality.  相似文献   
46.
As a fascinating alternative to the energy-intensive Haber-Bosch process,the electrochemically-driven N2 reduction reaction (NRR) utilizing the N2 and H2O for the production of NH3 has received enormous attention.The development and preparation of promising electrocatalysts are requisite to realize an effi-cient N2 conversion for NH3 production.In this research,we propose a template-assisted strategy to con-struct the hollow electrocatalyst with controllable morphology.As a paradigm,the hollow Cr2O3 nanocatalyst with a uniform size (~170 nm),small cavity and ultrathin shell (~15 nm) is successfully fabricated with this strategy.This promising hollow structure is favourable to trap N2 into the cavity,pro-vides abundant active sites to accelerate the three-phase interactions,and facilitates the reactant transfer across the shell.Attributed to these synergetic effects,the designed catalyst displays an outstanding behaviour in N2 fixation for NH3 production in ambient condition.In the neutral electrolyte of 0.1 mol·L-1 Na2SO4,an impressive electrocatalytic performance with the NH3 generation rate of 2.72 μg·h-1·cm 2 and a high FE of 5.31% is acquired respectively at-0.85 V with the hollow Cr2O3 cat-alyst.Inspired by this work,it is highly expected that this approach could be applied as a universal strat-egy and extended to fabricating other promising electrocatalysts for realizing highly efficient nitrogen reduction reaction (NRR).  相似文献   
47.
Glaze in the CaO–MgO–Al2O3–SiO2 system was heated at 950–1190 °C for 2 h and characterized. X-ray diffraction showed that only trace amount of mullite was formed in the glass-ceramic glaze heated at 950 °C. Both mullite and α-cordierite were formed in the glass-ceramic glaze heated at 1050 °C as primary and secondary phases. Glass-ceramic glazes heated at 1120 °C and 1190 °C contained α-cordierite and mullite as major and minor phases. Rietveld analysis revealed that the amount of α-cordierite increased and mullite decreased with increasing heating temperature. Field emission scanning electron microscopy showed presence of mullite crystals dispersed within residual glassy phase in the glass-ceramic glazes heated at 950 °C and 1050 °C. In the microstructures of glass-ceramic glazes heated at 1120 °C and 1190 °C α-cordierite crystals were mainly appeared. Energy Dispersive X-ray analysis corroborated X-ray diffraction results. Vickers microhardness measurement demonstrated highest hardness (8.38 ± 0.07 GPa) of the glass-ceramic glaze heated at 1190 °C.  相似文献   
48.
The quality and commercial value of fruits largely depend on color, texture, appearance, nutritional value, and other factors that cease the growth of the microbes causing food spoilage. Coating with suitable edible material would keep fruits fresh for a considerable time after their harvest till it reaches to the demanding consumers. The nonedible portions (peel, crown) of pineapple are identified as an inexpensive source for the production of such edible coating material. The present work is focused on the extraction and physicochemical analysis of cellulose prepared from waste bio-mass of pineapple fruit. Physicochemical characterization of the cellulose is performed using X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. The extracted cellulose is converted to carboxymethyl cellulose and formulated as a coating film in conjugation with other suitable substances. The formulated coating is applied on banana fruit to check the performance of protection against the natural degradation of the fruit. FTIR analysis of the extracted cellulose has confirmed the removal of lignin and hemicelluloses molecules from the waste biomass of pineapple. X-ray diffraction analysis has shown the crystal size of extracted cellulose was 3.23 nm with 35.62% crystallinity. Degree of substitution (DS) is estimated 0.523 for carboxymethyl cellulose prepared from the extracted cellulose. Application of coating has shown the increment in shelf-life period of banana in comparison with control up to 8 days of storage at ambient condition. This study has demonstrated a sustainable process to transform waste biomass into carboxymethyl cellulose based coating for improving storage capacity of banana fruit.  相似文献   
49.
The commercial hydrogen production by water electrolysis is limited by the high cost of electricity. The production cost can be minimized, if the cell module is operated with the minimum voltage at maximum current density. In the present study, porous nickel electrodes were developed indigenously on an engineering scale and used in an advanced zero gap filter press type bipolar electrolyser to minimize the cell voltage. As the cell voltage–current density characteristic of the cell module is unique feature of its design and the operating parameters, the polarization experiments were carried out using this cell module and the cell voltage–current density characteristics were generated at different operating temperatures. Further, the system is modelled for its electrochemical performance and the parameters accounting for different losses such as Ohmic and activation over potential, were estimated at different temperatures. These different parameters were compared with the data existing in literature and based on the analysis, the present cell module is found to be superior to the existing commercial electrolyzers in terms of energy efficiency.  相似文献   
50.
The present study is aimed to understand the influence of dynamic precipitation on the low cycle fatigue (LCF) behavior of an under-aged (UA) AA6063 Al–Mg–Si alloy. This was accomplished by the estimation of plastic strain energy density (PSED) at varied isolated cycles during LCF of the UA alloy with subsequent comparison of these results with those of peak-aged (PA) and over-aged (OA) ones. The LCF tests of the UA alloy were carried out in the range of strain amplitudes of 0.2–1.0 % together with the evolution of hardness and tensile properties. The UA alloy shows Masing behavior, evaluated in terms of the variation of Bauschinger strain with plastic strain amplitude, and exhibits continuous hardening till failure unlike the PA and OA alloys. Higher average PSED value for the UA alloy in comparison to that for the PA and the OA alloys indicates dynamic precipitation during cycling; the magnitudes of average PSED were calculated using a proposed method. In addition, pronounced increase in the post LCF hardness values substantiate the dynamic precipitation.  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