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   343篇
  免费   18篇
  国内免费   3篇
电工技术   2篇
化学工业   105篇
金属工艺   2篇
机械仪表   4篇
建筑科学   11篇
能源动力   17篇
轻工业   60篇
水利工程   3篇
石油天然气   7篇
无线电   23篇
一般工业技术   70篇
冶金工业   4篇
原子能技术   1篇
自动化技术   55篇
  2024年   3篇
  2023年   20篇
  2022年   20篇
  2021年   24篇
  2020年   15篇
  2019年   14篇
  2018年   22篇
  2017年   11篇
  2016年   19篇
  2015年   7篇
  2014年   9篇
  2013年   25篇
  2012年   20篇
  2011年   23篇
  2010年   16篇
  2009年   16篇
  2008年   16篇
  2007年   16篇
  2006年   6篇
  2005年   14篇
  2004年   6篇
  2003年   6篇
  2002年   2篇
  2001年   6篇
  2000年   3篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1996年   3篇
  1994年   1篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   2篇
  1984年   1篇
  1982年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
排序方式: 共有364条查询结果,搜索用时 15 毫秒
101.
102.
The optimal design of renewable-based distributed generations (DGs) is a challenging issue in order to maximise their benefits and to overcome power quality problems. Therefore, this paper proposes a methodology for optimal allocation and sizing of renewable DG units to minimise total power losses over radial distribution systems. The planning problem is formulated as a single objective nonlinear mixed integer-constrained optimisation problem and is solved by using the augmented Lagrangian genetic algorithm (ALGA) by combining the objective function and the nonlinear constraints. In that case, the ALGA solves a sequence of sub-problems where the objective function penalises the constraints violation in order to obtain the best solution. The proposed technique is applied to IEEE radial test systems including 33-bus, 69-bus and 119-bus and is implemented with different scenarios including all possible combinations and various types of renewable DG units to prove the effectiveness of the proposed methodology.  相似文献   
103.
Neat ethylacetoacetate (EAA) and its mixtures with a co-solvent and an anti-solvent have been studied for refining of heavy wax distillate fraction to produce substantially non-carcinogenic base oil. The co-solvent and anti-solvent used are dipropylene glycol (DPG) and ethylene glycol (EG) respectively. The solubility characteristics of the main solvent and its mixed solvent systems were studied. Selection of the optimum solvent mixture and extraction variables has been studied. The effect of co-solvent and anti-solvent addition on the carcinogenic potential and raffinate quality has been determined under clearly comparable conditions.  相似文献   
104.
NiO-Samaria-Doped-Ceria (NiO-SDC) composite powders was synthesized by a traditional mechanical mixing process and tested as anode material for Direct Carbon Fuel Cell (DCFC), which uses almond shell biochar as fuel and molten carbonate-doped ceria composite as electrolyte. A three-layer pellet cell, viz. cathode (Lithiated NiO-SDC), composite electrolyte and anode (NiO-SDC) is fabricated by a die-pressing, screen printing and sintering method.  相似文献   
105.
We have prepared polycrystalline R2NiMnO6 (R = Nd, Eu, Gd, Dy, and Y) samples by conventional solid‐state reaction and all the samples have shown monoclinic structure with P21/n space group. With the decrease in rare‐earth ionic size (<rR>), the <Ni–O–Mn> bond angle decreases, correspondingly a decrease in ferromagnetic (FM) Curie temperature is noticed. In the dielectric measurement, the dielectric anomaly shifts to high temperature with the decrease in the <rR> and shows no correlation with the FM Curie temperature and hints the absence of apparent magnetodielectric (MD) coupling. Appearance of multiple relaxations in the dielectric study suggests the electrical heterogeneity of the system. The dielectric/impedance analysis has revealed a close correlation between dc conductivity and the dielectrics; in fact, both dc resistivity and the grain relaxations follow the variable range hopping mechanism. The thermal activation of charge carriers at the grain boundary led to Maxwell–Wagner interfacial polarization. Finally, dielectric study under magnetic field showed no effect, it implies that not only the intrinsic MD is absent, but also the extrinsic MD due to the lack of magnetoresistance.  相似文献   
106.
A novel series of ferrocenyl surfactants was synthesized by the reaction of ferrocene disulfonic acid with different primary and tertiary fatty amines to produce the corresponding ammonium salts Fc[SO3 +NH3(CH2) n CH3]2, where n = 9, 11, or 15 and Fc[SO3− +NH(CH3)2(CH2) n CH3]2, where n = 7 or 11, respectively, and where Fc = ferrocene. Chemical structures were confirmed by microelemental analysis, FTIR, and 1H NMR spectroscopy. The critical micelle concentration of each prepared surfactant was determined using equilibrium surface tension. Furthermore, air/water interface parameters including effectiveness (π CMC), efficiency (Pc20), maximum surface excess (Гmax), and minimum surface area (A min) were determined at 30, 40, and 50 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) for both micellization and adsorption processes were recorded. The new synthesized surfactants were screened as antimicrobial agents against different bacterial and fungal organisms.  相似文献   
107.
108.
This work is confined to the preparation and characterization of acrylate polymeric additives. These additives were prepared by esterification of acrylic acid with different alcohols (decyl, 1-dodecyl, 1-tetradecyl, and hexadecyl) and then copolymerization of the prepared esters with different moles of styrene. The molecular weights of the prepared copolymers were determined by GPC. The efficiency of the prepared copolymers for improving the viscosity index of the lube oil was studied. It was found that the efficiency increases with increasing the molecular weight of the prepared copolymers.  相似文献   
109.
110.
Watermarking of digital images is required in diversified applications ranging from medical imaging to commercial images used over the web. Usually, the copyright information is embossed over the image in the form of a logo at the corner or diagonal text in the background. However, this form of visible watermarking is not suitable for a large class of applications. In all such cases, a hidden watermark is embedded inside the original image as proof of ownership. A large number of techniques and algorithms are proposed by researchers for invisible watermarking. In this paper, we focus on issues that are critical for security aspects in the most common domains like digital photography copyrighting, online image stores, etc. The requirements of this class of application include robustness (resistance to attack), blindness (direct extraction without original image), high embedding capacity, high Peak Signal to Noise Ratio (PSNR), and high Structural Similarity Matrix (SSIM). Most of these requirements are conflicting, which means that an attempt to maximize one requirement harms the other. In this paper, a blind type of image watermarking scheme is proposed using Lifting Wavelet Transform (LWT) as the baseline. Using this technique, custom binary watermarks in the form of a binary string can be embedded. Hu’s Invariant moments’ coefficients are used as a key to extract the watermark. A Stochastic variant of the Firefly algorithm (FA) is used for the optimization of the technique. Under a prespecified size of embedding data, high PSNR and SSIM are obtained using the Stochastic Gradient variant of the Firefly technique. The simulation is done using Matrix Laboratory (MATLAB) tool and it is shown that the proposed technique outperforms the benchmark techniques of watermarking considering PSNR and SSIM as quality metrics.  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