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   1115篇
  免费   32篇
  国内免费   8篇
电工技术   13篇
综合类   2篇
化学工业   181篇
金属工艺   45篇
机械仪表   65篇
建筑科学   21篇
能源动力   64篇
轻工业   28篇
水利工程   2篇
石油天然气   3篇
无线电   148篇
一般工业技术   267篇
冶金工业   103篇
原子能技术   13篇
自动化技术   200篇
  2024年   7篇
  2023年   14篇
  2022年   42篇
  2021年   63篇
  2020年   46篇
  2019年   36篇
  2018年   48篇
  2017年   29篇
  2016年   49篇
  2015年   27篇
  2014年   41篇
  2013年   64篇
  2012年   44篇
  2011年   61篇
  2010年   42篇
  2009年   49篇
  2008年   52篇
  2007年   33篇
  2006年   44篇
  2005年   31篇
  2004年   32篇
  2003年   19篇
  2002年   24篇
  2001年   12篇
  2000年   16篇
  1999年   13篇
  1998年   15篇
  1997年   14篇
  1996年   22篇
  1995年   16篇
  1994年   17篇
  1993年   9篇
  1992年   8篇
  1991年   15篇
  1990年   6篇
  1989年   11篇
  1988年   14篇
  1987年   8篇
  1986年   5篇
  1985年   11篇
  1984年   7篇
  1983年   2篇
  1982年   3篇
  1981年   8篇
  1979年   7篇
  1978年   2篇
  1977年   3篇
  1976年   5篇
  1975年   3篇
  1974年   3篇
排序方式: 共有1155条查询结果,搜索用时 281 毫秒
51.
This paper presents a micromagnetoelastic sensor array for simultaneously monitoring multiple biological agents. Magnetoelastic sensors, made of low-cost amorphous ferromagnetic ribbons, are analogous and complementary to piezoelectric acoustic wave sensors, which track parameters of interest via changes in resonance behavior. Magnetoelastic sensors are excited with magnetic ac fields, and, in turn, they generate magnetic fluxes that can be detected with a sensing coil from a distance. As a result, these sensors are highly attractive, not only due to their small size and low cost, but also because of their passive and wireless nature. Magnetoelastic sensors have been applied for monitoring pressure, temperature, liquid density, and viscosity, fluid How velocity and direction, and with chemical/biological responsive coatings that change mass or elasticity, various biological and chemical agents. In this paper, we report the fabrication and application of a six-sensor array for simultaneous measurement of Escherichia coli O157:H7, staphylococcal enterotoxin B, and ricin. In addition, the sensor array also monitors temperature and pH so the measurements are independent from these two parameters.  相似文献   
52.
A parallel, unstructured, high-order discontinuous Galerkin method is developed for the time-dependent Maxwell's equations, using simple monomial polynomials for spatial discretization and a fourth-order Runge–Kutta scheme for time marching. Scattering results for a number of validation cases are computed employing polynomials of up to third order. Accurate solutions are obtained on coarse meshes and grid convergence is achieved, demonstrating the capabilities of the scheme for time-domain electromagnetic wave scattering simulations.  相似文献   
53.
Solution techniques for Markov decision problems rely on exact knowledge of the transition rates, which may be difficult or impossible to obtain. In this paper, we consider Markov decision problems with uncertain transition rates represented as compact sets. We first consider the problem of sensitivity analysis where the aim is to quantify the range of uncertainty of the average per‐unit‐time reward given the range of uncertainty of the transition rates. We then develop solution techniques for the problem of obtaining the max‐min optimal policy, which maximizes the worst‐case average per‐unit‐time reward. In each of these problems, we distinguish between systems that can have their transition rates chosen independently and those where the transition rates depend on each other. Our solution techniques are applicable to Markov decision processes with fixed but unknown transition rates and to those with time‐varying transition rates.  相似文献   
54.
Wireless Personal Communications - Applications of wireless sensor networks (WSNs) are increasing tremendously to facilitate and establish a link between the physical world and information system....  相似文献   
55.
Optimization and Engineering - Aircraft ejection systems are lifesaving devices used, in case of emergencies for military pilots. As per current literature the success rate of ejections happening...  相似文献   
56.
57.
58.
The design of Cellular Manufacturing Systems (CMS) has attained the significant attention of academicians and practitioners over the last three decades. Minimizing intercellular movements while maximizing utilization of machines are the main objectives of interest in designing CMS and are considered in present research. In this paper, the drawbacks of former neural networks-based approaches to cell formation are discussed. The standard version of cell formation problem is formulated and a 'Transiently Chaotic Neural Network' (TCNN) with supplementary procedures is introduced as a powerful rival. A simplified network is constructed. After developing the related equations the approach is tested using the proposed algorithm with 18 problems selected from literature. The results are compared with various other approaches including ART1, Extended-ART1, Ortho-Synapse Hopfield Neural Network (OSHN), etc. The main advantages of our proposed method are: (1) the ability to avoid the local optima trap, (2) the ability to solve problems of different sizes with the same set of values for parameters, and (3) the less computation time. The results also indicate considerable improvement in grouping efficiency through the proposed approach.  相似文献   
59.
BACKGROUND: The constructed soil filter (CSF), also known as soil biotechnology is a system for water renovation, which makes use of formulated media, culture of soil micro‐ and macro‐organisms, additives and plantation to purify water and wastewater. The process gives benefits in terms of applicability across very small to large scale, natural aeration, absence of moving parts, no biological sludge generation, odor free green aesthetic ambience. RESULTS: Residence time distribution (RTD) studies were carried out using laboratory scale CSF. Pulse potassium bromide tracer tests were carried out to determine RTD, and the Peclet number found to be 9–13 for a 2 m bed, and 2–3 for a 0.30 m bed with oxygen transfer of 0.08 h?1. CONCLUSION: The two‐channel dispersion model for flow behavior shows a good fit to the experimental data, indicating a reactor Peclet number 9–13 for a 2 m bed and 2–3 for a 0.3m bed. Oxygen transfer studies carried out using various methods gave an oxygen transfer coefficient of about 0.08 h?1. Wastewater purification studies indicate overall COD removal rate of around 50 mg L?1 h?1, suggesting that highly aerobic conditions are prevalent in the CSF system. Copyright © 2009 Society of Chemical Industry  相似文献   
60.
The direct α‐Csp2 H functionalization and thiomethylation of α‐oxoketene dithioacetals (DTAs) has been accomplished with dimethyl sulfoxide (DMSO) in the presence of iodine and a copper(I) salt for the first time. A prerequisite is the in situ iodination of the α‐Csp2 atom of dithioacetals that could offer other reaction channels. The operationally simple one‐pot protocol includes region‐defined consecutive iodination and sulfenylation of the challenging α‐Csp2 H bond of dithioacetals employing cheap and readily available reagents. DMSO here plays a dual role as thiomethyl source and solvent.

  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