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   611篇
  免费   26篇
电工技术   6篇
综合类   1篇
化学工业   113篇
金属工艺   13篇
机械仪表   28篇
建筑科学   16篇
能源动力   23篇
轻工业   74篇
水利工程   4篇
石油天然气   1篇
无线电   110篇
一般工业技术   93篇
冶金工业   78篇
原子能技术   3篇
自动化技术   74篇
  2023年   10篇
  2022年   24篇
  2021年   29篇
  2020年   18篇
  2019年   20篇
  2018年   36篇
  2017年   25篇
  2016年   29篇
  2015年   19篇
  2014年   13篇
  2013年   53篇
  2012年   23篇
  2011年   22篇
  2010年   40篇
  2009年   36篇
  2008年   28篇
  2007年   15篇
  2006年   15篇
  2005年   11篇
  2004年   9篇
  2003年   5篇
  2002年   3篇
  2001年   5篇
  2000年   3篇
  1999年   5篇
  1998年   21篇
  1997年   13篇
  1996年   8篇
  1995年   8篇
  1994年   9篇
  1993年   6篇
  1992年   10篇
  1991年   8篇
  1990年   9篇
  1989年   7篇
  1988年   3篇
  1987年   5篇
  1986年   2篇
  1985年   3篇
  1984年   1篇
  1982年   2篇
  1981年   4篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   4篇
  1976年   7篇
  1974年   2篇
  1973年   2篇
  1961年   1篇
排序方式: 共有637条查询结果,搜索用时 15 毫秒
1.
Neural networks and blood cell identification   总被引:1,自引:0,他引:1  
The objective of this project is to propose a method of identifying cells found in human blood and to classify them based upon their morphological features using neural networks. The project focuses on three major blood cell types, namely, erythrocytes, leukocytes and platelets. The data are collected using peripheral blood smears from clinical patients. The image acquisition requires 100x magnification on all the blood smears, the preprocessing involves the use of median and edge enhance filters; the feature extraction is done by performing the wavelet transform on the images. Finally classification of the blood cell types is done using ALOPEX and Back Propagation trained neural networks. The efficacy of both networks is then compared by comparing their outputs and number of iterations required to reach the final result.  相似文献   
2.
Spent Ni–Cd batteries are now considered an important source for many valuable metals. The recovery of cadmium, cobalt, and nickel from spent Ni–Cd Batteries has been performed in this study. The optimum leaching process was achieved using 20% H2SO4, solid/liquid (S/L) 1/5 at 80 °C for 6 h. The leaching efficiency of Fe, Cd, and Co was nearly 100%, whereas the leaching efficiency of Ni was 95%. The recovery of the concerned elements was attained using successive different separation techniques. Cd(II) ions were extracted by a solvent, namely, Adogen® 464, and precipitated as CdS with 0.5% Na2S solution at pH of 1.25 and room temperature. The extraction process corresponded to pseudo-2nd-order. The prepared PTU-MS silica was applied for adsorption of Co(II) ions from aqueous solution, while the desorption process was performed using 0.3 M H2SO4. Cobalt was precipitated at pH 9.0 as Co(OH)2 using NH4OH. The kinetic and thermodynamic parameters were also investigated. Nickel was directly precipitated at pH 8.25 using a 10% NaOH solution at ambient temperature. FTIR, SEM, and EDX confirm the structure of the products.  相似文献   
3.
Quality-aware images.   总被引:4,自引:0,他引:4  
We propose the concept of quality-aware image, in which certain extracted features of the original (high-quality) image are embedded into the image data as invisible hidden messages. When a distorted version of such an image is received, users can decode the hidden messages and use them to provide an objective measure of the quality of the distorted image. To demonstrate the idea, we build a practical quality-aware image encoding, decoding and quality analysis system, which employs: 1) a novel reduced-reference image quality assessment algorithm based on a statistical model of natural images and 2) a previously developed quantization watermarking-based data hiding technique in the wavelet transform domain.  相似文献   
4.
A simple and inexpensive circuit for measuring the phase angle difference between two waves with lead/lag indication is described. The proposed circuit may be adopted in the laboratory as an attachment to a commercially available analogue/ digital multimeter to measure the phase difference. The response is linear over a range 0 to + 180° and is unaffected by the input frequencies in the range 6 Hz–1.2 kHz. For distorted waveforms, the paper also gives a simple scheme to measure the displacement angle which in turn suggests its use in a high-power-factor self-compensated alternating voltage controller.  相似文献   
5.
Measurement of visual quality is of fundamental importance to numerous image and video processing applications. The goal of quality assessment (QA) research is to design algorithms that can automatically assess the quality of images or videos in a perceptually consistent manner. Traditionally, image QA algorithms interpret image quality as fidelity or similarity with a "reference" or "perfecft" image in some perceptual space. Such "full-referenc" QA methods attempt to achieve consistency in quality prediction by modeling salient physiological and psychovisual features of the human visual system (HVS), or by arbitrary signal fidelity criteria. In this paper, we approach the problem of image QA by proposing a novel information fidelity criterion that is based on natural scene statistics. QA systems are invariably involved with judging the visual quality of images and videos that are meant for "human consumption." Researchers have developed sophisticated models to capture the statistics of natural signals, that is, pictures and videos of the visual environment. Using these statistical models in an information-theoretic setting, we derive a novel QA algorithm that provides clear advantages over the traditional approaches. In particular, it is parameterless and outperforms current methods in our testing. We validate the performance of our algorithm with an extensive subjective study involving 779 images. We also show that, although our approach distinctly departs from traditional HVS-based methods, it is functionally similar to them under certain conditions, yet it outperforms them due to improved modeling. The code and the data from the subjective study are available at.  相似文献   
6.
The tagged user analysis (TUA) is a generic approximate method developed to analyze random access protocols for finite-user finite-buffer systems that avoids complexities of Markovian analysis by using available queueing results. In this paper, TUA method is extended to the analysis of finite buffer S-ALOHA operating over flat fading radio channels when the user population is spatially distributed. The expressions for system performance indices are derived. It is shown that for moderate number of active users, the simulation and analytical results have a close fit.  相似文献   
7.
Technology and innovation become more important determinants of corporate competitiveness, and the telecommunications sector is no exception. A good example is found in the development of the mobile phones. Technological development, embodied in innovative functions developed from the first (1G) to third generation (3G) systems, has played significantly important roles in the growth and upheavals of the Japanese mobile phone market. In addition, development in contents, value-added services which are supplied by related firms formed in the vertical structure, charging systems, handset development; all these have made this small gadget an increasingly important part of daily life.  相似文献   
8.
Tagged user analysis (TUA) is a generic approximate method of analyzing random access protocols for finite-user finite-buffer systems. This technique decouples the channel contention behavior from the user queuing behavior and allows the use of classical queuing theory results to be directly applicable to the analysis of finite-user finite-buffer random access methods. In this paper, we extend TUA to analyze finite buffer S-ALOHA operating over flat fading radio channels and derive expressions for system performance indices like throughput, average packet delay, blocking probability and queue length. It is shown that for a moderate number of active users, the simulation and analytical results fit closely  相似文献   
9.
We propose a joint optimization network management framework for quality‐of‐service (QoS) routing with resource allocation. Our joint optimization framework provides a convenient way of maximizing the reliability or minimizing the jitter delay of paths. Data traffic is sensitive to droppage at buffers, while it can tolerate jitter delay. On the other hand, multimedia traffic can tolerate loss but it is very sensitive to jitter delay. Depending on the type of data, our scheme provides a convenient way of selecting the parameters which result in either reliability maximization or jitter minimization. We solve the optimization problem for a GPS network and provide the optimal solutions. We find the values of control parameters which control the type of optimization performed. We use our analytical results in a multi‐objective QoS routing algorithm. Finally, we provide insights into our optimization framework using simulations. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
10.
The aim of this paper is to introduce a novel frequency reuse concept especially for macro cellular networks to substantially increase the mobile network capacity, and simultaneously to avoid the implementation of low efficient small cells. Single path multiple access (SPMA) utilizes the characteristics of independent propagation paths for particular geographical location in the coverage area of mobile network. The proposed concept is based on the assumption that new approach will be adopted by the antenna manufacturers for producing advanced antennas by utilizing materials like metamaterials including carbon based nanotechnology, and graphene. In SPMA concept, communication between base station and mobile station happens through only single independent propagation path, and frequency resources can be reused in 5 m  \(\times \)  5 m areas or even more often in 1 m  \(\times \)  1 m areas, but limited by a base station/mobile station antenna requirement. Thus, the capacity of the network will be increased dramatically, and it can be managed in centralized manner at certain macro site locations. In already deployed cellular networks, these macro sites are mostly easily available, and that would help to implement SPMA to enhance the network capacity. Simulation results provided in this paper show the applicability of SPMA technique, by limiting the radiation of signal as single path propagation between base station and mobile station.  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