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   3396篇
  免费   795篇
  国内免费   566篇
电工技术   315篇
综合类   583篇
化学工业   97篇
金属工艺   25篇
机械仪表   179篇
建筑科学   142篇
矿业工程   53篇
能源动力   61篇
轻工业   81篇
水利工程   103篇
石油天然气   71篇
武器工业   46篇
无线电   606篇
一般工业技术   400篇
冶金工业   32篇
原子能技术   10篇
自动化技术   1953篇
  2024年   17篇
  2023年   74篇
  2022年   115篇
  2021年   161篇
  2020年   173篇
  2019年   210篇
  2018年   181篇
  2017年   189篇
  2016年   214篇
  2015年   245篇
  2014年   302篇
  2013年   292篇
  2012年   365篇
  2011年   341篇
  2010年   257篇
  2009年   223篇
  2008年   233篇
  2007年   198篇
  2006年   171篇
  2005年   142篇
  2004年   97篇
  2003年   70篇
  2002年   88篇
  2001年   57篇
  2000年   51篇
  1999年   39篇
  1998年   37篇
  1997年   35篇
  1996年   27篇
  1995年   23篇
  1994年   24篇
  1993年   16篇
  1992年   17篇
  1991年   13篇
  1990年   17篇
  1989年   14篇
  1988年   9篇
  1987年   5篇
  1986年   2篇
  1985年   2篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1973年   1篇
  1964年   1篇
  1963年   1篇
  1962年   1篇
  1960年   1篇
  1957年   1篇
排序方式: 共有4757条查询结果,搜索用时 62 毫秒
11.
图象中心加权中值滤波的改进与应用   总被引:2,自引:0,他引:2       下载免费PDF全文
中心加权中值滤波具有较好的边缘保持特性及快速实现的特点,但滤噪能力低于其它中值滤波。此文探 讨对中心加权中值滤波的改进方法,提出了中心加权分级实现的思想,使之同时具有边缘保持、快速滤波和噪声去 除的理想效果。  相似文献   
12.
Locally Weighted Learning   总被引:22,自引:0,他引:22  
This paper surveys locally weighted learning, a form of lazy learning and memory-based learning, and focuses on locally weighted linear regression. The survey discusses distance functions, smoothing parameters, weighting functions, local model structures, regularization of the estimates and bias, assessing predictions, handling noisy data and outliers, improving the quality of predictions by tuning fit parameters, interference between old and new data, implementing locally weighted learning efficiently, and applications of locally weighted learning. A companion paper surveys how locally weighted learning can be used in robot learning and control.  相似文献   
13.
线加权余量法及其在正交异性板弯曲分析中的应用   总被引:2,自引:1,他引:1  
曹志远  周汉斌 《工程力学》1992,9(2):129-135
利用有限差分法对控制方程和边界条件进行半离散化,使其定义在一些离散线上,然后采用加权余量法求解。这就是本文提出的线加权余量法,也可称之为有限差分-加权余量分维耦合法。文中以正交各向异性薄板弯曲平衡问题为例推导了有关具体算式,给出了数值算例,说明了本文方法的有效性。  相似文献   
14.
Melt index is considered an important quality variable determining product specifications. Reliable prediction of melt index (MI) is crucial in quality control of practical propylene polymerization processes. In this paper a least squares support vector machines (LS‐SVM) soft‐sensor model of propylene polymerization process is developed to infer the MI of polypropylene from other process variables. Considering the use of a SSE cost function without regularization might lead to less robust estimates; the weighted least squares support vector machines (weighted LS‐SVM) approach of propylene polymerization process is further proposed to obtain a robust estimation of melt index. The performance of standard SVM model is taken as a basis of comparison. A detailed comparison research among the standard SVM, LS‐SVM, and weighted LS‐SVM models is carried out. The research results confirm the effectiveness of the presented methods. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 285–289, 2006  相似文献   
15.
稀疏气泡流动的粒子跟踪测速技术研究   总被引:3,自引:1,他引:2  
许联锋  廖伟丽  陈刚  李建中 《水利学报》2005,36(7):0825-0829
采用动态阈值技术实现了对气泡图像的正确分割,利用灰度加权方法提高了气泡颗粒的定位精度。根据稀疏气泡流动图像的特点,提出了一种新的基于相关的粒子跟踪测速算法(2-HPTV)。通过进行两时刻中围绕待研究气泡所取的两个小的诊断窗口的相关运算,成功实现了气泡颗粒的轨迹追踪。实验表明本文算法较传统的PIV技术在测速精度上有很大程度的提高,与4帧粒子跟踪测速算法相比,降低了对摄像机帧频的要求,具有较强的实用性。  相似文献   
16.
New quadratic models are proposed to improve the upper-bound estimates in the maximum weighted cut problem. They are found by two original methods for deriving redundant quadratic constraints. A well-known linear model is shown to follow from the models proposed. Recommendations on how to develop its strengthened analogs are given. This study is partially sponsored from the grant UM2-2574-KV-03 (CRDF Cooperative Grants Program). __________ Translated from Kibernetika i Sistemnyi Analiz, No. 1, pp. 63—75, January–February 2006.  相似文献   
17.
Y Narahari  R Srigopal 《Sadhana》1996,21(4):415-433
Recently, efficient scheduling algorithms based on Lagrangian relaxation have been proposed for scheduling parallel machine systems and job shops. In this article, we develop real-world extensions to these scheduling methods. In the first part of the paper, we consider the problem of scheduling single operation jobs on parallel identical machines and extend the methodology to handle multiple classes of jobs, taking into account setup times and setup costs. The proposed methodology uses Lagrangian relaxation and simulated annealing in a hybrid framework. In the second part of the paper, we consider a Lagrangian relaxation based method for scheduling job shops and extend it to obtain a scheduling methodology for a real-world flexible manufacturing system with centralized material handling. This research was supported in part by the Office of Naval Research and the Department of Science and Technology grant N00014-93-1017.  相似文献   
18.
多级并接型权电阻解码网络结构简单,分析方便,文章给出了普通的和BCD码多级并接型权电阻解码网络,推导出了各级与运放的连接电阻的通用公式,并用EWB软件进行了电路模拟,这种方法对自行设计权电阻DAC有一定的参考价值。  相似文献   
19.
The weighted essentially non-oscillatory (WENO) method is an excellent spatial discretization for hyperbolic partial differential equations with discontinuous solutions. However, the time-step restriction associated with explicit methods may pose severe limitations on their use in applications requiring large scale computations. An efficient implicit WENO method is necessary. In this paper, we propose a prototype flux-implicit WENO (iWENO) method. Numerical tests on classical scalar equations show that this is a viable and stable method, which requires appropriate time-stepping methods. Future study will include the examination of such methods as well as extension of iWENO to systems and higher dimensional problems.Sigal Gottlieb - The work of this author supported by NSF grant DMS-0106743.Steven J. Ruuth - The work of this author was partially supported by a grant from NSERC Canada.  相似文献   
20.
The weighted principal component analysis technique is employed for reconstruction of reflectance spectra of surface colors from the related tristimulus values. A dynamic eigenvector subspace based on applying certain weights to reflectance data of Munsell color chips has been formed for each particular sample and the color difference value between the target, and Munsell dataset is chosen as a criterion for determination of weighting factors. Implementation of this method enables one to increase the influence of samples which are closer to target on extracted principal eigenvectors and subsequently diminish the effect of those samples which benefit from higher amount of color difference. The performance of the suggested method is evaluated in spectral reflectance reconstruction of three different collections of colored samples by the use of the first three Munsell bases. The resulting spectra show considerable improvements in terms of root mean square error between the actual and reconstructed reflectance curves as well as CIELAB color difference under illuminant A in comparison to those obtained from the standard PCA method. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 360–371, 2008  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