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   3285篇
  免费   113篇
  国内免费   39篇
电工技术   96篇
综合类   39篇
化学工业   794篇
金属工艺   76篇
机械仪表   137篇
建筑科学   111篇
矿业工程   24篇
能源动力   95篇
轻工业   283篇
水利工程   26篇
石油天然气   10篇
武器工业   2篇
无线电   289篇
一般工业技术   464篇
冶金工业   372篇
原子能技术   47篇
自动化技术   572篇
  2024年   3篇
  2023年   13篇
  2022年   40篇
  2021年   65篇
  2020年   30篇
  2019年   58篇
  2018年   68篇
  2017年   45篇
  2016年   63篇
  2015年   67篇
  2014年   87篇
  2013年   181篇
  2012年   144篇
  2011年   213篇
  2010年   201篇
  2009年   218篇
  2008年   223篇
  2007年   186篇
  2006年   151篇
  2005年   167篇
  2004年   107篇
  2003年   112篇
  2002年   108篇
  2001年   70篇
  2000年   62篇
  1999年   54篇
  1998年   96篇
  1997年   78篇
  1996年   75篇
  1995年   49篇
  1994年   46篇
  1993年   49篇
  1992年   34篇
  1991年   27篇
  1990年   27篇
  1989年   17篇
  1988年   23篇
  1987年   19篇
  1986年   11篇
  1985年   28篇
  1984年   21篇
  1983年   20篇
  1982年   12篇
  1981年   19篇
  1980年   13篇
  1979年   8篇
  1978年   3篇
  1977年   7篇
  1976年   7篇
  1973年   3篇
排序方式: 共有3437条查询结果,搜索用时 15 毫秒
951.
基于鞍点搜索的粘连对象图像分割方法   总被引:1,自引:0,他引:1       下载免费PDF全文
汪一聪  陈恳 《计算机工程》2009,35(10):203-205
针对图像中不规则形状物体接触的分割问题,提出一种采用Hessian矩阵来判断分割点(即鞍点)进行粘连对象分割的方法。根据对图像进行腐蚀操作得到的三维地貌图,结合鞍点的数学特性,运用Hessian矩阵的特征值对鞍点进行搜索定位,沿经过鞍点的最大梯度路径分割粘连对象。与目前已有的几种分割算法相比,该方法具有算法简捷、分割效果好以及易于实现的特点。  相似文献   
952.
参考目标模型中混入的背景噪声会弱化目标特征的描述,导致目标跟踪定位误差。为减少误差,依据目标与背景处于不同深度平面的特点,提出了基于深度信息辅助的和改进的背景加权直方图的MeanShift跟踪算法,能够有效削弱核窗口中的背景干扰信息,突出目标的颜色特征信息,并适时自适应更新核带宽,减少因目标尺寸变小时引入较多的背景干扰信息。实验结果表明该算法迭代次数更少,具有良好的跟踪定精度。  相似文献   
953.
We propose a proof system for reasoning on certain specifications of secure authentication systems. For this purpose, a new logic, sequence-indexed linear-time temporal logic (SLTL), is obtained semantically from standard linear-time temporal logic (LTL) by adding a sequence modal operator that represents a sequence of symbols. By this sequence modal operator, we can appropriately express message flows between clients and servers and states of servers in temporal reasoning. A Gentzen-type sequent calculus for SLTL is introduced, and the completeness and cut-elimination theorems for it are proved. SLTL is also shown to be PSPACE-complete and embeddable into LTL.  相似文献   
954.
Abstract— Organic light‐emitting‐device (OLED) devices are very promising candidates for flexible‐display applications because of their organic thin‐film configuration and excellent optical and video performance. Recent progress of flexible‐OLED technologies for high‐performance full‐color active‐matrix OLED (AMOLED) displays will be presented and future challenges will be discussed. Specific focus is placed on technology components, including high‐efficiency phosphorescent OLED technology, substrates and backplanes for flexible displays, transparent compound cathode technology, conformal packaging, and the flexibility testing of these devices. Finally, the latest prototype in collaboration with LG. Phillips LCD, a flexible 4‐in. QVGA full‐color AMOLED built on amorphous‐silicon backplane, will be described.  相似文献   
955.
The frequencies of purines and pyrimidines in double-strand DNA are in a symmetric ratio of 1: 1, while the asymmetric density ratios of purines and pyrimidines in RNA and artificial ribozymes are between 1: 1 and approximately 1: 1.5. The frequency ratio in DNA is deterministic, while that in RNA is fairly stochastic. Symbiotic fusion of deterministic symmetry and stochastic asymmetry, which can be seen at the molecular, cell and whole-body levels, is a key concept for understanding the self-organizing processes in living organisms. The left-right symmetric distribution of arms and legs is observed in outward appearance, although the inner body, including the heart and the liver, is asymmetric. A minimum hypercycle of four cycles at the origin of life is also in the symbiotic fusion of symmetry and asymmetry. The inevitability of deterministic symmetry and stochastic asymmetry underlying life is systematically revealed on the basis of physics as the weft and molecular biology as the warp. This work was presented in part at the First European Workshop on Artificial Life and Robotics, Vienna, Austria, July 12–13, 2007  相似文献   
956.
Proteins secreted from specific cancer cells have a high potential for use as tumor markers. We identified secreted proteins produced by 15 different carcinoma cell lines grown in serum-free medium using MS/MS. Proneurotensin/neuromedin N (proNT/NMN) was found in conditioned medium from four of seven small cell lung carcinoma cell lines but not from eight nonsmall cell lung carcinoma cell lines. These results indicate proNT/NMN has potential as a specific tumor marker of small cell lung carcinoma.  相似文献   
957.
958.
PC energy use is a growing cost to enterprises, with most machines remaining fully powered on, even while idle, for most of the time. The Network Connectivity Proxy maintains network presence for PCs but lets them sleep while idle, thus saving energy and reducing total cost of ownership.  相似文献   
959.
A decomposition of fuzzy relations   总被引:1,自引:0,他引:1  
This study is concerned with a decomposition of fuzzy relations, that is their representation with the aid of a certain number of fuzzy sets. We say that some fuzzy sets decompose an original fuzzy refraction if the sum of their Cartesian products approximate the given fuzzy relation. The theoretical underpinnings of the problem are presented along with some linkages with Boolean matrices (such as a Schein rank). Subsequently, we reformulate the decomposition of fuzzy relations as a problem of numeric optimizing and propose a detailed learning scheme leading to a collection of decomposing fuzzy sets. The role of the decomposition in a general class of data compression problems (including those of image compression and rule-based system condensation) is formulated and discussed in detail.  相似文献   
960.
We address the problem of filtering, selecting and placing labels on a dynamic map, which is characterized by continuous zooming and panning capabilities. This consists of two interrelated issues. The first is to avoid label popping and other artifacts that cause confusion and interrupt navigation, and the second is to label at interactive speed. In most formulations the static map labeling problem is NP-hard, and a fast approximation might have O(n log n) complexity. Even this is too slow during interaction, when the number of labels shown can be several orders of magnitude less than the number in the map. In this paper we introduce a set of desiderata for "consistent" dynamic map labeling, which has qualities desirable for navigation. We develop a new framework for dynamic labeling that achieves the desiderata and allows for fast interactive display by moving all of the selection and placement decisions into the preprocessing phase. This framework is general enough to accommodate a variety of selection and placement algorithms. It does not appear possible to achieve our desiderata using previous frameworks. Prior to this paper, there were no formal models of dynamic maps or of dynamic labels; our paper introduces both. We formulate a general optimization problem for dynamic map labeling and give a solution to a simple version of the problem. The simple version is based on label priorities and a versatile and intuitive class of dynamic label placements we call "invariant point placements". Despite these restrictions, our approach gives a useful and practical solution. Our implementation is incorporated into the G-Vis system which is a full-detail dynamic map of the continental USA. This demo is available through any browser  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