首页 | 官方网站   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   9441篇
  免费   514篇
  国内免费   439篇
工业技术   10394篇
  2024年   10篇
  2023年   60篇
  2022年   105篇
  2021年   103篇
  2020年   110篇
  2019年   149篇
  2018年   154篇
  2017年   225篇
  2016年   253篇
  2015年   279篇
  2014年   543篇
  2013年   681篇
  2012年   482篇
  2011年   704篇
  2010年   465篇
  2009年   610篇
  2008年   569篇
  2007年   591篇
  2006年   532篇
  2005年   445篇
  2004年   370篇
  2003年   358篇
  2002年   295篇
  2001年   207篇
  2000年   215篇
  1999年   199篇
  1998年   228篇
  1997年   161篇
  1996年   170篇
  1995年   138篇
  1994年   126篇
  1993年   102篇
  1992年   90篇
  1991年   84篇
  1990年   66篇
  1989年   69篇
  1988年   55篇
  1987年   40篇
  1986年   62篇
  1985年   87篇
  1984年   51篇
  1983年   40篇
  1982年   41篇
  1981年   25篇
  1980年   18篇
  1979年   6篇
  1978年   4篇
  1977年   5篇
  1976年   4篇
  1971年   2篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
71.
Those individual tests in a series of experiments that are not completed or must be suspended are known as “censored points,” or “runouts”. Inclusion of runouts in data analysis can be problematic, and such ad hoc approaches as ignoring the runout observation or treating it as a failure can significantly affect estimation. The methodology offered here alleviates the handling of runouts and censored data by using the maximum likelihood estimation (MLE) method to incorporate the censored data properly. The methodology is illustrated with an example problem using actual data and the affects of ad hoc approaches are illustrated.  相似文献   
72.
Linear mixture model applied to Amazonian vegetation classification   总被引:3,自引:0,他引:3  
Many research projects require accurate delineation of different secondary succession (SS) stages over large regions/subregions of the Amazon basin. However, the complexity of vegetation stand structure, abundant vegetation species, and the smooth transition between different SS stages make vegetation classification difficult when using traditional approaches such as the maximum likelihood classifier (MLC). Most of the time, classification distinguishes only between forest/non-forest. It has been difficult to accurately distinguish stages of SS. In this paper, a linear mixture model (LMM) approach is applied to classify successional and mature forests using Thematic Mapper (TM) imagery in the Rondônia region of the Brazilian Amazon. Three endmembers (i.e., shade, soil, and green vegetation or GV) were identified based on the image itself and a constrained least-squares solution was used to unmix the image. This study indicates that the LMM approach is a promising method for distinguishing successional and mature forests in the Amazon basin using TM data. It improved vegetation classification accuracy over that of the MLC. Initial, intermediate, and advanced successional and mature forests were classified with overall accuracy of 78.2% using a threshold method on the ratio of shade to GV fractions, a 7.4% increase over the MLC. The GV and shade fractions are sensitive to the change of vegetation stand structures and better capture biophysical structure information.  相似文献   
73.
In this paper, we propose a fast Evolutionary pursuit algorithm. It searches for optimal discriminant vectors through linearly combining standard bases. Experiments on the Yale and ORL databases verify its effectiveness and enhanced efficiency.  相似文献   
74.
综述了日本近10多年来α-Al2O3粉体的发展状况。特别介绍了日本对α-Al2O3粉体的标准化工作。这对提高电子陶瓷等产品的质量是非常重要的。  相似文献   
75.
Existence results for the LQG-controller are investigated. An infimal Riccati equation based controller may potentially give closed loop eigenvalues on the unit circle. Assuming left and right invertibility it is shown that there exists an optimal controller if and only if the Riccati equation based controller stabilizes the closed loop system after removal of all its unobservable and uncontrollable modes. Furthermore this reduced controller is the optimal controller, and its transfer function is unique. This existence condition is a considerable simplification of the more general geometric condition recently derived by Trentelman and Stoorvogel.  相似文献   
76.
条形药包药量计算公式探讨   总被引:5,自引:2,他引:3  
杨年华 《爆破》1994,11(4):65-67
本文通过现有诸药量计算公式的总结和统计分析,认为经验函数划(n)以二次式较合适。并根据流体动力学理论和临界能量密度破碎准则,推导出f(n)的二次项公式,得q=KW2(1十n2)/2;该式较符合实际,故推荐供参考。  相似文献   
77.
Inger Lytje 《AI & Society》1996,10(2):142-163
Participatory design strategies have placed the user at the center of the design process, leaving computer software designers without guidelines for how to design and implement the software system. This paper aims to bring the designer back to the center of the design process. and the way of doing it is to consider computer software as text. Three different text theories are presented in order to explain what is meant by text, namely pragmatics, structuralism and deconstructivism. Finally it is discussed how the design processes should be understood, and how they should be organized when taking the text point of view of computer software.  相似文献   
78.
This study examines the impact of positive mood on the effective usage of a Decision Support System (DSS). Using current cognitive theories, a theoretical argument about DSS usage is developed. This argument is then investigated via a lab experiment. The results of the lab experiment show that decision makers in positive mood used a greater number of informational cues provided by the DSS and made more accurate judgments.  相似文献   
79.
80.
Besides equidistribution properties and statistical independence the lattice profile, a generalized version of Marsaglia's lattice test, provides another quality measure for pseudorandom sequences over a (finite) field. It turned out that the lattice profile is closely related with the linear complexity profile. In this article we give a survey of several features of the linear complexity profile and the lattice profile, and we utilize relationships to completely describe the lattice profile of a sequence over a finite field in terms of the continued fraction expansion of its generating function. Finally we describe and construct sequences with a certain lattice profile, and introduce a further complexity measure.  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-23

京公网安备 11010802026262号