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   266248篇
  免费   20815篇
  国内免费   13931篇
电工技术   17048篇
技术理论   51篇
综合类   36916篇
化学工业   28542篇
金属工艺   9747篇
机械仪表   14333篇
建筑科学   37667篇
矿业工程   15062篇
能源动力   7913篇
轻工业   14589篇
水利工程   14031篇
石油天然气   11333篇
武器工业   2567篇
无线电   17299篇
一般工业技术   18602篇
冶金工业   15538篇
原子能技术   2635篇
自动化技术   37121篇
  2024年   817篇
  2023年   2503篇
  2022年   4814篇
  2021年   5777篇
  2020年   6183篇
  2019年   5221篇
  2018年   4926篇
  2017年   5994篇
  2016年   7095篇
  2015年   8004篇
  2014年   14690篇
  2013年   13413篇
  2012年   17539篇
  2011年   18689篇
  2010年   14922篇
  2009年   15606篇
  2008年   14701篇
  2007年   19274篇
  2006年   18248篇
  2005年   15975篇
  2004年   13587篇
  2003年   12237篇
  2002年   10090篇
  2001年   8512篇
  2000年   7167篇
  1999年   5845篇
  1998年   4414篇
  1997年   3870篇
  1996年   3595篇
  1995年   3043篇
  1994年   2722篇
  1993年   2036篇
  1992年   1806篇
  1991年   1344篇
  1990年   1176篇
  1989年   1030篇
  1988年   830篇
  1987年   570篇
  1986年   428篇
  1985年   355篇
  1984年   331篇
  1983年   243篇
  1982年   220篇
  1981年   165篇
  1980年   132篇
  1979年   111篇
  1978年   65篇
  1977年   72篇
  1976年   55篇
  1975年   56篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The main difficulty with EM algorithm for mixture model concerns the number of components, say g. This is the question of model selection, and the EM algorithm itself could not estimate g. On the contrary, the algorithm requires g to be specified before the remaining parameters can be estimated. To solve this problem, a new algorithm, which is called stepwise split-and-merge EM (SSMEM) algorithm, is proposed. The SSMEM algorithm alternately splits and merges components, estimating g and other parameters of components simultaneously. Also, two novel criteria are introduced to efficiently select the components for split or merge. Experimental results on simulated and real data demonstrate the effectivity of the proposed algorithm.  相似文献   
82.
于洪坤 《有色矿冶》2004,20(3):38-39
介绍了用自然澄清法降低、回收旋涡炉渣中的铜的方法。该方法工艺简单。操作方便,不仅降低冶炼成本,同时提高了经济效益。  相似文献   
83.
Presents the 2003 American Psychological Foundation's Gold Medal Award for Life Achievement in the Science of Psychology, which was presented to Robert Rosenthal. A biography of Rosenthal is provided, along with a selected bibliography and the text of the award citation: "For outstanding scientific contributions that have had a profound influence on research methods, empirical investigations, theory, and applications. Robert Rosenthal's seminal research on interpersonal expectancy inspired hundreds of studies with applications within and beyond psychology. His amplification of experimenter- and subject-related artifacts and his insights about ethical issues have improved the way that research is conducted. His statistical contributions are classic and wide ranging, including his body of work on meta-analysis and contrast analysis and his formulation of valuable procedures, such as the binomial effect-size display and counternull statistics. An exceptional scientist, teacher, mentor, and author, Rosenthal, with his generous and brilliant touch, has shaped the lives and work of countless others." (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
84.
The principle of maximum informational entropy is used to find the probability density function for the departure radius of a bubble in boiling on a solid surface. A general relation is derived, which leads to particular expressions.  相似文献   
85.
The paper gives the results of experimental investigations of the initial pressure gradient of bituminous oil and the time dependences of variation of the temperature in a formation model and of the well production rate in a microwave-frequency electromagnetic field. The effect of strong decay of the non-Newtonian properties of bituminous oil is revealed. The nonuniformity of temperature distribution over the formation thickness is demonstrated, which depends on the initial production rate of the well and on the duration of stimulation of the bottom-hole zone of formation.  相似文献   
86.
A problem of deformation of a curved shell loaded by internal pressure, axial force, and temperature difference is discussed. Physical equations are derived whereby the displacements and angles of rotation of the line of centers of mass of cross sections of a shell are related to loading parameters. A general constitutive set of equations for a curved element during its deformation is given. Using a method of initial parameters, an analytical solution is obtained for the differential equations for displacements and angles of rotation of the center line allowing for the action of distributed forces and moments.  相似文献   
87.
We present a linear time approximation algorithm with a performance ratio of 1/2 for finding a maximum weight matching in an arbitrary graph. Such a result is already known and is due to Preis [STACS'99, Lecture Notes in Comput. Sci., Vol. 1563, 1999, pp. 259-269]. Our algorithm uses a new approach which is much simpler than the one given by Preis and needs no amortized analysis for its running time.  相似文献   
88.
Enhanced matrix-filler adhesion is realized after filler treatment with a surface treatment process. The hydrosol/coupling agent treatment was applied to a wide range of inorganic and organic fillers, and adhesion to a variety of matrix resins was improved. Scanning Electron Microscopy (SEM) was used to determine the locus of failure in the filled systems. The locus of failure shows the relative degree of adhesion between the filler and the polymer matrix. Significant improvement in adhesion in humid environments is also observed.  相似文献   
89.
会计政策选择类型在理论上大体可分为机会主义型和效率(或有效契约)型。会计政策选择具有效率性,但也为经理人员的机会主义行为打开了大门。在我国,由于企业缺乏一系列有效的激励约束机制,会计政策选择的机会主义仍然严重。为此,必须建立适合我国企业有效的激励约束机制。  相似文献   
90.
This report summarizes the panel held at the 109th Annual Convention, American Psychological Association, August 26, 2001, San Francisco. The chair was William Glover and the speakers were Samuel Gerson, Karen Maroda, and Andre Patsalides. The invited symposium was directed at discussing different perspectives related to the presence of desire in the analytic process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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