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   15037篇
  免费   910篇
  国内免费   791篇
电工技术   748篇
综合类   996篇
化学工业   240篇
金属工艺   604篇
机械仪表   1860篇
建筑科学   308篇
矿业工程   356篇
能源动力   307篇
轻工业   128篇
水利工程   94篇
石油天然气   139篇
武器工业   206篇
无线电   798篇
一般工业技术   545篇
冶金工业   410篇
原子能技术   50篇
自动化技术   8949篇
  2024年   26篇
  2023年   70篇
  2022年   173篇
  2021年   187篇
  2020年   215篇
  2019年   237篇
  2018年   198篇
  2017年   300篇
  2016年   388篇
  2015年   469篇
  2014年   683篇
  2013年   718篇
  2012年   726篇
  2011年   877篇
  2010年   750篇
  2009年   933篇
  2008年   1011篇
  2007年   1126篇
  2006年   1167篇
  2005年   1004篇
  2004年   839篇
  2003年   831篇
  2002年   616篇
  2001年   522篇
  2000年   443篇
  1999年   421篇
  1998年   385篇
  1997年   292篇
  1996年   241篇
  1995年   203篇
  1994年   173篇
  1993年   126篇
  1992年   87篇
  1991年   73篇
  1990年   48篇
  1989年   57篇
  1988年   36篇
  1987年   20篇
  1986年   14篇
  1985年   14篇
  1984年   6篇
  1983年   5篇
  1982年   2篇
  1981年   5篇
  1980年   4篇
  1979年   2篇
  1977年   2篇
  1975年   2篇
  1962年   2篇
  1961年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
In order to avoid unnecessary damage of electrical equipments and installations,high quality power should be delivered to the end user and strict control on frequency should be made, Therefore, it is important to estimate the power system's harmonic components with higher accuracy. This paper presents a new approach for estimating harmonic component in a power system using secant - fuzzy linear regression method. In this approach the non - sinusoidal voltage or current waveform is written as I linear function. The coefficient of this function is assumed to be fuzzy number with a membership function that has center and spread value. The time dependent quantity is written as Taylor series with two different time dependent quantities. The objective is to use the sample obtained from the transmission line to find the power system harmonic components and frequencies. We used an experimental voltage signal from a sub power station as a numerical test.  相似文献   
42.
Biases in social comparative judgments, such as those illustrated by above-average and comparative-optimism effects, are often regarded as products of motivated reasoning (e.g., self-enhancement). These effects, however, can also be produced by information-processing limitations or aspects of judgment processes that are not necessarily biased by motivational factors. In this article, the authors briefly review motivational accounts of biased comparative judgments, introduce a 3-stage model for understanding how people make comparative judgments, and then describe how various nonmotivational factors can influence the 3 stages of the comparative judgment process. Finally, the authors discuss several unresolved issues highlighted by their analysis, such as the interrelation between motivated and nonmotivated sources of bias and the influence of nonmotivated sources of bias on behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
43.
In this paper, a routing protocol which utilizes the characteristics of Bluetooth technology is proposed for Bluetooth-based mobile ad hoc networks. The routing tables are maintained in the master devices and the routing zone radius for each table is adjusted dynamically by using evolving fuzzy neural networks. Observing there exists some useless routing packets which are helpless to build the routing path and increase the network loads in the existing ad hoc routing protocols, we selectively use multiple unicasts or one broadcast when the destination device is out of the routing zone radius coverage of the routing table. The simulation results show that the dynamic adjustment of the routing table size in each master device results in much less reply time of routing request, fewer request packets and useless packets compared with two representative protocols, Zone Routing Protocol and Dynamic Source Routing.  相似文献   
44.
This paper reports how the study of formal logical reasoning provides insight into more everyday types of reasoning, such as that involved in language comprehension. Both of these types of cognition are thought to involve the use of mental models, and so it is reasonable to think that the cognitive operations needed for formal logical reasoning would be involved in everyday reasoning as well. We focused on three aspects of formal reasoning: (a) the integration of information into a common mental model, (b) the drawing of inferences, and (c) the coordination of alternative possibilities. We were able to show that the integration and inference components were related to narrative comprehension processes, but the coordination of alternative models was not. Thus, there is evidence for some overlap in the mental processes used in formal and everyday reasoning. This further justifies the study of formal logical reasoning as a window into certain types of everyday reasoning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
45.
The effects of case libraries on problem solving   总被引:3,自引:0,他引:3  
Abstract The purpose of the study was to investigate the effects of providing access to a case library of related stories while undergraduates solved ill-structured problems. While solving complex food product development problems, the experimental group accessed experts' stories of similar, previously solved problems; the comparable group accessed fact sheets (expository representation of stories' content); and the control group accessed text selected at random from a textbook dealing with issues unrelated to the stories. On multiple-choice questions assessing processes related to problem solving (prediction, inferences, explanations, etc.), experimental students out-performed the comparable and control groups. Performance on short-answer questions also assessing problem-related skills was not significantly different, in part because of test fatigue. Analysis of interviews identified a number of factors that students used in deciding how to apply their study strategies, including causal factors, grounding phenomenon, grounding in context, and outcomes.  相似文献   
46.
Hemispheric involvement in reasoning abilities has been debated for some time, and it remains unclear whether the right hemisphere's involvement in problem solving is modality specific or dependent on the type of spatial reasoning required. In the current study, 2 types of nonverbal reasoning abilities were examined, spatial reasoning and proportional reasoning, in 109 patients with cerebrovascular disease that was confined to either the right or the left hemisphere or was diffuse in nature. Results indicated that no lateralizing effects were present based on type of spatial reasoning. Findings are consistent with the suggestion that higher order cognitive processes involved in nonverbal abstraction and problem solving are not strongly lateralized to the right hemisphere but rather are more generally distributed throughout the cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
47.
讨论了激光微焊点焊接质量的模糊识别的概念,数学模型及其应用方法,并介绍了系统的硬件组成。  相似文献   
48.
基于参考点的模糊知识表示   总被引:1,自引:0,他引:1  
黄京炜  王众托 《控制与决策》1994,9(2):127-130,155
本文分析了模糊关系模型的知识表示途径,并由此提出基于参考点的模糊知识表示,分析了它与人类记忆经验性知识的相信性,并证明模糊关系模型能以任意精度逼近具有有限个极值点的有界连续函数。  相似文献   
49.
本文分析了模糊字符串几种类型和它的表示方法,并给出模糊匹配的算法及C语言的源程序,同时也指出了在文枉编辑器的应用例子。  相似文献   
50.
用基函数神经网络实现多阈值图象分割   总被引:1,自引:0,他引:1  
本文介绍了一种用基函数神经网络实现多阈值图象分割的新方法。它从函数逼近的角度研究基于灰度直方图的多阈值分割问题,提出了一种模糊反向传播学习算法,采用该算法的高斯基函数网络能够准确检测直方图中包含的子区域和它们的分布函数,而且速度很快。实验表明本文的方法在实际图象分割中是有效的。  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