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   87845篇
  免费   7280篇
  国内免费   4989篇
电工技术   4643篇
技术理论   3篇
综合类   7312篇
化学工业   14896篇
金属工艺   6144篇
机械仪表   4319篇
建筑科学   8960篇
矿业工程   4191篇
能源动力   3824篇
轻工业   6153篇
水利工程   2750篇
石油天然气   3827篇
武器工业   1301篇
无线电   6535篇
一般工业技术   11337篇
冶金工业   6539篇
原子能技术   1463篇
自动化技术   5917篇
  2024年   341篇
  2023年   1024篇
  2022年   2180篇
  2021年   2676篇
  2020年   2874篇
  2019年   2291篇
  2018年   2264篇
  2017年   2976篇
  2016年   3155篇
  2015年   3121篇
  2014年   4948篇
  2013年   5212篇
  2012年   5997篇
  2011年   6465篇
  2010年   4959篇
  2009年   5176篇
  2008年   4542篇
  2007年   6108篇
  2006年   5290篇
  2005年   4674篇
  2004年   3924篇
  2003年   3551篇
  2002年   2955篇
  2001年   2483篇
  2000年   2103篇
  1999年   1690篇
  1998年   1335篇
  1997年   1120篇
  1996年   1008篇
  1995年   819篇
  1994年   674篇
  1993年   489篇
  1992年   381篇
  1991年   282篇
  1990年   248篇
  1989年   188篇
  1988年   130篇
  1987年   72篇
  1986年   65篇
  1985年   62篇
  1984年   42篇
  1983年   32篇
  1982年   27篇
  1981年   19篇
  1980年   25篇
  1979年   10篇
  1978年   12篇
  1975年   13篇
  1959年   12篇
  1951年   8篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
When humans plan to execute a tool-use action, they can only specify the bodily movement parameters by taking into account the external target or goal of the tool-use action and the target-movement mapping implemented by the tool. In this study, the authors used the movement precuing method to investigate how people prepare for actions made with tools. More specifically, they asked whether people would be able to specify the spatial target and the target-movement mapping of the tool-use action independently of each other, and to what degree they would be able to prepare these components in advance. In 3 experiments, they precued either the target or the target-movement mapping of tool-use actions involving either a compatible or an incompatible target-movement mapping. Results indicate that participants benefit from partial advance information about the target-movement mapping, whereas no significant effects were found for precuing the spatial target of the action. These results occurred regardless of whether the target-movement mapping was compatible or incompatible and provide evidence for the notion that the target-movement mapping of a tool-use action is part of its cognitive representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
52.
In various medium‐to‐large‐scale fire test equipments like the ISO room corner test (RC), and more recently, the single burning item test (SBI) the mass flow rate measurement of the combustion gases plays a key role in the determination of the heat‐release rate and smoke‐production rate. With the knowledge of the velocity profile and the temperature of the flow, the mass flow rate is obtained by measuring the velocity on the axis of the duct. This is done by means of a bi‐directional probe based on the pitot principle. However, due to the variation of the mean temperature and the temperature gradient in any cross section of the duct, introduced by ever changing combustion gas temperatures, the velocity nor the density profile are constant in time. This paper examines the resulting uncertainty on the mass flow rate. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
53.
The authors present a theory for understanding risk for problem drinking among reservation-dwelling American Indians. The theory offers an overall framework for understanding the risk process for this group. It considers the distinction between factors that influence mean levels of American Indian problem drinking and factors that influence individual differences in American Indian drinking. It proposes important contextual differences between reservation-dwelling American Indians and Caucasians that may help explain the higher mean levels of American Indian problem drinking. The theory further holds that, within the high mean level of problem drinking characteristic of many American Indian reservations, individual differences in problem drinking can be explained by very similar personality and learning factors as those that influence problem-drinking levels for other ethnic groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
54.
钢样成分化验分析结果网络传输系统将碳硫分析仪、光谱分析仪和相应的计算机控制系统按以太网络结构组联,形成"炉前分析网络",采用分析网主服务器系统软件和网络分析系统软件实现网络传输。该系统可将炉前钢样化验分析结果实时传输到炉前大屏,具有传输速度快、准确率高的特点,提高了工作效率和产品合格率,降低了生产成本。  相似文献   
55.
Longitudinal data from a representative sample of 1,978 Black and White adolescents were used to examine the role of personality in multiple risk or problem behaviors. Results indicate that covariation among diverse behaviors (educational underachievement, delinquent behavior, substance use, sexual behavior) can be adequately modeled by a single higher order factor, and that impulsivity and avoidance coping serve as generalized risk factors for involvement in these behaviors. Whereas none of the personality variables examined explained change in problem behaviors once established, avoidance coping prospectively predicted involvement among a subgroup of adolescents with little or no prior involvement. Results suggest that dysfunctional styles of regulating emotions and emotionally driven behaviors are core features of risky or problem behaviors during adolescence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
56.
本文概述了纳米科技的沿革,及其在国内外发展的情况,并就我国如何进一步发展纳米科技提出了自己的想法。  相似文献   
57.
The degree to which real and hypothetical rewards were discounted across delays ranging from 6 hr to 1 year was explored in a within-subjects design. An adjusting-amounts procedure was used to estimate the subjective value of real and hypothetical rewards at each delay. A hyperbolic discounting function provided a significantly better fit to individual participants' preferences than did an exponential function. No significant effect of reward type on degree of hyperbolic discounting or area under the discounting curves was detected. These findings offer some support for the validity of using hypothetical rewards to estimate discounting rates in substance-abusing and other populations, but caution is suggested because this support is gleaned from a failure to detect an effect of reward type. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
58.
近十年来,天铁集团炼铁厂通过改善原燃料条件;优化炉料结构,提高入炉品位;采用提高炉顶压力、富氧喷煤、低硅冶炼、炉顶气象系统等多项先进技术,使高炉各项经济技术指标逐年提高。  相似文献   
59.
张西民 《有色冶金节能》2003,20(6):24-25,31
本文通过对中州分公司正在考虑建设的信息网建设实际情况,结合山东分公司、广西分公司取得的经验,对计量管理信息网的应用进行了探讨。  相似文献   
60.
黄玲 《冶金动力》2003,(6):49-51
通过高炉鼓风机扩压叶片断裂事故,从化学分析、物理检验,结合使用情况对扩压叶片断裂原因进行了详细分析,并提出了改进措施。  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