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   28438篇
  免费   2648篇
  国内免费   1224篇
电工技术   5204篇
技术理论   2篇
综合类   2504篇
化学工业   1907篇
金属工艺   1951篇
机械仪表   3324篇
建筑科学   1540篇
矿业工程   1307篇
能源动力   1702篇
轻工业   1361篇
水利工程   1743篇
石油天然气   662篇
武器工业   357篇
无线电   2092篇
一般工业技术   1671篇
冶金工业   2045篇
原子能技术   146篇
自动化技术   2792篇
  2024年   139篇
  2023年   421篇
  2022年   817篇
  2021年   914篇
  2020年   855篇
  2019年   665篇
  2018年   666篇
  2017年   882篇
  2016年   941篇
  2015年   1025篇
  2014年   1758篇
  2013年   1349篇
  2012年   2031篇
  2011年   2217篇
  2010年   1575篇
  2009年   1619篇
  2008年   1439篇
  2007年   1916篇
  2006年   1713篇
  2005年   1505篇
  2004年   1177篇
  2003年   1182篇
  2002年   953篇
  2001年   938篇
  2000年   740篇
  1999年   614篇
  1998年   435篇
  1997年   403篇
  1996年   307篇
  1995年   261篇
  1994年   233篇
  1993年   128篇
  1992年   115篇
  1991年   76篇
  1990年   70篇
  1989年   79篇
  1988年   43篇
  1987年   31篇
  1986年   11篇
  1985年   9篇
  1984年   7篇
  1983年   5篇
  1982年   4篇
  1981年   4篇
  1980年   5篇
  1964年   3篇
  1962年   5篇
  1956年   2篇
  1955年   2篇
  1954年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
该文介绍一种简单、可靠、小巧的转速传感器。它的特点是在强振环境下仍具有很高的可靠,可用于坦克底盘、重型工程机械,燃气轮机组等机械作为转速监测。  相似文献   
132.
准连续波体制雷达最大熵方法的算法选择   总被引:1,自引:0,他引:1  
高彬  叶志铨 《雷达与对抗》2003,(1):13-15,53
准连续体制作为一种新型雷达体制以其固有的优越性给雷达界带来了巨大的冲击。其数字信号处理系统的开发是进一步完善该体制雷达的关键。本文针对数字信号处理系统中最大熵谱外推电路的算法选择进行了研究。  相似文献   
133.
The authors report results of a study into the role of components of first-language (L1; Dutch) and second-language (L2; English) reading comprehension. Differences in the contributions of components of L1 and L2 reading comprehension are analyzed, in particular processing speed in L1 and L2. Findings indicate that regression weights of the L1 and L2 components are different. Although correlations between most processing speed components and reading comprehension are substantial, there are no unique contributions to the explanation of either L1 or L2 reading comprehension when linguistic and metacognitive knowledge are accounted for. In addition, L1 reading comprehension is shown to have a large contribution to L2 reading comprehension, supporting theories of L1-L2 transfer of reading skills. Results are discussed from a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
134.
H. Heckhausen and J. Kuhl's (1985) goal typology provided the conceptual foundation for this research, which examined the independent and integrated effects of achievement orientation and goal-setting approaches on trainees' self-regulatory activity. Using a complex computer-based simulation, the authors examined the effects of 3 training design factors--goal frame, goal content, and goal proximity--cutting across these 2 theoretical domains on the nature, focus, and quality of the self-regulatory activities of 524 trainees. Results revealed that all 3 factors had a significant influence on self-regulation, with goal content exhibiting the greatest influence. In line with expectations, congruent learning frame and content compared with congruent performance frame and content was beneficial for trainees' self-regulatory activity, incongruent combinations of goal frame and content were better than congruent performance frames and content, and effects for the incongruent combinations cutting across the domains were asymmetrical. Theoretical extensions for further disentangling these distinct domains and training design implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
135.
The fat and protein content, and thus energy resources of young (parr) Atlantic salmon (Salmo salar) were examined in a temperate river. Juvenile salmon exhibited distinct seasonal patterns of energy storage and use. The lowest levels of energy were found towards the end of winter (mean mass specific energy about 4.3 kJ·g?1). There was a rapid accumulation of fat in spring/early summer in spite of low‐water temperatures (highest mean content of mass specific energy of about 5.0 kJ·g?1 in June). By early autumn (August) there was a rapid depletion of fat and energy resources. The decline in specific energy during late summer was of the same magnitude as the corresponding winter decline. Furthermore, total fat and protein content, and thus energy resources of juveniles below a hydroelectric power plant (hydrostation (HS)) differed from those at a (lower) reference station (RS). The younger fish exhibited higher gains, but also larger losses of energy resources compared to corresponding values at the RS. Specifically during the summer, young of year (YOY) had 31% lower total energy content at the regulated site (mean 1.27 kJ per individual) than the RS (mean 1.84 kJ). Higher mortality may occur at the site most affected by the hydroelectric plant, where energy resources on average were higher, but where depletion was also most severe. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
136.
天津钢铁有限公司引进了瑞士Concast公司6机6流方、圆坯连铸机及相关技术,文章简要介绍了Concast连铸机的自动控制系统的特点和功能。  相似文献   
137.
The authors propose a behavioral decision theory relevant to the maintenance of desirable identities. The theory, termed deviance regulation theory (DRT), predicts that actions translate into meaningful identities to the extent that they cause the individual to deviate from reference group norms. This straightforward proposition is used to predict the patterning of behavior across a wide array of social contexts. The authors present evidence that predictions generalize across Eastern and Western cultures and to both personal and collective identities. Finally, they show how DRT alters current theoretical assumptions about social motives and social and cultural influence, and they illustrate how it can help explain the structure of both informal and formal social forces. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
138.
介绍龙门铣床的直流调速控制系统的改造方案,根据龙门铣床工作台运动过程及原直流电机的容量来选择交流电机和变频器并对变频器的功能进行设定。  相似文献   
139.
Five studies examined the hypotheses that when people experience positive affect, those low in self-esteem are especially likely to dampen that affect, whereas those high in self-esteem are especially likely to savor it. Undergraduate participants' memories for a positive event (Study 1) and their reported reactions to a success (Study 2) supported the dampening prediction. Results also suggest that dampening was associated with worse mood the day after a success (Study 2), that positive and negative affect regulation are distinct, that self-esteem is associated with affect regulation even when Neuroticism and Extraversion are controlled (Studies 3 and 4), and that self-esteem may be especially important for certain types of positive events and positive affect regulation (Study 5). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
140.
通过对五级旋风筒下料管、回转窑转速、配料方案、物料稳定等四方面进行改进,达到提产目的。  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