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   1786篇
  免费   60篇
  国内免费   16篇
电工技术   3篇
综合类   73篇
化学工业   98篇
金属工艺   10篇
机械仪表   19篇
建筑科学   169篇
矿业工程   1篇
轻工业   203篇
水利工程   1篇
石油天然气   1篇
武器工业   1篇
无线电   34篇
一般工业技术   169篇
冶金工业   949篇
原子能技术   2篇
自动化技术   129篇
  2024年   15篇
  2023年   27篇
  2022年   58篇
  2021年   57篇
  2020年   59篇
  2019年   33篇
  2018年   34篇
  2017年   37篇
  2016年   28篇
  2015年   30篇
  2014年   65篇
  2013年   80篇
  2012年   87篇
  2011年   135篇
  2010年   115篇
  2009年   111篇
  2008年   85篇
  2007年   77篇
  2006年   99篇
  2005年   82篇
  2004年   110篇
  2003年   88篇
  2002年   73篇
  2001年   44篇
  2000年   6篇
  1999年   10篇
  1998年   11篇
  1993年   4篇
  1990年   7篇
  1989年   8篇
  1988年   9篇
  1987年   8篇
  1986年   5篇
  1984年   13篇
  1983年   5篇
  1981年   4篇
  1979年   5篇
  1966年   7篇
  1965年   6篇
  1964年   21篇
  1963年   6篇
  1962年   3篇
  1961年   14篇
  1960年   7篇
  1959年   5篇
  1958年   5篇
  1957年   6篇
  1956年   4篇
  1955年   14篇
  1954年   4篇
排序方式: 共有1862条查询结果,搜索用时 0 毫秒
21.
The purpose of this study is to explore the dynamics underlying disparities in Internet use among school age children in the US. The analysis found that a broad range of demographic, geographic and economic factors significantly influence Internet use among children. Significantly, the availability of household computing resources and adult Internet users in the household were most important in explaining disparities in use among children. To expand universal Internet access, future public policy should focus on providing support for in-home access; continued support for public access at out-of-home locations such as schools, and providing technical support, training and expertise to school age children.
Paul F. ClearyEmail:
  相似文献   
22.
Humorously describes fictional studies "proving" that motor and language development occur concurrently ("hand in hand") and that this development is independent of culture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
23.
《Ergonomics》2012,55(5):1025-1035
Abstract

Several studies indicate that the ISO standards for school furniture seem to be inappropriate, and there is increasing evidence that the inclination of the seat should be forward and that it should be possible to adjust the table-top to a certain non-horizontal angle. However, these studies have predominantly used objective measurement methods on adult subjects for short-term experiments in rather artificial surroundings. By means of structured interviews registering the school children's perception of ergonomic comfort, the present study has compared three types of school furniture—the original ISO-standard type, and two different new types characterized by forward slanting seats and tiltable desk-tops, the main difference between the two being approximately 15 cm in the height of the chair as well as the table. The study showed that the highest of the two tilting types was perceived to be significantly better than the two others in terms of table height, chair height, reading position, back-rest, and global assessment. Likewise, the feature of a tiltable table-top was considered overwhelmingly positive independently of the height of the furniture. It is recommended that school authorities, producers of school furniture, and relevant medical personnel consider these results for alternative designs of school furniture. It should be kept in mind, however, that school furniture is only one among many factors in the multifactorial field of the back health of school children.  相似文献   
24.
《Ergonomics》2012,55(7):1096-1108
Farm tractors account for the majority of fatal injuries to adolescents working in agriculture and therefore remain a leading occupational priority. The question of whether these injuries occur because adolescents are assigned tractor jobs beyond their physical capabilities has not been answered. The purpose of this study was to estimate the activation forces required to operate controls on 40 tractors in common use in the US and compare them with existing estimates of physical strength for children of varying ages and with recommended ergonomic force limits for repeatedly engaging controls. Activation forces for steering, brakes and clutch were measured on each tractor. The main study finding was that the activation forces required to operate tractors typically exceeded the physical abilities of most children aged 13 to 17 years. This raises serious questions about the ability of children to safely operate tractors in common use on US farms. This study provides an ergonomic approach for evaluating the potential mismatch between young people's strength capabilities and forces required in operating farm tractors. This approach could be used in similar situations where adolescents may operate vehicles (e.g. all-terrain vehicles), machinery or other mechanical devices requiring activation of levers and controls. Study findings potentially inform the establishment of occupational policies surrounding tractor operation by young people.  相似文献   
25.
《Ergonomics》2012,55(8):999-1008
Current shoe designs do not allow for the comprehensive 3-D foot shape, which means they are unable to reproduce the wide variability in foot morphology. Therefore, the purpose of this study was to capture these variations of children's feet by classifying them into groups (types) and thereby provide a basis for their implementation in the design of children's shoes. The feet of 2867 German children were measured using a 3-D foot scanner. Cluster analysis was then applied to classify the feet into three different foot types. The characteristics of these foot types differ regarding their volume and forefoot shape both within and between shoe sizes. This new approach is in clear contrast to previous systems, since it captures the variability of foot morphology in a more comprehensive way by using a foot typing system and therefore paves the way for the unimpaired development of children's feet. Previous shoe systems do not allow for the wide variations in foot morphology. A new approach was developed regarding different morphological foot types based on 3-D measurements relevant in shoe construction. This can be directly applied to create specific designs for children's shoes.  相似文献   
26.
《Ergonomics》2012,55(4):458-477
Computer use by children is common and there is concern over the potential impact of this exposure on child physical development. Recently principles for child-specific evidence-based guidelines for wise use of computers have been published and these included one concerning the facilitation of appropriate physical development. This paper reviews the evidence and presents detailed guidelines for this principle. The guidelines include encouraging a mix of sedentary and whole body movement tasks, encouraging reasonable postures during computing tasks through workstation, chair, desk, display and input device selection and adjustment and special issues regarding notebook computer use and carriage, computing skills and responding to discomfort. The evidence limitations highlight opportunities for future research. The guidelines themselves can inform parents and teachers, equipment designers and suppliers and form the basis of content for teaching children the wise use of computers.

Statement of Relevance: Many children use computers and computer-use habits formed in childhood may track into adulthood. Therefore child–computer interaction needs to be carefully managed. These guidelines inform those responsible for children to assist in the wise use of computers.  相似文献   
27.
The authors of this study examined the outcomes and processes of 2 types of group treatment--cognitive-behavioral treatment groups (CBTG) and humanistic group therapy (HGT)--offered to 200 elementary schoolchildren in a center for students with learning disabilities in Israel. Results indicated that the addition of either type of group treatment to individual academic assistance was more effective than the latter alone on most measures. In fact, on the majority of measures, group treatment without academic assistance was more effective than just individual assistance. Finally, HGT was more effective than CBTG on most measures. Most of the outcomes were sustained at follow-up, and some even increased from termination to follow-up, although effect sizes were quite low. Process measures included the Client Behavior System and the therapist Helping Skills System, which were measured at 5 points in time. Differences between the 2 treatment types were revealed on both process measures, including differences in the growth curve of these behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
28.
Observational methods were used to examine aggressive children's peer relations in 2 contexts: when being teased by a peer and when interacting with a best friend. Because aggressive children may have more difficulty than nonaggressive children in both peer contexts, the authors also examined whether relations between behaviors across contexts varied as a function of aggression. Results indicated that aggression was related to children's behavior when provoked. Children's behavior when provoked was associated with fewer positive and more negative interactions with their best friend, particularly for aggressive children. Results are discussed with respect to social norms in middle childhood and informing interventions for aggressive children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
29.
Six schools were randomly assigned to a multilevel bullying intervention or a control condition. Children in Grades 3-6 (N=1,023) completed pre- and posttest surveys of behaviors and beliefs and were rated by teachers. Observers coded playground behavior of a random subsample (n=544). Hierarchical analyses of changes in playground behavior revealed declines in bullying and argumentative behavior among intervention-group children relative to control-group children, increases in agreeable interactions, and a trend toward reduced destructive bystander behavior. Those in the intervention group reported enhanced bystander responsibility, greater perceived adult responsiveness, and less acceptance of bullying/aggression than those in the control group. Self-reported aggression did not differ between the groups. Implications for future research on the development and prevention of bullying are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
30.
Early Head Start, a federal program begun in 1995 for low-income pregnant women and families with infants and toddlers, was evaluated through a randomized trial of 3,001 families in 17 programs. Interviews with primary caregivers, child assessments, and observations of parent-child interactions were completed when children were 3 years old. Caregivers were diverse in race-ethnicity, language, and other characteristics. Regression-adjusted impact analyses showed that 3-year-old program children performed better than did control children in cognitive and language development, displayed higher emotional engagement of the parent and sustained attention with play objects, and were lower in aggressive behavior. Compared with controls, Early Head Start parents were more emotionally supportive, provided more language and learning stimulation, read to their children more, and spanked less. The strongest and most numerous impacts were for programs that offered a mix of home-visiting and center-based services and that fully implemented the performance standards early. (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