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   227篇
  免费   5篇
  国内免费   5篇
安全科学   12篇
废物处理   8篇
环保管理   30篇
综合类   62篇
基础理论   61篇
环境理论   1篇
污染及防治   24篇
评价与监测   21篇
社会与环境   17篇
灾害及防治   1篇
  2024年   3篇
  2023年   5篇
  2022年   2篇
  2021年   3篇
  2020年   9篇
  2019年   4篇
  2018年   4篇
  2017年   11篇
  2016年   20篇
  2015年   12篇
  2014年   12篇
  2013年   11篇
  2012年   7篇
  2011年   6篇
  2010年   12篇
  2009年   17篇
  2008年   7篇
  2007年   10篇
  2006年   10篇
  2005年   10篇
  2004年   4篇
  2003年   3篇
  2002年   4篇
  2000年   2篇
  1998年   3篇
  1997年   2篇
  1996年   2篇
  1975年   1篇
  1971年   1篇
  1969年   1篇
  1963年   1篇
  1962年   1篇
  1961年   1篇
  1959年   2篇
  1957年   1篇
  1956年   2篇
  1953年   1篇
  1941年   3篇
  1940年   1篇
  1939年   1篇
  1938年   3篇
  1937年   2篇
  1934年   1篇
  1932年   2篇
  1931年   3篇
  1930年   1篇
  1929年   1篇
  1927年   3篇
  1923年   1篇
  1918年   1篇
排序方式: 共有237条查询结果,搜索用时 14 毫秒
51.
IntroductionYard maintenance equipment is potentially dangerous, and some of the more frequency used equipment (e.g., lawn mowers) has been extensively studied. However, the extent of lawn trimmers as a source of injury has not previously been explored.MethodsData from the Consumer Product Safety Commission's National Electronic Injury Surveillance System were used to estimate the number of patients treated in U.S. emergency departments for lawn trimmer-related injuries. Injury rates were calculated according to age, sex, and race, and characteristics of the injury event were determined.ResultsAn estimated 81,907 injuries involving a lawn trimmer occurred from 2000–2009. The incidence generally increased over time. Men, people aged 40–49, and Caucasians were the groups most likely to be injured. The most commonly injured body part was the head, specifically the eye, accounting for 42.5% of the injuries. Contusions and abrasions were the most common type of injury to the head, but lacerations were the most common injury to the extremities, and strains/sprains were the most common injury to the trunk.DiscussionAlthough previous research on lawn trimmers has focused exclusively on injuries to the eyes, the results of the current study show that such injuries are one component of the problem. Because most of the injuries were due to foreign objects, it is important that the use of adequate safety gear be emphasized when operating lawn trimmers.Impact on IndustryResults suggest that lawn trimmer design changes and better safety education for trimmer use can reduce the rate of injury and reverse the current trend.  相似文献   
52.
    
This paper examines the relationships between measurable watershed hydrologic features, base flow recession rates, and the Q7,10 low flow statistic (the annual minimum seven‐day average streamflow occurring once every 10 years on average). Base flow recession constants were determined by analyzing hydrograph recession data from 24 small (>130 km2), unregulated watersheds across five major physiographic provinces of Pennsylvania, providing a highly variable dataset. Geomorphic, hydrogeologic, and land use parameters were determined for each watershed. The base flow recession constant was found to be most strongly correlated to drainage density, geologic index, and ruggedness number (watershed slope); however, these three parameters are intercorrelated. Multiple regression models were developed for predicting the recession rate, and it was found that only two parameters, drainage density and hydrologic soil group, were required to obtain good estimates of the recession constant. Equations were also developed to relate the recession rates to Q7,10 per unit area, and to the Q7,10/Q50 ratio. Using these equations, estimates of base flow recession rates, Q7,10, and streamflow reduction under drought conditions can be made for small, ungaged basins across a wide range of physiography.  相似文献   
53.
Challenges companies face and tools they use to identify and reduce their environmental footprints across their supply chains  相似文献   
54.
55.
56.
Food and Environmental Virology - Shellfish constitute an important protein source but may be contaminated by viruses from various origins. A study performed on clams collected in Cameroon showed a...  相似文献   
57.
Nanostructured materials are a relatively new class of materials that exhibit advanced mechanical properties, thus improving performance and capabilities of products, with potential applications in the automotive, aerospace and defense industries. Among the severe plastic deformation (SPD) methods currently used for achieving nanoscale structures, accumulative roll bonding (ARB) is the most favorable method to produce grain refinement for continuous production of metallic sheets at a bulk scale.In this article, a model that describes the evolution of material strength due to processing via accumulative roll bonding was developed. ARB experiments were conducted on CP-Ti Grade 2 at a selected set of conditions. The results showed significant grain refinement in the microstructure (down to ~120 nm) and a two-fold increase in tensile strength as compared to the as-received material. The developed model was validated using the experimental data, and exhibited a good fit over the entire range of ARB processing cycles. To further validate the model and ensure its robustness for a wider array of materials (beyond CP-Ti), a review of efforts on ARB processing was carried out for five other materials with different initial microstructures, mechanical properties, and even crystalline structures. The model was still able to capture the strengthening trends in all considered materials.  相似文献   
58.
    
This Incubator contends that the concept of validity generalization has been overgeneralized in its capacity to predict work performance for three reasons: sampling bias in the occupations selected for analysis, the prediction of acceptable performance to the exclusion of superior performance, and the conflation of statistical prediction and psychological meaning. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
59.
    
The present study examined the moderating role of reciprocation wariness in the association of employees' psychological contract fulfillment with psychosomatic strain and voluntary turnover, as mediated by perceived organizational support. To study these relationships longitudinally, 169 graduating college seniors were surveyed upon job acceptance and again 3 weeks, 3 months, 6 months, and 18 months following the start of employment. The findings showed that psychological contract fulfillment was positively related to perceived organizational support. However, this positive relationship was eliminated by reciprocation wariness, and this influence was carried over to psychosomatic strain and voluntary turnover. Thus, it appears that reciprocation wariness leads employees to discount psychological contract fulfillment as an indication of the organization's valuation and caring. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
60.
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