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   366篇
  免费   22篇
  国内免费   15篇
安全科学   82篇
废物处理   6篇
环保管理   52篇
综合类   115篇
基础理论   43篇
污染及防治   7篇
评价与监测   7篇
社会与环境   74篇
灾害及防治   17篇
  2023年   4篇
  2022年   8篇
  2021年   9篇
  2020年   14篇
  2019年   14篇
  2018年   15篇
  2017年   19篇
  2016年   21篇
  2015年   13篇
  2014年   9篇
  2013年   32篇
  2012年   17篇
  2011年   16篇
  2010年   11篇
  2009年   16篇
  2008年   9篇
  2007年   17篇
  2006年   14篇
  2005年   11篇
  2004年   17篇
  2003年   19篇
  2002年   17篇
  2001年   16篇
  2000年   10篇
  1999年   9篇
  1998年   11篇
  1997年   8篇
  1996年   6篇
  1995年   2篇
  1994年   7篇
  1993年   3篇
  1992年   3篇
  1991年   3篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
排序方式: 共有403条查询结果,搜索用时 31 毫秒
351.
Purpose: This is a study of the influence of an unbelted rear occupant on the risk of severe injury to the front seat occupant ahead of them in frontal crashes. It provides an update to earlier studies.

Methods: 1997–2015 NASS-CDS data were used to investigate the risk for severe injury (Maximum Abbreviated Injury Score [MAIS] 4+F) to belted drivers and front passengers in frontal crashes by the presence of a belted or unbelted passenger seated directly behind them or without a rear passenger. Frontal crashes were identified with GAD1 = F without rollover (rollover ≤ 0). Front and rear outboard occupants were included without ejection (ejection = 0). Injury severity was defined by MAIS and fatality (F) by TREATMNT = 1 or INJSEV = 4. Weighted data were determined. The risk for MAIS 4+F was determined using the number of occupants with known injury status MAIS 0+F. Standard errors were determined.

Results: The risk for severe injury was 0.803 ± 0.263% for the driver with an unbelted left rear occupant and 0.100 ± 0.039% with a belted left rear occupant. The driver's risk was thus 8.01 times greater with an unbelted rear occupant than with a belted occupant (P <.001). With an unbelted right rear occupant behind the front passenger, the risk for severe injury was 0.277 ± 0.091% for the front passenger. The corresponding risk was 0.165 ± 0.075% when the right rear occupant was belted. The front passenger's risk was 1.68 times greater with an unbelted rear occupant behind them than a belted occupant (P <.001). The driver's risk for MAIS 4+F was highest when their seat was deformed forward. The risk was 9.94 times greater with an unbelted rear occupant than with a belted rear occupant when the driver's seat deformed forward. It was 13.4 ± 12.2% with an unbelted occupant behind them and 1.35 ± 0.95% with a belted occupant behind them.

Conclusions: Consistent with prior literature, seat belt use by a rear occupant significantly lowered the risk for severe injury to belted occupants seated in front of them. The reduction was greater for drivers than for front passengers. It was 87.5% for the driver and 40.6% for the front passenger. These results emphasize the need for belt reminders in all seating positions.  相似文献   

352.
This paper investigates the nexus between greenhouse gas emissions and poverty alleviation in the Economic Commission of West African States between 1985 and 2020 applying autoregressive distributed lag and Granger causality techniques. The results reveal that carbon dioxide non-significantly relates to gross domestic product per capita positively while nitrous oxide and foreign direct investment impacts gross domestic product per capita positively. Methane negatively impacts gross domestic product per capita. The governments should use conventions to regulate greenhouse gas emissions’ effects on environmental degradation regionally and globally. The study underscores that countries should diversify to cleaner energy sources. This would reduce greenhouse gas emissions in the atmosphere. Massive technological investment is required to mitigate the greenhouse gas emissions’ negative impacts on the environment which create poverty. This policy implication ensures environmental sustainability and reverses the ugly trend of greenhouse gas emissions on poverty.  相似文献   
353.
354.

Introduction

A state by year panel is analyzed to simultaneously explore the statistical correlation between state level traffic fatality rates and state level behavioral regulations regarding teen licensing, seat belt use, and driving under the influence (DUI) in a model that also controls for other correlates.

Method

By including measures of all three of these policies, the estimated policy effects should not be overstated due to underspecification bias. The panel includes the 48 contiguous U.S. states for the time period from 1999 through 2003. State fatality rates are measured as fatalities per million miles traveled. Measures of state policies regarding traffic safety related behavior are based on information gathered by the Insurance Institute for Highway Safety. Estimates are calculated via a time fixed effects model that uses the double-log form to allow for interaction effects between the independent variables.

Results

Least squares estimates indicate that, on average, more restrictive graduated teen licensing and DUI policies significantly reduce traffic fatality rates, while stricter seat belt enforcement policies have a statistically insignificant negative impact on fatality rates.  相似文献   
355.
全面分析了中国西南喀斯特地区的开发潜力和制约其发展的 6个因素 ,提出了开发西南喀斯特地区的 5大战略措施  相似文献   
356.
为研究干熄焦焦粉燃爆的可能性,在某焦化厂干熄焦输焦皮带机头和除尘站两个位置,取焦粉尘样进行工业分析和粒度分析,并测量地下皮带通廊代表段的焦粉尘浓度。分析显示,干熄焦地下皮带通廊焦粉水分较低,均低于3%;所选两个位置的粒度分布较为接近;实验测得所取焦粉尘的爆炸下限质量浓度在160~180 g/m~3之间。现场地下皮带通廊焦粉质量浓度值最高为8.95 g/m~3,远低于其爆炸下限,燃爆的可能性较低。  相似文献   
357.
百花湖消落带常见植物氮磷钾营养元素含量分布特征研究   总被引:8,自引:0,他引:8  
于2011年9月在百花湖消落区进行随机采集,选取常见的30种百花湖消落带植物,如狗牙根(Cynodon dactylon)、牛鞭草(Hemarthria altissima)、白花三叶草(Trifolium repens)、喜旱莲子草(Alternanthera philoxeroides)、鬼针草(Bidens pilosa)、菖蒲(Acuros calamu Linn)等为研究对象,对其根、茎、叶中氮磷钾营养元素的分布进行比较研究.结果表明:大多数植物根、茎、叶中N、P、K含量表现出一致性,即K>N>P,并且N、P、K相互之间呈现出显著的正相关关系,这与该地区土壤中N、P、K的含量有着显著的关系.在同一植物不同器官中N、P、K的含量也表现出一致性,即叶>茎>根,并且根、茎、叶中的含量相互之间也呈现出现显著的正相关关系.消落区植物总体根、茎、叶的营养状况分别为低、中、高,并且地上部分的营养元素占整株植物总营养元素的平均值为80%以上.因此,收割地上部分的茎和叶,即可达到对土壤中N、P较好的处理效果.禾本科、蓼科及菊科植物中营养元素含量较低,又具有一定的耐水淹性,适宜在消落区水淹时间较长且土壤中N、P营养元素含量较低的这种特殊环境下生长.该研究揭示了百花湖消落区常见植物的营养状况,以及有助于筛选出适合消落区生长的植物,对控制水体富营养化和研究消落区生态系统的完整性有着重要的意义.  相似文献   
358.
关注耕地转出行为对农户贫困脆弱性的影响,对于农民家庭的持久脱贫及农村反贫困政策的制定意义重大。基于CFPS两期全国整合样本的面板数据,在对农户贫困脆弱性进行测算的基础上,运用倍差法、OLS模型及倾向得分匹配倍差法,实证检验耕地转出对农民家庭贫困脆弱性的影响及其区域差异。结果表明:(1)耕地转出行为的发生降低了农户的贫困脆弱性,是一种有效的扶贫手段,在帮助部分农户抵御收入风险上起到了积极作用;(2)耕地转出规模的扩大并未显著改善农户的贫困脆弱性状况;(3)控制变量也对农户贫困脆弱性产生了不同程度的影响,其中户主性别、户主年龄和家庭住房净资产显著正向影响农户的贫困脆弱性水平,而户主受教育程度、家庭劳动力数、健康状况、现金和存款数及当地经济发展水平等变量显著负向影响农户的贫困脆弱性水平;(4)耕地转出行为对农民家庭贫困脆弱性的影响呈现出一定的区域差异性,对东、中和东北地区农户贫困脆弱性的降低起到了显著促进作用,但对西部地区农户的减贫作用并不明显。  相似文献   
359.
The Main Geophysical Observatory 2D channel photochemical model is used to study the behavior of tropospheric OH within the 30–60°N zonal belt in relation to changing NOX and CO emissions. The changes of tropospheric OH as a function of the contributions by NOX and CO emissions during the period 1850–2050 are calculated. Our estimations show that the largest annual increment of total tropospheric OH within the belt considered occurs in the 1985–1995 period, about 0.27% yr−1. Based on scenarios of tropospheric pollution emissions in the first half of 21st century, the total tropospheric OH content will increase more slowly, by 0.12–0.15% yr−1. The maximum growth of OH concentration occurs close to air pollution locations—in the lower troposphere during 1850–1995 but in the upper troposphere in the 21st century when the NOX source from subsonic aircraft increases faster than the surface source.  相似文献   
360.
This article discusses the importance of social networks as survival strategies, testing the impact of segregation on the structure and organisation of personal networks of low-income individuals. It presents preliminary results of an ongoing study on personal networks of individuals living in situations of poverty in São Paulo. We analyse the characteristics of 89 personal networks of poor individuals living in three urban locations, characterised by different social contents and different contexts of segregation. The results indicate a considerable heterogeneity of networks (in terms of size, diversity of sociability spheres, among other dimensions) and a strong localism, which is commonly found in the three different urban contexts. At the same time, the analysis suggests a low impact of segregation and a more complex relationship between networks and space than previously described by the international literature.  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