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   107篇
  免费   2篇
  国内免费   4篇
安全科学   6篇
废物处理   1篇
环保管理   27篇
综合类   13篇
基础理论   35篇
污染及防治   19篇
评价与监测   3篇
社会与环境   8篇
灾害及防治   1篇
  2023年   1篇
  2022年   3篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   7篇
  2015年   2篇
  2013年   5篇
  2012年   3篇
  2011年   6篇
  2010年   2篇
  2009年   5篇
  2008年   2篇
  2007年   4篇
  2006年   10篇
  2005年   4篇
  2004年   5篇
  2003年   3篇
  2002年   4篇
  2001年   3篇
  2000年   4篇
  1999年   1篇
  1997年   2篇
  1994年   2篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1989年   1篇
  1988年   3篇
  1987年   4篇
  1986年   1篇
  1985年   5篇
  1984年   1篇
  1982年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1971年   2篇
  1969年   2篇
  1968年   1篇
排序方式: 共有113条查询结果,搜索用时 15 毫秒
61.
The intraspecific patterns of morphometric variation were examined in Fucus distichus L. and F. evanescens C.Ag., using samples gathered from 49 sites spread across the North Atlantic. Ten characters were measured on each plant. The data were subjected to bivariate regression analyses, canonical correlation analysis and nested analysis of variance (ANOVA). It was shown that the combined effects of the three environmental variables measured for each site (latitude, longitude and exposure) could only explain 23 and 15% respectively of the intraspecific morphometric variation. Inter-individual, within-site differences accounted for a further 62 and 53%. The remaining variation appears to be expressed on a geographic scale of tens of kilometres at most. Thus, the species seem to take the form of fine-scale phenotypic mosaics, superimposed on weak major clines. Such a pattern has not previously been described for any macroalga, although it is known in some angiosperms.  相似文献   
62.
63.
泥石流灾情综合评估模式   总被引:7,自引:2,他引:7  
泥石流灾情综合评估模式是在灾情绝对评估的基础上建立的。首先,建立了泥石流灾情评估的步骤框图;然后依据已有的泥石流灾情评估指标体系对各项指标进行量化分析处理,将得了各灾情评估指标公值分布及其量纲换算法,确定了反映直接损失的灾情绝对评估指标和相对评估指标(直接经济损失占灾区国民收入的比例),并对绝对和相对评估结果的等级进行了划分;最后,建立了绝对评估和相对评估结果对比的灾情综合评估模式。经过实例应用验证,评估结果能较好地反映灾情。  相似文献   
64.
65.
Despite efforts to enclose and control conservation zones around the world, direct human impacts in conservation areas continue, often resulting from clandestine violations of conservation rules through outright poaching, strategic agricultural encroachment, or noncompliance. Nevertheless, next to nothing is actually known about the spatially and temporally explicit patterns of anthropogenic disturbance resulting from such noncompliance. This article reviews current understandings of ecological disturbance and conservation noncompliance, concluding that differing forms of noncompliance hold differing implications for diversity. The authors suggest that forms of anthropogenic patchy disturbance resulting from violation may maintain, if not enhance, floral diversity. They therefore argue for extended empirical investigation of such activities and call for conservation biologists to work with social scientists to assess this conservation reality by analyzing how and when incomplete enforcement and rule-breaking drive ecological change.  相似文献   
66.
Despite compelling reasons to involve nonscientists in the production of ecological knowledge, cultural and institutional factors often dis-incentivize engagement between scientists and nonscientists. This paper details our efforts to develop a biweekly newspaper column to increase communication between ecological scientists, social scientists, and the communities within which they work. Addressing community-generated topics and written by a collective of social and natural scientists, the column is meant to foster public dialog about socio-environmental issues and to lay the groundwork for the coproduction of environmental knowledge. Our collective approach to writing addresses some major barriers to public engagement by scientists, but the need to insert ourselves as intermediaries limits these gains. Overall, our efforts at environmental communication praxis have not generated significant public debate, but they have supported future coproduction by making scientists a more visible presence in the community and providing easy pathways for them to begin engaging the public. Finally, this research highlights an underappreciated barrier to public engagement: scientists are not merely disconnected from the public, but also connected in ways that may be functional for their research. Many field scientists, for example, seek out neutral and narrowly defined connections that permit research access but are largely incompatible with efforts to address controversial issues of environmental governance.  相似文献   
67.
Tire wear particles filed from the treads of end-of-life vehicle tires have been added to sea water to examine the release of Zn and the toxicity of the resulting leachate and dilutions thereof to the marine macroalga, Ulva lactuca. Zinc release appeared to be diffusion-controlled, with a conditional rate constant of 5.4 μg[L(h)1/2]−1, and about 1.6% of total Zn was released after 120 h incubation. Exposure to increasing concentrations of leachate resulted in a non-linear reduction in the efficiency of photochemical energy conversion of U. lactuca and, with the exception of the undiluted leachate, increasing accumulation of Zn. Phototoxicity was significantly lower on exposure to equivalent concentrations of Zn added as Zn(NO3)2, suggesting that organic components of leachate are largely responsible for the overall toxicity to the alga. Given the ubiquity and abundance of TWP in urban coastal sediments, the generation, biogeochemistry and toxicity of tire leachate in the marine setting merit further attention.  相似文献   
68.
Objective: To investigate trends of motorcyclist fatalities and identify at-risk populations by motorcyclist demographics and crash characteristics.

Methods: We used the Fatality Analysis Reporting System (FARS) database (2000–2016) to track fatality rate trends, which were quantified by using Poisson mixed-effects regression models comparing 2000–2001 and 2007–2008, as well as 2009–2010 and 2015–2016.

Results: The overall fatality rate per 100,000 population increased from 2000 to 2016, defined by two trend lines—before and after the economic recession in 2008–2009. The overall fatality rate ratio between 2000–2001 and 2007–2008 was 1.60 [95% Confidence Interval (CI): 1.51–1.70], and between 2009–2010 and 2015–2016 was 1.09 (95% CI: 1.02–1.18). Fatality rates increased among all age groups, particularly for motorcyclists aged 60 and older. Those aged 18–29 had the highest fatality rates overall. Age-and-sex standardized state fatality rates were consistently highest in Wyoming, South Dakota, and South Carolina and lowest in Massachusetts, New York and New Jersey.

Conclusion: Motorcycle fatality rates increased overall and across all age groups between 2000 and 2016. Fatalities for the oldest riders showed the steadiest increasing trends. Results highlight the continued public health burden of motorcyclist fatalities and, by extension, the importance of improving motorcycle safety.  相似文献   

69.
Wood and other environmental samples were collected from sites that produced beef with higher than average residues of dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF). Analyses of these samples for PCDD/Fs and pentachlorophenol (PCP) indicated that the high beef residues were associated with PCP-treated wood in the animal facilities. Concentrations of PCDD/Fs in wood as toxic equivalents ranged from 10 to 320,000 pg/g. These concentrations were closely related to the concentrations of PCP, indicating that analysis for PCP provides an economical method to identify wood with high concentrations of PCDD/Fs. Further evidence for the PCP-treated wood as the source of the beef residues is provided by the similarity of the congener profiles in beef from the sites and those profiles predicted from the profiles in wood.  相似文献   
70.
Forty percent of pregnant women aged 37 years and over do not have prenatal diagnosis despite being eligible for a free test. The present study aimed to determine how often, and which, untested women were making a choice about this, how many declined an offer and why. A questionnaire was given to untested women, aged 37 years and over, at no less than 24 weeks gestation. A total of 375 (81.5%) women declined, 72 (16%) were not offered a test and 13 presented too late antenatally. There was a three-fold increased likelihood (OR 3.10 95% CI 1.44, 6.65) of no offer for urban non-English speaking background women, compared with the reference group (metropolitan, English speaking). Unpartnered women were also significantly less likely to receive an offer (OR 3.18, 95% CI 1.19, 8.46). Risk to the baby was the main reason for declining. When offered non-invasive prenatal screening, most decliners of prenatal diagnosis accepted, even those who declined because they were opposed to abortion. We estimate that overall 33% of older pregnant women were being offered and declining amniocentesis and/or chorion villus sampling (CVS). Only 6% were not offered a test, but this small proportion is over-represented by minority groups who must be given equal opportunity to make this choice. Copyright © 2001 John Wiley & Sons, Ltd.  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