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   334篇
  免费   12篇
  国内免费   3篇
安全科学   24篇
废物处理   12篇
环保管理   86篇
综合类   31篇
基础理论   100篇
污染及防治   66篇
评价与监测   17篇
社会与环境   13篇
  2023年   4篇
  2021年   3篇
  2020年   7篇
  2019年   5篇
  2018年   10篇
  2017年   10篇
  2016年   16篇
  2015年   11篇
  2014年   14篇
  2013年   27篇
  2012年   16篇
  2011年   12篇
  2010年   14篇
  2009年   18篇
  2008年   26篇
  2007年   6篇
  2006年   24篇
  2005年   7篇
  2004年   6篇
  2003年   5篇
  2002年   18篇
  2001年   6篇
  2000年   17篇
  1999年   7篇
  1998年   3篇
  1997年   3篇
  1996年   4篇
  1995年   2篇
  1994年   5篇
  1993年   6篇
  1992年   2篇
  1991年   6篇
  1990年   1篇
  1989年   1篇
  1986年   3篇
  1984年   1篇
  1983年   1篇
  1982年   4篇
  1981年   2篇
  1979年   3篇
  1978年   2篇
  1977年   1篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
  1968年   1篇
排序方式: 共有349条查询结果,搜索用时 15 毫秒
131.
IntroductionWe investigated falls at a metropolitan airport to determine fall incidence, identify potential causes of these falls, and suggest opportunities for mitigation.MethodsWe used deidentified incident reports of all falls requiring EMS response that occurred at the airport during 2009 and 2010.ResultsOn average, one fall occurred every 2.3 days. Ninety-six percent (96%) of falls occurred in terminals. Of all falls, 44% occurred on escalators, making escalators the most common location. Seventy-two percent (72%) of fallers were females; 43% were ≥ 65 years; 92% of all falls resulted in a documented injury; 37% of falls resulted in transport to hospital emergency departments. Escalator fall risks include carrying bags (due to changes in baggage fees), using cells phones, not using handrails, and compromised strength and balance.Conclusions and ImpactDiverting at-risk passengers to elevators could significantly reduce the overall falls. Interventions targeting escalator falls have the greatest promise for reducing falls at this airport.  相似文献   
132.
Severely fragmented habitats increase the risk of extirpation of native mammal populations through isolation, increased edge effects, and predation. Therefore, monitoring the movement of mammal populations through anthropogenically altered landscapes can inform conservation. We used metabarcoding of invertebrate-derived DNA (iDNA) from carrion flies (Calliphoridae and Sarcophagidae) to track mammal populations in the wheat belt of southwestern Australia, where widespread clearing for agriculture has removed most of the native perennial vegetation and replaced it with an agricultural system. We investigated whether the localization of the iDNA signal reflected the predicted distribution of 4 native species—echidna (Tachyglossus aculeatus), numbat (Myrmecobius fasciatus), woylie (Bettongia penicillata), and chuditch (Dasyurus geoffroii)—and 2 non-native, invasive mammal species—fox (Vulpes vulpes) and feral cat (Felis catus). We collected bulk iDNA samples (n = 150 samples from 3428 carrion flies) at 3 time points from 3 conservation reserves and 35 road edges between them. We detected 14 of the 40 mammal species known from the region, including our target species. Most detections of target taxa were in conservation reserves. There were a few detections from road edges. We detected foxes and feral cats throughout the study area, including all conservation reserves. There was a significant difference between the diversity (F3, 98 = 5.91, p < 0.001) and composition (F3, 43 = 1.72, p < 0.01) of taxa detections on road edges and conservation reserves. Conservation reserves hosted more native biodiversity than road edges. Our results suggest that the signals from iDNA reflect the known distribution of target mammals in this region. The development of iDNA methods shows promise for future noninvasive monitoring of mammals. With further development, iDNA metabarcoding could inform decision-making related to conservation of endangered taxa, invasive species management, and impacts of habitat fragmentation.  相似文献   
133.
Water quality and stream habitat in agricultural watersheds are under greater scrutiny as hydrologic pathways are altered to increase crop production. Agricultural drainage ditches function to remove water quickly from farmed landscapes. Conventional ditch designs lack the form and function of natural stream systems and tend to be unstable and provide inadequate habitat. In October of 2009, 1.89 km of a conventional drainage ditch in Mower County, Minnesota, was converted to an alternative system with a two‐stage channel to investigate the improvements in water quality, stability, and habitat. Longitudinal surveys show a 12‐fold increase in the pool‐riffle formation. Cross‐sectional surveys show an average increase in bankfull width of approximately 10% and may be associated to an increased frequency in large storm events. The average increase in bankfull depth was estimated as 18% but is largely influenced by pool formation. Rosgen Stability Analyses show the channel to be highly stable and the banks at a low risk of erosion. The average bankfull recurrence interval was estimated to be approximately 0.30 years. Overall, the two‐stage ditch design demonstrates an increase in fluvial stability, creating a more consistent sediment budget, and increasing the frequency of important instream habitat features, making this best management practice a viable option for addressing issues of erosion, sediment imbalance, and poor habitat in agricultural drainage systems.  相似文献   
134.
Watershed characteristics such as land‐use and land‐cover affect stream condition at multiple scales, but it is widely accepted that conditions in close proximity to the stream or survey site tend to have a stronger influence. Although spatially weighted watershed metrics have existed for years, nonspatial lumped landscape metrics (i.e., areal mean or percentage) are still widely used because relatively few technical skills are needed to implement them. The Inverse Distance Weighted Percent Land Use for Streams (IDW‐Plus) custom ArcGIS toolset provides the functionality to efficiently calculate six spatially explicit watershed metrics which account for the Euclidean or flow length distance to the stream or outlet, as well as the probability for overland runoff. These include four distance‐weighted metrics, those being inverse Euclidean distance to the stream or outlet, and the inverse flow length to the stream or outlet. Two tools are also included to generate hydrologically active (i.e., runoff potential), inverse flow length to the stream or outlet metrics. We demonstrate the tools using real data from Southeast Queensland, Australia. We also provide detailed instructions, so readers can recreate the examples themselves before applying the tools to their own data.  相似文献   
135.
Raman spectroscopy was used to investigate sorption mechanisms of cephapirin (CHP), a veterinary antibiotic, onto quartz (SiO2) and feldspar (KAlSi3O8) at different pH. Sorption occurs by electrostatic attraction, monodentate and bidentate complexation. The zwitterion (CHPo) adsorbs to a quartz(+) surface by electrostatic attraction of the carboxylate anion group (-COO) at low pH, but adsorbs to a quartz(−) surface through electrostatic attraction of the pyridinium cation, and possibly COO bridge complexes, at higher pH. CHP bonds to quartz(−) surfaces by bidentate complexation between one oxygen of -COO and oxygen from carbonyl of an acetoxymethyl group. On a feldspar(+/−) surface, CHPo forms monodentate complexes between CO, and possible -COO bridges and/or electrostatic attachments to localized edge (hydr)oxy-Al surfaces. CHP adsorbs to feldspar(−) through monodentate CO complexation. Similar mechanisms may operate for other cephalosporins. Results demonstrate, for the first time, that Raman techniques can be effective for evaluating sorption mechanisms of antibiotics.  相似文献   
136.
This study uses California data to compare redevelopment for properties subject to mandatory and voluntary cleanup. CalSites are subject to the CERCLA liability approach, while properties in the Voluntary Cleanup Program (VCP) are subject to a risk-based approach (RBA) that allows some contamination to remain for non-residential redevelopment. The expectation is that VCPs will show a greater proportion of industrial redevelopment, which has the least stringent standard, and a smaller proportion of residential redevelopment. The results show an overall trend toward more residential redevelopment of contaminated properties, but consistent with expectations, the trend is weaker for VCP properties than CalSites.  相似文献   
137.
In line with China's "going out" strategy, China's dam industry has in recent years significantly expanded its involvement in overseas markets. The Chinese Export-Import Bank and other Chinese financial institutions, state-owned enterprises, and private firms are now involved in at least 93 major dam projects overseas. The Chinese government sees the new global role played by China's dam industry as a "win-win" situation for China and host countries involved. But evidence from project sites such as the Merowe Dam in Sudan demonstrates that these dams have unrecognized social and environmental costs for host communities. Chinese dam builders have yet to adopt internationally accepted social and environmental standards for large infrastructure development that can assure these costs are adequately taken into account. But the Chinese government is becoming increasingly aware of the challenge and the necessity of promoting environmentally and socially sound investments overseas.  相似文献   
138.
139.
国际农业食品网络(IAFN)是1996年联合国粮农组织世界粮食高峰会议时为协调农业发展领域中与国际组织有关的活动而成立的.该网络只是一个讨论论坛,其中与会者可以确认他们的共同关注和分享各种思路的经验.......  相似文献   
140.
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