全文获取类型
收费全文 | 93篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 4篇 |
废物处理 | 2篇 |
环保管理 | 19篇 |
综合类 | 12篇 |
基础理论 | 24篇 |
环境理论 | 1篇 |
污染及防治 | 18篇 |
评价与监测 | 6篇 |
社会与环境 | 11篇 |
灾害及防治 | 2篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 8篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 1篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 1篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有99条查询结果,搜索用时 0 毫秒
91.
IntroductionCarbondioxide(CO2 )isaprincipalgreenhousegasandthereforetheirair waterexchangesareimportantproblemsinterrestrialecosystemsforclimatechangestudy(Frankignoulle ,1 998;Chimel,2 0 0 1 ) .ThedirectionofCO2 gasexchange(evasionorinvasion)isdependentonthedirectionoftheCO2concentrationgradientbetweentheairandthesurfacewater;themagnitudeoftheexchangedependsadditionallyonthegasexchangecoefficient,k.Alloflakesinland ,withitssmallareabutlargeatmosphericCO2 fluxrange ,playanimportantroleinev… 相似文献
92.
93.
The people of the Democratic Republic of Congo for decades have been living in a situation of chronic crisis. Violence, population displacement and the destruction of infrastructure and health services have devastated the health of the population. In 2001, Médicins Sans Frontières conducted a survey in five areas of western and central DRC to assess mortality, access to health-care, vaccination coverage and exposure to violence. High mortality rates were found in front-line zones, mainly due to malnutrition and infectious diseases. In Basankusu approximately 10 per cent of the total population and 25 per cent of the under-five population had perished in the year before the survey. Humanitarian needs remain acute across the country, particularly near the front line. Infectious-disease control and treatment are a priority, as is increasing access to health-care. Humanitarian assistance must be increased considerably, especially in rural areas and zones that have been affected directly by conflict. 相似文献
94.
Reducing the environmental impact of offshore operations is one of the most pressing challenges facing the oil and gas industry in Europe today. A study was conducted to review the issues by literature search, and consultation with stakeholders and experts. It was clear from the literature search that considerable research had been dedicated to: protecting the marine environment; achieving compliance with legislative controls; assessing the technical and economic feasibility of platform disposal options; and ecological surveying. By comparison, considerably less research had been carried out in other important areas such as: assessing the impacts wastes returned to shore for disposal; identifying sustainable strategies for operations; and assessing and mitigating against adverse impacts from atmospheric emissions. It is clear that the environmental regulatory regime offshore will become tougher and have an increasing influence on offshore oil and gas field environmental planning and management. Future regulatory developments include: a streamlining of the offshore oil and gas environmental regulatory regime; the introduction of the Habitats Directive into the licensing system; and the Offshore Combustion Installations (Prevention and Control of Pollution) Regulations 1999. In addition, post Kyoto regulatory developments and societal concern over atmospheric pollution, will increasingly focus efforts on reducing the emission of global warming gases. These changes, coupled with the uncertainty over how resilient the environment is to perturbation, present a need to clearly manage environmental information. 相似文献
95.
By changing riparian plants from Eucalypts to pasture and exotic deciduous trees, modern development has altered the type of carbon assimilated by Australian rivers. To investigate influences of plant litter substrates on biochemical oxygen demand, plant materials entering the Murray River were analyzed for their composition and mineralization potential. Plant materials were distinguished compositionally by two principal components, structural carbon and macronutrients, as: (i) Eucalyptus leaves, (ii) Eucalyptus bark and Casuarina cunninghamiana seed cone, (iii) grasses, (iv) macrophytes, (v) aquatic herbs, (vi) non-eucalypt leaf (Salix, Casuarina, Acacia). Ratios of C/P (1879-14524) and C/N (65-267) were relatively high in Eucalyptus bark, while mean N/P (7-60) ratios were similar among plant materials. Terrestrial weathering increased C/P and C/N ratios, while N/P ratios remained similar, due to greater loss of N and P relative to C. Aerobic decay experiments showed that nutrient supplementation accelerated decay of all organic substrates, except for grasses that decayed efficiently without supplementation. Aquatic herbs also had substantial carbon availability, macrophytes and non-eucalypt leaves had intermediate carbon availability, while eucalypt leaf and bark had intermediate to low carbon availabilities. Because biochemical oxygen demand varies with organic substrates sampled from the Murray River, and also with soluble nutrient availability, it is plausible that that modern changes to riverine plant communities and land use have influenced the biogeochemistry of this river toward faster, and more complete, processing of allochthonous carbon. 相似文献
96.
David T. Ford Darryl W. Davis 《Journal of the American Water Resources Association》1985,21(1):135-144
ABSTRACT: The U.S. Army Corps of Engineers has broad, nationwide water resources planning and management responsibilities. In response to the needs of Corps professionals, the Hydrologic Engineering Center (HEC) has developed and supports a family of computer programs designed to aid them in their work. These programs include catchment, channel, alluvial, and statistical process models, system operation models, plan evaluation models, and data management programs. These models individually and collectively have been used throughout the Corps in a wide range of water resources planning studies. 相似文献
97.
Morgan Gerlitz Jimmy Fox William Ford Admin Husic Tyler Mahoney Mindy Armstead Susan Hendricks Angela Crain Jason Backus Erik Pollock Wei Ren Bo Tao Brenden Riddle David White 《Journal of the American Water Resources Association》2023,59(4):635-651
The Ohio River Basin (ORB) is responsible for 35% of total nitrate loading to the Gulf of Mexico yet controls on nitrate timing require investigation. We used a set of submersible ultraviolet nitrate analyzers located at 13 stations across the ORB to examine nitrate loading and seasonality. Observed nitrate concentrations ranged from 0.3 to 2.8 mg L−1 N in the Ohio River's mainstem. The Ohio River experiences a greater than fivefold increase in annual nitrate load from the upper basin to the river's junction with the Mississippi River (74–415 Gg year−1). The nitrate load increase corresponds with the greater drainage area, a 50% increase in average annual nitrate concentration, and a shift in land cover across the drainage area from 5% cropland in the upper basin to 19% cropland at the Ohio River's junction with the Mississippi River. Time-series decomposition of nitrate concentration and nitrate load showed peaks centered in January and June for 85% of subbasin-year combinations and nitrate lows in summer and fall. Seasonal patterns of the terrestrial system, including winter dormancy, spring planting, and summer and fall growing-harvest seasons, are suggested to control nitrate timing in the Ohio River as opposed to controls by river discharge and internal cycling. The dormant season from December to March carries 51% of the ORB's nitrate load, and nitrate delivery is high across all subbasins analyzed, regardless of land cover. This season is characterized by soil nitrate leaching likely from mineralization of soil organic matter and release of legacy nitrogen. Nitrate experiences fast transit to the river owing to the ORB's mature karst geology in the south and tile drainage in the northwest. The planting season from April to June carries 26% of the ORB's nitrate and is a period of fertilizer delivery from upland corn and soybean agriculture to streams. The harvest season from July to November carries 22% of the ORB's nitrate and is a time of nitrate retention on the landscape. We discuss nutrient management in the ORB including fertilizer efficiency, cover crops, and nitrate retention using constructed measures. 相似文献
98.
A notable body of research has established a clear link between intersexuality and the feminising influence of microsporidia
infection in amphipods. In this study, we investigated the relationship between microsporidia infection and intersexuality
in the amphipod Echinogammarus marinus (Leach) from Portsmouth, southern England. The analysis revealed a male-biased population (~2:1) harbouring both Dictyocoela berillonum and Dictyocoela duebenum microsporidia, with ~38 and 6% of animals displaying ‘high’ levels of infection, respectively. We also reveal the presence
of several intersex phenotypes: intersex females (1%) that possess genital papillae. Two male intersex phenotypes—internal
intersex (8.2%), possessing an oviduct structure on their testes, and external intersex males (4.4%), which possess external
brood plates. We found a statistically significant relationship between D. berillonum infection and the external intersex male phenotype; however, the male-biased population and low levels of female infection
suggest that the correlation may not be the result of incomplete feminisation. In addition, we found that the internal and
external intersex characteristics are rarely seen on the same specimen, suggesting that the male intersex phenotypes are caused
by distinct mechanisms. In combination, these findings are suggestive of a more complex relationship between amphipod intersexuality
and their microsporidia than had previously been recognised. 相似文献
99.
Climate determines upper, but not lower, altitudinal range limits of Pacific Northwest conifers 总被引:1,自引:0,他引:1
Does climate determine species' ranges? Rapid rates of anthropogenic warming make this classic ecological question especially relevant. We ask whether climate controls range limits by quantifying relationships between climatic variables (precipitation, temperature) and tree growth across the altitudinal ranges of six Pacific Northwestern conifers on Mt. Rainier, Washington, USA. Results for three species (Abies amabilis, Callitropsis nootkatensis, Tsuga mertensiana) whose upper limits occur at treeline (> 1600 m) imply climatic controls on upper range limits, with low growth in cold and high snowpack years. Annual growth was synchronized among individuals at upper limits for these high-elevation species, further suggesting that stand-level effects such as climate constrain growth more strongly than local processes. By contrast, at lower limits climatic effects on growth were weak for these high-elevation species. Growth-climate relationships for three low-elevation species (Pseudotsuga menziesii, Thuja plicata, Tsuga heterophylla) were not consistent with expectations of climatic controls on upper limits, which are located within closed-canopy forest (< 1200 m). Annual growth of these species was poorly synchronized among individuals. Our results suggest that climate controls altitudinal range limits at treeline, while local drivers (perhaps biotic interactions) influence growth in closed-canopy forests. Climate-change-induced range shifts in closed-canopy forests will therefore be difficult to predict accurately. 相似文献