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   1263篇
  免费   27篇
  国内免费   9篇
安全科学   51篇
废物处理   47篇
环保管理   323篇
综合类   133篇
基础理论   383篇
污染及防治   193篇
评价与监测   107篇
社会与环境   47篇
灾害及防治   15篇
  2023年   6篇
  2022年   12篇
  2021年   22篇
  2020年   14篇
  2019年   16篇
  2018年   25篇
  2017年   27篇
  2016年   43篇
  2015年   31篇
  2014年   29篇
  2013年   76篇
  2012年   73篇
  2011年   73篇
  2010年   54篇
  2009年   45篇
  2008年   58篇
  2007年   68篇
  2006年   75篇
  2005年   52篇
  2004年   50篇
  2003年   55篇
  2002年   38篇
  2001年   19篇
  2000年   27篇
  1999年   19篇
  1998年   23篇
  1997年   24篇
  1996年   22篇
  1995年   18篇
  1994年   12篇
  1993年   15篇
  1992年   16篇
  1991年   8篇
  1990年   13篇
  1989年   9篇
  1988年   11篇
  1987年   9篇
  1986年   11篇
  1985年   7篇
  1984年   13篇
  1983年   10篇
  1982年   11篇
  1981年   16篇
  1980年   6篇
  1979年   12篇
  1978年   7篇
  1977年   6篇
  1976年   4篇
  1975年   2篇
  1974年   2篇
排序方式: 共有1299条查询结果,搜索用时 609 毫秒
941.
Following initial experiments presented elsewhere (2IOPS), the bacterial degradation of two vegetable oils was investigated in some detail. the number of aerobic and anaerobic heterotrophic bacteria, oil degrading and sulphate reducing bacteria were quantified during simulated spills on a salt marsh. the sediment fatty acid composition was also studied using GC-MS analysis. Degradation of linseed and sunflower oils was concomitant with an increase in the numbers of aerobic and anaerobic bacteria. Fatty acids analysis revealed preferential degradation of the principal components of the oils (18:3ω3 for linseed oil and 18:2ω6 for sunflower oil). the presence of several isomers of the usual polyunsaturated fatty acids was also detected. the identification of some of these new fatty acids has been carried out. Possible pathways of degradation of these vegetable oils are suggested.  相似文献   
942.
The World Bank has shifted its accountability over the past two decades away from borrowing countries towards external groups, such as advocacy non-governmental organizations (NGOs). One conduit for this external accountability is the environmental impact assessment (EM) process. EIA has both theoretical and practical challenges when applied in developing countries, but is bound by Bank guidelines designed in developed countries. Using the Bujagali Falls Hydropower Project, Uganda as a case study, this paper will demonstrate that the increase in external accountability at the World Bank via EIA has a negative effect on governments and civil society in the South and on global governance.  相似文献   
943.
We estimate the value of information (VOI) for three key parameters of climate integrated assessment models (IAMs): marginal damages at low temperature anomalies, marginal damages at high temperature anomalies, and equilibrium climate sensitivity. Most empirical studies of climate damages have examined temperature anomalies up to 3 °C, while some recent theoretical studies emphasize the risks of “climate catastrophes,” which depend on climate sensitivity and on marginal damages at higher temperature anomalies. We use a new IAM to estimate the VOI for each parameter over a range of assumed levels of study precision based on prior probability distributions calibrated using results from previous studies. We measure the VOI as the maximum fixed fraction of consumption that a social planner would be willing to pay to conduct a new study before setting a carbon tax. Our central results suggest that the VOI is greatest for marginal damages at high temperature anomalies.  相似文献   
944.
Predicting future impacts of temperature change require consideration of multiple impacts of temperature on organisms from different populations. We explored the impacts of temperature on feeding, growth, and mortality of emarginated dogwhelks, Nucella emarginata, from three populations (34.459, ?120.473; 34.435, ?119.930; 34.355, ?119.441) that are separated by a total distance of <100 km. Collections and experiments took place September–December 2012. Populations differed both in the number of mussels consumed at 16 and 20 °C and in the difference in feeding at these temperatures. Despite differences in feeding, increases in whelk mortality with temperature did not differ among populations, and in the 16 °C treatment changes in whelk mass did not differ among populations. These results indicate population-specific responses may differ even among geographically close populations. However, some traits may be more adaptable than others and impacts of a given change may be limited by various constraints (e.g., changes in feeding may accompany changes in metabolic needs). Improving our predictions of climate change impacts will require considering these issues, which may be especially important for marine communities where species differ widely in developmental mode, population connectivity, and other traits which may affect responses to changing temperatures.  相似文献   
945.
Studies of the importance of ecosystem engineers have focused on their benefit to biodiversity through ameliorating environmental stress, without understanding the exact benefits gained by associated organisms. On monsoonal tropical shores, species experience strong seasonality in environmental conditions from almost temperate winters to tropical summers when mass mortalities can occur during daytime emersion. The limpet, Cellana grata, associates with an ecosystem engineer, the barnacle Tetraclita japonica, in summer, but not in winter. To understand the benefits of this association, physiological responses (heart rates and osmotic responses) of the limpet either amongst Tetraclita or on open rock surfaces were investigated under three environmental conditions in a laboratory mesocosm: awash (non-stressed), low (30 °C) and high thermal stress (40 °C) of varying durations (3 or 6 h). In general, at 30 °C, limpets showed similar physiological responses under all conditions for both exposure durations. After 6 h at 40 °C, however, all limpets on open rock surfaces died, whereas those associated with barnacles survived. The surviving limpets experienced similar levels of stress as those exposed to 40 °C on open rock surfaces for half the time (3 h), showing that both the level and duration of stress were important. Limpets, therefore, gain benefits from engineering species when conditions are extreme or stress is prolonged. Under low temperatures or for short durations (e.g. winter), associating with barnacles does not provide physiological benefits. Understanding how, and to what extent, associates benefit from ecosystem engineers highlights how close the margin between survival and mortality can be when conditions are extreme.  相似文献   
946.
At least 225 people in the Fiji Islands died as a result of the 1931 hurricane and flood, representing the largest loss of life from a natural disaster in Fiji's recent history. This paper explores the causes of disaster and the potential for recurrence. The disaster occurred because a rare event surprised hundreds of people—especially recently settled Indian farmers—occupying highly exposed floodplains in north‐west Viti Levu island. The likelihood of a flood disaster of such proportions occurring today has been diminished by changed settlement patterns and building materials; however, a trend towards re‐occupancy of floodplains, sometimes in fragile dwellings, is exposing new generations to flood risks. The contribution of this paper to the global hazards literature is set out in three sections: the ethnicity, gender and age of flood fatalities; the naturalness of disasters; and the merit of choice and constraint as explanations for patterns of vulnerability.  相似文献   
947.
Roughly 45% of the assessed lakes in the United States are impaired for one or more reasons. Eutrophication due to excess phosphorus loading is common in many impaired lakes. Various strategies are available to lake residents for addressing declining lake water quality, including septic system upgrades and establishing riparian buffers. This study examines 25 lakes to determine whether septic upgrades or riparian buffers are a more cost-effective strategy to meet a phosphorus reduction target. We find that riparian buffers are the more cost-effective strategy in every case but one. Large transaction costs associated with the negotiation and monitoring of riparian buffers, however, may be prohibiting lake residents from implementing the most cost-effective strategy. An erratum to this article is available at .  相似文献   
948.
Understanding Managers’ Views of Global Environmental Risk   总被引:1,自引:0,他引:1  
This research investigated managers’ views of two global environmental risks: climate change and loss of biodiversity. The intent was to understand why different managers place varying levels of attention and priority on these issues. The data came from in-depth interviews with 28 senior corporate managers across Canada and a range of sectors, although most were employed in the energy sector. Approximately half had direct environmental responsibilities and half had other management duties. Grounded theory was used to collect and analyze the data. From the results, a theoretical framework was constructed to explain important factors that can influence managers’ mental models of environmental risk. Four factors relevant to managers’ appraisal of the threat of environmental risk include: (1) salience, (2) intrinsic value of nature, (3) knowledge, and (4) perceived resilience of nature. In addition, four factors relevant to managers’ view of the appeal of a particular response strategy were: (1) avoidability, (2) perceived costs and benefits, (3) fairness and equity, and (4) effectiveness. The time horizon for decision making was seen as being important in both portions of the mental model.  相似文献   
949.
Forestland application of poultry manure offers an alternative to the conventional practice of pastureland application. Before such a practice is considered viable, however, it must be demonstrated that the forest ecosystem is capable of absorbing the nutrients contained in poultry manure, especially nitrogen (N) and phosphorus (P). From the forestry perspective, it must also be demonstrated that tree growth is not diminished. We investigated these questions using loblolly pine (Pinus taeda L.) stands growing in central Mississippi in an area of high poultry production. Stockpiled broiler litter was applied to newly thinned, 8-yr-old stands at 0, 4.6, and 18.6 dry Mg ha-1, supplying 0, 200, and 800 kg N ha-1 and 0, 92, and 370 kg P ha-1, respectively. Levels of nitrate in soil water, monitored at a 50-cm depth with porous cup tension lysimeters, exceeded 10 mg N L-1 during the first two years after application in the 18.6 Mg ha-1 rate but only on two occasions in the first year for the lower rate of application. Phosphate was largely absent from lysimeter water in all treatments. Other macronutrients (K, Ca, Mg, S) were elevated in lysimeter water in proportion to litter application rates. Soil extractable nitrate showed similar trends to lysimeter water, with substantial elevation during the first year following application for the 18.6 Mg ha-1 rate. Mehlich III-extractable phosphate peaked in excess of 100 microg P g-1 soil during the third year of the study for the 18.6 Mg ha-1 rate. The 4.6 Mg ha-1 rate did not affect extractable soil P. Tree growth was increased by the poultry litter. Total stem cross-sectional area, or basal area, was approximately 20% greater after 2 yr for both rates of litter application. Overall, the nutrients supplied by the 4.6 Mg ha-1 rate were contained by the pine forest and resulted in favorable increases in tree growth. The higher rate, by contrast, did pose some risk to water quality through the mobilization of nitrate. These results show that, under the conditions of this study, application of poultry litter at moderate rates of approximately 5 Mg ha-1 to young stands of loblolly pine offers an alternative disposal option with minimal impacts to water quality and potential increases in tree growth.  相似文献   
950.
This article describes an airborne γ survey of a 7 × 5 km region around the rehabilitated Nabarlek uranium mine in northern Australia. An unusually tight line spacing (100 m) and low aircraft height (50 m) were used, enabling the survey to distinguish man-made structures such as ponds and accommodation areas, as well as creek lines. Positive correlations between airborne data and ground-based readings enabled an estimation of the average absorbed dose rate arising from terrestrial γ radiation over large areas of the site to be derived. For the fenced minesite area this estimate was 0.31 μ Gy hr− 1. The airborne survey data were found to be invaluable in helping to plan further ground-level investigations and showed promise as an assessment tool for rehabilitated minesites.  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