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   328篇
  免费   14篇
  国内免费   7篇
安全科学   29篇
废物处理   16篇
环保管理   57篇
综合类   47篇
基础理论   90篇
污染及防治   68篇
评价与监测   16篇
社会与环境   20篇
灾害及防治   6篇
  2023年   6篇
  2022年   3篇
  2021年   7篇
  2020年   7篇
  2019年   6篇
  2018年   8篇
  2017年   17篇
  2016年   14篇
  2015年   10篇
  2014年   11篇
  2013年   19篇
  2012年   18篇
  2011年   41篇
  2010年   19篇
  2009年   21篇
  2008年   18篇
  2007年   20篇
  2006年   14篇
  2005年   12篇
  2004年   11篇
  2003年   4篇
  2002年   3篇
  2001年   6篇
  2000年   5篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1996年   4篇
  1995年   7篇
  1994年   3篇
  1993年   3篇
  1992年   6篇
  1991年   3篇
  1990年   1篇
  1989年   2篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1984年   1篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1977年   1篇
  1975年   1篇
  1971年   1篇
排序方式: 共有349条查询结果,搜索用时 78 毫秒
21.
Stabilized landfill leachate is characterized by a high concentration of non-biodegradable organic matter, which is similar in chemistry to dissolved organic matter (DOM) in the natural aquatic environment. Magnetic ion exchange (MIEX) resin treatment is well-studied in drinking water for removal of DOM from natural waters. There are fewer studies evaluating MIEX treatment of waste waters, and there is no previous work evaluating MIEX treatment of landfill leachate. This work systematically evaluated MIEX treatment of stabilized landfill leachate and evaluated the results in the context of previous studies of MIEX treatment of natural and waste waters. Five leachates from four landfills were evaluated as a function of MIEX resin dose, mixing time, and regeneration efficiency. MIEX resin removed DOM from landfill leachate, even in the presence of a reported high background concentration of inorganic ions. MIEX resin that was exhausted with leachate DOM was effectively regenerated with a concentrated NaCl solution, and regenerated MIEX resin performed similarly to virgin resin. For a majority of the leachates, the removal trend for MIEX resin was color > UV-absorbing substances > dissolved organic carbon ≈ COD > total nitrogen. Finally, MIEX resin removed a wider range of DOM from leachate than coagulation. The most important contribution of this work is that MIEX treatment of leachate followed very similar trends as MIEX treatment of natural waters, which will allow previous MIEX data to be used to estimate the treatment efficiency of other waste waters.  相似文献   
22.
By discharging excess stormwater at rates that more frequently exceed the critical flow for stream erosion, conventional detention basins often contribute to increased channel instability in urban and suburban systems that can be detrimental to aquatic habitat and water quality, as well as adjacent property and infrastructure. However, these ubiquitous assets, valued at approximately $600,000 per km2 in a representative suburban watershed, are ideal candidates to aid in reversing such cycles of channel degradation because improving their functionality would not necessarily require property acquisition or heavy construction. The objective of this research was to develop a simple, cost‐effective device that could be installed in detention basin outlets to reduce the erosive power of the relatively frequent storm events (~ < two‐year recurrence) and provide a passive bypass to maintain flood control performance during infrequent storms (such as the 100‐year recurrence). Results from a pilot installation show that the Detain H2O device reduced the cumulative sediment transport capacity of the preretrofit condition by greater than 40%, and contributed to reduced flashiness and prolonged baseflows in receiving streams. When scaling the strategy across a watershed, these results suggest that potential gains in water quality and stream channel stability could be achieved at costs that are orders of magnitude less than comparable benefits from newly constructed stormwater control measures.  相似文献   
23.
Twenty-eight polycyclic aromatic hydrocarbons (PAH) and methylated PAHs (Me-PAH) were measured in daily PM2.5 samples collected at an urban site, a suburban site, and a rural site in and near Atlanta during 2004 (5 samples/month/site). The suburban site, located near a major highway, had higher PM2.5-bound PAH concentrations than did the urban site, and the rural site had the lowest PAH levels. Monthly variations are described for concentrations of total PAHs (∑PAHs) and individual PAHs. PAH concentrations were much higher in cold months than in warm months, with average monthly ∑PAH concentrations at the urban and suburban-highway monitoring sites ranging from 2.12 to 6.85 ng m?3 during January–February and November–December 2004, compared to 0.38–0.98 ng m?3 during May–September 2004. ∑PAH concentrations were found to be well correlated with PM2.5 and organic carbon (OC) within seasons, and the fractions of PAHs in PM2.5 and OC were higher in winter than in summer. Methyl phenanthrenes were present at higher levels than their un-substituted homologue (phenanthrene), suggesting a petrogenic (unburned petroleum products) input. Retene, a proposed tracer for biomass burning, peaked in March, the month with the highest acreage and frequency of prescribed burning and unplanned fires, and in December, during the high residential wood-burning season, indicating that retene might be a good marker for burning of all biomass materials. In contrast, potassium peaked only in December, indicating that it might be a more specific tracer for wood-burning.  相似文献   
24.
Thermal evaporation of a variety of simulated pore waters from the region of Yucca Mountain, Nevada, produced acidic liquids and gases during the final stages of evaporation. Several simulated pore waters were prepared and then thermally distilled in order to collect and analyze fractions of the evolved vapor. In some cases, distillates collected towards the end of the distillation were highly acidic; in other cases the pH of the distillate remained comparatively unchanged during the course of the distillation. The results suggest that the pH values of the later fractions are determined by the initial composition of the water. Acid production stems from the hydrolysis of magnesium ions, especially at near dryness. Near the end of the distillation, magnesium nitrate and magnesium chloride begin to lose water of hydration, greatly accelerating their thermal decomposition to form acid. Acid formation is promoted further when precipitated calcium carbonate is removed. Specifically, calcium chloride-rich pore waters containing moderate (10–20 ppm) levels of magnesium and nitrate and low levels of bicarbonate produced mixtures of nitric and hydrochloric acid, resulting in a precipitous drop in pH to values of 1 or lower after about 95% of the original volume was distilled. Waters with either low or moderate magnesium content coupled with high levels of bicarbonate produced slightly basic fractions (pH 7–9). If calcium was present in excess of bicarbonate, waters containing moderate levels of magnesium produced acid even in the presence of bicarbonate, due to the precipitation of calcium carbonate. Other salts such as halite and anhydrite promote the segregation of acidic vapors from residual basic solids. The concomitant release of wet acid gas has implications for the integrity of the alloys under consideration for containers at the Yucca Mountain nuclear waste repository. Condensed acid gases at very low pH, especially mixtures of nitric and hydrochloric acid, are capable of corroding even alloys, such as nickel-based Alloy 22, which are considered to be corrosion-resistant under milder conditions.  相似文献   
25.
Regional Environmental Change - Ocean acidification poses an increasing threat to marine ecosystems and also interacts with other anthropogenic environmental drivers. A planned response strategy...  相似文献   
26.
A marginal abatement cost curve (MACC) traces out the relationship between the quantity of pollution abated and the marginal cost of abating each additional unit. In the context of air quality management, MACCs are typically developed by sorting control technologies by their relative cost-effectiveness. Other potentially important abatement measures such as renewable electricity, energy efficiency, and fuel switching (RE/EE/FS) are often not incorporated into MACCs, as it is difficult to quantify their costs and abatement potential. In this paper, a U.S. energy system model is used to develop a MACC for nitrogen oxides (NOx) that incorporates both traditional controls and these additional measures. The MACC is decomposed by sector, and the relative cost-effectiveness of RE/EE/FS and traditional controls are compared. RE/EE/FS are shown to have the potential to increase emission reductions beyond what is possible when applying traditional controls alone. Furthermore, a portion of RE/EE/FS appear to be cost-competitive with traditional controls.

Implications: Renewable electricity, energy efficiency, and fuel switching can be cost-competitive with traditional air pollutant controls for abating air pollutant emissions. The application of renewable electricity, energy efficiency, and fuel switching is also shown to have the potential to increase emission reductions beyond what is possible when applying traditional controls alone.  相似文献   

27.
Abstract

This study is a part of an ongoing investigation of the types and locations of emission sources that contribute fine particulate air contaminants to Underhill, VT. The air quality monitoring data used for this study are from the Interagency Monitoring of Protected Visual Environments network for the period of 2001–2003 for the Underhill site. The main source-receptor modeling techniques used are the positive matrix factorization (PMF) and potential source contribution function (PSCF). This new study is intended as a comparison to a previous study of the 1988–1995 Underhill data that successfully revealed a total of 11 types of emission sources with significant contributions to this rural site. This new study has identified a total of nine sources: nitrate-rich secondary aerosol, wood smoke, East Coast oil combustion, automobile emission, metal working, soil/dust, sulfur-rich aerosol type I, sulfur-rich aerosol type II, and sea salt/road salt. Furthermore, the mass contributions from the PMF identified sources that correspond with sampling days with either good or poor visibility were analyzed to seek possible correlations. It has been shown that sulfur-rich aerosol type I, nitrate aerosol, and automobile emission are the most important contributors to visibility degradation. Soil/dust and sea salt/road salt also have an added effect.  相似文献   
28.
Glandular trichomes on the leaves of wild tomato, L. hirsutum f. hirsutum Mull, also known as Solanum habrochaites (Solanaceae), synthesize and accumulate high levels of methyl ketones (MKs). L. hirsutum accession LA 407, having high concentration of MKs, was grown from seeds under greenhouse conditions. Four MKs (2-undecanone, 2-dodecanone, 2-tridecanone, and 2-pentadecanone) were screened for their toxicity to spider mites, Tetranychus urticae Koch and cowpea aphids, Aphis craccivora Koch. The objectives of this investigation were to: (1) develop a bioassay for testing MKs on spider mite and cowpea aphid mortality and (2) compare the efficacies of wild tomato leaf crude extracts and pure standard materials of MKs against spider mite and cowpea aphid mortality. Our results revealed that spider mites are most sensitive to 2-tridecanone (LC50 = 0.08 μmole cm?2 of treated leaf surface) and least sensitive to 2-undecanone (LC50 = 1.5 μmole cm?2 of treated leaf surface) 4 h after treatment. Similarly, 2-tridecanone caused greatest mortality (LC50 = 0.2 μmole cm?2 of treated leaf surface), whereas 2-undecanone caused the lowest morality (LC50 = 0.48 μmole cm?2 of treated surface) of cowpea aphid. We concluded that all MKs tested in this investigation are toxic to spider mites and aphids. 2-Tridecanone is more effective in killing mites and aphids compared to other MKs. Toxicity of crude extracts, prepared from the leaves of L. hirsutum accession LA 407, to spider mites and cowpea aphids revealed greater mortality compared to a combined mixture of MKs standard material (used at the same concentration as found on LA 407 leaves). This indicates that in addition to MKs, other unidentified compounds in LA 407 leaf extract also have pesticidal properties. Accordingly, leaf extracts of LA 407 could be explored in crop protection, and they might open a new area of MK formulations and discovery of biorational alternatives for pest control in agricultural fields.  相似文献   
29.
PROBLEM: Adolescents who drive with peers are known to have a higher risk of crashes. While passengers may distract drivers, little is known about the circumstances of these distractions among teen drivers. METHOD: This study used survey data on driving among 2,144 California high school seniors to examine distractions caused by passengers. RESULTS: Overall, 38.4% of youths who drove reported having been distracted by a passenger. Distractions were more commonly reported among girls and students attending moderate- to high-income schools. Talking or yelling was the most commonly reported type of distraction. About 7.5% of distractions reported were deliberate, such as hitting or tickling the driver or attempting to use the vehicle's controls. Driving after alcohol use and having had a crash as a driver were both significant predictors of reporting passenger-related distraction. CONCLUSION: Adolescents often experience distractions related to passengers, and in some cases these distractions are intentional. IMPACT ON INDUSTRY: These results provide information about teenage drivers who are distracted by passenger behaviors. In some cases, passengers attempted to use vehicle controls; however, it seems unlikely that this behavior is common enough to warrant redesign of controls to make them less accessible to passengers.  相似文献   
30.
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