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   872篇
  免费   3篇
  国内免费   3篇
安全科学   16篇
废物处理   17篇
环保管理   134篇
综合类   271篇
基础理论   155篇
污染及防治   203篇
评价与监测   50篇
社会与环境   25篇
灾害及防治   7篇
  2020年   7篇
  2018年   16篇
  2017年   11篇
  2016年   16篇
  2015年   13篇
  2014年   21篇
  2013年   68篇
  2012年   23篇
  2011年   31篇
  2010年   23篇
  2009年   23篇
  2008年   36篇
  2007年   36篇
  2006年   21篇
  2005年   21篇
  2004年   36篇
  2003年   19篇
  2002年   24篇
  2001年   14篇
  2000年   14篇
  1999年   18篇
  1998年   8篇
  1997年   12篇
  1996年   17篇
  1995年   12篇
  1994年   25篇
  1993年   7篇
  1991年   7篇
  1990年   9篇
  1988年   6篇
  1983年   6篇
  1982年   6篇
  1981年   8篇
  1980年   9篇
  1979年   7篇
  1978年   7篇
  1977年   7篇
  1968年   6篇
  1965年   6篇
  1964年   9篇
  1963年   6篇
  1962年   6篇
  1961年   6篇
  1960年   8篇
  1959年   11篇
  1957年   7篇
  1956年   11篇
  1954年   9篇
  1939年   6篇
  1924年   6篇
排序方式: 共有878条查询结果,搜索用时 468 毫秒
481.
In a typical "EPA train" for stack sampling, there are two meters, the dry gas meter and the orifice meter, which require periodic calibration. The controversy which presently exists over the required frequency of calibration is the result of using meters which rarely need calibration, but which have the potential of changing calibration at any time.  相似文献   
482.
The following is the first in a series of articles on various efforts to encourage and support innovation in hazardous waste treatment technologies for sites and affected groundwater. This article provides a brief discussion of the origins of the U.S. EPA’s Office of Solid Waste and Emergency Response (OSWER) Technology Innovation Office (T1O), its mission, and the major initiatives underway or under contemplation. Subsequent articles will provide progress reports on these initiatives and other activities related to technology innovation by federal and state regulators, technology developers, responsible parties, the engineering community, and other interested parties.  相似文献   
483.
In 1998, the Aznalcóllar mine tailings dyke in southwestern Spain broke, flooding the Agrio-Guadiamar river system with acid tailings up to the borders of one of the largest breeding colonies of white storks in the western Palearctic, Dehesa de Abajo. Over the following years, a high proportion of nestlings developed leg defects not seen before the spill, prompting this study. Nestlings with deformed legs had significantly lower plasma phosphorous (P) and higher Ca:P ratios than non-deformed cohorts in the first two years, but in the third year, when more, younger birds were studied, plasma P ranged from much higher to much lower in the affected colony compared with reference birds. Coefficients of variation for phosphorous were 19% and 60%, in reference and contaminated colonies, respectively. Storks from the contaminated colony were unable to control P levels and Ca:P ratios within the narrow limits necessary for normal bone development.  相似文献   
484.
Individual eggs of six species of birds from Norway representing different food chains were analysed for residues of polybrominated biphenyls (PBBs). In all species, the residue pattern was dominated by hexaBBs. The dominating congeners were PBB 153, PBB 154, and PBB 155. Whereas PBB 153 is present in technical hexabromobiphenyl, PBB 154 and PBB 155 are formed by the reductive debromination of decabromobiphenyl. This was evidenced by the detection of several heptaBBs and octaBBs all of which are typical degradation intermediates of PBB 209. Hepta- and octaBBs were more than one order of magnitude less abundant than the hexaBBs. The second most prevailing homologue group was pentaBBs. The most relevant pentabrominated isomers were PBB 99 and PBB 101. Concentrations of the three hexaBBs - PBB 153, PBB 154, and PBB 155 - amounted to 1.3-13 ng/g wet weight or 3-23% of the contamination with polybrominated diphenyl ethers.  相似文献   
485.
Developing a globally responsive Science‐Practitioner‐Humanist model (Lefkowitz, 2008 ) means articulating professional values (supply) and meeting global demand. The United Nations' Millennium Development Goals (MDGs) seek to halve human poverty by 2015 and how organizations respond to this constitutes a formidable demand on Organizational Psychology. A key process for delivering more effective aid is the Paris Declaration on Aid Effectiveness, which seeks collaborative contributions from a plethora of Organizations, including business organizations and professions like ours. We argue that a thoughtful articulation of what Organizational Psychology uniquely stands for, and can offer, is therefore needed. It is proposed that a key mechanism for addressing this challenge is a Task Force, whose functions will include the coordination of institutions within psychology, and linking them to those in development. We describe such a task force and outline its core mission (Reichman, Frese, Schein, Carr, MacLachlan, & Landy, 2008 ). Organizational Psychology's response to poverty reduction should meet Lefkowitz's criteria for developing a more humanist model of science and practice as the MDGs are inherently humanist and values‐based. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
486.
The effects of pollutants on primary producers ramify through ecosystems because primary producers provide food and structure for higher trophic levels and they mediate the biogeochemical cycling of nutrients and contaminants. Periphyton (attached algae) were studied as part of a long-term biological monitoring program designed to guide remediation efforts by the Department of Energy’s Y-12 National Security Complex on East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee. High concentrations of nutrients entering EFPC were responsible for elevated periphyton production and placed the stream in a state of eutrophy. High rates of primary production at upstream locations in EFPC were associated with alterations in both invertebrate and fish communities. Grazers represented >50% of the biomass of invertebrates and fish near the Y-12 Complex but <10% at downstream and reference sites. An index of epilithic periphyton production accounted for 95% of the site-to-site variation in biomass of grazing fish. Analyses of heavy metals in EFPC periphyton showed that concentrations of zinc, cadmium, copper and nickel in periphyton decreased exponentially with distance downstream from Y-12. Zinc uptake by periphyton was estimated to reduce the concentration of this metal in stream water ~60% over a 5-km reach of EFPC. Management options for mitigating eutrophy in EFPC include additional reductions in nutrient inputs and/or allowing streamside trees to grow and shade the stream. However, reducing periphyton growth may lead to greater downstream transport of contaminants while simultaneously causing higher concentrations of mercury and PCBs in fish at upstream sites.  相似文献   
487.
Long-term integrity of existing wells in a CO2-rich environment is essential for ensuring that geological sequestration of CO2 will be an effective technology for mitigating greenhouse gas-induced climate change. The potential for wellbore leakage depends in part on the quality of the original construction as well as geochemical and geomechanical stresses that occur over its life-cycle. Field data are essential for assessing the integrated effect of these factors and their impact on wellbore integrity, defined as the maintenance of isolation between subsurface intervals. In this report, we investigate a 30-year-old well from a natural CO2 production reservoir using a suite of downhole and laboratory tests to characterize isolation performance.These tests included mineralogical and hydrological characterization of 10 core samples of casing/cement/formation, wireline surveys to evaluate well conditions, fluid samples and an in situ permeability test. We find evidence for CO2 migration in the occurrence of carbonated cement and calculate that the effective permeability of an 11′-region of the wellbore barrier system was between 0.5 and 1 milliDarcy. Despite these observations, we find that the amount of fluid migration along the wellbore was probably small because of several factors: the amount of carbonation decreased with distance from the reservoir, cement permeability was low (0.3–30 microDarcy), the cement–casing and cement-formation interfaces were tight, the casing was not corroded, fluid samples lacked CO2, and the pressure gradient between reservoir and caprock was maintained. We conclude that the barrier system has ultimately performed well over the last 3 decades. These results will be used as part of a broader effort to develop a long-term predictive simulation tool to assess wellbore integrity performance in CO2 storage sites.  相似文献   
488.
Polybrominated biphenyls (PBBs) have been introduced as flame retardants in 1970. Despite decreasing application rates since the mid-1970s, PBB residues are still reported in the environment. Furthermore, environmental PBB residues often do not match the PBB pattern in technical products. To get insights into the structures of environmentally-relevant PBBs, the congener patterns of technical hexabromobiphenyl (THBB), octabromobiphenyl (TOBB), synthesized PBB 209 were compared to PBB residues in a cod liver sample from the Baltic Sea. The most relevant PBB congeners in Baltic cod liver were not present in the technical products and therefore most likely metabolites. For this reason, TOBB and HPLC-fractions obtained from this technical product were incubated with super-reduced cyanocobalamine. Reductive debromination was found to be the predominant transformation process. Bromine substituents in ortho-positions proved to be more recalcitrant, and several of the unknown PBBs were tri- and tetra-ortho substituted congeners. Furthermore, the key-PBBs determined in Baltic cod liver were formed during this process. The most important hexabromobiphenyl in Baltic cod liver was identified as PBB 155 by parallel synthesis. PBB 155 which was not detected in the technical PBB product analyzed was suggested as an indicator PBB congener suited to decide whether PBB residues originate from the previous use of THBB (low relative abundance of PBB 155) or TOBB/TDBB (high relative abundance of PBB 155). The latter scenario was found to be valid for the Baltic cod liver sample. Thus, PBBs in the Baltic Sea appeared to originate from partially-weathered residues of PBB 209.  相似文献   
489.
Weiss K  Schüssler W  Porzelt M 《Chemosphere》2008,72(9):1292-1297
Pharmaceuticals are widely used in modern livestock production and can reach the environment via the application of manure containing excreted drugs. Limited information is available on the transport and fate of veterinary medicines applied to soils. Therefore, we assessed the potential for the sulphonamide antibiotic sulfamethazine (SMT) and the antiparasitic drug flubendazole (FLUB) including their metabolites to move from agricultural manure to drainage waters at 1m depth. A comparison was made of losses from sites under different land use (grassland versus arable cropping) as well as losses from neighbouring plots under the same land use. Liquid manure from pigs treated with SMT and FLUB was spread on 10 x 30 m2 plots (750l per plot). SMT concentration in slurry ranged from 600 to 1700 microg l(-1) (metabolite acetyl-SMT 280-1700 microg l(-1)) and FLUB concentration ranging from 25 to 56 microg l(-1) (metabolite amino-FLUB 32-110 microg l(-1), hydroxy-FLUB 19-38 microg l(-1)). About 1h after application heavy rainfall (50mm in 2.5h) was simulated by sprinkler irrigation. Drainage flow started within 1h after the commencement of sprinkling. SMT and FLUB concentrations in leachate reached values of up to 16 microg l(-1) and 0.3 microg l(-1), respectively. Loss rates (relative to the applied amounts) from the neighbouring sites under arable cropping ranged from 2.8% to 5.4% for SMT and 0.8% to 3.1% for FLUB (including metabolites). On the permanent grassland plot, due to its multitude of macropores, loss rates reached values up to 10% for SMT and 16% for FLUB (including metabolites). These results demonstrate that the variability in leaching of veterinary drugs may be high even between large neighbouring plots, depending on site heterogeneity and land use.  相似文献   
490.
Seitz W  Jiang JQ  Schulz W  Weber WH  Maier D  Maier M 《Chemosphere》2008,70(7):1238-1246
The present work describes the investigation of the formation of oxidation by-products of the iodinated X-ray contrast medium (ICM) iomeprol during ozonation in water treatment. Bench-scale investigations revealed that ICM can be partly oxidized during ozonation processes, whereas the ionic diatrizoic acid showed the lowest reactivity. Iomeprol, as a representative of ICM, was not fully mineralized during ozonation. Thus, unknown oxidation by-products were formed. Aqueous solutions of iomeprol were treated by ozonation in order to assess the formation of oxidation by-products. The by-products were characterized by different liquid chromatography methods including detection of single-stage mass spectra, product ion mass spectra, and induced in-source fragmentation for analysis of iodine containing oxidation by-products. Aldehyde and carbonyl containing compounds were proposed to be among the stable by-products. A derivatization step confirms that the aldehyde and carbonyl moieties are major functional groups in oxidation by-products of iomeprol. Furthermore, oxidation by-products of iomeprol were detected at the outlet of an ozone reactor at a full-scale waterworks. However, the toxicological relevance of the by-products is a major future research tasks.  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