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   624篇
  免费   8篇
  国内免费   2篇
安全科学   22篇
废物处理   18篇
环保管理   85篇
综合类   92篇
基础理论   135篇
环境理论   2篇
污染及防治   190篇
评价与监测   39篇
社会与环境   45篇
灾害及防治   6篇
  2023年   2篇
  2022年   8篇
  2021年   13篇
  2020年   4篇
  2019年   8篇
  2018年   21篇
  2017年   17篇
  2016年   18篇
  2015年   27篇
  2014年   28篇
  2013年   47篇
  2012年   26篇
  2011年   36篇
  2010年   43篇
  2009年   38篇
  2008年   30篇
  2007年   36篇
  2006年   31篇
  2005年   20篇
  2004年   28篇
  2003年   21篇
  2002年   26篇
  2001年   10篇
  2000年   16篇
  1999年   16篇
  1998年   6篇
  1997年   7篇
  1996年   4篇
  1995年   7篇
  1994年   9篇
  1993年   3篇
  1991年   2篇
  1989年   2篇
  1984年   2篇
  1980年   3篇
  1976年   1篇
  1972年   1篇
  1971年   1篇
  1966年   1篇
  1965年   1篇
  1964年   1篇
  1963年   1篇
  1962年   1篇
  1961年   1篇
  1958年   1篇
  1955年   1篇
  1949年   1篇
  1948年   1篇
  1937年   1篇
  1920年   1篇
排序方式: 共有634条查询结果,搜索用时 31 毫秒
541.

Background, aim, and scope  

Fluorotelomer alcohols (FTOH) are widely used substances that were detected even in remote regions of the world. For the determination of FTOH in the atmosphere, appropriate sampling techniques are needed. In this study, triolein-filled low-density polyethylene tubes were used as semipermeable membrane devices (SPMD) and tested for their suitability as passive air samplers for FTOH.  相似文献   
542.
Relative kinetic studies have been performed on the reactions of Cl atoms with a series of methyl alkyl esters in a 405-liter borosilicate glass chamber at (298 ± 3) K and one atmosphere of synthetic air using in situ FTIR spectroscopy to monitor the reactants. Rate coefficients (in units of cm3 molecule?1 s?1) were determined for the following compounds: methyl acetate (2.48 ± 0.58) × 10?12; methyl propanoate (1.68 ± 0.36) × 10?11; methyl butanoate (4.77 ± 0.87) × 10?11; methyl pentanoate (7.84 ± 1.15) × 10?11; methyl hexanoate (1.09 ± 0.31) × 10?10; methyl heptanoate (1.56 ± 0.37) × 10?10; methyl cyclohexane carboxylate (3.32 ± 0.76) × 10?10; methyl-2-methyl butanoate (9.41 ± 1.39) × 10?11.In addition rate coefficients (in units of 10?11 cm3 molecule?1 s?1) have been obtained for the reactions of OH radicals with the following compounds: methyl butanoate (3.55 ± 0.71), methyl pentanoate (5.41 ± 1.08), and methyl-2-methyl butanoate (4.08 ± 0.82).Using the kinetic rate data tropospheric lifetimes for the methyl alkyl esters with respect to their reactions with OH, and Cl have been estimated for typical ambient air concentrations of these oxidants.  相似文献   
543.
Abstract: A numerical model has been developed to simulate the hydraulic and heat transfer properties of a stormwater detention pond, as part of a simulation tool to evaluate thermal pollution of coldwater streams from stormwater runoff. The model is dynamic (unsteady) and based on principles of fluid mechanics and heat transfer. It is driven by hourly weather data, and specified inflow rates and temperatures. To calibrate and validate the pond model field data were collected on a commercial site in Woodbury, Minnesota. The relationship between pond inflow and outflow rates to precipitation was effectively calibrated using continuously recorded pond levels. Algorithms developed for surface heat transfer in lakes were found to be applicable to the pond with some modification, resulting in agreement of simulated and observed pond surface temperature within 1.0°C root mean square error. The use of an unshaded pond for thermal mitigation of runoff from paved surfaces was evaluated using the pond model combined with simulated runoff from an asphalt parking lot for six years of observed rainfall events. On average, pond outflow temperature was 1.2°C higher than inflow temperature, but with significant event‐to‐event variation. On average, the pond added heat energy to runoff from an asphalt parking lot. Although the pond added total heat energy to runoff, it did reduce the rate of heat outflow from the pond by an order of magnitude due to reductions in volumetric outflow rate compared with the inflow rate. By reducing the rate of heat flow, the magnitude of temperature impacts in a receiving stream were also reduced, but the duration of impacts was increased.  相似文献   
544.
Two sets of experiments on typical Class G well cement were carried out in the laboratory to understand better the potential processes involved in well leakage in the presence of CO2. In the first set, good-quality cement samples of permeability in the order of 0.1 μD (10?19 m2) were subjected to 90 days of flow through with CO2-saturated brine at conditions of pressure, temperature and water salinity characteristic of a typical geological sequestration zone. Cement permeability dropped rapidly at the beginning of the experiment and remained almost constant thereafter, most likely mainly as a result of CO2 exsolution from the saturated brine due to the pressure drop along the flow path which led to multi-phase flow, relative-permeability effects and the observed reduction in permeability. These processes are identical to those which would occur in the field as well if the cement sheath in the wellbore annulus is of good quality. The second set of experiments, carried out also at in situ conditions and using ethane rather than CO2 to eliminate any possible geochemical effects, assessed the effect of annular spaces between wellbore casing and cement, and of radial cracks in cement on the effective permeability of the casing-cement assemblage. The results show that, if both the cement and the bond are of good quality, the effective permeability of the assemblage is extremely low (in the order of 1 nD, or 10?21 m2). The presence of an annular gap and/or cracks in the order of 0.01–0.3 mm in aperture leads to a significant increase in effective permeability, which reaches values in the range of 0.1–1 mD (10?15 m2). The results of both sets of experiments suggest that good cement and good bonding with casing and the surrounding rock will likely constitute a good and reliable barrier to the upward flow of CO2 and/or CO2-saturated brine. The presence of mechanical defects such as gaps in bonding between the casing or the formation, or cracks in the cement annulus itself, leads to flow paths with significant effective permeability. This indicates that the external and internal interfaces of cements in wells would most probably constitute the main flow pathways for fluids leakage in wellbores, including both gaseous/supercritical phase CO2 and CO2-saturated brine.  相似文献   
545.
In line with the aims of waste management, the handling of waste should hinder any damage to the environment as much as possible. There are a number of approaches for solving this action in practice, e.g. different treatment technologies for residual waste, from which the most favourable should be chosen. We have several different methods for supporting such choices. An evaluation of studies published in recent years that assess waste management measures has clearly showed that the impact on the environment alone is not a sufficient basis for decision-making. In most cases, the cost aspect is also of primary concern while the technical implementation and social aspects also have to be taken into consideration. In recent years a great number of assessment methods have been developed as tools in the decision-making process. However, the multitude of methods leads to different results depending on the methods, parameters and criteria of the research. The following paper will characterise the most important decision-making concepts, such as the Life Cycle Assessment, Product Line Analysis, Cost-Benefit Analysis, Scoring Model, etc. Examples will show how these methods can be applied to the issues of waste management. The conclusion will describe the current state of development for waste management applications.  相似文献   
546.
In Axelved, Denmark, an abandoned gas filling station serves as a test field for phytoremediation. Laboratory studies accompany the project. The toxicity of fresh and weathered gasoline and diesel to willow and poplar trees was studied by use of a tree transpiration toxicity test. The correlation between diesel content in soil and decrease in willow tree transpiration (Salix viminalis x schwerinii) was highly significant (r 2=0.81, n=19). the EC50 (50% inhibition of transpiration) for the sum of hydrocarbons (HC) was determined to be 3910 mg/kg (95% confidence interval from 2900 to 5270 mg/kg). The EC10 was 810 mg/kg (95% confidence interval 396 to 1660 mg/kg). The results were verified with artificially mixed diesel and gasolinecontaminated soils and two willow and one poplar species (S. viminalis, S. alba andPopulus nigra). The degradation of radiolabeledm-xylene was studied with and without willows. The compound was readily degraded. Willow trees accelerated the elimination, but mainly due to the volatilization ofm-xylene. Model studies provided the result that biodegradation in soil is the fastest elimination process at the site, but it is limited by the availability of electron acceptors. The pollutants are almost persistent in the groundwater, but in aerated soil, 10000 mg/kg hydrocarbons at 1 m depth are degraded within 13 years. The main effect of willows on the pollutants’ persistence is that willows transpire water, lower the groundwater level and aerate the soil, hereby speeding up biodegradation.  相似文献   
547.
Diclofenac is a non-steroidal anti-inflammatory drug, which tends to be relatively persistent in the environment. Now, a fixed-bed column bioreactor filled with sediment from the creek Münzbach (Freiberg/Saxony) under aerobic conditions showed rapid removal of diclofenac in a concentration range of 3-35 microM without previous adaptation. The conversion of higher concentrations up to 260 microM was accompanied by conspicuously decreased turnover rates indicating a toxic effect of this drug or its resulting metabolic burden on the indigenous microflora. A major metabolite occurred transiently and was identified by NMR and MS to be the p-benzoquinone imine of 5-hydroxydiclofenac. Abiotic adsorption to the biofilm was shown to determine the further fate of this reactive product of 5-hydroxydiclofenac (aut-)oxidation. The apparent lack of a degradative potential for this compound as well as the failure to detect an enrichment of diclofenac-depleting microbial activity both indicate a cometabolic nature of diclofenac transformation. 4'-Hydroxy-diclofenac, the favoured transformation product of eucaryotic diclofenac metabolism, could not be identified. The ability to convert diclofenac was shown to be widespread among biofilms from different river sediments, but measured rates obviously do not correlate with the total microbial activity. In addition, application of sediments from locations exposed to communal waste water effluents did not indicate any form of adaptation measured as an increased specific diclofenac depletion rate.  相似文献   
548.
PAH and PCB in soils of Switzerland--status and critical review   总被引:1,自引:0,他引:1  
The surface soil concentrations (0-20 cm) of the Swiss soil monitoring network (NABO) with 105 observation sites representing all major land use types ranged for the sum of 16 EPA PAH (PAH(16)) from 32 to 8465 microg kg(-1) (median 163 microg kg(-1)), for benzo[a]pyrene (BaP) from 0.5 to 1129 microg kg(-1) (median 13 microg kg(-1)) and for the sum of seven IRMM PCB (PCB(7)) from 0.5 to 12 microg kg(-1) (median 1.6 microg kg(-1)). The legal guide values of Switzerland were exceeded for PAH(16) at only three and for BaP at two sites. The PCB(7) concentrations were clearly below any assessment value. The concentration ranges were overlapping between all land use types. Tendencies for higher concentrations were observed at urban and viticulture sites. The overall measurement precision at repeatability conditions ranged from 1 to 37% RSD for PAH(16), BaP and PCB(7). The median bias for the chemical analysis was around zero for PAH(16), +5% for BaP and -5% for PCB(7) with spreads ranging from less than -20% up to more than +30%. The PAH profiles were clearly dominated by phenanthrene. Stratification by land use revealed a prevalence of benzo[a]pyrene at urban and naphthalene at conservation sites. For PCB, the general congener rank order was PCB no. 153 > 138 > 101 > 180. From a broad correlation screening only PAH(16)/BaP (r = 0.88**) were relevant for practical soil protection. The extensive comparison with other studies was severely biased by the lack of harmonisation, especially concerning sampling depth, sampling support, analytical method and the sum calculation procedure.  相似文献   
549.
In this study a large dataset on the polycyclic aromatic hydrocarbon (PAH) content of Swiss soils was analysed to evaluate two source apportionment tools, i.e., characteristic PAH ratios/molecular markers and a linear mixing model. Population density and total organic carbon (TOC) content were identified by a multiple regression model as independently and positively influencing the PAH concentrations in Swiss background soil. Specifically, TOC was more strongly positively correlated with the sum of light PAH (naphthalene to phenanthrene) than with the sum of heavy PAH (anthracene to benzo[ghj]perylene), whereas population density was more strongly positively correlated with the sum of heavy PAH than with light PAH. In addition, the sum of the heavy PAH as well as the total sum correlated negatively with sample site altitude. It is therefore hypothesised that heavy PAH are less mobile, whereas light PAH were closer to equilibrium with TOC in the soil. Similar results were found for polychlorinated biphenyls (PCB). The characteristic ratios and molecular markers pointed to pyrogenic origin of PAH in Swiss background soil but did not allow for further differentiation of individual fuel contributions, even though attempts to take environmental fractionation processes into account were made. The comparison of three soil profiles identified with a linear mixing model from the pattern of 16 PAH with >300 PAH emission profiles from the literature suggested urban dust, wood combustion and binders from asphalt as PAH sources. However, also here, environmental fractionation processes probably obscured source characteristic PAH ratios and fingerprints, which thus need to be interpreted with caution.  相似文献   
550.
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