全文获取类型
收费全文 | 445篇 |
免费 | 48篇 |
国内免费 | 195篇 |
专业分类
安全科学 | 19篇 |
废物处理 | 24篇 |
环保管理 | 119篇 |
综合类 | 341篇 |
基础理论 | 64篇 |
污染及防治 | 59篇 |
评价与监测 | 42篇 |
社会与环境 | 20篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 21篇 |
2014年 | 34篇 |
2013年 | 46篇 |
2012年 | 43篇 |
2011年 | 44篇 |
2010年 | 34篇 |
2009年 | 32篇 |
2008年 | 31篇 |
2007年 | 39篇 |
2006年 | 40篇 |
2005年 | 34篇 |
2004年 | 24篇 |
2003年 | 34篇 |
2002年 | 23篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有688条查询结果,搜索用时 15 毫秒
631.
632.
Trace elements in atmospheric particulate matter over a coal burning power production area of western Macedonia, Greece 总被引:1,自引:0,他引:1
Total suspended particle (TSP) concentrations were determined in the Eordea basin (western Macedonia, Greece), an area with intensive lignite burning for power generation. The study was conducted over a one-year period (November 2000–November 2001) at 10 sites located at variable distances from the power plants. Ambient TSP samples were analyzed for 27 major, minor and trace elements. Annual means of TSP concentrations ranged between 47 ± 33 μg m−3 and 110 ± 50 μg m−3 at 9 out of the 10 sites. Only the site closest to the power stations and the lignite conveyor belts exhibited annual TSP levels (210 ± 97 μg m−3) exceeding the European standard (150 μg m−3, 80/779/EEC). Concentrations of TSP and almost all elemental components exhibited significant spatial variations; however, the elemental profiles of TSP were quite similar among all sites suggesting that they are affected by similar source types. At all sites, statistical analysis indicated insignificant (P < 0.05) seasonal variation for TSP concentrations. Some elements (Cl, As, Pb, Br, Se, S, Cd) exhibited significantly higher concentrations at certain sites during the cold period suggesting more intense emissions from traffic, domestic heating and other combustion sources. On the contrary, concentrations significantly higher in the warm period were found at other sites mainly for crustal elements (Ti, Mn, K, P, Cr, etc.) suggesting stronger influence from soil resuspension and/or fly ash in the warm months. The most enriched elements against local soil or road dust were S, Cl, Cu, As, Se, Br, Cd and Pb, whereas negligible enrichment was found for Ti, Mn, Mg, Al, Si, P, Cr. At most sites, highest concentrations of TSP and elemental components were associated with low- to moderate-speed winds favoring accumulation of emissions from local sources. Influences from the power generation were likely at those sites located closest to the power plants and mining activities. 相似文献
633.
以香港近岸海域为研究区,基于2009~2012年HJ-1A/B CCD数据和实测数据,建立悬浮固体浓度遥感反演模型,运用地统计学方法对模型反演结果进行分析,探索研究区内悬浮固体浓度空间分布及其变异特征.结果表明:香港近岸海域北部深圳湾附近常年处于悬浮固体浓度的高值区,东北部珠江入海口海域悬浮固体浓度受季节影响明显,大屿山以南的南部海域的浓度值常年处于较低水平,并具有明显的季节特征.2009~2012年的地统计数据表明,香港近岸海域悬浮固体浓度值总体处于较低水平,月均值为12.25mg/L,由北向南递减趋势明显.全年大部分时间空间变异特征明显,空间自相关性较强,其中3月份的块金值/基台值最小,仅约为0.0005. 相似文献
634.
采用生物滴滤塔(BTF)与光催化一体化(PCO)联用工艺应用于电子垃圾拆解现场废气处理的中试研究,研究结果表明:电子垃圾拆解现场排放的废气中含有高浓度的总悬浮颗粒物(TSP)和挥发性有机污染物(VOCs)。其中TSP的质量浓度为3792.5~7387.9μg·m-3,远高于中国环境空气质量控制标准(GB3095—2012)的二级标准(300μg·m-3);VOCs主要由芳香烃类VOCs、含氮含氧类VOCs、卤代烃类VOCs和脂肪烃类VOCs组成,总VOCs的质量浓度为(5 499.1±854.7)~(26 834.0±447.0)μg·m-3,其中芳香烃类VOCs含量最高,其质量浓度为(2369.9±359.8)~(24419.6±229.5)μg·m-3,其次是含氮含氧类VOCs和卤代烃类VOCs,分别为(1018.2±142.1)~(2144.2±167.5)和(1170.6±146.5)~(1 936.6±353.3)μg·m-3,脂肪烃类VOCs的质量浓度最低,只有(44.6±0.8)~(174.4±0.5)μg·m-3。相较单一BTF和PCO工艺,BTF-PCO联用工艺可以更为有效地去除电子垃圾拆解现场排放废气中的TSP和VOCs。研究结果表明,经过BTF-PCO处理后,出口TSP的质量浓度降低到747.4~1750.9μg·m-3,其去除率在76.3%以上,而对于VOCs来说,出口浓度下降更为明显,芳香烃类VOCs、含氮含氧类VOCs、卤代烃类VOCs和脂肪烃类VOCs的去除率分别大于或者等于97.0%、92.4%、83.4%和100%。 相似文献
635.
蠡湖水体透明度的时空变化及其影响因素 总被引:3,自引:0,他引:3
为揭示浅水湖泊水体SD(透明度)下降的主导因子,根据2012—2013年现场调查资料和历史监测资料,分析了浅水湖泊蠡湖SD的时空分布特征、变化规律及主要影响因素,并重点探讨了SD与ρ(TSS)(TSS为总悬浮物)、ρ(Chla)和ρ(DOC)的相互关系. 结果表明:SD在年内变化范围为20.0~209.0 cm,平均值为64.1 cm,总体上呈西蠡湖大于东蠡湖、湖心大于沿岸区的分布趋势;春、夏、秋、冬四季的SD分别为(51.1±15.1)、(41.3±10.6)、(28.3±7.4)和(127.1±43.2)cm,表现为冬季>春季>夏季>秋季,冬季SD平均值可达127.1 cm,而秋季仅有28.3 cm. 多元回归分析表明,ρ(TSS)是影响水体SD的最主要因子,其次为浮游藻类生物量;SD与ρ(TSS)呈幂函数关系,拟合方程为y=220.61x-0.545 0. 相似文献
636.
采用环境扫描电镜(ESEM)分析颗粒污泥和悬浮填料生物膜的微生物群落形态,并与扫描电镜(SEM)观察结果进行比较.结果表明,ESEM观察悬浮填料生物膜的适宜条件为样品台温度5℃,样品室汽压5.91×102Pa,相对湿度75%,加速电压15.00kV.观察颗粒污泥样品的适宜条件为样品台温度0℃,样品室汽压7.00×102Pa,相对湿度100%,加速电压10.00kV.表面存在的水滴凝聚和含水量高、结构脆弱的样品易因气压和入射电子束轰击收缩变形,是影响ESEM观察样品真实面貌的主要因素.悬浮填料生物膜的ESEM观察说明,相较于SEM,未经任何处理的载体生物膜样品在合适的ESEM条件下可得到的高放大倍数的清晰照片,能更真实的表征生物膜的微生物群落结构.含水量高、结构脆弱,承受能力差的颗粒污泥样品,则需要通过锇酸或者戊二醛等固定剂进行化学固定,降低ESEM的加速电压,并且尽量缩短观察时间,避免因气压和高速入射电子束的轰击而收缩变形,获得其原始形貌照片. 相似文献
637.
Forfeiture programs in California: why so few? 总被引:1,自引:0,他引:1
PROBLEM: It is estimated that at least 75% of suspended or revoked drivers continue to drive illegally. In states like California, there are also a substantial and growing number of people who drive without ever having been licensed. Some states, such as Ohio and California, have enacted vehicle impoundment and forfeiture programs as sanctions to reduce these offenses. Published evaluations indicate that vehicle impoundment laws reduce recidivism and crash rates. However, vehicle forfeiture programs have been less successful, mostly because of low levels of enforcement. METHOD: Police officers and district attorneys from 17 jurisdictions were interviewed by phone or in person to determine current enforcement levels and impediments to more aggressive application of statutory authority. RESULTS AND DISCUSSION: The survey found that most California jurisdictions are enforcing vehicle impoundments for first-time offenders. However, very few jurisdictions were enforcing the vehicle forfeiture law for repeat offenders. Among the reasons for not enforcing the vehicle forfeiture law was a perception that it was too time-consuming and/or not a priority among prosecutors. However, a number of authorities indicated that the simple vehicle impoundment procedure is often functionally equivalent to forfeiture because many drivers fail to retrieve the vehicle at the end of the impoundment period. IMPACT ON INDUSTRY: Vehicle impoundment programs are effective mechanisms in deterring illicit driving, and states should be encouraged to initiate vehicle impoundment laws. States could achieve even greater safety benefits if vehicle forfeiture sanctions were extensively used for repeat offenders. However, based on California's experience, the incremental benefits of vehicle forfeiture (over vehicle impoundment) may not be very great. 相似文献
638.
Barry R. Taylor Hal R. Hamilton 《Journal of the American Water Resources Association》1993,29(2):221-234
ABSTRACT: In the Saskatchewan River Basin (365,000 km2), which drains the Canadian prairie from the Rocky Mountains east to Manitoba, concentrations of total solutes are usually within the range of 100 to 1000 mg/L. Total solutes levels in tributaries increase markedly from west to east across the basin, as mountain snowmelt and dilute surface runoff are replaced by ion-rich ground water and concentrated prairie runoff as the major influences on solute concentrations. In contrast, total solutes concentrations in main-stem rivers are nearly constant, ranging 200–300 mg/L, with only a small increase across the basin. Dilute mountain runoff dominates solute concentrations in main-stem rivers, despite the influx of increasingly ion-rich water from tributaries. The principal long-term trends in total solute concentrations across the basin, as revealed by linear and sine-curve regressions, were due to the construction of reservoirs, which depress the natural winter maximum in solute concentrations and disrupt the sinusoidal annual pattern, while sharply reducing seasonal variation. These regression methods did not show anticipated anthropogenic increases in salt load in the Red Deer or South Saskatchewan Rivers, but a trend of slowly increasing solutes concentrations (2 mg/L/yr) was detected for autumn flows in the lower Bow River. Municipal wastes from the City of Calgary or irrigation return flows are probably responsible for this increase. 相似文献
639.
Sewage sludge from four publicly-owned treatment works was sampled and characterized in terms of parameters affecting transport at the 106-mile deep ocean disposal site as part of the US Environmental Protection Agency's site monitoring programme. Samples from treatment plants in Passaic Valley, Rahway, and Elizabeth, New Jersey and New York City were characterized in terms of dynamic size distribution, suspended solids and density. the transport characteristics of sludge particles were measured using a 2 metre computer-interfaced laboratory settling column. Experiments were conducted at constant salinity (35 ppt) while varying hydrodynamic mixing, sludge type and concentration using a modified factorial experimental design. Hydrodynamic power dissipation was varied so that the vertical dispersion and rms fluid shear rate ranged between 0-6 cm2S-1 and 0-30s-1 respectively. Results indicate that at least 80% of suspended sludge particles will eventually settle under mixed conditions. the average settling velocities ranged between 0.05-4.05 × 10-3 cm s-1. Shear rates above 15 s-1 inhibited sludge settling due to aggregate breakup and boundary effects, but at a lower shear rate, differential settling and fluid shear were the dominant transport mechanisms. Sludge dilution (1/500-1/5000) had a limited effect on the settling rate. Results from this study can be used to calibrate particle transport models to determine the fate of sludge disposed at an ocean disposal site. 相似文献
640.