全文获取类型
收费全文 | 742篇 |
免费 | 38篇 |
国内免费 | 258篇 |
专业分类
安全科学 | 44篇 |
废物处理 | 62篇 |
环保管理 | 50篇 |
综合类 | 379篇 |
基础理论 | 136篇 |
污染及防治 | 280篇 |
评价与监测 | 37篇 |
社会与环境 | 28篇 |
灾害及防治 | 22篇 |
出版年
2023年 | 9篇 |
2022年 | 45篇 |
2021年 | 31篇 |
2020年 | 23篇 |
2019年 | 18篇 |
2018年 | 33篇 |
2017年 | 22篇 |
2016年 | 41篇 |
2015年 | 42篇 |
2014年 | 48篇 |
2013年 | 73篇 |
2012年 | 58篇 |
2011年 | 59篇 |
2010年 | 57篇 |
2009年 | 58篇 |
2008年 | 55篇 |
2007年 | 37篇 |
2006年 | 44篇 |
2005年 | 27篇 |
2004年 | 25篇 |
2003年 | 29篇 |
2002年 | 19篇 |
2001年 | 31篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 27篇 |
1997年 | 24篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1983年 | 1篇 |
排序方式: 共有1038条查询结果,搜索用时 80 毫秒
851.
Liu J Yu H Song H Qiu J Sun F Li P Yang S 《Journal of environmental monitoring : JEM》2008,10(8):975-978
A novel, simple and sensitive liquid chromatography-hydride generation online coupled with atomic fluorescence spectrometry (LC-HG-AFS) method was developed for simultaneous determination of p-arsanilic acid (p-ASA) and roxarsone in feed. 20% Methanol aqueous was used as extraction reagent, after preprocessing samples by ultrasonic oscillation, then injected into the chromatography Waters symmetry shield RP18 analytical column (150mm x 4.6mm, 5 microm), finally detected by an atomic fluorescence spectrometer. The calibration curves of analyses were linear over a range of concentrations (0.2-4mg L-1 and the correlation coefficients were higher than 0.9990. The limits of detection were 0.2 mg L-1. The method has been validated by linearity, precision and recovery. p-ASA and roxarsone in feed can be successfully and simultaneously determined using the developed method without a tedious pretreatment procedure. 相似文献
852.
853.
Emergy Assessment of a Wheat-Maize Rotation System with Different Water Assignments in the North China Plain 总被引:1,自引:0,他引:1
Sustainable water use is seriously compromised in the North China Plain (NCP) due to the huge water requirements of agriculture,
the largest use of water resources. An integrated approach which combines the ecosystem model with emergy analysis is presented
to determine the optimum quantity of irrigation for sustainable development in irrigated cropping systems. Since the traditional
emergy method pays little attention to the dynamic interaction among components of the ecological system and dynamic emergy
accounting is in its infancy, it is hard to evaluate the cropping system in hypothetical situations or in response to specific
changes. In order to solve this problem, an ecosystem model (Vegetation Interface Processes (VIP) model) is introduced for
emergy analysis to describe the production processes. Some raw data, collected by investigating or observing in conventional
emergy analysis, may be calculated by the VIP model in the new approach. To demonstrate the advantage of this new approach,
we use it to assess the wheat-maize rotation cropping system at different irrigation levels and derive the optimum quantity
of irrigation according to the index of ecosystem sustainable development in NCP. The results show, the optimum quantity of
irrigation in this region should be 240–330 mm per year in the wheat system and no irrigation in the maize system, because
with this quantity of irrigation the rotation crop system reveals: best efficiency in energy transformation (transformity = 6.05E + 4 sej/J);
highest sustainability (renewability = 25%); lowest environmental impact (environmental loading ratio = 3.5) and the greatest
sustainability index (Emergy Sustainability Index = 0.47) compared with the system in other irrigation amounts. This study
demonstrates that application of the new approach is broader than the conventional emergy analysis and the new approach is
helpful in optimizing resources allocation, resource-savings and maintaining agricultural sustainability. 相似文献
854.
855.
Zeyuan Qiu 《Journal of the American Water Resources Association》2010,46(5):944-956
Qiu, Zeyuan, 2010. Prioritizing Agricultural Lands for Conservation Buffer Placement Using Multiple Criteria. Journal of the American Water Resources Association (JAWRA) 1-13. DOI: 10.1111/j.1752-1688.2010.00466.x Abstract: Although conservation buffers are multifunctional, the current conservation buffer planning strategies tend to use a single criterion, most frequently a hydrological or soil condition indicator, to guide conservation buffer placement. This study presents a watershed planning approach that prioritizes agricultural lands for conservation buffers based on multiple selection criteria and applies the approach to Raritan Basin in central New Jersey. The multiple selection criteria include soil erodibility, hydrological sensitivity, wildlife habitat, and impervious surface rate. These criteria capture the conservation buffers’ benefits in reducing soil erosion, controlling runoff generation, enhancing wildlife habitat, and mitigating stormwater impacts, respectively. An expert panel was used to identify and define the section criteria, review the measured values of those criteria, and develop the classification scales that assign the class score to each criterion. The prioritization is based on the summation of the criteria class scores. About one-third of agricultural lands are prioritized for conservation buffers in Raritan Basin. The total program cost of converting those prioritized agricultural lands to conservation buffers in Raritan Basin is estimated to be between $54.8 and 102.9 million depending on the composition of installed conservation buffer practices. 相似文献
856.
洪湖是湖北省最大的湖泊,具有调蓄、灌溉、供水、渔业、物种保护、航运、旅游等多种功能,是长江中下游典型的大型浅水型湖泊。传统的设点监测费力、费时,随着遥感技术和手段的进步,遥感反演洪湖叶绿素a浓度成为技术上可能。利用2005年至2010年6年监测数据与同期MODIS数据进行统计分析,研究业务上进行洪湖叶绿素a含量反演的可能性,结果表明:当叶绿素a含量比较高时,它成为影响湖中NDVI指数的主要因素,当浓度较低时,它与NDVI指数相关性差,表明它不是主要要素;通过分析不同时段两者统计关系结果为:12~2月因藻类浓度比较小,叶绿素a浓度低,加上其它要素干扰湖中NDVI指数,监测数据与同期MODIS数据中NDVI指数相关性比较低(也是极显著相关),其它时间都有较好的相关性(相关系数都高于085),研究表明:运用MODIS数据中的NDVI指数能准确监测洪湖叶绿素a含量。并提出相应的业务处理流程与方法 相似文献
857.
Particulate matter (PM) has long been recognized as an air pollutant due to its adverse health and environmental impacts. As emission of PM from agricultural operations is an emerging air quality issue, the Agricultural Particulate Matter Emissions Indicator (APMEI) has been developed to estimate the primary PM contribution to the atmosphere from agricultural operations on Census years and to assess the impact of practices adopted to mitigate these emissions at the soil landscape polygon scale as part of the agri-environmental indicator report series produced by Agriculture and Agri-Food Canada. In the APMEI, PM emissions from animal feeding operations, wind erosion, land preparation, crop harvest, fertilizer and chemical application, grain handling, and pollen were calculated and compared for the Census years of 1981-2006. In this study, we present the results for PM10 and PM2.5, which exclude chemical application and pollen sources as they only contribute to total suspended particles. In 2006, PM emissions from agricultural operations were estimated to be 652.6 kt for PM10 and 158.1 kt for PM2.5. PM emissions from wind erosion and land preparation account for most of PM emissions from agricultural operations in Canada, contributing 82% of PM10 and 76% of PM2.5 in 2006. Results from the APMEI show a strong reduction in PM emissions from agricultural operations between 1981 and 2006, with a decrease of 40% (442.8 kt) for PM10 and 47% (137.7 kt) for PM2.5. This emission reduction is mainly attributed to the adoption of conservation tillage and no-till practices and the reduction in the area of summer fallow land. 相似文献
858.
Biodiesels are often marketed as being cleaner than regular diesel for emissions. Emission test results depend on the biodiesel blend, but laboratory tests suggest that biodiesels decrease particulate matter, carbon monoxide, hydrocarbons, and air toxins when compared to regular diesel. Results for the amount of oxides of nitrogen (NOx) have been less conclusive. Tests have also not evaluated the commonly available ranges of biodiesel blends in the laboratory. Additionally, little information is available from on-road studies, so the effectiveness of using biodiesels to reduce actual emissions is unknown. A more complex relationship exists between engine operation and the rate of emission production than is typically evaluated using engine or chassis dynamometer tests. On-road emissions can vary dramatically because emissions are correlated to engine mode. Additionally, activity such as idling, acceleration, deceleration, and operation against a grade can produce higher emissions than more stable engine operating modes. Because these modes are not well captured in a laboratory environment, understanding on-road relationships is critical in evaluating the emissions reductions that may be possible with biodiesels. More tests and quantifications of the effects of different blends on engine and vehicle performance are required to promote widespread use of biodiesel. The objective of this research was to conduct on-road tests to compare the emission impacts of different blends of biodiesel to regular diesel fuel under different operating conditions. The team conducted on-road tests that utilized a portable emissions monitoring system that was used to instrument transit buses. Regular diesel and different blends of biodiesel were evaluated during on-road engine operation by instrumenting three in-use transit buses, from the CyRide system of Ames, Iowa, along an existing transit route. 相似文献
859.
NaClO2/NaClO复合吸收液同时脱硫脱硝 总被引:3,自引:0,他引:3
针对NaClO2氧化吸收法脱硫脱硝成本过高,难以实现工业化的现状,提出了以NaClO2/NaClO为复合吸收剂的同时脱硫脱硝新方法,比单独NaClO2方法效率高,成本低。考虑实际工况条件,给定SO2与NO的初始浓度分别为2 850 mg/m3和670 mg/m3。结果表明,吸收液初始pH为6.0,液气比L/G为20 L/m3,反应温度为55℃时,平均脱硫脱硝效率分别可达99.8%和94.0%。在此基础上对反应机理进行了分析,总结出实验反应主反应方程式。该方法设备简约,操作简单,容易实现全自动控制,综合成本可以接受,比较适合中小型燃煤锅炉的烟气污染治理。 相似文献
860.
Kangjing Zhang Huiying Yang Zhaobin Qiu 《Journal of Polymers and the Environment》2018,26(4):1320-1327
In this research, the thermal properties and crystallization behavior of novel poly(hexamethylene succinate-co-6 mol% butylene succinate) (PHBS) and its homopolymer poly(hexamethylene succinate) (PHS) were extensively studied. With respect to PHS, the introduction of a small content of butylene succinate (BS) unit slightly reduces the melting point and equilibrium melting point but hardly influences the glass transition temperature of PHBS. Despite crystallization temperature, PHS and PHBS crystallize through the same crystallization mechanism. At the same crystallization temperature, PHBS crystallizes more slowly than PHS; furthermore, lowering crystallization temperature enhances the crystallization rates of PHBS and PHS. The spherulites morphologies were observed for both of them, with the spherulites nucleation density of the copolymer being smaller than that of the homopolymer. PHBS and PHS share the same crystal structures, indicative of the location of BS unit in the amorphous region. 相似文献