全文获取类型
收费全文 | 588篇 |
免费 | 16篇 |
国内免费 | 10篇 |
专业分类
安全科学 | 16篇 |
废物处理 | 38篇 |
环保管理 | 114篇 |
综合类 | 99篇 |
基础理论 | 165篇 |
环境理论 | 4篇 |
污染及防治 | 100篇 |
评价与监测 | 50篇 |
社会与环境 | 25篇 |
灾害及防治 | 3篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 14篇 |
2017年 | 22篇 |
2016年 | 31篇 |
2015年 | 26篇 |
2014年 | 24篇 |
2013年 | 53篇 |
2012年 | 41篇 |
2011年 | 42篇 |
2010年 | 26篇 |
2009年 | 36篇 |
2008年 | 29篇 |
2007年 | 22篇 |
2006年 | 29篇 |
2005年 | 18篇 |
2004年 | 14篇 |
2003年 | 17篇 |
2002年 | 15篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1961年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有614条查询结果,搜索用时 15 毫秒
21.
Odor emissions during manure spreading events have become a source of concern, particularly where farms are located nearby urban areas. The objective of the present study was to compare odor concentrations and odor emission rates due to pig manure application using two different types of applicators, a sub-surface deposition system and a conventional splash-plate applicator. Air samples were collected using a Surface Isolation Flux Chamber and the "bag-in-vacuum chamber" techniques, at 0.5, 1.5 and 2.5 hours after manure application. A three-station forced-choice dynamic dilution olfactometer was used by an odor panel for determining odor concentration. Preliminary results indicated that with the sub-surface deposition system applicator odor emission rate was reduced by 8% to 38% compared to that of the conventional splash-plate applicator. The highest reduction in odor strength and odor emission rate was observed in the most offensive period after manure application. The sub-surface deposition system may be a solution for hog producers who wish to reduce odor complaints from applying manure without the cost and problems associated with deep injection systems. 相似文献
22.
Anthony B. Muller 《Journal of the American Water Resources Association》1974,10(2):245-255
ABSTRACT: A groundwater quality change of +0.13 millimhos electrical conductivity was documented between 1940 and 1 972 in the Safford Valley. The change is attributable to four principal mechanisms: pumping-encouraged saline artesian aquifer leakage, natural recharge of the water table aquifer by saline waters, leaching of agricultural waters into the aquifer and the lateral flow of groundwater through saline lacustrine beds. A hydrologic study of the area has shown the first of these mechanisms to be predominant. Salinity modeling has shown three regions of salinity change, and salinity increase projections for each are determined. An economic analysis and an economic model are then combined with the physical model, yielding information as to when certain economic conditions are reached with respect to the salinity increase. This combined model shows that, based on projected salinity trends, cotton, the principal agricultural crop of the valley, will remain economical to cultivate for a significant time beyond the model's limit of prediction. Alfalfa, on the other hand, should go out of production in large areas of the valley by 1990, and not be under economical cultivation by 2040. A sociologic model, based on the cluster analysis of questionnaire data, shows an awareness of the salinity problems of the area but little concern over them. Interdisciplinary model based salinity control regulations are made. 相似文献
23.
24.
In recent years, many electronic manufacturing firms have looked upon Cleaner Production (CP) as the means by which they could maintain environmental practice and competitive advantages. CP has been adopted by companies as an important factor in enhancing industrial productivity. Sustainable projects that deal appropriately with environmental and social factors are also more likely to be the most profitable.This paper investigated the criteria and attributes that determine a successful adoption and implementation of CP in reference to PWB manufacture in Taiwan. Fuzzy Analytic Hierarchy Process (FAHP) methodology is used to discuss the different decision criteria that include Organizing, Systems and Technologies, Measurement and Feedback, Working environment and Worker's Culture which are all vital factors in an effective CP implementation. AHP is an efficient tool in controlling the fuzziness of the data involved in choosing the most preferred decision variables. The linguistic level of comparisons produced by the manufacturers and experts are tapped and constructed in a form of triangular fuzzy numbers in order to construct fuzzy pairwise comparison matrices. The implementation of the system is demonstrated by a problem involving three stages of hierarchy which contains different criteria and attributes at a wider perspective within an environmental uncertainty. The findings advocate that these enterprises would need to setup the priorities of the CP implementation. The results suggest a generic hierarchical model of organizations of which the highest level is to be prioritized among the CP implementation factors. 相似文献
25.
P. Kaniewska K. R. N. Anthony E. M. Sampayo P. R. Campbell O. Hoegh-Guldberg 《Marine Biology》2014,161(2):313-328
Reef-building corals are an example of plastic photosynthetic organisms that occupy environments of high spatiotemporal variations in incident irradiance. Many phototrophs use a range of photoacclimatory mechanisms to optimize light levels reaching the photosynthetic units within the cells. In this study, we set out to determine whether phenotypic plasticity in branching corals across light habitats optimizes potential light utilization and photosynthesis. In order to do this, we mapped incident light levels across coral surfaces in branching corals and measured the photosynthetic capacity across various within-colony surfaces. Based on the field data and modelled frequency distribution of within-colony surface light levels, our results show that branching corals are substantially self-shaded at both 5 and 18 m, and the modal light level for the within-colony surface is 50 μmol photons m?2 s?1. Light profiles across different locations showed that the lowest attenuation at both depths was found on the inner surface of the outermost branches, while the most self-shading surface was on the bottom side of these branches. In contrast, vertically extended branches in the central part of the colony showed no differences between the sides of branches. The photosynthetic activity at these coral surfaces confirmed that the outermost branches had the greatest change in sun- and shade-adapted surfaces; the inner surfaces had a 50 % greater relative maximum electron transport rate compared to the outer side of the outermost branches. This was further confirmed by sensitivity analysis, showing that branch position was the most influential parameter in estimating whole-colony relative electron transport rate (rETR). As a whole, shallow colonies have double the photosynthetic capacity compared to deep colonies. In terms of phenotypic plasticity potentially optimizing photosynthetic capacity, we found that at 18 m, the present coral colony morphology increased the whole-colony rETR, while at 5 m, the colony morphology decreased potential light utilization and photosynthetic output. This result of potential energy acquisition being underutilized in shallow, highly lit waters due to the shallow type morphology present may represent a trade-off between optimizing light capture and reducing light damage, as this type morphology can perhaps decrease long-term costs of and effect of photoinhibition. This may be an important strategy as opposed to adopting a type morphology, which results in an overall higher energetic acquisition. Conversely, it could also be that maximizing light utilization and potential photosynthetic output is more important in low-light habitats for Acropora humilis. 相似文献
26.
27.
28.
"二噁英"是指具有相似化学结构和生物特征的一族化合物,分别属于三大类别:多氯代二苯并二噁英(PC-DDs),多氯代二苯并呋喃(PCDFs)以及多氯联苯(PCBs).PCDDs和PCDFs无商业目的性生产,而是在大量的人类活动中产生的.自然过程也可以产生PCDDs和PCDFs.在过去的十年里,环境立法机构和企业一起致力于减少二噁英的排放. 相似文献
29.
30.
Influence of Riparian Seepage Zones on Nitrate Variability in Two Agricultural Headwater Streams
下载免费PDF全文
![点击此处可从《Journal of the American Water Resources Association》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mark R. Williams Anthony R. Buda Herschel A. Elliott Kamini Singha James Hamlett 《Journal of the American Water Resources Association》2015,51(4):883-897
Riparian seeps have been recognized for their contributions to stream flow in headwater catchments, but there is limited data on how seeps affect stream water quality. The objective of this study was to examine the effect of seeps on the variability of stream NO3‐N concentrations in FD36 and RS, two agricultural catchments in Pennsylvania. Stream samples were collected at 10‐m intervals over reaches of 550 (FD36) and 490 m (RS) on 21 occasions between April 2009 and January 2012. Semi‐variogram analysis was used to quantify longitudinal patterns in stream NO3‐N concentration. Seep water was collected at 14 sites in FD36 and 7 in RS, but the number of flowing seeps depended on antecedent conditions. Seep NO3‐N concentrations were variable (0.1‐29.5 mg/l) and were often greater downslope of cropped fields compared to other land uses. During base flow, longitudinal variability in stream NO3‐N concentrations increased as the number of flowing seeps increased. The influence of seeps on the variability of stream NO3‐N concentrations was less during storm flow compared to the variability of base flow NO3‐N concentrations. However, 24 h after a storm in FD36, an increase in the number of flowing seeps and decreasing streamflow resulted in the greatest longitudinal variability in stream NO3‐N concentrations recorded. Results indicate seeps are important areas of NO3‐N delivery to streams where targeted adoption of mitigation measures may substantially improve stream water quality. 相似文献