全文获取类型
收费全文 | 2064篇 |
免费 | 132篇 |
国内免费 | 284篇 |
专业分类
安全科学 | 216篇 |
废物处理 | 86篇 |
环保管理 | 919篇 |
综合类 | 824篇 |
基础理论 | 172篇 |
环境理论 | 3篇 |
污染及防治 | 84篇 |
评价与监测 | 87篇 |
社会与环境 | 42篇 |
灾害及防治 | 47篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 30篇 |
2021年 | 34篇 |
2020年 | 34篇 |
2019年 | 23篇 |
2018年 | 29篇 |
2017年 | 37篇 |
2016年 | 47篇 |
2015年 | 41篇 |
2014年 | 56篇 |
2013年 | 51篇 |
2012年 | 48篇 |
2011年 | 73篇 |
2010年 | 68篇 |
2009年 | 51篇 |
2008年 | 76篇 |
2007年 | 58篇 |
2006年 | 51篇 |
2005年 | 48篇 |
2004年 | 55篇 |
2003年 | 104篇 |
2002年 | 191篇 |
2001年 | 172篇 |
2000年 | 191篇 |
1999年 | 151篇 |
1998年 | 110篇 |
1997年 | 93篇 |
1996年 | 217篇 |
1995年 | 68篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 24篇 |
1984年 | 41篇 |
1983年 | 39篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1971年 | 14篇 |
1967年 | 1篇 |
排序方式: 共有2480条查询结果,搜索用时 15 毫秒
991.
Pollution in urban zoos arises from diffuse and small point sources. However, its control has received little attention in past decades. Online and ofttine modes of ecological engineering technology were designed to control pollution from small point and diffuse sources in Wuhan City Zoo, China. Their characteristics and performances were investigated in sixteen runoff events from 2003 to 2005. The results showed that the two modes both improved runoff water quality and had high retention rates for water and pollutants. In the outflows, the event mean concentrations (EMCs) of total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were reduced by 88%, 59%, 46% and 71% for the online mode, and those were 77%, 42%, 50% and 66% for the ofttine mode. The annual retention rates of pollutant loads for the online mode were 94.9%-98.5% in the three study years; those for the ofitine mode were 70.5%-86.4%. Based on calculation, the online mode was able to store the runoff of 66.7 mm rainfall completely, and the ofttine mode could store that of 31.3 mm rainfall. In addition, the online mode can provide an effective way for rainwater utilization and good habitats for aquatic wildlives, and has an excellent aesthetics value for recreationsal pastimes. The ofiline mode can save land resources and may be an effective and economical measure for diffuse pollution control in urban areas. 相似文献
992.
The paper gives a special dynamic pursuing ecological model on the bio-geochemical cycle of nitrogen in the whole range 9.6 million square kilometers of Chinese mainland, basing on the reservoir-content and flux-rate of nitrogen and among the four spheres: atmosphere, pedosphere, biosphere, and hydrosphere, and the law of bio-geochemical cycle of nitrogen, the model predicted the size of reservoir capacities and fluxes of nitrogen in each sphere. Through tested and verified, the model was proven reasonable and reliable. 相似文献
993.
珠江口底栖生物重金属含量现状与评价 总被引:5,自引:0,他引:5
根据2003年的调查资料,结合国内外有关生物残毒理论,对珠江口海域底栖生物重金属含量现状进行分析与评价。结果表明,底栖生物中Hg、Ph、Cd、As含量较低,但甲壳动物和软体动物体内Ph和Cd具有潜在的严重积累问题;甲壳类Cd含量已严重超人体消费标准,软体类的Cd含量等于人体消费标准值,甲壳动物和软体动物的可食性应引起人们的关注。 相似文献
994.
995.
加强环境保护打破绿色贸易壁垒 总被引:6,自引:0,他引:6
本文通过分析绿色壁垒对我国外贸的影响,从政府和企业的角度提出了相关的政策建议。 相似文献
996.
Detection of Coastal Saline Land Uses with Multi-Temporal Landsat Images in Shangyu City,China 总被引:11,自引:0,他引:11
Many coastal regions in China are confronted with pressing problems of scarce land resources and heavy population. Over the
past 30 years, considerable parts of coastal tidelands have been enclosed and reclaimed for agricultural land uses. To assess,
plan, and implement large-scale reclamation programs, up-to-date and reliable information concerning the nature, areal extent,
and physical and chemical characteristics of coastal saline lands is essential. This paper reports a remote sensing approach
to detecting coastal saline land uses in Shangyu City, China, by using multi-temporal Landsat images. First, with the aid
of resolution-sharpened Landsat-7 ETM+ images and their enhanced linear features, a visual interpretation is applied to extract
individual dikes. Based on time series images and local government records, a spatial zoning procedure is then used to define
six sub-zones with different historical years of reclamation. It shows that a total of 15,668 ha of coastal saline lands were
enclosed and reclaimed from 1969 to 1996. Second, a modified land-use classification system for the study area is prescribed,
and both unsupervised and supervised classifiers are performed for land-use classifications of grouped sub-zones. Information
obtained from the spatial zoning, Tasseled Cap transformation and Normalized Difference Vegetation Index, is also utilized
to facilitate the supervised classification process. Finally, a detailed land-use map is produced, with an overall classification
accuracy of 77.8%. Results show that dominant agricultural land uses of sub-zones are changed with historical reclamation
years, from saline lands with wildgrass (very recently reclaimed) to aqua-farm ponds, to cotton fields, and to paddy fields
and orchards (very early reclaimed). This transform process is primarily affected by soil salinities, and according to a soil
survey an electrical conductivity of saturation extract decreased from 7.3 ds/m in the saline land reclaimed in 1996 to below
2 ds/m in the land reclaimed before 1969. The study concludes that multi-temporal remotely sensed images are important and
effective data sources for monitoring the rapid changes of coastal land uses. 相似文献
997.
Assessing Watershed-Scale, Long-Term Hydrologic Impacts of Land-Use Change Using a GIS-NPS Model 总被引:25,自引:0,他引:25
Land-use change, dominated by an increase in urban/impervious areas, has a significant impact on water resources. This includes
impacts on nonpoint source (NPS) pollution, which is the leading cause of degraded water quality in the United States. Traditional
hydrologic models focus on estimating peak discharges and NPS pollution from high-magnitude, episodic storms and successfully
address short-term, local-scale surface water management issues. However, runoff from small, low-frequency storms dominates
long-term hydrologic impacts, and existing hydrologic models are usually of limited use in assessing the long-term impacts
of land-use change. A long-term hydrologic impact assessment (L-THIA) model has been developed using the curve number (CN)
method. Long-term climatic records are used in combination with soils and land-use information to calculate average annual
runoff and NPS pollution at a watershed scale. The model is linked to a geographic information system (GIS) for convenient
generation and management of model input and output data, and advanced visualization of model results.
The L-THIA/NPS GIS model was applied to the Little Eagle Creek (LEC) watershed near Indianapolis, Indiana, USA. Historical
land-use scenarios for 1973, 1984, and 1991 were analyzed to track land-use change in the watershed and to assess impacts
on annual average runoff and NPS pollution from the watershed and its five subbasins. For the entire watershed between 1973
and 1991, an 18% increase in urban or impervious areas resulted in an estimated 80% increase in annual average runoff volume
and estimated increases of more than 50% in annual average loads for lead, copper, and zinc. Estimated nutrient (nitrogen
and phosphorus) loads decreased by 15% mainly because of loss of agricultural areas. The L-THIA/NPS GIS model is a powerful
tool for identifying environmentally sensitive areas in terms of NPS pollution potential and for evaluating alternative land
use scenarios for NPS pollution management. 相似文献
998.
An Aquifer Vulnerability Assessment of the Paluxy Aquifer, Central Texas, USA, Using GIS and a Modified DRASTIC Approach 总被引:8,自引:1,他引:8
D epth to water, net Recharge, Aquifer media, Soil media,
Topography, Impact of the vadose zone, and
Conductivity of the aquifer). Using such an approach allows one to investigate the potential for groundwater contamination
on a regional, rather than site-specific, scale. Based upon data from variables such as soil permeability, depth to water,
aquifer hydraulic conductivity, and topography, subjective numerical weightings have been assigned according to the variable's
relative importance in regional groundwater quality. The weights for each variable comprise a GIS map layer. These map layers
are combined to formulate the final groundwater pollution potential map. Using this method of investigation, the pollution
potential map for the study area classifies 47% of the area as having low pollution potential, 26% as having moderate pollution
potential, 22% as having high pollution potential, and 5% as having very high pollution potential. 相似文献
999.
Resource management issues continually change over time in response to coevolving social, economic, and ecological systems.
Under these conditions adaptive management, or “learning by doing,” offers an opportunity for more proactive and collaborative
approaches to resolving environmental problems. In turn, this will require the implementation of learning-based extension
approaches alongside more traditional linear technology transfer approaches within the area of environmental extension. In
this paper the Integrated Systems for Knowledge Management (ISKM) approach is presented to illustrate how such learning-based
approaches can be used to help communities develop, apply, and refine technical information within a larger context of shared
understanding. To outline how this works in practice, we use a case study involving pest management. Particular attention
is paid to the issues that emerge as a result of multiple stakeholder involvement within environmental problem situations.
Finally, the potential role of the Internet in supporting and disseminating the experience gained through ongoing adaptive
management processes is examined. 相似文献
1000.
催化湿式氧化法处理三环唑生产废水 总被引:10,自引:2,他引:10
在高压釜中进行了三环唑农药生产敦水间歇催化湿式氧化试验,结果表明,该法处理高浓度有有毒有机废水是有效的。在试验条件下,COD去除率达80%。反应温度对处理效果影响最大,铜系催化剂具有较高的催化活性。 相似文献