全文获取类型
收费全文 | 3292篇 |
免费 | 140篇 |
国内免费 | 410篇 |
专业分类
安全科学 | 38篇 |
废物处理 | 5篇 |
环保管理 | 706篇 |
综合类 | 1594篇 |
基础理论 | 534篇 |
环境理论 | 2篇 |
污染及防治 | 54篇 |
评价与监测 | 106篇 |
社会与环境 | 729篇 |
灾害及防治 | 74篇 |
出版年
2024年 | 26篇 |
2023年 | 39篇 |
2022年 | 90篇 |
2021年 | 91篇 |
2020年 | 107篇 |
2019年 | 100篇 |
2018年 | 110篇 |
2017年 | 169篇 |
2016年 | 158篇 |
2015年 | 136篇 |
2014年 | 102篇 |
2013年 | 195篇 |
2012年 | 196篇 |
2011年 | 227篇 |
2010年 | 193篇 |
2009年 | 132篇 |
2008年 | 161篇 |
2007年 | 234篇 |
2006年 | 220篇 |
2005年 | 159篇 |
2004年 | 151篇 |
2003年 | 144篇 |
2002年 | 100篇 |
2001年 | 83篇 |
2000年 | 74篇 |
1999年 | 88篇 |
1998年 | 51篇 |
1997年 | 33篇 |
1996年 | 54篇 |
1995年 | 23篇 |
1994年 | 27篇 |
1993年 | 30篇 |
1992年 | 20篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1975年 | 9篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有3842条查询结果,搜索用时 15 毫秒
991.
Bruce K. Ferguson 《Journal of the American Water Resources Association》1985,21(2):253-263
Acid drainage from abandoned mines is a widespread problem in old mining regions. Agencies seeking to abate it face the prospect of dealing with hundreds of potential abatement projects, stretching decades into the future. A systematic regional analysis is necessary to establish locations, objectives, priorities, and phasing of such projects. The U.S. Bureau of Mines developed a novel procedure for abatement planning in the 420 square mile Blacklick Creek Watershed in Pennsylvania. The plan sought to direct abatement projects toward pollution sources where degradation was worst and adverse effects greatest. It established abatement priorities by comparing the “supply” of sources to be reclaimed (the degrees of old mines' water quality degradation) with the “demand” for abatement to be done (the natural and cultural values represented by the region's demography, land use and other non-mining characteristics). Matrices were used to define the relationships among mining and non-mining factors; maps were developed to show the geographic distribution of the conclusions. The locations, priorities, and phasing of abatement objectives shown on the maps should provide guidance for any abatement effort, no matter what type of technology is applied to achieve the objectives. Over the many years in which abatement projects are to be performed in the Watershed, the plan can be used to define, coordinate, and establish priorities for the projects in a manner that can result in maximum abatement benefits from the application of limited funds. 相似文献
992.
This article analyzes landscape pattern in the WesternGhats mountain ranges in south-western India at two scales,comparing small-scale, detailed studies of landscapepattern, with broader, regional-scale assessments of theWestern Ghats. Due in large part to their inaccessibility,relatively little is known about the landscapes of thisbiodiverse region, which also supports some of the highestpopulation densities in the world. A broad-scale NDVI-basedIRS 1B satellite image classification is used to analyzenorth-south and east-west trends across the entire WesternGhats and western coast of India, an area over 170 000 km2. Northern and eastern landscapes are morefragmented compared to the southern and western slopes.Western slopes also have greater landscape diversity withland cover types more interspersed compared to the easternslopes. These differences can be related to north-south andeast-west variations in rainfall and plant distribution. Data from thirteen landscapes 10–50 km2 in area, arefurther utilized to analyze trends in landscape pattern, anddescribe the geographical distribution of major natural andmanaged ecotope types. At this scale, very high levels ofintra-ecotope type variability in landscape pattern areencountered for all land cover types. Results at these twoscales are integrated to suggest a hierarchical stratifiedapproach for monitoring land cover and biodiversity in the region. 相似文献
993.
Burger J 《Environmental monitoring and assessment》2005,101(1-3):147-165
Considerable attention has been devoted to the concerns and perceptions of people residing around contaminated facilities, both brownfields in urban areas and others located in remote and lightly populated areas. This paper examines the concerns of recreationists and sportsmen residing near the Department of Energys (DOE) Brookhaven National Laboratory, in central Long Island, one of the most densely populated regions in the United States, where tourism is of prime importance. On an open-ended question, the greatest concern was pollution, followed by environmental health as a global concern, and human health as a concern for Brookhaven. Accidents/spills, loss of public health, and loss of ecological health were rated highest among a list of concerns, and change in property values was rated lowest. When asked to rank seven concerns, protecting human health was ranked the highest, and economic interests were ranked the lowest. For future land use at Brookhaven, recreational uses were rated the highest, while building houses and factories, and storage of nuclear material were rated the lowest. These data can be used by managers, decision and policy makers, and the general public to assess and manage local and regional environmental concerns and to consider future land uses for decommissioned lands, such as those at Brookhaven. 相似文献
994.
Integration of Case Studies on Global Change by Means of Qualitative Differential Equations 总被引:2,自引:0,他引:2
We present a novel methodology to integrate qualitative knowledge from different case studies on Global Change related issues
into a single framework. The method is based on the concept of qualitative differential equations (QDEs) which represents
a mathematically well-defined approach to investigate classes of ordinary differential equations (ODEs) used in conventional
modeling exercises. These classes are defined by common qualitative features, e.g., monotonicity, signs, etc. Using the QSIM-algorithm
it is possible to derive the set of possible solutions of all ODEs in the class. By this one can formulate a common, qualitatively
specified cause–effect scheme valid for all case studies. The scheme is validated by testing it against the actually observed
histories in the study regions with respect to their reconstruction by the corresponding QDE. The method is outlined theoretically
and exemplary applied to the problem of land-use changes due to smallholder agriculture in developing countries. It is shown
that the seven case-studies used can be described by a single cause–effect scheme which thus constitutes a pattern of Global Change. As a generally valid prerequisite for sustainability of this kind of land-use the presence of wage labor is shown to represent
a decisive factor.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
A holistic approach towards assessment of severity of land degradation along the Great Wall in northern Shaanxi Province,China 总被引:26,自引:0,他引:26
The farming and grazing interlocked transitional zone along theGreat Wall in northern Shaanxi Province is particularly vulnerable to desertification due to its fragile ecosystem and intensive human activity. Studies reveal that desertification isboth a natural and anthropogenic process. Four desertificationindicators (vegetative cover, proportion of drifting sand area, desertification rate, and population pressure) were used to assess the severity of desertification in a GIS. The first threefactors were derived from multitemporal remote sensing and landinventory data. The last factor was calculated from census data.It was found that the overall severity of land degradation in thestudy area has worsened during the last two decades with severely, highly and moderately degraded land accounting for 84.2% of the total area in 1998. While the area affected by desertification has increased, the rate of desertification has also accelerated from 0.74 to 0.87%. Risk of land degradation in the study area has increased, on an average, by 155% since 1985. Incorporation of both natural and anthropogenic factors inthe analysis provides realistic assessment of risk of desertification. 相似文献
996.
Impervious Surface Area as a Predictor of the Effects of Urbanization on Stream Insect Communities in Maine, U.S.A. 总被引:2,自引:0,他引:2
The influence of urbanization on stream insect communities was determined by comparing physical, chemical, and biological characteristics of streams draining 20 catchments with varyinglevels of urban land-cover in Maine (U.S.A). Percent total impervious surface area (PTIA), which was used to quantify urbanland-use, ranged from 1–31% among the study catchments.Taxonomic richness of stream insect communities showed an abruptdecline as PTIA increased above 6%. Streams draining catchmentswith PTIA < 6% had the highest levels of both total insect and EPT (Ephemeroptera + Plecoptera + Trichoptera) taxonomic richness. These streams contained insect communities with a totalrichness averaging 33 taxa in fall and 31 taxa in spring; EPT richness ranged from an average of 15 taxa in fall and 13 taxa inspring. In contrast, none of the streams draining catchments with6–27% PTIA had a total richness > 18 taxa or an EPT richness> 6 taxa. Insect communities in streams with PTIA > 6% were characterized by the absence of pollution-intolerant taxa. The distribution of more pollution-tolerant taxa (e.g.Acerpenna (Ephemeroptera); Paracapnia, Allocapnia (Plecoptera); Optioservus, Stenelmis (Coleoptera); Hydropsyche, Cheumatopsyche (Trichoptera)), however, showed little relation to PTIA. In contrast to the apparent threshold relationship between PTIA and insect taxonomic richness, both habitat qualityand water quality tended to decline as linear functions of PTIA.Our results indicate that, in Maine, an abrupt change in stream insect community structure occurs at a PTIA above a threshold ofapproximately 6% of total catchment area. The measurement of PTIA may provide a valuable tool for predicting thresholds for adverse effects of urbanization on the health of headwater streams in Maine. 相似文献
997.
Spatial based compromise programming for multiple criteria decision making in land use planning 总被引:1,自引:0,他引:1
Sumbangan Baja David M. Chapman Deirdre Dragovich 《Environmental Modeling and Assessment》2007,12(3):171-184
Today, competing land use is continuing to occur in many developed regions. In the Agricultural Development Zone of Western
Sydney Region, which is characterised by complex landscape patterns, land use competition is widespread. From a land use planning
perspective, identification of suitable locations for a given type of land use is necessary for decision makers to formulate
land use alternatives in different locations, based on existing land potential and constraints. For such a region, use of
a simple method that implements a categorical system and considers only inherent land characteristics in the analysis is often
inadequate to arrive at an optimal spatial decision. The primary aim of this paper is to develop spatial modelling procedures
for agricultural land suitability analysis using compromise programming (CoPr) and fuzzy set approach within a geographical
information systems (GIS) environment. Five main sets of spatial data for use as decision criteria were developed by using
fuzzy set methodology: a land suitability index (LSI) for maximising the land productivity objective; an erosion tolerance
index (ETI) for minimising the erosion risk objective; a runoff curve number (CN) for maximising the water discharge regulation
objective; an accessibility (RP) measure for maximising the land accessibility objective; and the proximity to water body
(WP) for minimising the water pollution objective. An L
p
-metric was used in the analysis utilising different strategies with representative indices ranging from a situation where
full tradeoff among criteria occurs to a noncompensatory condition. Different weighting combinations were also applied, and decision analysis was carried out by using values ranging
from 0 to 1.0, where 1.0 is considered as an ideal point. The CoPr model demonstrated in this paper yielded a promising result,
as several different techniques of sensitivity analysis show reasonably good results. Likewise, an overlay of that result
with the present land use/land cover indicates a good corresponding spatial matching between existing land use (orchard and
cultivated land), and the cells (land parcels) classified as the best in CoPr. The results are amenable to various map display
techniques, either using continuous values or by defining different cut off points in the data space within a raster GIS environment. 相似文献
998.
John W. Hunt Brian S. Anderson Bryn M. Phillips Ron S. Tjeerdema Nancy Richard Val Connor Karen Worcester Mark Angelo Amanda Bern Brian Fulfrost Dustin Mulvaney 《Environmental monitoring and assessment》2006,121(1-3):243-260
Pesticide applications to agricultural lands in California, USA, are reported to a central data base, while data on water and sediment quality are collected by a number of monitoring programs. Data from both sources are geo-referenced, allowing spatial analysis of relationships between pesticide application rates and the chemical and biological condition of water bodies. This study collected data from 12 watersheds, selected to represent a range of pesticide usage. Water quality parameters were measured during six surveys of stream sites receiving runoff from the selected watershed areas. This study had three objectives: to evaluate the usefulness of pesticide application data in selecting regional monitoring sites, to provide information for generating and testing hypotheses about pesticide fate and effects, and to determine whether in-stream nitrate concentration was a useful surrogate indicator for regional monitoring of toxic substances. Significant correlations were observed between pesticide application rates and in-stream pesticide concentrations (p < 0.05) and toxicity (p < 0.10). In-stream nitrate concentrations were not significantly correlated with either the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.30). Neither total watershed area nor the area in which pesticide usage was reported correlated significantly with the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.14). In-stream pesticide concentrations and effects were more closely related to the intensity of pesticide use than to the area under cultivation. 相似文献
999.
玉溪市中心城区土地利用布局及其优化研究 总被引:3,自引:0,他引:3
本文系统分析了玉溪市中心城区土地利用强度、土地利用效率、土地利用结构的现状 ,研究了玉溪市中心城区土地利用优化对策 ,探索在城市总体布局中 ,如何充分利用地形特点 ,从可持续发展的角度出发 ,创造舒适宜人的城市生态环境空间。 相似文献
1000.
兖州矿区采煤塌陷地状况与综合治理途径研究 总被引:5,自引:0,他引:5
通过对兖州矿区采煤塌陷地状况进行现状分析和趋势预测,结果表明,至2000年底,已累计塌陷土地5389.40hm2;预计到21世纪中叶,兖州、济东2个煤田最终将形成两个塌陷中心,面积达4.4×104hm2。这不仅使大面积农田被毁,造成生态失衡,而且给当地工农业生产以及社会和生态环境等方面带来一系列严重问题,应该彻底进行采煤塌陷地的综合治理。据此,根据矿区工农业持续协调发展的需要,从宏观和微观的角度,全方位提出了采煤塌陷地的综合治理途径。 相似文献