全文获取类型
收费全文 | 1060篇 |
免费 | 43篇 |
国内免费 | 32篇 |
专业分类
安全科学 | 65篇 |
废物处理 | 4篇 |
环保管理 | 418篇 |
综合类 | 198篇 |
基础理论 | 214篇 |
污染及防治 | 94篇 |
评价与监测 | 59篇 |
社会与环境 | 57篇 |
灾害及防治 | 26篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 25篇 |
2020年 | 22篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 32篇 |
2016年 | 36篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 44篇 |
2012年 | 34篇 |
2011年 | 86篇 |
2010年 | 52篇 |
2009年 | 100篇 |
2008年 | 89篇 |
2007年 | 72篇 |
2006年 | 53篇 |
2005年 | 27篇 |
2004年 | 32篇 |
2003年 | 30篇 |
2002年 | 25篇 |
2001年 | 15篇 |
2000年 | 23篇 |
1999年 | 25篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 26篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1973年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1135条查询结果,搜索用时 212 毫秒
991.
Walter T. Sittner 《Journal of the American Water Resources Association》1973,9(4):655-659
The National Weather Service is nearing the conclusion of a five year period of transition from index type catchment modelling to the use of conceptual hydrologic models. The decision to make this technological change was based on an extensive research project in which various catchment models were tested in a wide variety of basins and their strong and weak points ascertained. This project is described. Some of the problems involved in the changeover, which are discussed, are practical parameter optimization methods, computer requirements for the more complex technology, data requirements, fitting of the catchment model to major river systems, training of personnel and staffing problems. 相似文献
992.
John F. Lehmkuhl 《Environmental management》1984,8(2):167-176
The concept of minimum populations of wildlife and plants has only recently been discussed in the literature. Population genetics has emerged as a basic underlying criterion for determining minimum population size. This paper presents a genetic framework and procedure for determining minimum viable population size and dispersion strategies in the context of multiple-use land management planning. A procedure is presented for determining minimum population size based on maintenance of genetic heterozygosity and reduction of inbreeding. A minimum effective population size (N
e
) of 50 breeding animals is taken from the literature as the minimum shortterm size to keep inbreeding below 1% per generation. Steps in the procedure adjustN
e
to account for variance in progeny number, unequal sex ratios, overlapping generations, population fluctuations, and period of habitat/population constraint. The result is an approximate census number that falls within a range of effective population size of 50–500 individuals. This population range defines the time range of short- to long-term population fitness and evolutionary potential. The length of the term is a relative function of the species generation time. Two population dispersion strategies are proposed: core population and dispersed population. 相似文献
993.
This paper describes the development and implementation ofPREPLAN, A Pristine Environment Planning Language and Simulator, for two conservation areas in Australia, Kosciusko National Park (New South Wales) and Tutanning Nature Reserve (Western Australia).PREPLAN was derived from the North American gradient modeling systems and theForest Planning Language and Simulator (FORPLAN), but includes unique characteristics not previously available.PREPLAN includes an integrated resource management data base, modules for predicting site-specific vegetation, fuels, animals, fire behavior, and fire effects, and an English language instruction set.PREPLAN was developed specifically to provide available information and understanding of ecosystems to managers in a readily accessible and usable form, and to provide the motivation to conduct additional required research projects. An evaluation of the system's advantages and limitations is presented, and the way the utilization of such systems is improving natural area decision making throughout Australia is discussed. 相似文献
994.
995.
遥感和GIS在森林病虫害监测管理中的应用模式 总被引:20,自引:1,他引:19
介绍了遥感技术,地理信息系统技术在森林病虫害监测管理中的应用模式,以及整个系统的集成。在整个系统中遥感用于获取森林病虫害信息,地理信息系统用于管理和处理森林病虫害信息。同时,也说明了全球定位系统可用于定位采集地面数据和导路。 相似文献
996.
Wrathall JE 《Disasters》1985,9(2):104-114
The annual hazard of fire in the forest, maquis and garrigue of southern France is related both to the fragile nature of the Mediterranean ecosystem and to man's activities. The Mediterranean vegetation is adapted to withstand the aridity of the summer months, but the combination of high temperatures, low precipitation, critical soil-moisture levels and occasional bouts of strong winds (mistral) desiccate the vegetation cover and create conditions in which outbreaks of forest fires are inevitable. Although the annual incidence and impact of forest fires are related to the occurrence of extreme weather conditions they are also exacerbated by depopulation of the remoter rural areas, the spread of urbanization and the growth of tourist facilities in the more accessible coastal zones, and above dl by man's carelessness. This article reviews the factors affecting the nature and severity of forest fires and discusses the attempts being made to prevent and control forest fires in the Mediterranean zone of southern France 相似文献
997.
Morgan R 《Disasters》1985,9(1):44-50
This article describes the indicators and data sources used by the Botswana Drought Early Warning System formally established in early 1984, the main uses of the indicators in the assessment of drought conditions and the design of relief programmes are outlined. Limitations of the sources of data available are discussed, as is the feasibility of adding some possible further indicators. In conclusion, the importance of a functioning Early Warning System in a country highly susceptible to repeated droughts is stressed, in the context of die current effort to elaborate a comprehensive National Food Strategy and to establish a Regional Early Warning System for Southern Africa. 相似文献
998.
Farrell AE 《Environmental monitoring and assessment》2005,107(1-3):59-80
The Montreal Process was formed in 1994 to develop an internationally agreed upon set of criteria and indicators for the conservation and sustainable management of temperate and boreal forests. In response to this initiative, the Forest Inventory and Analysis (FIA) and Forest Health Monitoring (FHM) programs of the United States Department of Agriculture Forest Service have implemented soil measurements as part of a national monitoring program to address specific questions related to the conservation of soil and water resources. Integration of soil assessments into the national FIA program provides for systematic monitoring of soil properties across all forested regions of the U.S. using standardized collection, laboratory, and statistical procedures that are compatible with existing forest inventory data. The resulting information will provide quantitative benchmarks for regional, national, and international reporting on sustainable forest management and enhance our understanding of management effects on soil quality. This paper presents an overview of the FIA soil monitoring program, outlines the field and laboratory protocols as currently implemented, and provides examples of how these data may be used to assess indicators of sustainable management as defined by the Montreal Process. 相似文献
999.
De França EJ De Nadai Fernandes EA Bacchi MA Rodrigues RR Verburg TG 《Environmental monitoring and assessment》2005,102(1-3):349-357
The Atlantic Forest with its exuberant vegetation of high level of biodiversity is classified as one hotspot of the world. Chemical composition of leaves from native trees and underlying soils was evaluated by INAA. The predominant species Euterpe edulis, Bathysa meridionalis, Hyeronima alchorneoides, Marlierea tomentosa, Gomidesia flagellaris, and Gomidesia spectabilis belonging to the diverse plant families were studied. Euterpe edulis, the most abundant understory specie, presented the lowest element concentrations except for Zn. Some variation in chemical composition was noted, however, the chemical specificity of tree species can be more predominant than the soil variability for the obtained leaf concentrations. Factor values obtained through the Monte-Carlo assisted factor analysis were used for species discrimination. The results indicate that chemical investigation of native trees is a quite promising tool for biodiversity studies in the Atlantic Forest. 相似文献
1000.
Environmental concerns such as loss of biological diversity and stratospheric ozone depletion have heightened awareness of the need to assess cumulative impacts in environmental documents. More than 20 years of experience with the National Environmental Policy Act (NEPA) have provided analysts in the United States with opportunities for developing successful techniques to assess site-specific impacts of proposed actions. Methods for analyzing a proposed action's incremental contribution to cumulative impacts are generally less advanced than those for project-specific impacts.The President's Council on Environmental Quality (CEQ) defines cumulative impact to include the impacts of past, present and reasonably foreseeable future actions regardless of who undertakes the action. Court decisions have helped clarify the distinction between reasonably foreseeable future actions and other possible future actions. This paper seeks to clarify how past and present impacts should be included in cumulative impact analyses.The definition of cumulative impacts implies that cumulative impact analyses should include the effects of all past and present actions on a particular resource. Including past and present impacts in cumulative impact assessments increases the likelihood of identifying significant impacts. NEPA requires agencies to give more consideration to alternatives and mitigation and to provide more opportunities for public involvement for actions that would have significant impacts than for actions that would not cause or contribute to significant impacts. For an action that would contribute to significant cumulative impacts, the additional cost and effort involved in increased consideration of alternatives and mitigation and in additional public involvement may be avoided if the action can be modified so that its contributions to significant cumulative impacts are eliminated.Managed by Lockheed Martin Energy Research Corporation under contract DE-AC05-84OR21400 with the US Department of Energy. 相似文献