全文获取类型
收费全文 | 1606篇 |
免费 | 29篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 55篇 |
废物处理 | 57篇 |
环保管理 | 364篇 |
综合类 | 148篇 |
基础理论 | 437篇 |
环境理论 | 1篇 |
污染及防治 | 396篇 |
评价与监测 | 93篇 |
社会与环境 | 74篇 |
灾害及防治 | 13篇 |
出版年
2022年 | 10篇 |
2021年 | 11篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 27篇 |
2017年 | 14篇 |
2016年 | 51篇 |
2015年 | 34篇 |
2014年 | 37篇 |
2013年 | 170篇 |
2012年 | 38篇 |
2011年 | 72篇 |
2010年 | 50篇 |
2009年 | 66篇 |
2008年 | 70篇 |
2007年 | 86篇 |
2006年 | 70篇 |
2005年 | 57篇 |
2004年 | 49篇 |
2003年 | 60篇 |
2002年 | 52篇 |
2001年 | 44篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 22篇 |
1997年 | 22篇 |
1996年 | 24篇 |
1995年 | 34篇 |
1994年 | 27篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 25篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 15篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 14篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1971年 | 8篇 |
排序方式: 共有1638条查询结果,搜索用时 31 毫秒
1.
2.
Norman Myers 《The Environmentalist》1992,12(1):15-27
Summary Tropical forests are being destroyed faster than ever, the rate having almost doubled during the 1980s. The main agent of deforestation now turns out to be the displaced peasant or landless farmer, sometimes known as the shifted cultivator; that group accounts for more forest loss than the combined impacts of the commercial logger, the cattle rancher and all other better known sources of deforestation. Yet, the over-riding target of conservation efforts remains the minor players in the forest's decline. All too little attention is directed towards the shifted cultivator, and next to nothing is done to address the problem which this group represents. Policy purviews need to be expanded to include the key factor of the shifted cultivator. In turn, it must determined what impels these people to abandon established farming areas in the countries concerned and to migrate into the forests. It appears that these people are driven by an array of forces: population growth, maldistribution of arable lands, inadequate rural infrastructure and lack of government attention to subsistence agriculture. In other words, the source problem is an amalgam of non-forestry factors, and conservationists will not achieve success in safeguarding the remaining forests unless they direct much more emphasis towards these root causes of deforestation.Dr Norman Myers is a consultant in environment and development, a member of this journal's Advisory Board and a regular contributor to the journal (seeThe Environmentalist,8(3), 187–208 and10(4), 243–256). 相似文献
3.
4.
5.
6.
J. Christian Franson William L. Hohman Joseph L. Moore Milton R. Smith 《Environmental monitoring and assessment》1996,43(2):181-188
We used 363 blood samples collected from wild canvasback dueks (Aythya valisineria) at Catahoula Lake, Louisiana, U.S.A. to evaluate the effect of sample storage time on the efficacy of erythrocytic protoporphyrin as an indicator of lead exposure. The protoporphyrin concentration of each sample was determined by hematofluorometry within 5 min of blood collection and after refrigeration at 4 °C for 24 and 48 h. All samples were analyzed for lead by atomic absorption spectrophotometry. Based on a blood lead concentration of 0.2 ppm wet weight as positive evidence for lead exposure, the protoporphyrin technique resulted in overall error rates of 29%, 20%, and 19% and false negative error rates of 47%, 29% and 25% when hematofluorometric determinations were made on blood at 5 min, 24 h, and 48 h, respectively. False positive error rates were less than 10% for all three measurement times. The accuracy of the 24-h erythrocytic protoporphyrin classification of blood samples as positive or negative for lead exposure was significantly greater than the 5-min classification, but no improvement in accuracy was gained when samples were tested at 48 h. The false negative errors were probably due, at least in part, to the lag time between lead exposure and the increase of blood protoporphyrin concentrations. False negatives resulted in an underestimation of the true number of canvasbacks exposed to lead, indicating that hematofluorometry provides a conservative estimate of lead exposure.The U.S. Government's right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledgedDeceased 相似文献
7.
A national framework for monitoring and reporting on environmental sustainability in Canada 总被引:1,自引:0,他引:1
Ian B. Marshall C. A. Scott Smith Corrine J. Selby 《Environmental monitoring and assessment》1996,39(1-3):25-38
In 1991, a collaborative project to revise the terrestrial component of a national ecological framework was undertaken with a wide range of stakeholders. This spatial framework consists of multiple, nested levels of ecological generalization with linkages to existing federal and provincial scientific databases. The broadest level of generalization is the ecozone. Macroclimate, major vegetation types and subcontinental scale physiographic formations constitute the definitive components of these major ecosystems. Ecozones are subdivided into approximately 200 ecoregions which are based on properties like regional physiography, surficial geology, climate, vegetation, soil, water and fauna. The ecozone and ecoregion levels of the framework have been depicted on a national map coverage at 1:7 500 000 scale. Ecoregions have been subdivided into ecodistricts based primarily on landform, parent material, topography, soils, waterbodies and vegetation at a scale (1:2 000 000) useful for environmental resource management, monitoring and modelling activities. Nested within the ecodistricts are the polygons that make up the Soil Landscapes of Canada series of 1:1 000 000 scale soil maps. The framework is supported by an ARC-INFO GIS at Agriculture Canada. The data model allows linkage to associated databases on climate, land use and socio-economic attributes. 相似文献
8.
9.
Bass B Economou V Lee CK Perks T Smith SA Yip Q 《Environmental monitoring and assessment》2003,85(2):199-219
Indoor environmental health is now recognized as an important factor in preventing respiratory health problems in the United States. It is also a concern in Canada due to the amount of time that Canadians spend indoors because of cold weather and the potential for increased time indoors during the summer if theclimate warms. The negative health effects are often labeled assick building syndrome, but diagnosing a building or itsoccupants as sick is complicated by the variety of symptoms, thepresence of chronic versus acute symptoms and social andpsychological (socio-psychological) factors that may reduce theeffectiveness of an engineering solution. As a case study, thecontribution of various factors to indoor environmental health,in three buildings at the University of Toronto, was examinedusing five different methods. The results indicate that theinhabitants of the buildings consider features other than airquality in considering building health such as design,maintenance, funding cuts and socio-psychological factors. 相似文献
10.
Dr Marianne Johansen Marian Knight Edward J. Maher Kim Smith Ian L. Sargent 《黑龙江环境通报》1995,15(10):921-931
Trophoblast deportation is known to occur in normal human pregnancy, but it is not yet clear whether these cells routinely enter the maternal peripheral circulation and are available as a source of fetal DNA for non-invasive prenatal diagnosis of genetic disorders. To resolve this issue requires an efficient method of enriching trophoblast from maternal blood combined with a means to confirm its identity. Five different techniques were tested on ten retroplacental blood samples to determine the most sensitive and operator-efficient method. Lysis of red cells alone gave the best recovery of trophoblast but had to be discounted, together with Ficoll density gradient centrifugation, due to the very low purity and the excessive time required. Fluorescence-activated cell sorting (FACS) of pre-enriched trophoblast resulted in the lowest recovery rate (8 per cent) despite a 3250-fold enrichment and a very high purity. Immunomagnetic beads (Dynabeads) coated with anti-CD 16 antibody proved to be the best method for the subsequent immunocytochemical characterization of deported trophoblast. However, IO beads coated with anti-CD45 antibody may be more useful for isolating trophoblast for prenatal diagnosis due to the high purity, enrichment (32-fold), and recovery rate (78 per cent) obtained with this method. 相似文献