全文获取类型
收费全文 | 21008篇 |
免费 | 1377篇 |
国内免费 | 3848篇 |
专业分类
安全科学 | 1524篇 |
废物处理 | 221篇 |
环保管理 | 4578篇 |
综合类 | 11512篇 |
基础理论 | 2632篇 |
环境理论 | 21篇 |
污染及防治 | 1508篇 |
评价与监测 | 2496篇 |
社会与环境 | 1202篇 |
灾害及防治 | 539篇 |
出版年
2024年 | 81篇 |
2023年 | 360篇 |
2022年 | 566篇 |
2021年 | 695篇 |
2020年 | 809篇 |
2019年 | 618篇 |
2018年 | 592篇 |
2017年 | 788篇 |
2016年 | 918篇 |
2015年 | 929篇 |
2014年 | 1044篇 |
2013年 | 1379篇 |
2012年 | 1319篇 |
2011年 | 1710篇 |
2010年 | 1051篇 |
2009年 | 1392篇 |
2008年 | 1088篇 |
2007年 | 1395篇 |
2006年 | 1193篇 |
2005年 | 933篇 |
2004年 | 790篇 |
2003年 | 869篇 |
2002年 | 741篇 |
2001年 | 638篇 |
2000年 | 683篇 |
1999年 | 555篇 |
1998年 | 458篇 |
1997年 | 416篇 |
1996年 | 338篇 |
1995年 | 273篇 |
1994年 | 294篇 |
1993年 | 216篇 |
1992年 | 175篇 |
1991年 | 130篇 |
1990年 | 79篇 |
1989年 | 68篇 |
1988年 | 69篇 |
1987年 | 57篇 |
1986年 | 56篇 |
1985年 | 37篇 |
1984年 | 47篇 |
1983年 | 36篇 |
1982年 | 50篇 |
1981年 | 43篇 |
1980年 | 51篇 |
1979年 | 35篇 |
1978年 | 36篇 |
1977年 | 24篇 |
1974年 | 17篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
111.
112.
Bioindicator organisms: Heavy metal pollution evaluation in the Ionian Sea (Mediterranean Sea—Italy)
Trace metal concentrations of mercury, cadmium, lead and chromium in Patella caerulea, and Mullus barbatus were investigated to provide information on pollution of Ionian Sea, since these metals have the highest toxic potential. High chromium levels (0.47–0.97 g g–1 ww) were registered in limpet samples collected from two station near the Gulf of Taranto, while elevated concentration of mercury (0.31–1.50 g g–1 ww) were found in mullet specimens from Sicily. The metal concentrations recorded at the clean stations may be considered as useful background levels to which to refer for comparison within the Mediterranean area. On the contrary, the high levels of chromium and mercury found respectively in the areas near the Gulf of Taranto and at Capo Passero being of concern in terms of environmental health need frequent monitoring. 相似文献
113.
Selecting Socio-Economic Metrics for Watershed Management 总被引:1,自引:0,他引:1
The selection of social and economic metrics to document baseline conditions and analyze the dynamic relationships between
ecosystems and human communities are important decisions for scientists, managers, and watershed citizens. A large variety
of social and economic data is available but these have limited use without theoretical frameworks. In this paper, several
frameworks for reviewing social-ecosystem relations are offered, namely social sanctions, sense of place, civic structure,
and cultural differences. Underlying all of these frameworks are attitudes, beliefs, values, and norms that affect which questions
are asked and which indicators are chosen. Much work and significant challenges remain in developing a standard set of spatially
based socio-economic metrics for watershed management. 相似文献
114.
Mehaffey MH Nash MS Wade TG Ebert DW Jones KB Rager A 《Environmental monitoring and assessment》2005,107(1-3):29-44
The Catskill/Delaware reservoirs supply 90% of New York City’s drinking water. The City has implemented a series of watershed protection measures, including land acquisition, aimed at preserving water quality in the Catskill/Delaware watersheds. The objective of this study was to examine how relationships between landscape and surface water measurements change between years. Thirty-two drainage areas delineated from surface water sample points (total nitrogen, total phosphorus, and fecal coliform bacteria concentrations) were used in step-wise regression analyses to test landscape and surface-water quality relationships. Two measurements of land use, percent agriculture and percent urban development, were positively related to water quality and consistently present in all regression models. Together these two land uses explained 25 to 75% of the regression model variation. However, the contribution of agriculture to water quality condition showed a decreasing trend with time as overall agricultural land cover decreased. Results from this study demonstrate that relationships between land cover and surface water concentrations of total nitrogen, total phosphorus, and fecal coliform bacteria counts over a large area can be evaluated using a relatively simple geographic information system method. Land managers may find this method useful for targeting resources in relation to a particular water quality concern, focusing best management efforts, and maximizing benefits to water quality with minimal costs.The United States Environmental Protection Agency through its Office of Research and Development funded and managed the research described here. It has been subjected to Agency’s administrative review and approved for publication as an EPA document. 相似文献
115.
Evaluation of Water Quality in the Chillán River (Central Chile) Using Physicochemical Parameters and a Modified Water Quality Index 总被引:4,自引:0,他引:4
Debels P Figueroa R Urrutia R Barra R Niell X 《Environmental monitoring and assessment》2005,110(1-3):301-322
The Chillán River in Central Chile plays a fundamental role in local society, as a source of irrigation and drinking water,
and as a sink for urban wastewater. In order to characterize the spatial and temporal variability of surface water quality
in the watershed, a Water Quality Index (WQI) was calculated from nine physicochemical parameters, periodically measured at
18 sampling sites (January–November 2000). The results indicated a good water quality in the upper and middle parts of the
watershed. Downstream of the City of Chillán, water quality conditions were critical during the dry season, mainly due to
the effects of the urban wastewater discharge. On the basis of the results from a Principal Component Analysis (PCA), modifications
were introduced into the original WQI to reduce the costs associated with its implementation. WQIDIR2 and WQIDIR, which are both based on a laboratory analysis (Chemical Oxygen Demand) and three (pH, temperature and conductivity), respectively,
four field measurements (pH, temperature, conductivity and Dissolved Oxygen), adequately reproduce the most important spatial
and temporal variations observed with the original index. They are proposed as useful tools for monitoring global water quality
trends in this and other, similar agricultural watersheds in the Chilean Central Valley. Possibilities and limitations for
the application of the used methodology to watersheds in other parts of the world are discussed. 相似文献
116.
117.
详细介绍了“城市空气质量日报自动发布系统”的开发背景和开发过程 ,并对系统整体的架构和所用到的技术作了针对性的说明 ,阐明了作者对此类系统的前景和发展方向的看法。 相似文献
118.
质量保证体系是网格实测法环境空气质量监测优化布点研究工作的重要组成 ,该体系可确保实测数据准确可靠和研究成果质量 ,具有可操作性并已在实践中应用 ,取得满意效果 相似文献
119.
120.
The Variability of Estimates of Variance, and Its Effect on Power Analysis in Monitoring Design 总被引:1,自引:0,他引:1
Power analysis can be a valuable aid in the design of monitoringprograms. It requires an estimate of variance, which may come from a pilot study or an existing study in a similar habitat. For marine benthic infauna, natural variation in abundances canbe considerable, raising the question of reliability of varianceestimates. We used two existing monitoring programs to generatemultiple estimates of variance. These estimates were found to differ from nominated best estimates by 50% or more in 43% of cases, in turn leading to under or over-estimation of samplesize in the design of a notional monitoring program. The twostudies, from the same general area, using the same samplingmethods and spanning a similar time scale, gave estimatesvarying by more than an order of magnitude for 25% of taxa.We suggest that pilot studies for ecological monitoring programsof marine infauna should include at least two sampling times. 相似文献