全文获取类型
收费全文 | 91295篇 |
免费 | 1240篇 |
国内免费 | 1101篇 |
专业分类
安全科学 | 3825篇 |
废物处理 | 3322篇 |
环保管理 | 14043篇 |
综合类 | 21221篇 |
基础理论 | 26551篇 |
环境理论 | 73篇 |
污染及防治 | 14749篇 |
评价与监测 | 5537篇 |
社会与环境 | 3766篇 |
灾害及防治 | 549篇 |
出版年
2022年 | 804篇 |
2021年 | 809篇 |
2020年 | 668篇 |
2019年 | 875篇 |
2018年 | 1169篇 |
2017年 | 1218篇 |
2016年 | 2206篇 |
2015年 | 1860篇 |
2014年 | 2606篇 |
2013年 | 9314篇 |
2012年 | 2265篇 |
2011年 | 2545篇 |
2010年 | 3351篇 |
2009年 | 3442篇 |
2008年 | 2062篇 |
2007年 | 1916篇 |
2006年 | 2305篇 |
2005年 | 2285篇 |
2004年 | 2603篇 |
2003年 | 2413篇 |
2002年 | 1985篇 |
2001年 | 2260篇 |
2000年 | 1991篇 |
1999年 | 1509篇 |
1998年 | 1376篇 |
1997年 | 1372篇 |
1996年 | 1493篇 |
1995年 | 1580篇 |
1994年 | 1495篇 |
1993年 | 1342篇 |
1992年 | 1323篇 |
1991年 | 1296篇 |
1990年 | 1227篇 |
1989年 | 1218篇 |
1988年 | 1045篇 |
1987年 | 982篇 |
1986年 | 991篇 |
1985年 | 1064篇 |
1984年 | 1155篇 |
1983年 | 1167篇 |
1982年 | 1174篇 |
1981年 | 1102篇 |
1980年 | 946篇 |
1979年 | 920篇 |
1978年 | 822篇 |
1977年 | 714篇 |
1976年 | 637篇 |
1975年 | 602篇 |
1973年 | 630篇 |
1972年 | 635篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
501.
Wiersma YF 《Environmental monitoring and assessment》2005,100(1-3):1-9
Environmental benchmarks are widely used in Canadian environmental assessment as a standard against which to monitor air or water quality in response to human activities in the environment. Recent work in Canada has developed the concept of ecological benchmarks as a complement to environmental benchmarks. However, implementation of ecological benchmarks may be challenging. This paper presents an analogy between ecological benchmarks and the more commonly used environmental benchmarks, as an attempt to increase understanding and use of ecological benchmarks in resource management, assessment, and monitoring. Ecological benchmarks, and their corresponding indicators, will be challenging to identify and use. However, through the use of the principles of adaptive management, effective ecological indicators and benchmarks can be established. Although it is essential that ecological benchmarks are site-specific, the analogy and general principles outlined here are applicable to assessment and monitoring in any part of the world. 相似文献
502.
A modular approach to Integrated Assessment modeling 总被引:1,自引:0,他引:1
In this paper, we present a new approach to model coupling that probably forms the methodological basis of a new generation of Integrated Assessment models. This approach respects the knowledge and expertise that is embodied in existing models and encourages their gradual evolution. Modularity is the guiding principle. Our approach is distinguished by the way modules are coupled which is based on an interplay of a job control module, a numerical coupling module, and a couple of stand-alone functional modules. The numerical coupling module - the core component - serves to treat the feedbacks between the functional modules. A first implemented example that couples an economic and a climate module by means of a two-phase meta-optimization is presented here. The algorithm and mathematical structure behind are discussed as well as important features such as convergence behavior and reliability. 相似文献
503.
504.
505.
506.
Summary As stated at the beginning of this paper conclusions reached thus far cannot be discussed in this paper. However, a great deal of information is available for examination.EPA displayed its ability to coordinate widely separated laboratories, both Federal and private, into a smooth working team in a very short period of time. A very comprehensive study plan was also developed and implemented quickly. EPA was fortunate to have already had GCA under contract when the emergency arose. In no small part the success of the field effort was due to the managerial and technical abilities of the GCA team.Within a period of 6 weeks a plan was developed, a prime contractor retained, subcontractors hired, and field activities begun. Within a period of 3 months in excess of 8600 field samples were collected and over 12,000 field and QC samples were analyzed. During this same period 2 major data systems were developed, debugged, and placed into operation.In short this EPA project was probably the most comprehensive multimedia field project ever attempted by EPA and certainly the data is being subjected to the most strenuous quality control measures ever imposed by this Agency. The entire program is presently under peer review and the results are being prepared for publication by EPA Headquarters.Note. Originally intended to be published as part of the special issue on Exposure Monitoring: An International Workshop (Las Vegas, Nevada, October 19–22, 1981). 相似文献
507.
508.
509.
In the present study, the influence of aluminium on the regeneration potential of leaf and stem-cuttings of Portulaca oleracea was studied in order to identify a terrestrial plant species as an alternate biomonitoring toolof fresh water environment. The leaves and stem cuttings of theterrestrial plant, P. oleracea grew well in the distilled water producing adventitious and lateral roots. The aluminium treated leaves and stem cuttings showed a reduction in the growthof the adventitious and lateral roots and increase in the decay of leaves and stem cuttings with increasing aluminium concentration. The tolerance index calculated for the leaves and the stem cuttings showed that the leaves were more sensitivethan stems to aluminium. Since all the parameters studied showedconcentration dependent changes, the terrestrial plant, P. oleracea can be considered a suitable biomonitoring tool of fresh water environment besides its usage in the Al toxicity testing. 相似文献
510.
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