全文获取类型
收费全文 | 4277篇 |
免费 | 328篇 |
国内免费 | 238篇 |
专业分类
安全科学 | 451篇 |
废物处理 | 39篇 |
环保管理 | 599篇 |
综合类 | 1608篇 |
基础理论 | 278篇 |
污染及防治 | 164篇 |
评价与监测 | 1527篇 |
社会与环境 | 73篇 |
灾害及防治 | 104篇 |
出版年
2024年 | 15篇 |
2023年 | 73篇 |
2022年 | 123篇 |
2021年 | 116篇 |
2020年 | 172篇 |
2019年 | 101篇 |
2018年 | 93篇 |
2017年 | 120篇 |
2016年 | 160篇 |
2015年 | 202篇 |
2014年 | 240篇 |
2013年 | 297篇 |
2012年 | 303篇 |
2011年 | 314篇 |
2010年 | 234篇 |
2009年 | 227篇 |
2008年 | 156篇 |
2007年 | 236篇 |
2006年 | 226篇 |
2005年 | 215篇 |
2004年 | 152篇 |
2003年 | 221篇 |
2002年 | 130篇 |
2001年 | 126篇 |
2000年 | 112篇 |
1999年 | 84篇 |
1998年 | 60篇 |
1997年 | 77篇 |
1996年 | 58篇 |
1995年 | 39篇 |
1994年 | 34篇 |
1993年 | 36篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有4843条查询结果,搜索用时 31 毫秒
951.
P. Steven Porter Robert C. Ward 《Journal of the American Water Resources Association》1991,27(4):687-700
ABSTRACT: The statistical analysis of data which have trace level measurements has traditionally been a two-step process in which data are first censored using criteria based on measurement precision, and then analyzed with statistical methods for censored data. The process might be more informative if data were left uncensored. In this paper, information loss attributable to censoring and measurement noise are assessed by comparing the sample mean and median of uncensored measurements with a log regression mean and median based on censored data. Measurements are derived from lognormal parent distributions which have random variability characteristic of trace level measurement. The relative performance of estimators used with error-free samples and with samples having measurement noise can be explained by differences between the probability distributions of parents and measurements. Measurement introduces bias and dispersion and transforms lognormal parent distributions toward greater symmetry. Estimates using uncensored data are less biased and more accurate than the log regression mean and median when censoring exceeds about 50 percent, and are not much worse at any fraction censored. For data with many (80 percent) results below the limit of detection, bias may be quite severe. 相似文献
952.
R. W. P. M. Laane J. Van Der Meer A. De Vries A. Van Der Giessen 《Environmental management》1990,14(2):221-227
During the winter period an inverse linear relation is found between the concentration of dissolved nutrients (phosphorus
and nitrogen) and salinity in the Dutch coastal zone. This indicates a conservative behavior of these compounds from the river,
through the estuary to the sea. During summer this relation is much more scattered because of biological processes. The physical
and statistical properties of the relationship between salinity and the concentration of dissolved inorganic phosphorus and
nitrogen are used to calculate when, where, and how many samples have to be taken in order to monitor a reduction of a compound
accurately. It appeared that at any given salinity in the estuary and in the sea, the winter period is the most suitable season
to detect a reduction of a given dissolved compound. The higher the salinity in the estuary, the more samples are required
to prove the reduction significantly. A reduction of only 10% cannot even be demonstrated by field measurements during summer
at salinities above 25. It is concluded that one cruise from the river to the sea, covering the salinities from 0 to 35 during
the winter period, aimed at establishing the relationship between the concentration and salinity by taking samples at a salinity
interval of for instance 1%, is sufficient to monitor a wide-ranging reduction of 10%–50% in both the fresh water and marine
water. This program must be combined with a sampling at a salinity of 0, directed to determine the riverine temporal variability. 相似文献
953.
利用云南早期温度层结探空实测资料对山区逆温的特征进行了分析,结果表明:干季逆温出现频率高,山区逆温维持时间长,逆温主要发生在低层。并对同一区域内代表不同下垫面的山区与河谷同期探空资料作了逆温层结的对比分析。 相似文献
954.
955.
956.
分析了室内环境污染的由来、危害及内容,提出了对室内环境污染进行检测与控制,指出对室内环境污染的一些防治对策,表明室内空气污染必将引起广泛的关注和重视. 相似文献
957.
对环境监测布点采样中的QC/QA以及由采样引起的误差来源做了简要分析,并对监测采样过程中QC/QA的操作提出了一些设想。 相似文献
958.
云南省省控地表水监测断面优化认证 总被引:1,自引:0,他引:1
通过对地表水监测点位的代表性、合理性、数据获取率、可操作性等指标的分析和论证,对设置欠合理的点位进行了调整,对存在漏设监测点或监测点不足的水域增设了点位,全面考虑了全省饮用水源地和城市综合整治定量考核对地表水环境的要求。 相似文献
959.
960.
为了处理生活垃圾,减少城市污染,保护环境,经过多年研究,制造开发出日处理焚烧150m^3生活垃圾的垃圾焚烧炉。在高温作业下,为了使工作人员能清晰观察炉内燃烧状况。配备了适用于垃圾焚烧炉的高温电视自动化监控系统。通过它可以在监控室内直接观测、掌握焚烧炉运行情况,从而改善了工人的工作条件,提高了工作效率,经专家审定.认为可以推广。文中主要介绍了电视监控系统的结构、性能等情况。 相似文献