全文获取类型
收费全文 | 771篇 |
免费 | 96篇 |
国内免费 | 87篇 |
专业分类
安全科学 | 267篇 |
废物处理 | 18篇 |
环保管理 | 76篇 |
综合类 | 343篇 |
基础理论 | 92篇 |
污染及防治 | 50篇 |
评价与监测 | 80篇 |
社会与环境 | 9篇 |
灾害及防治 | 19篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 33篇 |
2021年 | 36篇 |
2020年 | 46篇 |
2019年 | 38篇 |
2018年 | 21篇 |
2017年 | 32篇 |
2016年 | 29篇 |
2015年 | 39篇 |
2014年 | 44篇 |
2013年 | 50篇 |
2012年 | 62篇 |
2011年 | 61篇 |
2010年 | 36篇 |
2009年 | 38篇 |
2008年 | 47篇 |
2007年 | 51篇 |
2006年 | 37篇 |
2005年 | 35篇 |
2004年 | 25篇 |
2003年 | 29篇 |
2002年 | 20篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有954条查询结果,搜索用时 359 毫秒
41.
水中总氮测定相关问题的实验探讨 总被引:1,自引:0,他引:1
通过对国家标准测定方法《碱性过硫酸钾消解紫外分光光度法》进行水样中总氮的测定,进一步理解在220nm、275nm波长处进行吸光度测定的重要性。并提出:在已经知道水样中没有氨氮、亚硝酸盐氮,只有硝酸盐氮的情况下.就能通过快速的方法一即不加氧化剂、不加压,可以进行总无机氮的测定。快速测定无机总氮对于工程应用来说很有意义。因为国标的方法需要半天时间测定。而用此方法则仅需几分钟就可完成测定。、另外对于有机物对于测定结果的影响,参考吸光度比值(A275/A220×100%)应小于20%,越小越好,超过时应予鉴别。 相似文献
42.
43.
Malcolm J. R. Clark Paul H. Whitfield 《Journal of the American Water Resources Association》1994,30(6):1063-1079
ABSTRACT: Current conventions for reporting analytical results from environmental samples brings the objectives of laboratory scientists into conflict with those of environmental scientists. The objective of chemical analyses is to provide estimates of the true composition of samples. Reported results must reflect the analytical uncertainty. Current conventions require left-censoring of those results below the Limit of Detection. The objective of statistical interpretation of environmental data is to provide estimates of the characteristics of ecosystems. Such statistical analyses are often confounded by left-censoring of analytical results. We review the different points of view and propose a compromise which recognizes these conflicting perspectives. 相似文献
44.
James P. Hughes Steven P. Millard 《Journal of the American Water Resources Association》1988,24(3):521-531
ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied. 相似文献
45.
大空间室内火灾早期自动探测与定位研究 总被引:10,自引:0,他引:10
本文在深入研究早期火灾一般燃烧火焰在彩色影像上所呈现的光谱及运动特性基础上,首次提出利用彩色影像实时探测室内火灾的新方法,通过物方坐标与像方坐标的直接线性变换,实现了早期火灾的自动探测与空间定位,实验证明了该方法的有效性与稳健性,且具有巨大的应用前景。 相似文献
46.
Summary. Detection of heterospecific predators and prey
via chemical cues is well known, but only a few studies have
examined the potential for such discrimination in cannibalistic
systems. In newts, Notophthalmus viridescens, adults are
opportunistic predators of conspecific larvae. I used a laboratory
bioassay to determine whether larvae and adults distinguish
between chemical stimuli from members of the
different age classes. Larvae distinguished between chemical
stimuli from larvae and adults by decreasing their activity
only following exposure to stimuli from adults. Decreased
activity is consistent with an antipredator response in many
prey species, including larval newts. In contrast, adults
increased their activity and increased time spent in open
areas in response to stimuli from larvae, but not to stimuli
from adults. Increased activity is consistent with a feeding
response; adults also showed increased activity and
increased time in open areas in response to chemical stimuli
from familiar heterospecific prey (brine shrimp). The proximate
cue that allowed the newts to distinguish between the
different age classes is not associated with short-term
dietary differences because all stimulus animals were fed the
same prey. Stimulus strength was controlled by diluting the
stimulus solutions according to the volume of the stimulus
animal. Therefore, there appear to be intrinsic differences in
the chemical signatures of larval and adult newts. 相似文献
47.
48.
49.
50.