全文获取类型
收费全文 | 441篇 |
免费 | 66篇 |
国内免费 | 87篇 |
专业分类
安全科学 | 68篇 |
废物处理 | 10篇 |
环保管理 | 115篇 |
综合类 | 238篇 |
基础理论 | 70篇 |
污染及防治 | 20篇 |
评价与监测 | 32篇 |
社会与环境 | 20篇 |
灾害及防治 | 21篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 28篇 |
2021年 | 21篇 |
2020年 | 18篇 |
2019年 | 26篇 |
2018年 | 20篇 |
2017年 | 21篇 |
2016年 | 27篇 |
2015年 | 21篇 |
2014年 | 24篇 |
2013年 | 34篇 |
2012年 | 38篇 |
2011年 | 26篇 |
2010年 | 19篇 |
2009年 | 25篇 |
2008年 | 17篇 |
2007年 | 33篇 |
2006年 | 19篇 |
2005年 | 26篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 17篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1971年 | 5篇 |
排序方式: 共有594条查询结果,搜索用时 15 毫秒
11.
12.
The Multiple Streams Framework offers a theoretical account of how policy proposals move from latent possibilities to becoming favored for implementation. We apply this framework in the context of the policy response to the 2013–2014 flooding of the Somerset Levels and Moors. Stakeholder interviews and analysis of news media coverage evidence the way in which a specific policy option that had fallen out of favor with the national Environment Agency – dredging – came to the fore and was eventually adopted during the period in which the conjunction of problem, policy, and political pressures came to a head. Local political activists mobilized a wider campaign with the help of social media and capitalized on national political sensitivities to successfully promote dredging. What is less clear is the longevity of the policy reversal, given funding constraints. 相似文献
13.
14.
15.
新安江流域土地利用结构对水质的影响 总被引:12,自引:4,他引:8
以新安江上游流域为研究区域,用该流域2010年5月TM遥感影像图作为底图,通过实地野外调查获取了新安江流域的土地利用图.运用ArcGIS的水文、空间分析功能,将流域划分为8个子流域,并分析各子流域的土地利用结构.根据2010年1~12月的水质监测数据,分析TN、TP、高锰酸盐指数、NH4+-N、粪大肠菌群的时空变化特征,以及与土地利用结构之间的定量关系.结果表明,TN和NH4+-N有明显的时间变化特征,为枯时期>丰水期>平水期,而其他几种指标没有明显的时间变化.在空间上,整体上呈现出渔梁、浦口污染最为严重.流域内土地利用结构与水质之间的相关关系表现为:耕地、水体、建筑用地起源作用,林地、草地起汇作用.在年度上看,耕地对TN、NH4+-N、高锰酸盐指数影响最大,草地对TP影响最大;不同水期上,枯水期和丰水期,对各指标影响最大的土地利用类型为耕地,在平水期,对TN、TP、粪大肠菌群影响最大的土地利用类型分别为耕地、草地、林地. 相似文献
16.
采用稀释与接种法测定工业废水中的BOD5,并结合CODcr的测定结果,分析影响BOD5测定的因素如稀释倍数、接种液配比等条件进行试验后,得出了最佳试验条件,从而达到提高测定BOD5准确度的目的。 相似文献
17.
空间相关性对大跨度空间结构的影响不容忽视。本文采用动力时程分析方法对圆柱面巨型网格结构进行了多点激励下的地震响应分析,并与一致激励下的结构地震响应进行对比,探讨了主体结构单独承载和子结构参与协同承载这2种情况下,不同行波激励对结构关键节点和杆件响应的影响及其变化特点;通过比较分析结构在多点激励和一致激励下的响应差异,得出圆柱面巨型网格结构在地震输入时需考虑多点激励的结论,可供该类结构的抗震设计参考。 相似文献
18.
Humic substances 总被引:2,自引:1,他引:1
Steinberg CE Meinelt T Timofeyev MA Bittner M Menzel R 《Environmental science and pollution research international》2008,15(2):128-135
GOAL, SCOPE AND BACKGROUND: Freshwater bodies which chemistry is dominated by dissolved humic substances (HS) seem to be the major type on Earth, due to huge non-calcareous geological formations in the Northern Hemisphere and in the tropics. Based on the paradigm of the inertness of being organic, direct interactions of dissolved HS with freshwater organisms are mostly neglected. However, dissolved organic carbon, the majority of which being HS, are natural environmental chemicals and should therefore directly interact with organisms. Major results that widened our perspective on humic substance ecology come from experiments with the compost nematode, Caenorhabditis elegans, which behaved contradictorily to textbook knowledge and provoked an in-depth re-consideration of some paradigms. APPROACH: To overcome old paradigms on HS and their potential interactions with organisms, we reviewed recent international literature, as well as 'grey' literature. We also include results from own ongoing studies. RESULTS: This review focuses on direct interactions of dissolved HS with freshwater organisms and disregards indirect effects, such as under-water light quenching. Instead we show with some macrophyte and algal species that HS adversely interfere with photosynthesis and growth, whereby closely related algal species show different response patterns. In addition to this, HS suppress cyanobacteria more than eukaryotic algae. Quinones in the HS appear to be the effective structure. Furthermore, HS can modulate the offspring numbers in the nematode C. elegans and cause feminization of fish and amphibians--they possess hormone-like properties. The ecological consequences of this potential remain obscure at present. HS also have the potential to act as chemical attractants as shown with C. elegans and exert a mild chemical stress upon aquatic organisms in many ways: induction of molecular chaperons (stress proteins), induction and modulation of biotransformation and anti-oxidant enzymes. Furthermore, they produce an oxidative stress with lipidperoxidation as one clear symptom or even stress defense strategy. Stronger chemical stresses by HS may even lead to teratogenic effects as shown with fish embryos; all physiological responses to HS-mediated stress require energy, which were compensated on the expense of yolk as shown with zebra fish embryos. One Finnish field survey supports the view of a strong chemical stress, as the weight yield in fish species decreases with increasing HS content in the lakes. DISCUSSION: HS exert a variety of stress symptoms in aquatic and compost organisms. According to current paradigms of ecotoxicology, these symptoms have to be considered adverse, because their compensation consumes energy which is deducted from the main metabolism. However, the nematode C. elegans looks actively for such stressful environments, and this behavior is only understandable in the light of new paradigms of aging mechanisms, particularly the Green Theory of Aging. In this respect, we discuss the mild HS-mediated stress to aquatic and compost organisms. New empirical findings with HS themselves and HS building blocks appear to be consistent with this emerging paradigm and show that the individual lifespan may be expanded. At present the ecological consequences of these findings remain obscure. However, a multiple-stress resistance may be acquired which improves the individual fitness in a fluctuating environment. CONCLUSIONS: It appears that dissolved HS have to be considered abiotic ecological driving forces, somewhat less obvious than temperature, nutrients, or light. PERSPECTIVES: The understanding of the ecological control by dissolved humic substances is still fragmentary and needs to be studied in more details. 相似文献
19.
The comparison of increasing doses of a treatment to a negative control is frequently part of toxicological studies. For normally distributed data Williams (1971, 1972) introduced a maximum likelihood test under total order restriction. But until now there seems to have been no solution for the arbitrary unbalanced case. According to the idea proposed by Robertson et al. (1988) we will apply in this article the basic concept of Williams on the class of multiple contrast tests for the general unbalanced parametric set-up. Simulation results for size and power and two examples for estimating the minimal toxic dose (MTD) are given. 相似文献
20.
城市污泥模拟堆肥过程中高温菌群的筛选、鉴定及降解效果 总被引:5,自引:1,他引:4
在城市污泥模拟堆肥过程的高温期通过平板培养法筛选出一组强化菌群.该组菌群不但可以分解污泥有机质,还可以分解淀粉、蛋白质、油脂、纤维素等大分子有机物.经鉴定,筛选出的菌种分别为地衣芽孢杆菌(B.licheniformis)、短小芽孢杆菌(B.pumilus)、高温放线菌(Thermoactinomyces)、凝结芽孢杆菌(B.coagulans)、枯草芽孢杆菌(B.subtilis);将菌株两两接种到平板,发现各菌株间可以共存.将上述菌种混合后添加到堆肥样品中,其有机质去除率、脱氢酶增加率、比耗氧速率SOUR增加率均高出不加菌样品40%以上,表明该组菌群具有使堆肥腐熟进程加快的应用潜力. 相似文献