全文获取类型
收费全文 | 575篇 |
免费 | 54篇 |
国内免费 | 263篇 |
专业分类
安全科学 | 4篇 |
废物处理 | 15篇 |
环保管理 | 115篇 |
综合类 | 442篇 |
基础理论 | 227篇 |
污染及防治 | 48篇 |
评价与监测 | 19篇 |
社会与环境 | 22篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 20篇 |
2021年 | 16篇 |
2020年 | 21篇 |
2019年 | 27篇 |
2018年 | 18篇 |
2017年 | 25篇 |
2016年 | 20篇 |
2015年 | 36篇 |
2014年 | 40篇 |
2013年 | 74篇 |
2012年 | 47篇 |
2011年 | 53篇 |
2010年 | 50篇 |
2009年 | 36篇 |
2008年 | 18篇 |
2007年 | 52篇 |
2006年 | 35篇 |
2005年 | 30篇 |
2004年 | 42篇 |
2003年 | 33篇 |
2002年 | 27篇 |
2001年 | 19篇 |
2000年 | 17篇 |
1999年 | 17篇 |
1998年 | 22篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有892条查询结果,搜索用时 15 毫秒
71.
河流型硅藻水华研究进展 总被引:7,自引:0,他引:7
通过对硅藻水华发生机制相关文献的研究分析,对硅藻水华发生机制做了一般性探讨,并重点关注了河流型水华的发生机制的独特点。河流水华种类主要为中心硅藻纲,静水生态系统水华种类除中心硅藻纲还包括部分羽纹硅藻纲种类。河流水华硅藻种类对营养盐浓度、温度和光照等环境因子具有一定的适应范围。与静水生态系统相比,河流硅藻水华受气象和水文等物理指标的影响更为明显。河流硅藻水华中常具有时滞现象,其中由气象和水文因素引起的时滞现象最为明显。目前河流硅藻水华的防治仍然以上游水库下泄稀释为主,但是这种方法会造成一定的水资源浪费。河流水华硅藻的生理属性、硅藻水华对生态系统的影响、节水与抑制水华的统筹以及其他控制水华的方法都是未来河流硅藻水华研究的重点。 相似文献
72.
Spatial distribution of nutrient and phytoplankton variables is often illustrated using categorical mapping for each variable.
However, the assessment of eutrophication cannot be derived from a single parameter since a synthesis of the environmental
variables related to eutrophication is required. These shortcomings are further complicated since it is difficult to discriminate
between distinct trophic states along natural environmental gradients. In the present work, a methodological procedure for
quantitative assessment of eutrophication at a spatial scale was examined in the Gulf of Saronicos, Greece, based on a thematic
map generated from the synthesis of four variables characterising eutrophication. The categorical map of each variable was
developed using the Kriging interpolation method and four trophic levels were indicated (eutrophic, upper-mesotrophic, lower-mesotrophic
and oligotrophic) based on nutrient and phytoplankton concentration scaling. Multi-criteria choice methods were applied to
generate a final categorical map showing the four trophic levels in the area. This synthesis of categorical maps for assessing
eutrophication at a spatial scale is proposed as a methodological procedure appropriate for coastal management studies. 相似文献
73.
74.
Nutrient transfer functions: the site of integration between feeding behaviour and nutritional physiology 总被引:6,自引:0,他引:6
Summary. We describe and extend a graphical approach to quantitative nutrition that focuses on the interplay between behavioural and
physiological components of nutritional regulation. The site of integration is the nutrient transfer function, which is the
function describing the time course of nutrient transfer between serially connected nutritional compartments (e.g., from the gut to the blood). The relationship between the shape of the nutrient transfer function and the temporal patterns
of feeding determines the values of two key quantitative parameters of nutrition: the rate ('power') and the efficiency of nutrient acquisition. The approach can be extended to consider, in addition to the short-term behavioural and physiological
decisions made by animals, some ecological determinants and longer-term, life history consequences of such decisions. Most
importantly, this category of models can provide insights into the interplay among the various nutrients in an animal's diet.
We illustrate this using hypothetical examples, and also present preliminary data for the power-efficiency relationships of
protein and digestible carbohydrates in locusts. Finally, we consider existing evidence for the various means available to
these and other insects for regulating such relationships.
Received 24 September 1997; accepted 9 December 1997. 相似文献
75.
76.
2012年4~10月采用自制沉降颗粒收集装置收集主养草鱼和黄颡鱼池塘生态系统中沉降颗粒物,开展了颗粒物质的垂直沉降量以及沉降颗粒中碳氮磷等营养物质的组成及沉降通量的季节变化特征的研究。结果表明:养殖可以显著提高池塘颗粒物质的垂直沉降量,主养草鱼池塘中颗粒物质垂直沉降量显著高于主养黄颡鱼池塘(p0.01),且两种养殖模式池塘颗粒物质沉降量随着养殖时间推进有显著增加的趋势。主养草鱼的池塘中颗粒物质垂直沉降量在100.39~414.66g/(m2·d)之间变化,平均为224.46g/(m2·d),主养黄颡鱼池塘中沉降颗粒物质垂直沉降量在34.14~272.91g/(m2·d)之间变化,平均为155.18g/(m2·d)。两种养殖模式沉降颗粒的碳氮磷成分在养殖周期内的变化规律不明显但具有相似的变化趋势,主养黄颡鱼池塘沉降颗粒中TN、TC、TOC和TON的含量均比同时期主养草鱼高,且均随着养殖时间的推进,沉降颗粒中碳氮磷的总量呈增加趋势。两种养殖模式池塘沉降颗粒中的C/N比值与沉积物中的C/N比值较为接近,表明沉降颗粒与沉积物营养物质来源具有一定的相似性,同时养殖系统内养殖对象与其所处环境的相互依存和相互影响对颗粒物质的产生以及沉降具有重要作用。 相似文献
77.
Ruina Zhang Zhihua Li Yali Zhang Zhenyu Hang Meng Lu Haiguang Wang Xingdong Gao 《环境科学学报(英文版)》2022,34(11):112-121
Respirogram technology has been widely applied for aerobic process, however, the response of respirogram to anoxic denitrification is still unclear. To reveal such response may help to design a new method for the evaluation of the performance of denitrification. The size distribution of flocs measured at different denitrification moments demonstrated a clear expansion of flocs triggered by denitrification, during which higher specific endogenous and quasi-endogenous respiration rates (SOURe and SOURq) were also observed. Furthermore, SOURq increases exponentially with the specific denitrification rate (SDNR), suggesting that there should be a maximum SDNR in conventional activated sludge systems. Based on these findings, an index Rq/t, defined as the ratio of quasi-endogenous (OURq) to maximum respiration rate (OURt), is proposed to estimate the denitrification capacity that higher Rq/t indicates higher denitrification potential, which can be readily obtained without complex measurement or analysis, and it offers a novel and promising respirogram-based approach for denitrification estimation and control by taking measures to extend anoxic time to maintain its value at a high level within a certain range. 相似文献
78.
以亚热带北部皖南丘陵地区小流域定位实地观测为基础 ,研究了农林共存小流域氮素径流输出规律。发现小流域氮素径流输出季节性变化明显。降雨和施肥是影响这一变化的重要因子 ,模拟分析表明 ,它们与氮素输出之间具有很好的线性相关关系 相似文献
79.
80.
Kwang V. Lo Winnie W. I. Chan Selina K. Yawson Ping H. Liao 《Journal of environmental science and health. Part. B》2013,48(4):362-367
This study investigated the treatment of dairy manure using the microwave enhanced advanced oxidation process (MW-AOP) at pH 2. An experimental design was developed based on a statistical program using response surface methodology to explore the effects of temperature, hydrogen peroxide dosage and heating time on sugar production, nutrient release and solids destruction. Temperature, hydrogen peroxide dosage and acid concentration were key factors affecting reducing sugar production. The highest reducing sugar yield of 7.4% was obtained at 160°C, 0 mL, 15 min heating time, and no H2O2 addition. Temperature was a dominant factor for an increase of soluble chemical oxygen demand (SCOD) in the treated dairy manure. The important factors for volatile fatty acids (VFA) production were microwave temperature and hydrogen peroxide dosage. Temperature was the most important parameter, and heating time, to a lesser extent affecting orthophosphate release. Heating time, hydrogen peroxide dosage and temperature were significant factors for ammonia release. There was a maximum of 96% and 196% increase in orthophosphate and ammonia concentration, respectively at 160°C, 0.5 mL H2O2 and 15 min heating time. The MW-AOP is an effective method in dairy manure treatment for sugar production, nutrient solubilisation, and solids disintegration. 相似文献