全文获取类型
收费全文 | 739篇 |
免费 | 27篇 |
国内免费 | 251篇 |
专业分类
安全科学 | 34篇 |
废物处理 | 19篇 |
环保管理 | 89篇 |
综合类 | 465篇 |
基础理论 | 119篇 |
污染及防治 | 214篇 |
评价与监测 | 58篇 |
社会与环境 | 17篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 30篇 |
2021年 | 22篇 |
2020年 | 23篇 |
2019年 | 29篇 |
2018年 | 24篇 |
2017年 | 24篇 |
2016年 | 42篇 |
2015年 | 56篇 |
2014年 | 52篇 |
2013年 | 61篇 |
2012年 | 65篇 |
2011年 | 68篇 |
2010年 | 56篇 |
2009年 | 70篇 |
2008年 | 64篇 |
2007年 | 66篇 |
2006年 | 47篇 |
2005年 | 25篇 |
2004年 | 28篇 |
2003年 | 20篇 |
2002年 | 30篇 |
2001年 | 15篇 |
2000年 | 21篇 |
1999年 | 11篇 |
1998年 | 2篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有1017条查询结果,搜索用时 421 毫秒
761.
通过对水中氮的内循环及氮支出的叙述,分析了屠宰废水经SBR法处理后氨氮升高的原因,并提出了改进措施。 相似文献
762.
763.
Amrita G. Desoyza Walter G. Whitford Sandra J. Turner Justin W. Van Zee Alan R. Johnson 《Environmental monitoring and assessment》2000,64(1):153-166
The most important function of watersheds in the western U.S. is the capacity to retain soil and water, thereby providing stability in hydrologic head and minimizing stream sediment loads. Long-term soil and water retention varies directly with vegetation cover. Data on ground cover and plant species composition were collected from 129 sites in the Rio Grande drainage of south-central New Mexico. This area was previously assessed by classification of Advanced Very High Resolution Radiometry (AVHRR) imagery. The classification of irreversibly degraded sites failed to identify most of the severely degraded sites based on size of bare patches and 35% of the sites classified as degraded were healthy based on mean bare patch size and vegetation cover. Previous research showed that an index of unvegetated soil (bare patch size and percent of ground without vegetative cover) was the most robust indicator of the soil and water retention function. Although the regression of mean bare patch size on percent bare ground was significant (p < 0.001), percent bare ground accounted for only 11% of the variability in bare patch size. Therefore bare patch size cannot be estimated from data on percent bare ground derived from remote sensing. At sites with less than 25% grass cover, and on sites with more than 15% shrub cover, there were significant relationships between percent bare soil and mean bare patch size (p < 0.05). Several other indicators of ecosystem health were related to mean bare patch size: perennial plant species richness (r = 0.6, p < 0.0001), percent cover of increaser species (r = 0.5, p < 0.0001) and percent cover of forage useable by livestock (r = 0.62, p < 0.0001). There was no relationship between bare patch size and cover of species that are toxic to livestock. In order to assess the ability of western rangeland watersheds to retain soil and water using remote sensing, it will be necessary to detect and estimate sizes of bare patches ranging between at least 0.5 m in diameter to several meters in diameter. 相似文献
764.
氮氧化物的污染控制对策 总被引:8,自引:0,他引:8
详细地介绍了日本针对不同的排放源--固定源和流动源--所采取的氮氧化物污染控制对策。对固定源,在实施全国统一的排放标准的基础上,对于一些工厂相对集中、污染问题严重的地区实施总量控制,同时积极促进技术革新以及降低氮氧化物的排放;对流动源所采取的措施有,确定不同车型汽车排放尾气递减的短期目标和长期目标,实施汽车氮氧化物法,积极推进低公害车的普及。通过采取上述措施,在日本,固定源排放的氮氧化物得到了较好 相似文献
765.
The main objective of this research was to estimate the total mass of nitrogen discharged from various sources in Korea using
the mass balance approach. Three different nitrogen mass balances were presented: (1) agricultural activities including raising
crops and animal husbandry; (2) domestic activities, and (3) activities in forest and urban areas. These nitrogen balances
were combined to estimate riverine discharge of nitrogen to the ocean in national scale. Nitrogen inputs include atmospheric
deposition, biological nitrogen fixation, application of inorganic fertilizers/manures, animal feed/imported foodstuffs, and
meat/fish. Nitrogen outputs include ammonia volatilization, denitrification, human/animal waste generation, crop/meat production,
and riverine discharge to the ocean. The estimated total nitrogen input in Korea was 1,194.5 × 103 tons N/year. Nitrogen discharged into rivers was estimated as 408–422 × 103 tons N/year, of which 66–71% was diffuse in origin. The estimated diffuse discharges for land uses were estimated as 82 × 103 tons N/year from agricultural areas, 7 × 103 tons N/year from forestry and 75 × 103 tons N/year from urban and industrial areas. 相似文献
766.
福建泉州市东、西湖水体中氮的空间分布研究 总被引:1,自引:0,他引:1
初步探讨了东湖和西湖水体中氯的空间分布特征以及3种不同形态的氮与溶解氧的相关性.结果表明,(1)泉州东湖、西湖水体中总氮的平均含量分别为3.396、3.929mg/L,氨氮的平均含量分别为1.927、2.182mg/L,硝酸盐氮的平均含量分别为1.061、1.236mg/L,亚硝酸盐氮的平均含量分别为0.084、0.059 mg/L,东湖和西湖水体的主要氮素形式均是氨氮.(2)东湖出水口和位于动物园附近的采样点总氮、氨氮和亚硝酸盐氮浓度较其它采样点高,入水口、湖区北部及湖心区采样点的氨氤和硝酸盐氮的分布趋势基本一致.西湖东南部采样点总氮、氨氯、硝酸盐氯和亚硝酸盐氮的含量都较其它采样点高.(3)东湖水体的DO浓度与氨氛、硝酸盐氮和亚硝酸盐氯的含量都不具有相关性,而西湖水体的DO浓度与这3种形态氮显著相关. 相似文献
767.
于2012年10月—2013年8月对中国北方地区2种典型水库:山区水库(卧虎山、锦绣川)和引黄水库(鹊山、玉清)进行了采样调查,对其水质特征和富营养化现状进行分析研究。结果表明:2类水库水质的最大差异在于山区水库的氮含量显著高于引黄水库,这主要与水源、氮素来源和水库的进水方式有关。山区水库中SD与藻类生物量、TP关系密切;而引黄水库中,影响SD的环境因素较复杂,除藻类生物量和氮、磷外,碱度和水温也与SD密切相关。全年水平上,卧虎山水库营养状态指数显著高于其他水库,属中-富营养水体,锦绣川水库、鹊山水库和玉清水库均属中营养水平。时间上,同类型水库的营养状态指数季节变化基本一致。参与营养状态计算的4个因子中,Chla和TN对营养状态指数的贡献最大,表明这两者是引起2类水库营养状态加重的重要原因。典型的水源及进水方式、流域人类活动类型和强度是影响山区水库和引黄水库营养状态的主要外部因素。 相似文献
768.
Menglei Guo Ying Jiang Junxiang Xie Qianfei Cao Qun Zhang Adams Mabruk Chongjun Chen 《环境科学学报(英文版)》2022,34(5):55-64
The effects of different chemical oxygen demand(COD) concentrations on the anammox granular sludge with Bamboo Charcoal(BC) addition were evaluated in UASB reactor. The results showed that the average total nitrogen(TN) removal efficiency was reduced from85.9% to 81.4% when COD concentration was increased from 50 to 150 mg/L. However, the TN removal efficiency of BC addition reactors was dramatically 3.1%–6.4% higher than that without BC under different COD concentrations. The average diameter o... 相似文献
769.
文章研究了C/N对悬浮填料生物反应器脱氮效果的影响。出水中NH4+-N、NO2--N和NO3--N浓度以及pH值变化均受C/N的影响,实验得到的最佳C/N质量比为12∶1,TN去除率平均在85%。 相似文献