全文获取类型
收费全文 | 2449篇 |
免费 | 422篇 |
国内免费 | 1171篇 |
专业分类
安全科学 | 180篇 |
废物处理 | 126篇 |
环保管理 | 334篇 |
综合类 | 2461篇 |
基础理论 | 260篇 |
污染及防治 | 178篇 |
评价与监测 | 262篇 |
社会与环境 | 214篇 |
灾害及防治 | 27篇 |
出版年
2024年 | 26篇 |
2023年 | 97篇 |
2022年 | 161篇 |
2021年 | 213篇 |
2020年 | 191篇 |
2019年 | 169篇 |
2018年 | 166篇 |
2017年 | 181篇 |
2016年 | 200篇 |
2015年 | 207篇 |
2014年 | 213篇 |
2013年 | 254篇 |
2012年 | 273篇 |
2011年 | 286篇 |
2010年 | 178篇 |
2009年 | 152篇 |
2008年 | 98篇 |
2007年 | 121篇 |
2006年 | 125篇 |
2005年 | 95篇 |
2004年 | 79篇 |
2003年 | 91篇 |
2002年 | 66篇 |
2001年 | 86篇 |
2000年 | 66篇 |
1999年 | 53篇 |
1998年 | 35篇 |
1997年 | 36篇 |
1996年 | 29篇 |
1995年 | 25篇 |
1994年 | 16篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1982年 | 1篇 |
排序方式: 共有4042条查询结果,搜索用时 530 毫秒
881.
882.
基于2003年1月至2005年6月用气相色谱法对太湖流域近地表大气中二氧化碳本底体积分数的监测资料,对太湖流域近地表大气二氧化碳体积分数的变化特征进行了分析研究。结果表明:在观测时段内,太湖流域近地表大气二氧化碳体积分数平均值为(413.7±19.2)×10-6,且呈上升的趋势,主要受人类活动、工农业生产和交通运输业发展的影响;二氧化碳体积分数季节变化明显,冬春季高,夏秋季低,冬季出现峰值,平均体积分数为(417.8±3.7)×10-6,夏季出现谷值,平均体积分数为(400.8±14.7)×10-6,一年中最高值(424.0±1.1)×10-6出现在12月份,最低值(387.7±1.4)×10-6出现在8月份,主要受源汇强度变化影响;二氧化碳体积分数日变化基本呈双峰态,这是源汇强度变化和边界层稳定程度相互作用的结果。 相似文献
883.
884.
徐新华 《生态与农村环境学报》1997,(3)
对1990年江浙沪地区人为氨排放进行了统计计算,结果表明江浙沪地区人为氨排放总量为769.30kt,主要的氨来源为化肥的使用、家畜以及能源的消耗,其中家畜占300%、化肥使用占250%、能源消耗占258%。江浙沪地区单位面积排放强度为3.65t/km2,而人均排放量为626kg/人。 相似文献
885.
886.
Chan-Wei Wu Rong-Horng Chen Jen-Yung Pu Ta-Hui Lin 《Atmospheric environment (Oxford, England : 1994)》2004,38(40):7093
Ethanol–gasoline-blended fuel was tested in a conventional engine under various air–fuel equivalence ratios (λ) for its performance and emissions. The amount of fuel injection was adjusted manually by an open-loop control system using a CONSULT controller. It was found that without changing throttle opening and injection strategy, λ could be extended to a leaner condition as ethanol content increased. The results of engine performance tests showed that torque output would increase slightly at small throttle valve opening when ethanol–gasoline-blended fuel was used. It was also shown that CO and HC emissions were reduced with the increase of ethanol content in the blended fuel, which resulted from oxygen enrichment. At an air–fuel equivalence ratio slightly larger than one, the smallest amounts of CO and HC and the largest amounts of CO2 resulted. It was noted that under the lean combustion condition, CO2 emission was controlled by air–fuel equivalence ratio; while under the rich combustion condition, CO2 emission is offset by CO emission. It was also found that CO2 emission per unit horse power output for blended fuel was similar or less than that for gasoline fuel. From the experimental data, the optimal ethanol content in the gasoline and air–fuel equivalence ratio in terms of engine performance and air pollution was found. 相似文献
887.
Sergey Kakareka Sergey Gromov Jozef Pacyna Tamara Kukharchyk 《Atmospheric environment (Oxford, England : 1994)》2004,38(40):7101-7109
As the result of our research, the specific procedures to use emission factor methodology were developed and applied for trace metal emission evaluation into the atmosphere over the territory of the former Soviet Union. The existing data on heavy metal emissions were revised as background information from official sources and expert estimations. Source categories and different initial information as well as the concept of spatial emission distribution were defined and observed. The calculated atmospheric emissions of lead, cadmium and mercury were produced among the main source categories of 12 NIS countries for 1990, 1995 and 1997, using modified emission coefficients.Total cadmium emissions into the atmosphere from determined source categories were estimated as 388.4 tonnes in 1990 for the whole domain with reduction by up to 207.0 tonnes per year for 1997. Mercury emissions were estimated as equal to 303.2 tonnes in 1990 and 159.8 tonnes in 1997. Lead emission amounted to 24903.0 tonnes in 1990, and 9652.5 tonnes in 1997.The results of the evaluation demonstrated the general trends of atmospheric heavy metal emissions with a greater decrease during the first half of the 1990s followed later by the rather stable level to be explained by recession in industrial activity and fuel consumption in NIS in that period. The significant spatial variations of atmospheric emissions over vast territories are described based on the results of their distribution according to 1×1 degree grid with remarkably higher values in the location of industrial cities. 相似文献
888.
综述了国内外几种常用的机动车颗粒污染物排放因子的确定方法,介绍了各模型的使用概况及其优缺点,最后提出对机动车颗粒污染物排放因子应深入开展有关研究。 相似文献
889.
以上海市某冶金企业为例,该厂有正常运行的冶炼炉13座,每年向大气中排放大量颗粒污染物.基于高斯倾斜烟羽模式,整理了2003年上海市全年的气象资料,运用气象概率矩阵法计算了该厂直排点源及无组织面源排放颗粒物的影响,得出了厂区内无组织排放颗粒物落地浓度等值线图.计算结果表明,厂区内颗粒物污染主要来自无组织面源,污染集中在厂区中心的污染源附近;直排点源对环境的影响较小,污染主要集中在下风向. 相似文献
890.
A. K. Djien Liem Job A. van Zorge 《Environmental science and pollution research international》1995,2(1):46-56
Several countries have put much effort in dioxin research programmes with the aim to assess the risks of dioxin exposure,
to identify dioxin sources and to quantify their contribution to environmental emissions and human exposure. In this review,
the accent has been put on: sources of dioxins and their contribution to the total dioxin emissions, sources of human exposure
and their contribution to exposure and measures to reduce emission and exposure. The information from countries with existing
dioxin regulations is reviewed and compared. Uncertainties which hamper comparability of data are indicated. Results of measures
and expectations for the near future are presented. 相似文献