全文获取类型
收费全文 | 2604篇 |
免费 | 667篇 |
国内免费 | 1012篇 |
专业分类
安全科学 | 221篇 |
废物处理 | 120篇 |
环保管理 | 175篇 |
综合类 | 1737篇 |
基础理论 | 1429篇 |
污染及防治 | 402篇 |
评价与监测 | 122篇 |
社会与环境 | 35篇 |
灾害及防治 | 42篇 |
出版年
2024年 | 10篇 |
2023年 | 72篇 |
2022年 | 106篇 |
2021年 | 137篇 |
2020年 | 108篇 |
2019年 | 119篇 |
2018年 | 195篇 |
2017年 | 226篇 |
2016年 | 242篇 |
2015年 | 263篇 |
2014年 | 272篇 |
2013年 | 316篇 |
2012年 | 321篇 |
2011年 | 251篇 |
2010年 | 270篇 |
2009年 | 223篇 |
2008年 | 180篇 |
2007年 | 155篇 |
2006年 | 150篇 |
2005年 | 114篇 |
2004年 | 80篇 |
2003年 | 73篇 |
2002年 | 63篇 |
2001年 | 54篇 |
2000年 | 49篇 |
1999年 | 42篇 |
1998年 | 26篇 |
1997年 | 32篇 |
1996年 | 19篇 |
1995年 | 32篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有4283条查询结果,搜索用时 15 毫秒
31.
This paper deals with the release of base cations and Al3+ at the treatment with simulated acid rain (SAR) in main soil types collected from South China. Results showed that the amounts of base cations increased obviously when the pH value of simulated acid rain was lower than 3.0 or 3.5. Compared with the leaching of K+ and Na+, the leaching of Ca2+ and Mg2+ was affected by the pH value of SAR. Only when the amounts of base cations leached from soils exceeded the cation exchange capacity, the pH value of leaching solutions decreased sharply and the amounts of released Al3+ increased. The H+ buffering mechanisms, which were affected notonly by the pH values of SAR, but also by the types and solid components of soils, were proposed for the main soils studied. 相似文献
32.
33.
34.
毛细管气相色谱法分析1,3—丁二烯中炔烃杂质含量 总被引:2,自引:0,他引:2
介绍了一种毛细管毛相谱法测定1,3-丁烯中炔烃质含量的新试验方法,该方法以氮气为载气,采用氢火焰离子化检测器,样品经分离后,采用外标法定量,操作简便,准确。该方法还可用于1,3-丁二烯纯度分析 。 相似文献
35.
36.
37.
38.
上海市大气中NMHC,NOx,O3和SO2变化规律 总被引:7,自引:0,他引:7
通过对上海市大气中光化学主要污染物如NMHC、NOx、O3及SO2等的日变化监测,发现NOx、O3的日浓度变化与气象条件密切相关,高浓度O3多出现在晴朗少云,气温较高的大气条件下同步监测发现,O3与NOx呈负相关,相关系数r=-0.785;dmj SO2gn NMHCe tve vb r ghd sh ud ,sh ud txi ovt r= 相似文献
39.
Picea mongolica W. D. Xu. is an endemic species in China. The spruce forest is only found in semi-arid habitat in Inner Mongolia Autonomous Region of China. Based on the simulative defoliation experiment, it was proved that Picea mongolica seedlings had the compensatory and overcompensatory effects under the certain defoliation rate. The results of variance analysis on growth indexes showed that in PM I (natural regeneration seedlings under Picea mongolica forest), the differences of H1 (height in June 23 ) and H2 (height in September 3) were extremely significant, and the difference of D(diameter at the breast height) were not significant. In PM Ⅱ (artificial regeneration seedlings under Betula platyphylla Suk. forest), the difference of H1 was significant, the difference of H2 was not significant, and the difference of D was extremely significant. The regression equations were established and the compensatory and overcompensatory points were obtained. In PM I, the compensatory points of H1, H2, and D were 0.7628, 0.7436, 0.5725, and the overcompensatory points were 0.6056, 0.5802 and 0.2909 respectively. In PM Ⅱ, the compensatory points of H1, H2, and D are 0.5012, 0.3421, 0.2488, and the overcompensatory points are 0.4137, 0.2633 and 0.0747 respectively. These results suggested that the induction of compensatory growth mechanisms in spruce seedlings required a threshold level of defoliation, and the insects in Picea mongolica forest could be controlled in a certain de clree. 相似文献
40.