收费全文 | 3807篇 |
免费 | 496篇 |
国内免费 | 1333篇 |
安全科学 | 497篇 |
废物处理 | 160篇 |
环保管理 | 310篇 |
综合类 | 2668篇 |
基础理论 | 567篇 |
污染及防治 | 821篇 |
评价与监测 | 216篇 |
社会与环境 | 196篇 |
灾害及防治 | 201篇 |
2024年 | 29篇 |
2023年 | 125篇 |
2022年 | 263篇 |
2021年 | 284篇 |
2020年 | 319篇 |
2019年 | 199篇 |
2018年 | 197篇 |
2017年 | 250篇 |
2016年 | 243篇 |
2015年 | 266篇 |
2014年 | 252篇 |
2013年 | 397篇 |
2012年 | 369篇 |
2011年 | 380篇 |
2010年 | 283篇 |
2009年 | 250篇 |
2008年 | 287篇 |
2007年 | 227篇 |
2006年 | 214篇 |
2005年 | 160篇 |
2004年 | 109篇 |
2003年 | 97篇 |
2002年 | 79篇 |
2001年 | 59篇 |
2000年 | 67篇 |
1999年 | 46篇 |
1998年 | 43篇 |
1997年 | 28篇 |
1996年 | 18篇 |
1995年 | 28篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
The Sanjiang Plain, the largest inland freshwater marshland in China, was extensive reclaimed into agricultural land. To assess the effects of marshland reclamation on Collembola, we investigated collembolan communities in a chronosequence of soybean plantations (2, 15, and 25 years) in Sanjiang marshland, Northeastern China. We found that: 1) the densities and species richness of Collembola were promoted after short-term (2 years) cultivation of soybean, but significantly decreased after medium-term cultivation (15 years); 2) the densities of epi-edaphic Collembola increased while the densities of hemi-edaphic Collembola decreased as the elongation of soybean cultivation; 3) compared with S0, two species of Collembola appeared while five species disappeared in S25. The changes of plant communities and the soil traits were supposed to be the key factors affecting the composition of soil Collembola. We thus suggest that original marshland should be saved for preserving high diversity and densities of Collembola in the Sanjiang Plain.
相似文献Hg emission flux from various land covers, such as forests, wetlands, and urban areas, have been investigated. China has the largest area of coalfield in the world, but data of Hg flux of coalfields, especially, those with coal fires, are seriously limited. In this study, Hg fluxes of a coalfield were measured using the dynamic flux chamber (DFC) method, coupled with a Lumex multifunctional Hg analyzer RA-915+ (Lumex Ltd., Russia). The results show that the Hg flux in Wuda coalfield ranged from 4 to 318 ng m?2 h?1, and the average value for different areas varied, e.g., coal-fire area 99 and 177 ng m?2 h?1; no coal-fire area 19 and 32 ng m?2 h?1; and backfilling area 53 ng m?2 h?1. Hg continued to be emitted from an underground coal seam, even if there were no phenomena, such as vents, cracks, and smog, of coal fire on the soil surface. This phenomenon occurred in all area types, i.e., coal-fire area, no coal-fire area, and backfilling area, which is universal in Wuda coalfield. Considering that many coalfields in northern China are similar to Wuda coalfield, they may be large sources of atmospheric Hg. The correlations of Hg emission flux with influence factors, such as sunlight intensity, soil surface temperature, and atmospheric Hg content, were also investigated for Wuda coalfield.
?