全文获取类型
收费全文 | 272926篇 |
免费 | 16095篇 |
国内免费 | 40018篇 |
专业分类
安全科学 | 24243篇 |
废物处理 | 11942篇 |
环保管理 | 33006篇 |
综合类 | 109674篇 |
基础理论 | 53357篇 |
环境理论 | 228篇 |
污染及防治 | 56603篇 |
评价与监测 | 17206篇 |
社会与环境 | 15586篇 |
灾害及防治 | 7194篇 |
出版年
2024年 | 853篇 |
2023年 | 3957篇 |
2022年 | 9499篇 |
2021年 | 9499篇 |
2020年 | 8936篇 |
2019年 | 7165篇 |
2018年 | 8513篇 |
2017年 | 10181篇 |
2016年 | 10350篇 |
2015年 | 9733篇 |
2014年 | 11528篇 |
2013年 | 22701篇 |
2012年 | 16353篇 |
2011年 | 18250篇 |
2010年 | 16054篇 |
2009年 | 15930篇 |
2008年 | 16165篇 |
2007年 | 15806篇 |
2006年 | 14861篇 |
2005年 | 11576篇 |
2004年 | 8996篇 |
2003年 | 7977篇 |
2002年 | 7047篇 |
2001年 | 6540篇 |
2000年 | 5622篇 |
1999年 | 3887篇 |
1998年 | 2747篇 |
1997年 | 2501篇 |
1996年 | 2613篇 |
1995年 | 2735篇 |
1994年 | 2421篇 |
1993年 | 1856篇 |
1992年 | 1884篇 |
1991年 | 1774篇 |
1990年 | 1634篇 |
1989年 | 1538篇 |
1988年 | 1334篇 |
1987年 | 1208篇 |
1986年 | 1135篇 |
1985年 | 1232篇 |
1984年 | 1319篇 |
1983年 | 1294篇 |
1982年 | 1332篇 |
1981年 | 1235篇 |
1980年 | 1006篇 |
1979年 | 1046篇 |
1978年 | 900篇 |
1977年 | 800篇 |
1973年 | 717篇 |
1972年 | 709篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
V. Thomas Parker 《Conservation biology》2002,16(5):1444-1446
95.
96.
97.
98.
To prevent acid mine drainage arising from oxygen and water penetration of sulphide-rich mine tailings, the tailings are covered with layers of dry sealing material. Plant roots have a great ability to penetrate dense materials, and if the roots are able to penetrate the sealing layer of a tailings deposit, its oxygen-shielding properties could be reduced. The objective of this study was to evaluate whether plant roots are able to penetrate sealing layers covering mine tailings deposits. Root penetration into layers of various sealing materials, such as clayey moraine (clay, 8-10%; silt, 22-37%; sand, 37-55%; gravel, 15-18%), moraine (unspecified), 6-mm bentonite (kaolin clay) fabric, lime and clay, Cefyll (mixture of pulverized coal fly ash, cement and water) and a mixture containing biosludge (30-35%) and bioashes (65-70%), was investigated. In the field, roots were studied by digging trenches alongside vegetation growing in 3- and 10-year-old mine sites. In the greenhouse root growth of Betula pendula, Pinus sylvestris, Poa pratensis and Salix viminalis were studied in compartments where the plants had been growing for 22 months. The results from the field experiment indicated that roots are able to penetrate both deep down in the cover layer (1.7 m) and also into the sealing layers of various materials, and even to penetrate hard Cefyll. The addition of nutrients in the top cover reduced deep root growth and thereby also penetration through the sealing layer. Low hydraulic conductivity of the sealing layer or a thick cover layer had less effect on root penetration. In the greenhouse experiment roots did not penetrate the thin bentonite fabric, due to low pH (2.1-2.7) that was created from the underlying weathered mine tailings. The clayey moraine was penetrated by all species used in the greenhouse experiment; Pinus sylvestris had the greatest ability to penetrate. To prevent root penetration of the other sealing layer, a suitable condition for the plants should be created in the upper part of the cover layer, namely a sufficient amount of plant nutrients. However, to define such a condition is difficult since different plant species have different requirements. 相似文献
99.
This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997. 相似文献
100.