全文获取类型
收费全文 | 10779篇 |
免费 | 133篇 |
国内免费 | 104篇 |
专业分类
安全科学 | 332篇 |
废物处理 | 518篇 |
环保管理 | 1440篇 |
综合类 | 1285篇 |
基础理论 | 2880篇 |
环境理论 | 2篇 |
污染及防治 | 3022篇 |
评价与监测 | 784篇 |
社会与环境 | 698篇 |
灾害及防治 | 55篇 |
出版年
2023年 | 53篇 |
2022年 | 111篇 |
2021年 | 90篇 |
2020年 | 79篇 |
2019年 | 91篇 |
2018年 | 166篇 |
2017年 | 164篇 |
2016年 | 248篇 |
2015年 | 186篇 |
2014年 | 266篇 |
2013年 | 892篇 |
2012年 | 344篇 |
2011年 | 486篇 |
2010年 | 386篇 |
2009年 | 435篇 |
2008年 | 513篇 |
2007年 | 527篇 |
2006年 | 461篇 |
2005年 | 400篇 |
2004年 | 353篇 |
2003年 | 405篇 |
2002年 | 354篇 |
2001年 | 516篇 |
2000年 | 342篇 |
1999年 | 203篇 |
1998年 | 151篇 |
1997年 | 145篇 |
1996年 | 147篇 |
1995年 | 168篇 |
1994年 | 139篇 |
1993年 | 114篇 |
1992年 | 131篇 |
1991年 | 124篇 |
1990年 | 136篇 |
1989年 | 135篇 |
1988年 | 95篇 |
1987年 | 95篇 |
1986年 | 73篇 |
1985年 | 98篇 |
1984年 | 94篇 |
1983年 | 90篇 |
1982年 | 90篇 |
1981年 | 79篇 |
1980年 | 65篇 |
1979年 | 72篇 |
1977年 | 55篇 |
1976年 | 52篇 |
1975年 | 54篇 |
1974年 | 53篇 |
1973年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
981.
982.
I. Vigano T. Rckmann R. Holzinger A. van Dijk F. Keppler M. Greule W.A. Brand H. Geilmann H. van Weelden 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5637-5646
Recent experiments have shown that dry and fresh leaves, other plant matter, as well as several structural plant components, emit methane upon irradiation with UV light. Here we present the source isotope signatures of the methane emitted from a range of dry natural plant leaves and structural compounds. UV-induced methane from organic matter is strongly depleted in both 13C and D compared to the bulk biomass. The isotopic content of plant methoxyl groups, which have been identified as important precursors of aerobic methane formation in plants, falls roughly halfway between the bulk and CH4 isotopic composition. C3 and C4/CAM plants show the well-established isotope difference in bulk 13C content. Our results show that they also emit CH4 with different δ13C value. Furthermore, δ13C of methoxyl groups in the plant material, and ester methoxyl groups only, show a similar difference between C3 and C4/CAM plants. The correlation between the δ13C of emitted CH4 and methoxyl groups implies that methoxyl groups are not the only source substrate of CH4.Interestingly, δD values of the emitted CH4 are also found to be different for C3 and C4 plants, although there is no significant difference in the bulk material. Bulk δD analyses may be compromised by a large reservoir of exchangeable hydrogen, but no significant δD difference is found either for the methoxyl groups, which do not contain exchangeable hydrogen. The δD difference in CH4 between C3 and C4 plants indicates that at least two different reservoirs are involved in CH4 emission. One of them is the OCH3 group, the other one must be significantly depleted, and contribute more to the emissions of C3 plants compared to C4 plants. In qualitative agreement with this hypothesis, CH4 emission rates are higher for C3 plants than for C4 plants. 相似文献
983.
984.
985.
986.
987.
988.
Joseph E. Odencrantz 《补救:环境净化治理成本、技术与工艺杂志》1998,8(3):7-16
MTBE in groundwater has been shown to travel over 1,000 feet downgradient from its source in several comprehensive field studies conducted across North America. The biodegradability of MTBE is examined by summarizing all the significant literature on the subject and by detailing the findings of recent field investigations of MTBE transport. In Orange County, California, the persistence of MTBE is analyzed and statistical representations of source variability are presented. Regional and far field transport of MTBE in groundwater sourced from underground gasoline storage tanks are summarized in comprehensive tables of frequency and plume length. Estimates of source mass and duration allow for comparison of associated plume size. The conclusion reached after reviewing all the available literature on MTBE is that its biodegradability seems slight and the size of the plumes are surprisingly large. Intrinsic or natural attenuation remedies for MTBE merit close scrutiny. 相似文献
989.
990.