全文获取类型
收费全文 | 1221篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 21篇 |
废物处理 | 12篇 |
环保管理 | 101篇 |
综合类 | 825篇 |
基础理论 | 112篇 |
环境理论 | 1篇 |
污染及防治 | 122篇 |
评价与监测 | 16篇 |
社会与环境 | 10篇 |
灾害及防治 | 3篇 |
出版年
2021年 | 5篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 10篇 |
2014年 | 10篇 |
2013年 | 59篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 20篇 |
2009年 | 18篇 |
2008年 | 26篇 |
2007年 | 26篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 17篇 |
2002年 | 15篇 |
2001年 | 4篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1995年 | 57篇 |
1994年 | 53篇 |
1993年 | 43篇 |
1992年 | 34篇 |
1991年 | 27篇 |
1990年 | 33篇 |
1989年 | 26篇 |
1988年 | 34篇 |
1987年 | 29篇 |
1986年 | 21篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1979年 | 5篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1973年 | 10篇 |
1971年 | 5篇 |
1963年 | 5篇 |
1919年 | 47篇 |
1918年 | 44篇 |
1917年 | 36篇 |
1916年 | 53篇 |
1915年 | 37篇 |
1914年 | 71篇 |
1913年 | 106篇 |
排序方式: 共有1223条查询结果,搜索用时 28 毫秒
991.
992.
993.
994.
995.
996.
997.
Albert Llausàs Anna Ribas Diego Varga Josep Vila 《Agriculture, ecosystems & environment》2009,129(1-3):73-82
During the last 50 years, mechanisation of the rural environment, and, more recently, the Common Agricultural Policy have led to profound changes in agrarian landscapes throughout Europe, and in particular in the rich and diverse Mediterranean landscapes (Meeus et al., 1990). In the north-east of the Iberian Peninsula, a small area of hedgerow landscape persists as a remnant of what was once an important centre for livestock production. This paper presents the results of a study carried out in this area with the aim of clarifying the relationship between the structural change of this hedgerow landscape and the evolution of farming practices developed by its owners and workers. It also considers these farmers’ perceptions of their pastures, of their farms and of the region. Up to 61 statistically significant relationships were found between the physical landscape characteristic variables and the socio-economical variables. Results depict a hedgerow landscape determined by the combination of two management models. Here, and contrary to conclusions reported in similar literature, traditional pasture activity leads to a weaker hedgerow network than a farming model based on crop cultivation. Management guidance required to move from the current situation towards a hedgerow landscape supporting both biodiversity and agrarian activity is discussed. 相似文献
998.
999.
P. Kolbitsch J. Bolhàr-Nordenkampf T. Pröll H. Hofbauer 《International Journal of Greenhouse Gas Control》2010,4(2):180-185
This study presents first operating experience with a 120 kW chemical looping pilot rig. The dual circulating fluidized bed reactor system and its auxiliary units are discussed. Two different oxygen carriers, i.e. ilmenite, which is a natural iron titanium ore, and a designed Ni-based particle, are tested in the CLC unit. The pilot rig is fueled with H2, CO and CH4 respectively at a fuel power of 65–145 kW. High solids circulation, very low solids residence time and low solids inventory are observed during operation. Owing to the scalability of the design concept, these characteristics should be quite similar to those of commercial CLC power plants. Ilmenite shows a high potential for the combustion of H2-rich gases (e.g. from coal gasification with steam). The H2 conversion is quite high but there is still a high potential for further improvement. The Ni-based oxygen carrier achieves the thermodynamic maximum H2 and CO conversion and also very high CH4 conversion. A variation of the air/fuel ratio and the reaction temperature indicates that the Ni/NiO ratio of the particle has an influence on the performance of the chemical looping combustor. Generally, low solids conversion in air and fuel reactors is observed in almost any conditions. Despite a very low H2O/CH4 molar ratio, no carbon formation is observed. 相似文献
1000.
Toms LM Guerra P Eljarrat E Barceló D Harden FA Hobson P Sjodin A Ryan E Mueller JF 《Chemosphere》2012,89(4):398-403
Brominated flame retardants, including hexabromocyclododecane (HBCD) and polybrominated diphenyl ethers (PBDEs) are used to reduce the flammability of a multitude of electrical and electronic products, textiles and foams. The use of selected PBDEs has ceased, however, use of decaBDE and HBCD continues. While elevated concentrations of PBDEs in humans have been observed in Australia, no data is available on other BFRs such as HBCD. This study aimed to provide background HBCD concentrations from a representative sample of the Australian population and to assess temporal trends of HBCD and compare with PBDE concentrations over a 16 year period. Samples of human milk collected in Australia from 1993 to 2009, primarily from primiparae mothers were combined into 12 pools from 1993 (2 pools); 2001; 2002/2003 (4 pools); 2003/2004; 2006; 2007/2008 (2 pools); and 2009. Concentrations of ∑HBCD ranged from not quantified (nq) to 19 ng g(-1)lipid while α-HBCD and γ-HBCD ranged from nq to 10 ng g(-1)lipid and nq to 9.2 ng g(-1)lipid. β-HBCD was detected in only one sample at 3.6 ng g(-1)lipid while ∑(4)PBDE ranged from 2.5 to 15.8 ng g(-1)lipid. No temporal trend was apparent in HBCD concentrations in human milk collected in Australia from 1993 to 2009. In comparison, PBDE concentrations in human milk show a peak around 2002/03 (mean ∑(4)PBDEs=9.6 ng g(-1)lipid) and 2003/04 (12.4 ng g(-1)lipid) followed by a decrease in 2007/08 (2.7 ng g(-1)lipid) and 2009 (2.6 ng g(-1)lipid). In human blood serum samples collected from the Australian population, PBDE concentrations did not vary greatly (p=0.441) from 2002/03 to 2008/09. Continued monitoring including both human milk and serum for HBCD and PBDEs is required to observe trends in human body burden of HBCD and PBDEs body burden following changes to usage. 相似文献