全文获取类型
收费全文 | 356篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
废物处理 | 6篇 |
环保管理 | 24篇 |
综合类 | 139篇 |
基础理论 | 78篇 |
污染及防治 | 94篇 |
评价与监测 | 12篇 |
社会与环境 | 4篇 |
出版年
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 12篇 |
2004年 | 4篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1975年 | 3篇 |
1967年 | 3篇 |
1965年 | 5篇 |
1964年 | 3篇 |
1963年 | 2篇 |
1962年 | 4篇 |
1961年 | 7篇 |
1960年 | 7篇 |
1959年 | 6篇 |
1958年 | 4篇 |
1957年 | 6篇 |
1956年 | 8篇 |
1955年 | 7篇 |
1954年 | 6篇 |
1953年 | 7篇 |
1951年 | 4篇 |
1950年 | 2篇 |
1947年 | 3篇 |
1942年 | 2篇 |
1941年 | 3篇 |
1939年 | 2篇 |
1934年 | 2篇 |
1931年 | 2篇 |
排序方式: 共有357条查询结果,搜索用时 15 毫秒
71.
72.
Lyophilization of the amber-colored, fluorescent oils obtained via thermolysis of amino acid mixtures (Lys, Ala, Gly) leads to a cellular-structured material—with an average cell diameter of 50 μm. The cellular aggregates show a resemblance to epithel tissues. Single cellular entities find their analogs in Fox microspheres as well as in the microfossilsIsuasphaera. Short-wave UV (254 nm) irradiation of the aqueous suspensions destroys the cells, whereas suspension in saline solutions (NaCl) offers protection against dissolution by UV light. The fluorescence spectrum of the microscopic preparations containing the highly fluorescent cellular material (“lumispheres”) was registered. 相似文献
73.
74.
75.
76.
77.
78.
Goal and Scope
Which impact does the use of non-energetic abiotic resources (ores, minerals, etc.) have in life cycles of energy systems based on biogenic and fossil fuels? Is this kind of resource use less or more environmentally harmful than the utilisation of energetic abiotic resources (mineral oil, natural gas, etc.) in the same life cycles? This paper aims at answering these questions. In Part 1, a methodology is presented and applied to the life cycles of selected energy systems. Part 2 presents and discusses the results.Method
This study looks at the complete life cycles of selected energy systems. The methodology used bases on the state-of-the-art of life cycle assessment (LCA) methodology. For the assessment of energetic abiotic resource use, a widely recognised method can be used. For the assessment of non-energetic abiotic resource use, no overall recognised methodological approach exists. That is why for this aspect two different methods are exemplarily applied and compared with each other.Results and Conclusion
Results will be presented and discussed in Part 2.Recommendation and Perspective
Recommendation and conclusions will be derived from study results in Part 2. 相似文献79.
Michael J Gundale Kerry L Metlen Carl E Fiedler Thomas H DeLuca 《Ecological applications》2006,16(2):479-489
The resource heterogeneity hypothesis (RHH) is frequently cited in the ecological literature as an important mechanism for maintaining species diversity. The RHH has rarely been evaluated in the context of restoration ecology in which a commonly cited goal is to restore diversity. In this study we focused on the spatial heterogeneity of total inorganic nitrogen (TIN) following restoration treatments in a ponderosa pine (Pinus ponderosa)/Douglas-fir (Pseudotsuga menziesii) forest in western Montana, USA. Our objective was to evaluate relationships between understory species richness and TIN heterogeneity following mechanical thinning (thin-only), prescribed burning (burn-only), and mechanical thinning with prescribed burning (thin/burn) to discern the ecological and management implications of these restoration approaches. We employed a randomized block design, with three 9-ha replicates of each treatment and an untreated control. Within each treatment, we randomly established a 20 x 50 m (1000 m2) plot in which we measured species richness across the entire plot and in 12 1-m(2) quadrats randomly placed within each larger plot. Additionally, we measured TIN from a grid consisting of 112 soil samples (0-5 cm) in each plot and computed standard deviations as a measure of heterogeneity. We found a correlation between the net increase in species richness and the TIN standard deviations one and two years following restoration treatments, supporting RHH. Using nonmetric multidimensional scaling ordination and chi-squared analysis, we found that high and low TIN quadrats contained different understory communities in 2003 and 2004, further supporting RHH. A comparison of restoration treatments demonstrated that thin/burn and burn-only treatments created higher N heterogeneity relative to the control. We also found that within prescribed burn treatments, TIN heterogeneity was positively correlated with fine-fuel consumption, a variable reflecting burn severity. These findings may lead to more informed restoration decisions that consider treatment effects on understory diversity in ponderosa pine/Douglas-fir ecosystems. 相似文献
80.
Vyas NB Spann JW Heinz GH Beyer WN Jaquette JA Mengelkoch JM 《Environmental pollution (Barking, Essex : 1987)》2000,107(1):159-166
Our objective was to determine if ground foraging passerines in a woodland surrounding a trap and skeet range were subject to lead poisoning. Lead availability to birds was determined by shot counts and soil and earthworm analysis. Avian exposure to lead was identified by measuring free-erythrocyte protoporphyrin levels in blood and lead in tissues of three passerine species. Results showed that most shot were found in the top 3 cm of soil. Lead measurements ranged from 110 to 27,000 ppm (dry wt) in soil and were 660 and 840 ppm in earthworms. Sparrows held in an aviary at the range (p=0.02) and free-flying juncos (p=0.0005) mist-netted at the range displayed significantly higher protoporphyrin levels than those at an uncontaminated site. Sparrow and cowbird carcasses from the aviary carried 37 and 39 ppm lead (dry wt), respectively, whereas a junco liver contained 9.3 ppm lead. 相似文献