全文获取类型
收费全文 | 78篇 |
免费 | 0篇 |
专业分类
废物处理 | 3篇 |
环保管理 | 2篇 |
综合类 | 67篇 |
基础理论 | 2篇 |
污染及防治 | 4篇 |
出版年
2019年 | 1篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2005年 | 1篇 |
2002年 | 2篇 |
1994年 | 1篇 |
1970年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1962年 | 4篇 |
1961年 | 3篇 |
1960年 | 2篇 |
1959年 | 4篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1956年 | 4篇 |
1955年 | 5篇 |
1954年 | 2篇 |
1952年 | 4篇 |
1951年 | 2篇 |
1943年 | 1篇 |
1942年 | 2篇 |
1941年 | 2篇 |
1940年 | 3篇 |
1939年 | 1篇 |
1936年 | 1篇 |
1933年 | 1篇 |
1930年 | 1篇 |
1929年 | 1篇 |
1928年 | 1篇 |
1926年 | 1篇 |
1925年 | 1篇 |
1924年 | 2篇 |
1923年 | 1篇 |
1922年 | 2篇 |
1921年 | 1篇 |
1920年 | 1篇 |
1918年 | 1篇 |
1914年 | 2篇 |
1913年 | 3篇 |
排序方式: 共有78条查询结果,搜索用时 31 毫秒
41.
42.
43.
In addition to their obvious negative effects (“pathogens”), endoparasites of various kinds play an important role in shaping
and maintaining modern animal communities. In the long-term, parasites including pathogens are indispensable entities of any
ecosystem. To understand this, it is essential that one changes the viewpoint from the host’s interests to that of the parasite.
Together with geographic isolation, trophic arms race, symbiosis, and niche partitioning, all parasites (including balance
strategists, i.e. seemingly non-pathogenic ones) modulate their hosts’ population densities. In addition, heteroxenic parasites
control the balance between predator and prey species, particularly if final and intermediate hosts are vertebrates. Thereby,
such parasites enhance the bonds in ecosystems and help maintain the status quo. As the links between eukaryotic parasites
and their hosts are less flexible than trophic connections, parasite networks probably contributed to the observed stasis
and incumbency of ecosystems over geologic time, in spite of continuous Darwinian innovation. Because heteroxenic parasites
target taxonomic levels above that of the species (e.g. families), these taxa may have also become units of selection in global
catastrophies. Macroevolutionary extrapolations, however, are difficult to verify because endoparasites cannot fossilize. 相似文献
44.
Due to its chemical composition, waste sludge generated in the paper industry may be used as a raw material for brick production. Brick manufacture is limited to the warmer months of the year whereas sludge is produced continuously by different effluent treatment devices. Therefore, it has to be stored until further processing. For this reason, it is essential that it is not subject to significant chemical and microbiological decomposition during storage. In the experiment, sludge from a tissue paper mill was tested for its stability. It was stored for several weeks during winter and summer periods in a pile, 2 m in height, in an open but covered store. Different leachable organic and inorganic compounds indicating possible ongoing deterioration processes, as well as pH value, redox potential, temperature, humidity and dry matter content were evaluated weekly in water extracts of homogenized sludge samples. According to the test results, the material may be considered to be chemically and microbiologically stable as there was practically no emission of odorous and toxic compounds such as H2S, NH3 and butyric acid despite prolonged storage times and elevated environmental temperatures. All the microbial species identified in the sludge during storage belong to the typical microflora of the environment. 相似文献
45.
46.
47.
48.
49.
50.