全文获取类型
收费全文 | 504篇 |
免费 | 2篇 |
国内免费 | 6篇 |
专业分类
安全科学 | 1篇 |
废物处理 | 12篇 |
环保管理 | 32篇 |
综合类 | 341篇 |
基础理论 | 44篇 |
环境理论 | 1篇 |
污染及防治 | 56篇 |
评价与监测 | 10篇 |
社会与环境 | 15篇 |
出版年
2021年 | 7篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 14篇 |
2011年 | 22篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 7篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 11篇 |
1999年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 9篇 |
1972年 | 9篇 |
1971年 | 6篇 |
1970年 | 9篇 |
1969年 | 12篇 |
1968年 | 8篇 |
1958年 | 4篇 |
1957年 | 6篇 |
1952年 | 4篇 |
排序方式: 共有512条查询结果,搜索用时 203 毫秒
71.
M. Kunter L. Jaenicke J. Heinze W. Jaenicke H. Meinhardt 《Die Naturwissenschaften》1994,81(11):513-517
72.
Johannes H. P. Hackstein Peter Langer Jörg Rosenberg 《Environmental monitoring and assessment》1996,42(1-2):39-56
It has been assumed that the feeding habits of animals predispose the composition of the microbial biota living in their intestinal tracts. Here we show that in arthropods and vertebrates the presence of methanogenic bacteria requires a quality of the host that is under phylogenetic rather than dietary constraint: competence for intestinal methanogenic bacteria is a primitive-shared character among reptiles, birds, and mammals, and a shared-derived trait of millipedes, termites, cockroaches and scarab beetles. The presence of methanogenic bacteria seems to be a prerequisite for the evolution of anatomic specializations of the intestinal tract such as hindguts, caeca or rumina, and it is likely that it also has consequences for the reproductive strategies of the animals.Methanogenic animals contribute to atmospheric methane by their breath and faeces. Because the status as either methane-producer or non-producer is shared by most species belonging to a higher taxonomic unit, it is possible to calculate methane emissions that are characteristic for whole taxa. In combination with ecological field data on the biomass it is possible to arive at estimates concerning the global contributions by animals.The demonstration of a genetic basis for the symbiosis between methanogens and animals will allow new approaches for the reduction of methane emission by domestic animals. 相似文献
73.
74.
75.
Sven Steiner Johannes L.M. Steidle Joachim Ruther 《Behavioral ecology and sociobiology》2005,58(2):111-120
Sexual selection by competition for mates is a formidable force that has led to extraordinary adaptations in males. Here we present results suggesting a novel case of pheromone mimicry in males of Lariophagus distinguendus, a parasitic wasp of beetle larvae that develop in stored grain. Females of L. distinguendus produce a pheromone even before they emerge from a grain. Males are attracted to the parasitised grain and wait for females to emerge. Males emerging later than others are under enormous selection pressure since females mate only once. We show evidence that developing males fool their earlier emerging competitors by mimicking the female pheromone. Males exposed to pupae of either sex exhibit typical courtship behaviour. Searching males are not only arrested by grains containing developing females but spend as much time on grains containing developing males. Hence, by distracting their competitors away from receptive females late males may increase their own chance to mate with these females. After emergence, males decompose the active compounds within 32 h probably to decrease molestation during their own search for mates. Chemical analyses of active pheromone extracts and bioassays using fractions demonstrate that the active compounds are among the cuticular hydrocarbons. 相似文献
76.
77.
78.
79.
80.