全文获取类型
收费全文 | 609篇 |
免费 | 2篇 |
国内免费 | 6篇 |
专业分类
安全科学 | 4篇 |
废物处理 | 2篇 |
环保管理 | 17篇 |
综合类 | 364篇 |
基础理论 | 100篇 |
污染及防治 | 92篇 |
评价与监测 | 19篇 |
社会与环境 | 16篇 |
灾害及防治 | 3篇 |
出版年
2018年 | 9篇 |
2017年 | 9篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 22篇 |
2012年 | 11篇 |
2011年 | 13篇 |
2010年 | 17篇 |
2009年 | 15篇 |
2008年 | 15篇 |
2007年 | 18篇 |
2006年 | 10篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 19篇 |
1998年 | 6篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1992年 | 6篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1967年 | 6篇 |
1966年 | 8篇 |
1965年 | 7篇 |
1964年 | 8篇 |
1961年 | 9篇 |
1960年 | 6篇 |
1955年 | 7篇 |
1952年 | 6篇 |
1950年 | 5篇 |
1942年 | 6篇 |
1941年 | 8篇 |
1940年 | 9篇 |
1939年 | 5篇 |
1938年 | 6篇 |
1937年 | 12篇 |
1936年 | 10篇 |
1935年 | 9篇 |
1934年 | 11篇 |
1933年 | 7篇 |
1931年 | 7篇 |
1929年 | 8篇 |
1922年 | 6篇 |
1921年 | 7篇 |
1920年 | 5篇 |
排序方式: 共有617条查询结果,搜索用时 0 毫秒
141.
Vocalisations of many songbirds, anurans, and insects are shaped by sexual selection. Males acoustically compete for territories, and females choose their mates by means of male courtship songs. In courtship, richness and complexity of elements are often favoured characters. Only a few examples of complex songs are known in mammals. Males of the harem-polygynous sac-winged bat (Saccopteryx bilineata, Emballonuridae) have an uncommonly complex vocal repertoire, and different song types of males are used in the context of territorial defence and in courting females. We classified the daytime vocalisations of 16 male S. bilineata from a colony in Costa Rica, both on the basis of their acoustical properties and the social context in which they occurred. Seven vocalisation types were differentiated: echolocation pulses, barks, chatter, whistles, screeches, territorial songs and courtship songs. Territorial songs were short, rather stereotyped and not obviously directed towards a certain conspecific. They appear to be of importance in male competition for harem territories, in which females roost during the day. Courtship songs were exclusively observed when males displayed towards a female; they were long and complex, and consisted of highly variable elements (calls). We classified the calls in courtship songs of six males into call types, based on acoustical properties, mainly spectral purity and duration. Four call types are described in detail: trills, noise-bursts, short tonal calls, and quasi constant frequency calls. Twelve parameter values were extracted from the most common call type, the trill. Discriminant function analysis of trills showed that different males had different repertoires. This could allow females to use trill parameters for recognition of individual males and thus for mate choice.Communicated by G. Wilkinson 相似文献
142.
Manfred von Ardenne 《Die Naturwissenschaften》1954,41(21):494-494
143.
144.
145.
Ein Grünrezeptor im Drohnenauge (Apis mellifica ♂) 总被引:1,自引:0,他引:1
146.
J. von Uexküll 《Die Naturwissenschaften》1913,1(34):801-805
147.
148.
149.
150.