全文获取类型
收费全文 | 418篇 |
免费 | 48篇 |
出版年
2023年 | 3篇 |
2021年 | 5篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 19篇 |
2014年 | 14篇 |
2013年 | 33篇 |
2012年 | 31篇 |
2011年 | 18篇 |
2010年 | 20篇 |
2009年 | 17篇 |
2008年 | 21篇 |
2007年 | 18篇 |
2006年 | 23篇 |
2005年 | 22篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 16篇 |
2001年 | 16篇 |
2000年 | 13篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1976年 | 2篇 |
1970年 | 1篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有466条查询结果,搜索用时 62 毫秒
461.
Véronique Pinard Christian Dussault Jean-Pierre Ouellet Daniel Fortin Réhaume Courtois 《The Journal of wildlife management》2012,76(1):189-199
Logging negatively affects the threatened forest-dwelling caribou (Rangifer tarandus caribou) through its positive effects on large predator populations. As recruitment is a key component of caribou population growth rate, we assessed calving rates of females and calf survival rates during the most critical period for calf survival, the calving period. We also identified causes of calf mortality and investigated the influence of predation risk, food availability, and human disturbance on habitat selection of females during the calving period at both the home-range and forest stand scales. We hypothesized that caribou should display habitat selection patterns to reduce predation risk at both scales. Using telemetry, we followed 22 females and their calves from 2004 to 2007 in a highly managed study area in Québec, Canada. Most females (78.5 ± 0.05 [SE]) gave birth each year, but only 46.3 ± 8.0% of the calves survived during the first 50 days following birth, and 57.3 ± 14.9% of them died from black bear (Ursus americanus) predation. At the home-range scale, caribou selected calving areas located at upper slope positions and avoided high road density areas. Surprisingly, they also selected the forested habitat type having the lowest lateral cover (mixed and deciduous stands) while avoiding the highest cover (regenerating conifer stands). At the forest stand scale, caribou selected areas located at relatively high elevations and with a lower basal area of black spruce trees. The selection of upper slope positions likely favored spatial segregation between calving females and wolves (Canis lupus) but not black bear. Our results suggest that calving females used areas from which they could visually detect approaching predators. While wolf avoidance appeared to be effective in a highly managed landscape, caribou did not appear to have adjusted their predator avoidance strategy to the recent increase in black bear abundance, who have benefited from increased food abundance. This situation requires focused attention from wildlife managers as logging activities are progressing towards the north within the core of forest-dwelling caribou range. © 2011 The Wildlife Society. 相似文献
462.
463.
464.
465.
Genetic differences among language families in Europe 总被引:6,自引:0,他引:6
R R Sokal N L Oden P Legendre M J Fortin J Y Kim A Vaudor 《American journal of physical anthropology》1989,79(4):489-502
We investigated whether 59 allele frequencies and 10 cranial variables differed among speakers of the 12 modern language families in Europe. Although this is a classical analysis of variance design, special techniques had to be developed for the analysis because of spatial autocorrelation of both biological and language data. The method examines pooled sums of squares within language families. These are compared with the same quantities obtained by randomly partitioning the available data points in Europe into internally cohesive subsets representing the same sample sizes for each language family as in the originally observed data. Our results suggest that for numerous genetic systems, population samples differ more among language families than they do within families. These findings are considered in relation to two contrasting models: a model of random spatial differentiation of gene frequencies unrelated to language and a model of aboriginal genetic differences among speakers of different language groups. Our observed findings suggest partial validity of both models. 相似文献
466.