首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   261篇
  免费   8篇
  国内免费   3篇
  2023年   4篇
  2022年   4篇
  2021年   7篇
  2020年   3篇
  2019年   7篇
  2018年   9篇
  2017年   7篇
  2016年   4篇
  2015年   7篇
  2014年   12篇
  2013年   15篇
  2012年   6篇
  2011年   6篇
  2010年   10篇
  2009年   16篇
  2008年   21篇
  2007年   21篇
  2006年   15篇
  2005年   7篇
  2004年   7篇
  2003年   4篇
  2000年   5篇
  1999年   2篇
  1998年   3篇
  1997年   4篇
  1996年   8篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1992年   4篇
  1991年   4篇
  1990年   5篇
  1989年   3篇
  1988年   3篇
  1987年   4篇
  1986年   3篇
  1984年   1篇
  1982年   1篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1977年   2篇
  1976年   1篇
  1973年   1篇
  1972年   1篇
  1970年   1篇
  1969年   1篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
排序方式: 共有272条查询结果,搜索用时 15 毫秒
221.
We studied territorial behaviour of Calomys musculinus, a promiscuous-polygynous species, in order to test the predictions that during the breeding period, home-range-owner females are more aggressive than home-range intruders and that males do not display territorial behaviour. At the core of the breeding season, we conducted 136 intrasexual and 66 intersexual encounters. The study was carried out in four 0.25-ha enclosures, each containing one independent population. We studied territorial behaviour utilising focal animal sampling to record behaviour. Encounters were conducted in a circular opaque arena (COA) near the home-range’s activity mathematical centre (AMC). Amicable behaviour was not observed in any of the 78 trials among females. The rates of aggressive and submissive behaviour per female–female encounters varied in relation to whether they were home-range owners or intruders, the former being aggressive, the latter submissive. So we could link these drives to the territorial behaviour of C. musculinus. This result fits well with the already known territoriality of C. musculinus during the breeding season. In contrast, the 58 intrasexual male encounters did not show direct aggressive interactions between them. The rates of the different behaviours between males did not vary in relation to whether they were home-range owners or intruders. In our study, which took place during the breeding period, C. musculinus males were nonterritorial, and they never exhibited aggressiveness towards females.  相似文献   
222.
Previous studies on Japanese macaque (Macaca fuscata) densities suggest that both total annual food abundance and the quality of fallback foods in the winter bottleneck period affects density. We reviewed data on the seasonal changes in home range size to explain how both factors affect density. In general, home range was large in summer or autumn and small in spring or winter, indicating that density is determined by the home range size in the seasons before winter. The main foods in these seasons are fruits and seeds. If these foods are not abundant, macaques need to range over a larger area, thus decreasing density. Macaques survive the winter by depending on the fat deposited before winter through eating these high-quality foods. If the food condition in winter is severe and the amount of required fat deposition is large, macaques need a larger home range before winter, and thus density becomes lower.  相似文献   
223.
Synopsis The protogynous, Indo-Pacific serranid fish Anthias squamipinnis forms three types of social groupings, often within the same population: discrete groups, continuous masses, and intermediate groupings. In an intermediate grouping on Aldabra Island, Indian Ocean, females had larger home ranges than males and moved over the home range of several males. The movement rate of females into and out of specific locations within the grouping depended on the continuous presence of males. When males were removed, the movement rate increased. After females had completed sex reversal, thereby replacing the removed males, movement rate declined. These aspects of space use were identical to previous findings in discrete groups. It is suggested that the three types of social grouping each result from the interaction of these patterns of space use with plastic behavioral features at a particular site with particular substrate characteristics and a particular demographic history.  相似文献   
224.
Synopsis On the basis that -emitting artificial radionuclides, present in nuclear plant radioactive wastes, can be considered as natural collective markers of fish living downstream from a radioactive discharge, we studied the restricted movements of chub in a reservoir on the Lower Rhône river where the Marcoule nuclear plant is located. A qualitative determination, based on the detection of specific radioelements in our samples originating from radioactive waste, and a quantitative determination of the cesium-137 concentration in the samples, were used to identify fish radioactively marked by the effluent. Individual measurements of -radioactivity in 49 adult chub captured at two stations, each 2 km long and 6 km apart, divided the fish into two distinct sub-units: one living downstream of the discharge pipe, in which 73% were marked, and the other upstream, in which 79% were not marked. Similar results were found in two neighbouring stations when we analysed previous radioecological measurements of -radioactivity in groups of chub. After combining all the data concerning chub, detailed information was obtained on the spatial stability of the chub population in the reservoir. Two spatially different stocks were found and each stock can be divided in two components: a sedentary component that remains in a restricted zone (its home range), and a mobile component that undertakes movements between the two zones.  相似文献   
225.
西藏东南部地区马麝家域的研究   总被引:19,自引:6,他引:13  
运用三维空间中的家域模型及其计算分析方法,结合全球定位系统和电子计算机计算技术,讨论了西藏东南部地区马麝的家域形态、面积及其不同性别与季节的差异。马麝的家域近圆形,不同时间它们虽有沿海拔高度的垂直迁移现象,但整个活动中心变化不大。夏季时,马麝的家域面积较小,进入秋冬季节则显著增加;其中,无性别特异性的普遍增加与秋冬季节的食物减少有关,而不同性别的变化比例差异与繁殖活动相联系。  相似文献   
226.
动物巢区二维正态概率模型的探讨   总被引:3,自引:1,他引:2  
本文根据二维正态分布的性质以及识别动物极端活动位点的技术建立了一种动物巢区二维正态概率模型。应用中,首先对动物活动位点进行二维正态分布检验,采用加权法消除了极端位点的影响。在二维正态分布条件下,动物巢区定义为由下列方程决定的椭圆区域d_β由下列方程组确定其中β为巢区所含活动位点百分比,a_i(i=1,2,…6)为常数。椭圆巢区两半轴长分别为d_β·面积为π·d_β·σ_x~2 ·椭圆的方向由坐标轴旋转角  相似文献   
227.
Fungal species from 130 samples of mattress dust have been identified. The number of moulds varies from one mattress to another with extreme values ranging from less than 1000 to more than 70 000 000 CFU/g of dust (median value of 30 000 CFU/g).Eurotium repens is undoubtedly the most frequent species detected in mattress dust.Aureobasidium pullulans, Alternaria alternata, Penicillium chrysogenum, Aspergillus penicilloides andAspergillus restrictus, which were frequently isolated and/or revealed important concentrations in dust samples, are the other main occurring species. Fungal flora in mattresses are more numerous in winter, the peak period being December-January. The most important contaminations by xerophilic species occurred during that peak period, whereas non-osmophilous species were constantly present during the year. The qualitative conditions of the habitat have an influence on the abundance of moulds in mattresses. Mattresses from damp houses could be a source forAlternaria throughout the year. No significant difference has been detected between the contamination level of men and women's mattresses (P=0.651). Children's mattresses are less contaminated than adults (P=0.025). The level of contamination could be affected by perspiration.  相似文献   
228.
Synopsis Five adult or subadult muskellunge, Esox masquinongy (Salmoniformes: Esocoidei), were tracked over periods of 6–11 days by means of ultrasonic (74 ± 1 Khz) transmitters, surgically implanted in the body cavity. One of these fish demonstrated that survival and well-being for over a year is probable. There was no apparent effect on equilibrium, swimming, or feeding. There was also no apparent abnormally high amount of movement immediately after release.Signal range was at times no greater than 10 m (in contrast to a potential of 1 km) as a result of the air in the dense aquatic vegetation.Area occupied by a single individual for a protracted period could be described as a linear distance of 300–800 m in the stream, or a circle 300 m in diamter in the lake. Displaced individuals returned to a specific locality. Following spawning they do so over a distance as great as 6.4 km in a maximum of two days. There was evidence that two individuals used the same general area simultaneously.Subsequent results with some of the same individuals indicated that radio transmitters are more practical and yield better results in the situation under study.  相似文献   
229.
繁殖期巢域的研究对了解繁殖期间动物的社群关系、种群动态、繁殖策略等有重要作用。2009 年3 ~12月和2010 年3 ~9 月对洪雅县赤腹松鼠的巢域面积变化进行观察。使用最小凸多边形(Minimum convex polygon,MCP)法计算赤腹松鼠各时期的巢域面积,结果显示: (1)整个繁殖期,雄性赤腹松鼠的巢域面积为1.34 ±0. 34 hm2 ,显著大于雌性的巢域面积(0.60 ± 0. 08 hm2 ); (2)雄性赤腹松鼠在求偶交配期主动增加其巢域面积,可能会增加雄性与雌性的遇见率,从而增加与雌性的交配数量;雌性赤腹松鼠在求偶交配期不主动增加巢域面积,而是具有较为稳定的活动范围。在妊娠育幼期雌性的巢域面积会减小,这可能是雌性为提高后代的成活率,在增加能量和降低捕食风险两者间做出的权衡;(3)整个繁殖期,雌性赤腹松鼠间无巢域重叠现象,而雄性间存在巢域重叠。两性之间仅在求偶交配期存在巢域重叠现象,因此,雌性赤腹松鼠在繁殖期有较强的领域性。  相似文献   
230.
藏狐家域功能分区及其生物学特性比较   总被引:1,自引:1,他引:0  
家域是野生动物生态学研究中重要的基础概念之一,对家域的研究有助于认识动物在特定时期的生态学需求和采取的生活史对策.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号