全文获取类型
收费全文 | 464篇 |
免费 | 21篇 |
国内免费 | 18篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 15篇 |
2013年 | 21篇 |
2012年 | 10篇 |
2011年 | 26篇 |
2010年 | 19篇 |
2009年 | 32篇 |
2008年 | 36篇 |
2007年 | 26篇 |
2006年 | 39篇 |
2005年 | 29篇 |
2004年 | 21篇 |
2003年 | 11篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 12篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有503条查询结果,搜索用时 140 毫秒
391.
2009年12月至2010年12月,经过一个年周期的调察与统计,共记录雅安市区林地鸟类79种,隶属于8目32科。通过多样性指数与均匀度指数的测算发现,春秋两季大于夏冬两季,农田类型明显低于次生林、人工林及其他生境。在所有鸟类中,灰喉鸦雀(Paradoxornis alphonsianus)、白头鹎(Pycnonotussinensis)、红头长尾山雀(Aegithalos concinnus)、白颊噪鹛(Garrulax sannio)在不同季节均具有较高的优势度,发冠卷尾(Dicrurus hottentottus)、松鸦(Garrulus glandarius)、大山雀(Parus major)、绿背山雀(P.monticolus)具有最高的生态位宽度值。自20世纪60年代,雅安市区鸟类物种组成及栖息地随城市化进程均发生了较大变化。 相似文献
392.
Aim To introduce rangeMapper, an R package for the study of the macroecological patterns of life‐history traits, and demonstrate its capabilities using three case studies. The first case study addresses an important topic in conservation biology: biodiversity hotspots. Specifically, we investigate the congruence between global hotspots of three parameters that describe avian diversity: species richness, endemic species richness and relative body mass diversity. The second case study investigates a topic of relevance for macroecology: the inter‐specific relationship between range size and body size for avian assemblages, and how it varies geographically. The third case study tackles a methodological problem in macroecology: the influence of map resolution on statistical inference, i.e. the question of whether and how the relationship between species richness and body mass varies with map resolution. Innovation rangeMapper offers a tight integration of spatial and statistical tools for macroecological projects and it relies on a high‐performance database engine which makes it suitable for managing projects using a large number of species. rangeMapper's architecture follows closely the concepts described by Gaston et al. (2008 Journal of Biogeography, 35 , 483–500) and its flexibility allows for both complex data manipulation procedures and easy implementation of new functions. By choosing case studies to cover various technical and conceptual issues we demonstrate rangeMapper's capabilities to address a wide array of questions. Main conclusion rangeMapper ( http://cran.r‐project.org/package=rangeMapper ) is an open source front end software which can be used to address questions in both fundamental ecological research and conservation biology. 相似文献
393.
Using bird survey data taken in three cities in Southern Chile, we evaluated the hypothesis that changes in community composition from periurban to urban areas are not random. Furthermore, the consistency of species and guild loss was assessed across cities. A consistent pattern of difference in community and guild structure between urban and periurban habitats was found. In addition, a nonrandom loss of species was found in urban areas compared to periurban areas, and non‐native species dominated urban communities in all cities. The average abundance of omnivores, granivores, and habitat generalists was higher in urban areas, while insectivores and open habitat species were more abundant in periurban areas. These results strongly suggest that urban habitats act as filters offering suitable conditions for only a fraction of the bird species present in a given area, and the lack of suitable conditions may be facilitating local biotic homogenization in the three studied cities. The results of this study not only fill a biogeographical knowledge gap, but the work presented here also aids the general understanding of factors that affect community structure in habitats with varied levels of local and global urbanization. 相似文献
394.
Species' responses to climate change are variable and diverse, yet our understanding of how different responses (e.g. physiological, behavioural, demographic) relate and how they affect the parameters most relevant for conservation (e.g. population persistence) is lacking. Despite this, studies that observe changes in one type of response typically assume that effects on population dynamics will occur, perhaps fallaciously. We use a hierarchical framework to explain and test when impacts of climate on traits (e.g. phenology) affect demographic rates (e.g. reproduction) and in turn population dynamics. Using this conceptual framework, we distinguish four mechanisms that can prevent lower‐level responses from impacting population dynamics. Testable hypotheses were identified from the literature that suggest life‐history and ecological characteristics which could predict when these mechanisms are likely to be important. A quantitative example on birds illustrates how, even with limited data and without fully‐parameterized population models, new insights can be gained; differences among species in the impacts of climate‐driven phenological changes on population growth were not explained by the number of broods or density dependence. Our approach helps to predict the types of species in which climate sensitivities of phenotypic traits have strong demographic and population consequences, which is crucial for conservation prioritization of data‐deficient species. 相似文献
395.
利用红外相机技术于2017年冬季对河北太行山东坡南段的野生动物进行了调查。通过系统抽样,野外选取4个样区共安置红外相机78台,实际工作4753个相机日,获有效照片1903张。结果表明:共鉴定出兽类4目7科7种,鸟类9目14科27种,其中国家Ⅱ级重点保护鸟类有勺鸡(Pucrasia macrolopha)、雀鹰(Accipiter nisus)、灰林鸮(Strix aluco)和燕隼(Falco subbuteo)。物种相对丰度指数较高的兽类和鸟类分别为岩松鼠(Sciurotamias davidianus)(10.10)和红嘴蓝鹊(Urocissa erythroryncha)(5.49)。对拍摄率较高的前6种兽类的日活动节律进行了分析,发现野猪(Sus scrofa)和蒙古兔(Lepus tolai)主要集中在晨昏和夜间活动,西伯利亚狍(Capreolus pygargus)和岩松鼠多在昼间活动,赤狐(Vulpes vulpes)和黄鼬(Mustela sibirica)则为全天性活动。土门—黄北坪乡样区和鹿头乡样区具有较高的物种数(24种和23种)和Shannon-Weiner指数(2.35和2.06)。该地区农业开发程度高、森林景观破碎化程度大、人类活动干扰重,应加强野生动物栖息地的保护与恢复。 相似文献
396.
We examined the relationships between cavity temperature, ambient temperature outside the cavity and structural characteristics
of 70 cavities measured for 1 night to determine if cavity roosting birds may potentially select warmer tree cavities for
wintertime roosting. The mean temperature increment of the cavity (=cavity-ambient temperature) varied from −2.4 to 4.9°C
and increased with higher day-to-night fluctuations in the ambient temperature, smaller cavity entrance and better health
status of the cavity tree. Cavities in healthy trees were warmer than those in dead trees, but this difference disappeared
with rising mean ambient temperatures. This interaction between the effects of tree health status and mean ambient temperature,
as well as the effect of day-to-night fluctuations in the ambient temperature, were supported by the analysis of repeated
measurements of temperature taken on 12 consecutive nights in five cavities. The variability in cavity microclimates makes
the selection of warmer roost sites possible, and the predictors of microclimate may provide indirect cues to prospecting
birds. 相似文献
397.
M. K. Mohanty S. P. Bhunya 《Journal of Zoological Systematics and Evolutionary Research》1990,28(1):20-25
Karyological investigations of three birds: Surniculus lugubris dicruroides (Cuculidae, Cuculi-formes), Orthotomus sutorius guzuratus and Hippolais caligata caligata (Sylviidae, Passeriformes) were carried out. In the somatic male karyotype of S. l. dicruroides the modal 2 n value was determined to be 78 with 14 macro and 64 microchromosomes. In the female karyotyps of, O.s. guzuratus (2n = 86) there were 18 macro and 68 microchromosomes and in that of H.c. caligata (2n = 80) the number of macro and micros were 17 and 63 respectively. 相似文献
398.
Agricultural intensification typically leads to changes in bird diversity and community composition, with fewer species and
foraging guilds present in more intensively managed parts of the landscape. In this study, we compare bird communities in
small (2–32 ha) brigalow (Acacia harpophylla) remnants with those in adjacent uncultivated grassland, previously cultivated grassland and current cropland, to determine
the contribution of different land uses to bird diversity in the agricultural landscape. Twenty remnant brigalow patches and
adjacent agricultural (‘matrix’) areas in southern inland Queensland, Australia were sampled for bird composition and habitat
characteristics. The richness, abundance and diversity of birds were all significantly higher in brigalow remnants than in
the adjacent matrix of cropping and grassland. Within the matrix, species richness and diversity were higher in uncultivated
grasslands than in current cultivation or previously cultivated grasslands. Forty-four percent of bird species were recorded
only in brigalow remnants and 78% of species were recorded in brigalow and at least one other land management category. Despite
high levels of landscape fragmentation and modification, small patches of remnant brigalow vegetation provide important habitat
for a unique and diverse assemblage of native birds. The less intensively managed components of the agricultural matrix also
support diverse bird assemblages and thus, may be important for local and regional biodiversity conservation. 相似文献
399.
The ability to track change in biodiversity is essential to guide sustainable management and meet biodiversity monitoring,
evaluation and reporting requirements, yet long-term data are usually scarce. Birds Australia has developed a simple survey
methodology for use by their nationwide network of volunteers; it involves the collection of data on the presence–absence
of species at repeatedly visited sites. Here we present a statistical methodology for use with these binary data to examine
long-term change, using as an example records from a major bioregion of eastern Australia, 1999–2007. Regression splines were
employed to model trend as a smooth nonlinear function of time within a generalised linear modelling framework. Confidence
intervals based on bootstrap resampling provided a basis for assessing the significance of change, and a method was incorporated
for identifying important change points in the trajectory from second derivatives of the curve. The methodology proved sensitive
to change and the impact of extended dry periods was evident. The populations of several woodland species were found to be
in significant decline. Two composite indices to track change common to a group of birds were developed and/or adapted from
the existing literature. The results confirm the usefulness of repeated 2-ha presence–absence survey data to provide insight
into patterns of long-term trends in bird populations. The statistical methodology described offers a means of tracking trends
and identifying important time points and is particularly useful in situations where surveys of presence–absence of species
are the most efficient way to gather long-term data. 相似文献
400.
José Luis Tellería 《Biodiversity and Conservation》2009,18(7):1781-1791
The number of wind power plants installed in Spain has increased dramatically, and many are located in important wildlife
areas. This paper explores the geographical overlap of wind power plants with the ranges of flying vertebrate species. The
list of animals studied includes bats, soaring birds, and other birds that may be killed by turbines. Results show that the
10 × 10 km UTM squares occupied by wind power plants fell within the range of more bat and bird species than squares free
of these infrastructures. For species included in the Spanish Red List, there were more wind power plants than expected inside
the range of two raptors (Neophron
percnopterus and Circus
pygargus) and less than expected in six species (Ciconia
nigra, Aquila
adalberti, Hieraetus
fasciatus
Myotis
capaccinii, Rhinolophus
mehelyi and Myotis
myotis). The rest of endangered species (15) had a range occupation similar to that predicted by random sampling, a result that
reflects a poor strategy to prevent the overlap. These patterns may be explained by the small amount of overlap of the range
of many of these animals with the windiest areas in Spain, where wind power plants are concentrated today. However, this situation
is changing rapidly with the densification and expansion of wind power plants promoted under the Spanish Plan of Renewable
Energies. This may produce the occupation of many areas important to bird and bat conservation, and therefore preventive measures
should be implemented to protect these species and their habitats. 相似文献