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   111篇
  免费   6篇
  2023年   5篇
  2022年   3篇
  2021年   4篇
  2020年   3篇
  2019年   1篇
  2018年   5篇
  2017年   4篇
  2016年   2篇
  2015年   4篇
  2014年   5篇
  2013年   10篇
  2012年   6篇
  2011年   6篇
  2010年   4篇
  2009年   7篇
  2008年   5篇
  2007年   1篇
  2006年   2篇
  2005年   3篇
  2004年   4篇
  2003年   5篇
  2002年   5篇
  2001年   2篇
  1998年   3篇
  1997年   1篇
  1995年   2篇
  1979年   1篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1971年   2篇
  1970年   2篇
  1968年   3篇
  1963年   1篇
  1954年   1篇
  1949年   1篇
排序方式: 共有117条查询结果,搜索用时 578 毫秒
101.
The Asian songbird crisis which is currently unfolding in Southeast Asia has seen multiple bird taxa go extinct in the wild and even more slip into regional or local extinction over the span of only a few years. The hill mynas Gracula spp. are among its main victims, encompassing the Critically Endangered Nias Hill Myna Gracula [religiosa] robusta and other endangered populations across the West Sumatran Archipelago. Hill mynas are known to be present throughout this island chain but the taxonomic relationships of West Sumatran Gracula populations remain poorly understood. We hypothesized that the unique history of this island chain may have given rise to multiple distinct insular forms. Here we use genome‐wide DNA data in concert with morphological analyses to investigate the evolutionary distinctness of these taxa. Our results identify one taxon that is surprisingly distinct despite lacking recognition in most classifications, the ‘Simeulue Hill Myna’ (taxon miotera), and a range extension of the Nias Hill Myna. Despite their lack of recognition, Simeulue Hill Mynas are genomically and morphologically as unique as their Nias counterpart, in accordance with the lack of glacial land bridges between the island of Simeulue and mainland Sumatra. Simeulue Hill Mynas went extinct in the wild sometime within the last 2–3 years, and the rescue of the last captive individuals should now be the highest priority.  相似文献   
102.
103.
The Indonesian island of Sulawesi, a globally important hotspot of avian endemism, has been relatively poorly studied ornithologically, to the extent that several new bird species from the region have been described to science only recently, and others have been observed and photographed, but never before collected or named to science. One of these is a new species of Muscicapa flycatcher that has been observed on several occasions since 1997. We collected two specimens in Central Sulawesi in 2012, and based on a combination of morphological, vocal and genetic characters, we describe the new species herein, more than 15 years after the first observations. The new species is superficially similar to the highly migratory, boreal-breeding Gray-streaked Flycatcher Muscicapa griseisticta, which winters in Sulawesi; however, the new species differs strongly from M. griseisticta in several morphological characters, song, and mtDNA. Based on mtDNA, the new species is only distantly related to M. griseisticta, instead being a member of the M. dauurica clade. The new species is evidently widely distributed in lowland and submontane forest throughout Sulawesi. This wide distribution coupled with the species'' apparent tolerance of disturbed habitats suggests it is not currently threatened with extinction.  相似文献   
104.
Industrial timber plantations severely impact biodiversity in Southeast Asia. Forest fragments survive within plantations, but their conservation value in highly deforested landscapes in Southeast Asia is poorly understood. In this study, we compared bird assemblages in acacia plantations and fragmented forests in South Sumatra to evaluate each habitat’s potential conservation value. To clarify the impact of habitat change, we also analyzed the response of feeding guild composition. Five habitat types were studied: large logged forest (LLF), burnt logged forest (BLF), remnant logged forest (RLF), 4-year-old acacia plantation (AP4), and 1-year-old acacia plantation (AP1). Estimated species richness (Chao 2) was highest in LLF then AP4 and BLF, while AP1 and RLF had lower estimated species richness. Community composition was roughly divided into two groups by non-metric multidimensional scaling ordination: acacia plantation and logged forest. Sallying substrate-gleaning insectivores, such as drongos, broadbills, and some flycatchers, were restricted to LLF, whereas acacia plantation hosted many terrestrial frugivores, such as doves. Although fragmented forests in our study site lacked several common tropical forest species, these fragments provide an important habitat for some sallying and terrestrial insectivores. A network of small riparian remnant forests could be a complementary habitat for some species, while the conservation value of burnt forest might be low. In conclusion, the highly fragmented forests in plantations are suboptimal habitats for birds but are still very important, because large primary forest blocks have been nearly lost in the surrounding landscape.  相似文献   
105.
The effects of a mud snail, Cipangopaludina chinensis laeta (Martens) (Architaenioglossa: Viviparidae), on terrestrial arthropods through rice plant development in a paddy field were investigated in 2013 and 2014 by a field experiment. There were no significant differences between treatments in the abundance of aquatic organisms, which comprised several functional feeding groups in both years. The presence of mud snails did not significantly affect plant height and soil plant analysis development values, either, except in June 2014, when tiller number and biomass of the rice plants tended to be larger in plots with snails versus those without. Significantly higher abundances of terrestrial organisms, including phytophagous pest insects and other insects, but not natural enemies of the pest insects, occurred in plots with snails. As shown by principal component analysis, the community structure of the terrestrial organisms was significantly different between the two treatments in both years. The results of this study indicate that mud snails play an important role in the paddy field ecosystem, in which they influence the biomass production of rice plants and the abundance of organisms in terrestrial ecosystems through direct and indirect interactions at different trophic levels.  相似文献   
106.
107.
International Journal of Peptide Research and Therapeutics - Several reports have suggested that glutathione (GSH) has antibacterial activity. However, the mechanism by which GSH inhibits microbial...  相似文献   
108.
109.
110.
Bioplastics were developed to overcome environmental problems that are difficult to decompose in the environment. This study analyzes Thai cassava starch-based bioplastics' tensile strength, biodegradability, moisture absorption, and thermal stability. This study used Thai cassava starch and polyvinyl alcohol (PVA) as matrices, whereas Kepok banana bunch cellulose was employed as a filler. The ratios between starch and cellulose are 10:0 (S1), 9:1 (S2), 8:2 (S3), 7:3 (S4), and 6:4 (S5), while PVA was set constant. The tensile test showed the S4 sample's highest tensile strength of 6.26 MPa, a strain of 3.85%, and a modulus of elasticity of 166 MPa. After 15 days, the maximum soil degradation rate in the S1 sample was 27.9%. The lowest moisture absorption was found in the S5 sample at 8.43%. The highest thermal stability was observed in S4 (316.8°C). This result was significant in reducing the production of plastic waste for environmental remediation.  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