排序方式: 共有47条查询结果,搜索用时 15 毫秒
21.
文中的高技术指标(High Tech Indicators,HTI)为佐治亚理工大学发布的沿用多年的指标。数据对
比的时间段分别为1993年、1996年、1999年、2002/3年和2007年。论文给出了33个国家(地区)当前的竞争
力指标——技术排名(Technological Standing, TS), 同时提供了四个表征未来竞争力前景的主要指标——国家
发展取向指标(National Orientation, NO)、社会经济基础指标(Socio-Economic Infrastructure, SE)、技术基础指
标(Technological Infrastructure, TI)与生产能力指标(Productive Capacity, PC)。论文无意在高技术指标的结果上
多加笔墨,但是也的确注意到,中国已经取代美国占据了技术排名的首位。这一结果反映了高技术指标的特
点,更重要的是,它反映了中国过去15年的惊人发展速度。 相似文献
比的时间段分别为1993年、1996年、1999年、2002/3年和2007年。论文给出了33个国家(地区)当前的竞争
力指标——技术排名(Technological Standing, TS), 同时提供了四个表征未来竞争力前景的主要指标——国家
发展取向指标(National Orientation, NO)、社会经济基础指标(Socio-Economic Infrastructure, SE)、技术基础指
标(Technological Infrastructure, TI)与生产能力指标(Productive Capacity, PC)。论文无意在高技术指标的结果上
多加笔墨,但是也的确注意到,中国已经取代美国占据了技术排名的首位。这一结果反映了高技术指标的特
点,更重要的是,它反映了中国过去15年的惊人发展速度。 相似文献
22.
First insights into the biodiversity and biogeography of the Southern Ocean deep sea 总被引:1,自引:0,他引:1
Brandt A Gooday AJ Brandão SN Brix S Brökeland W Cedhagen T Choudhury M Cornelius N Danis B De Mesel I Diaz RJ Gillan DC Ebbe B Howe JA Janussen D Kaiser S Linse K Malyutina M Pawlowski J Raupach M Vanreusel A 《Nature》2007,447(7142):307-311
Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental features, including a very deep continental shelf and a weakly stratified water column, and are the source for much of the deep water in the world ocean. These features suggest that deep-sea faunas around the Antarctic may be related both to adjacent shelf communities and to those in other oceans. Unlike shallow-water Antarctic benthic communities, however, little is known about life in this vast deep-sea region. Here, we report new data from recent sampling expeditions in the deep Weddell Sea and adjacent areas (748-6,348 m water depth) that reveal high levels of new biodiversity; for example, 674 isopods species, of which 585 were new to science. Bathymetric and biogeographic trends varied between taxa. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. In other taxa, the shelf and slope assemblages were more distinct. Abyssal faunas tended to have stronger links to other oceans, particularly the Atlantic, but mainly in taxa with good dispersal capabilities, such as the Foraminifera. The isopods, ostracods and nematodes, which are poor dispersers, include many species currently known only from the Southern Ocean. Our findings challenge suggestions that deep-sea diversity is depressed in the Southern Ocean and provide a basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment. 相似文献
23.
24.
25.
Linking climate change to lemming cycles 总被引:2,自引:0,他引:2
Kausrud KL Mysterud A Steen H Vik JO Østbye E Cazelles B Framstad E Eikeset AM Mysterud I Solhøy T Stenseth NC 《Nature》2008,456(7218):93-97
The population cycles of rodents at northern latitudes have puzzled people for centuries, and their impact is manifest throughout the alpine ecosystem. Climate change is known to be able to drive animal population dynamics between stable and cyclic phases, and has been suggested to cause the recent changes in cyclic dynamics of rodents and their predators. But although predator-rodent interactions are commonly argued to be the cause of the Fennoscandian rodent cycles, the role of the environment in the modulation of such dynamics is often poorly understood in natural systems. Hence, quantitative links between climate-driven processes and rodent dynamics have so far been lacking. Here we show that winter weather and snow conditions, together with density dependence in the net population growth rate, account for the observed population dynamics of the rodent community dominated by lemmings (Lemmus lemmus) in an alpine Norwegian core habitat between 1970 and 1997, and predict the observed absence of rodent peak years after 1994. These local rodent dynamics are coherent with alpine bird dynamics both locally and over all of southern Norway, consistent with the influence of large-scale fluctuations in winter conditions. The relationship between commonly available meteorological data and snow conditions indicates that changes in temperature and humidity, and thus conditions in the subnivean space, seem to markedly affect the dynamics of alpine rodents and their linked groups. The pattern of less regular rodent peaks, and corresponding changes in the overall dynamics of the alpine ecosystem, thus seems likely to prevail over a growing area under projected climate change. 相似文献
26.
27.
DPH-induced macrocytosis in the 14-day rat foetus 总被引:1,自引:0,他引:1
C Petter 《Experientia》1979,35(11):1493-1494
Phenytoin injected in the pregnant rat induces in the 14-day-old foetus macrocytosis of the primitive red blood cells which is sometimes linked with limb haemorrhages. The action of the drug is possibly the result of a blood circulation disturbance. 相似文献
28.
Sauropod dinosaurs were the largest animals ever to inhabit the land, with truly gigantic forms in at least three lineages. Small species with an adult body mass less than five tonnes are very rare, and small sauropod bones generally represent juveniles. Here we describe a new diminutive species of basal macronarian sauropod, Europasaurus holgeri gen. et sp. nov., and on the basis of bone histology we show it to have been a dwarf species. The fossils, including excellent skull material, come from Kimmeridgian marine beds of northern Germany, and record more than 11 individuals of sauropods 1.7 to 6.2 m in total body length. Morphological overlap between partial skeletons and isolated bones links all material to the same new taxon. Cortical histology of femora and tibiae indicates that size differences within the specimens are due to different ontogenetic stages, from juveniles to fully grown individuals. The little dinosaurs must have lived on one of the large islands around the Lower Saxony basin. Comparison with the long-bone histology of large-bodied sauropods suggests that the island dwarf species evolved through a decrease in growth rate from its larger ancestor. 相似文献
29.
30.