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   209篇
  免费   2篇
  2013年   6篇
  2012年   5篇
  2011年   3篇
  2010年   13篇
  2009年   3篇
  2008年   8篇
  2007年   8篇
  2006年   12篇
  2005年   6篇
  2004年   6篇
  2003年   4篇
  1999年   3篇
  1998年   2篇
  1995年   5篇
  1994年   5篇
  1992年   4篇
  1991年   2篇
  1989年   4篇
  1988年   3篇
  1987年   6篇
  1985年   3篇
  1984年   4篇
  1982年   2篇
  1981年   3篇
  1980年   6篇
  1979年   4篇
  1978年   4篇
  1977年   3篇
  1976年   6篇
  1974年   2篇
  1973年   6篇
  1972年   4篇
  1971年   4篇
  1970年   4篇
  1969年   2篇
  1968年   2篇
  1959年   5篇
  1957年   2篇
  1955年   4篇
  1954年   7篇
  1952年   2篇
  1948年   1篇
  1943年   1篇
  1938年   1篇
  1936年   1篇
  1934年   1篇
  1932年   1篇
  1925年   1篇
  1924年   1篇
  1922年   1篇
排序方式: 共有211条查询结果,搜索用时 15 毫秒
91.
92.
We isolated a total of 22 microsatellite loci from two Haliaeetus species: the Madagascar fish‐eagle (Haliaeetus vociferoides) and the bald eagle (Haliaeetus leucocephalus). Five loci were monomorphic in both the Madagascar fish‐eagle (n = 24–43) and the bald eagle (n = 2–8) but were found to be polymorphic in other Haliaeetus species. Haliaeetus loci have proved useful for investigating gene flow in Haliaeetus and Aquila eagles. Ten loci were polymorphic in the critically endangered Madagascar fish‐eagle and will be used to investigate the genetic population structure and mating system in this species.  相似文献   
93.
Terrestrial gross primary production (GPP) is an important parameter to explore and quantify carbon fixation by plant ecosystems at various scales. Remote sensing (RS) offers a unique possibility to investigate GPP in a spatially explicit fashion; however, budgeting of terrestrial carbon cycles based on this approach still remains uncertain. To improve calculations, spatio-temporal variability of GPP must be investigated in more detail on local and regional scales. The overarching goal of this study is to enhance our knowledge on how environmentally induced changes of photosynthetic light-use efficiency (LUE) are linked with optical RS parameters. Diurnal courses of sun-induced fluorescence yield ( F Syield) and the photochemical reflectance index of corn were derived from high-resolution spectrometric measurements and their potential as proxies for LUE was investigated. GPP was modeled using Monteith's LUE-concept and optical-based GPP and LUE values were compared with synoptically acquired eddy covariance data. It is shown that the diurnal response of complex physiological regulation of photosynthesis can be tracked reliably with the sun-induced fluorescence. Considering structural and physiological effects, this research shows for the first time that including sun-induced fluorescence into modeling approaches improves their results in predicting diurnal courses of GPP. Our results support the hypothesis that air- or spaceborne quantification of sun-induced fluorescence yield may become a powerful tool to better understand spatio-temporal variations of fluorescence yield, photosynthetic efficiency and plant stress on a global scale.  相似文献   
94.
95.
96.
97.
SUMMARY: From the mortality curves of Escherichia coli cells heated at 55° in Ringer's solution both Decimal Reduction Times (DRTs) and 99–9% mortality times were obtained. In terms of these measures of heat resistance, cells harvested from broth cultures 0–8 hr old were more susceptible than those from more mature cultures. The time of commencement and the approximate duration of the logarithmic phase of growth of the organism in broth were determined from growth curves, and it was observed that the heat resistance was minimal during that phase.
Death rates were not always uniform for the whole of a given population. Particularly among young cultures, a period of rapid death was frequently followed by the slower death of a relatively small number of survivors. In one instance only was an initial period of slow death followed by one of more rapid death.  相似文献   
98.
Ultra-thin sections of the red algae Rhodymenia palmata andLaurencia caespitosa were examined in the electron microscopein order to determine the fine structure of the Floridean pits.The pits found in the two species examined are shown to be quitedifferent from each other, in Rhodymenia the pit is open sothat the cytoplasm is continuous through the cell wall, whilstin Laurencia the pit is completely closed by a lamella of thecell wall. These two types are shown to be equivalent to thosedescribed by Jungers (1933) on the basis of light microscopeobservations.  相似文献   
99.
100.
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