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   903篇
  免费   23篇
  国内免费   3篇
测绘学   28篇
大气科学   45篇
地球物理   259篇
地质学   308篇
海洋学   86篇
天文学   129篇
综合类   2篇
自然地理   72篇
  2019年   6篇
  2018年   14篇
  2017年   17篇
  2016年   18篇
  2015年   15篇
  2014年   27篇
  2013年   37篇
  2012年   21篇
  2011年   31篇
  2010年   28篇
  2009年   36篇
  2008年   37篇
  2007年   29篇
  2006年   31篇
  2005年   19篇
  2004年   20篇
  2003年   19篇
  2002年   22篇
  2001年   21篇
  2000年   12篇
  1999年   22篇
  1998年   19篇
  1997年   15篇
  1995年   10篇
  1994年   12篇
  1993年   11篇
  1992年   9篇
  1991年   13篇
  1990年   20篇
  1989年   11篇
  1988年   11篇
  1987年   12篇
  1986年   7篇
  1985年   8篇
  1984年   13篇
  1983年   16篇
  1982年   18篇
  1981年   19篇
  1980年   18篇
  1979年   10篇
  1978年   8篇
  1977年   7篇
  1976年   9篇
  1974年   8篇
  1973年   7篇
  1968年   6篇
  1965年   6篇
  1962年   7篇
  1953年   8篇
  1949年   11篇
排序方式: 共有929条查询结果,搜索用时 588 毫秒
211.
Summary History and results of a 41/2-years-expedition to Argentine. A determination of the sun's «temperature» can only be given by the laws ofBoltzmann-Stefan andWien, because the temperature of the different layers is different. In the measurements of the sun's radiation the law ofBoltzmann-Stefan was introduced (T 4, where is a constant, andT the Kelvin-Temperature) while in the passed 100 years the difference between the sun's and the instruments radiation was taken as radiation, although this difference was arbitrariously variable with the instruments temperature. The effect of the vertical exchange of airmasses, on the radiation of the sun and the radiation of the air between the sun and the instrument was cleared. With these corrections one can not receive more as the difference between the so called solar constant and the albedo of the atmosphere. If the highest values are used (smallest albedo) the approximated value of the solar constant becomes 2.4, corresponding well to the value, derived from the supposed temperature of the sun.  相似文献   
212.
Riassunto Usufruendo delle più recenti serie di misure della gravità, l'A. esamina la distribuzione di tale grandezza lungo alcuni profili degli Oceani Atlantico, Pacifico e Indiano, traendone diverse conclusioni e confermando precedenti risultati.
Zusammenfassung Auf Grund der neueren Reihen der Schweremessungen auf dem Meer, untersucht der Verf. die Schwereverteilung längs einiger Profile des Atlantischen, des Pazifischen und des Indischen Ozeans; daraus zieht er einige Schlussfolgerungen und bestätigt andere schon bekannte Ergebnisse.
  相似文献   
213.
214.
215.
216.
217.
Northern Adriatic Rocky Reef Fishes at Low Winter Temperatures   总被引:1,自引:0,他引:1  
Kurt  Kotrschal 《Marine Ecology》1983,4(3):275-286
Abstract. The behavioural ecology of certain northern Adriatic fishes was observed from January to April at a water temperature of 7–11 oC. The fishes studied here do not migrate to deeper waters. Most of the benthic fishes show a similar distribution over the substrate in winter and in summer; in winter, however, they are very inactive and hide in the substrate. Suprabenthic fishes aggregate in littoral caves where they form dense, inactive, mixed aggregations. Certain hemipelagic and pelagic fishes join to form very dense aggregations at specific sites in the open waters of bays. Littoral predators display high feeding activity at a time when their prey is inactive. I present a hypothesis concerning possible implications of seasonally cyclic environmental temperatures for a sympatric community of non-migrating fishes.  相似文献   
218.
219.
Systems for the determination of trace element compounds consisting of liquid chromatographs (LC) (high pressure liquid chromatographs, ion chromatographs) and graphite furnace atomic absorption spectrometers (GFAAS) or inductively coupled argon plasma emission spectrometers (ICP) as single- or multi-element-specific detectors are described. The applications of these systems to the determination of arsenic compounds are reviewed. The absolute detection limits of these systems for arsenic are in the low nanogram range. These detection limits can probably be improved by two-three orders of magnitude by coupling an inductively coupled argon plasma-mass spectrometer instrument to the liquid chromatograph. The advantages and drawbacks of the LC-GFAAS and LC-ICP systems are outlined. These systems can separate and identify trace element compounds that are kinetically or thermodynamically stable under the conditions of the chromatography. Labile compounds cannot be determined by these systems. Wide application of these systems to problems of trace element research will lead to the identification of hitherto unknown trace element compounds, to a better understanding of the nutritional and toxic properties of trace element compounds, and to a better definition of trace element cycles.  相似文献   
220.
Total suspended matter in the water column of the Caribbean was determined quantitatively by means of filtration through 0.45 μ membrane filters. Results show that prior values obtained by centrifuging methods are too low, and that the existence of a nepheloid layer cannot be gravimetrically demonstrated in the Caribbean.  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