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   304篇
  免费   3篇
测绘学   1篇
大气科学   26篇
地球物理   94篇
地质学   142篇
海洋学   5篇
天文学   35篇
自然地理   4篇
  2016年   4篇
  2015年   7篇
  2013年   6篇
  2009年   6篇
  2007年   7篇
  2006年   6篇
  2005年   5篇
  2004年   4篇
  2003年   4篇
  2002年   9篇
  2000年   4篇
  1999年   5篇
  1998年   5篇
  1994年   5篇
  1985年   4篇
  1982年   3篇
  1980年   5篇
  1979年   5篇
  1978年   5篇
  1976年   7篇
  1975年   6篇
  1974年   4篇
  1973年   4篇
  1972年   3篇
  1967年   3篇
  1964年   3篇
  1963年   3篇
  1961年   3篇
  1959年   3篇
  1958年   4篇
  1956年   4篇
  1955年   3篇
  1954年   8篇
  1952年   5篇
  1951年   7篇
  1950年   6篇
  1949年   10篇
  1948年   8篇
  1938年   3篇
  1930年   4篇
  1927年   3篇
  1926年   4篇
  1925年   3篇
  1924年   3篇
  1922年   3篇
  1920年   4篇
  1918年   3篇
  1913年   3篇
  1912年   4篇
  1911年   3篇
排序方式: 共有307条查询结果,搜索用时 78 毫秒
41.
42.
Ohne Zusammenfassung
400 years mathematics and astronomy at the Wurzburg University: Alma Julia herbipolensis 1582–1982

s. O. Volk, Mathematik, Astronomie und Physik in der Vergangenheit der Universität Würzburg, Festschrift 1982.

Paper presented at the 1981 Oberwolfach Conference on Mathematical Methods in Celestial Mechanics.  相似文献   
43.
We found a hydrodynamic pulsation model of yellow supergiants under subharmonic resonance. It is confirmed that the feature of pulsation by the resonance is long-lived in the model by performing the hydrodynamical simulation for a long time.  相似文献   
44.
Ohne ZusammenfassungMit 3 Textabbildungen.  相似文献   
45.
46.
47.
Earlier analyses of the Pioneer 8 and 9 experimental meteoroid data have shown that the detectors on these two spacecraft are intercepting meteoroids with hyperbolic orbital parameters. It is shown in this paper that these results are entirely consistent with and, indeed, to be expected from other observations of the interplanetary meteoroid complex. Collisional breakup of meteoroids and post-collision radiation pressure modification of their orbits is found to be a sufficient cause for the observed results. Details of the calculations as well as of the results are presented.  相似文献   
48.
The influence of an internal boundary layer and a roughness sublayer on flux–profile relationships for momentum and sensible heat have been investigated for a closed beech forest canopy with limited fetch conditions. The influence was quantified by derivation of local scaling functions for sensible heat flux and momentum (h and m) and analysed as a function of atmospheric stability and fetch. For heat, the influences of the roughness sublayer and the internal boundary layer were in agreement with previous studies. For momentum, the strong vertical gradient of the flow just above the canopy top for some wind sectors led to an increase in m, a feature that has not previously been observed. For a fetch of 500 m over the beech forest during neutral atmospheric conditions, there is no height range at the site where profiles can be expected to be logarithmic with respect to the local surface. The different influence of the roughness sublayer on h and m is reflected in the aerodynamic resistance for the site. The aerodynamic resistance for sensible heat is considerably smaller than the corresponding value for momentum.  相似文献   
49.
The first results of a comprehensive computer analysis of over 300 front film and grid coincidence events is presented using statistical tests on the observed data. The short term time dependence of the observed flux is entirely commensurate with a random Poisson distribution and any possible contributions from discrete “cometary showers” must certainly be of relatively minor significance compared to the sporadic background for mass > 10?13 g. Periodic seasonal variations of ~ 20 per cent of the average rate are observed common to Pioneers 8 and 9. These variations could reflect on the cometary nature of the source or alternatively indicate the presence of an interstellar component. The mass spectrum of the flux in the range 10?11?10?13 g indicates an increasing flux of particles to the lowest limits of mass detected, with a derived flux of Φ = 1·4 × 10?12m?0·68 (g) m?2 sec?1(2π ster.)?1.  相似文献   
50.
Abstract— The recently discovered Jiddat al Harasis (JaH) 073 strewn field is the largest found so far in the Sultanate of Oman, covering an area of 19 × 6 km. The 3463 single stones collected range in weight from 52.2 kg down to <1 g (total weight 600.8 kg) and show a pronounced mass sorting. The strewn field shape can be approximated by a NW‐SE‐oriented ellipsoid, indicating an atmospheric entry from SE at a low angle relative to the surface. The meteorite belongs to the L6 ordinary chondrite group and shows S4 average shock grade. Smaller stones generally show a higher weathering grade resulting in a spread from W2 and W4. Enhanced weathering of the stones causing fragmentation after the fall is observed in sandy depressions. Five 14C measurements on stones of variable size and weathering grade yielded 14C from 3.8 to 49.9 dpm/kg. Three samples give a 14C/ 10Be age consistent with about 14.4 ka. For two samples the cosmogenic, trapped, and radiogenic noble gases were measured. The ratio of the 4He and 40Ar gas retention ages of 0.29 ± 0.10 and that of the 3He and 21Ne cosmic ray exposure ages of 0.36 ± 0.08 Ma indicate that JaH 073 experienced a complex exposure history and lost 4He and 40Ar due to a major collision. Fragmentation statistics indicate a single major atmospheric disruption and an originally relatively spherical shape of the object. Assuming the material collected represents the majority of fallen mass, and 90–99% of the original weight was lost by ablation, the pre‐atmospheric minimum radius of the meteoroid with density 3.4 g cm?3would have been at least 75 cm.  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