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   4728篇
  免费   373篇
  国内免费   464篇
测绘学   68篇
大气科学   183篇
地球物理   1051篇
地质学   941篇
海洋学   989篇
天文学   1704篇
综合类   152篇
自然地理   477篇
  2024年   4篇
  2023年   32篇
  2022年   76篇
  2021年   97篇
  2020年   95篇
  2019年   110篇
  2018年   92篇
  2017年   112篇
  2016年   125篇
  2015年   104篇
  2014年   151篇
  2013年   186篇
  2012年   107篇
  2011年   175篇
  2010年   165篇
  2009年   348篇
  2008年   366篇
  2007年   400篇
  2006年   395篇
  2005年   304篇
  2004年   268篇
  2003年   279篇
  2002年   233篇
  2001年   178篇
  2000年   237篇
  1999年   218篇
  1998年   200篇
  1997年   96篇
  1996年   85篇
  1995年   81篇
  1994年   64篇
  1993年   44篇
  1992年   32篇
  1991年   13篇
  1990年   27篇
  1989年   13篇
  1988年   5篇
  1987年   11篇
  1986年   7篇
  1985年   8篇
  1984年   4篇
  1983年   2篇
  1982年   7篇
  1981年   5篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
排序方式: 共有5565条查询结果,搜索用时 988 毫秒
51.
The physical meaning of the terms of the potential and kinetic energy expressions, expanded by means of the density variation function for a nonuniform self-gravitating sphere, is discussed. The terms of the expansions represent the energy and the moment of inertia of the uniform sphere, the energy and the moment of inertia of the nonuniformities interacting with the uniform sphere, and the energy of the nonuniformities interacting with each other. It follows from the physical meaning of the above components of the energy structure, and also from the observational fact of the expansion of the Universe that the phase transition, notably, fusion of particles and nuclei and condensation of liquid and solid phases of the expanded matter accompanied by release of energy, must be the physical cause of initial thermal and gravitational instability of the matter. The released kinetic energy being constrained by the general motion of the expansion, develops regional and local turbulent (cyclonic) motion of the matter, which should be the second physical effect responsible for the creation of celestial bodies and their rotation.  相似文献   
52.
53.
54.
55.
Mass heterogeneities in the earth's mantle are retrieved from the gravity data and the topography of the core-mantle boundary as well as the topography of the earth's surface. A mantle circulation induced by the heterogeneities is modelled by solving the Stokes problem for incompressible Newtonian fluid. The derived models of mantle motions correlate well with the plate tectonics and point at a close relation between the surface tectonic activity and the processes in the vicinity of the core-mantle boundary.  相似文献   
56.
饱和软黏土动力学特性循环扭剪试验研究   总被引:2,自引:0,他引:2  
李驰  王建华 《岩土力学》2008,29(2):460-464
以饱和软黏土的循环扭剪试验研究为基础,阐明不固结不排水条件下饱和软黏土的动力学特性。在循环扭剪和循环三轴两种不同试验应力状态下,通过研究不同围压和不同静、动应力组合下饱和软黏土的应力等效破坏关系和应变等效破坏关系,提出在循环荷载作用下饱和软黏土的循环破坏同样遵循Mises屈服准则,且在Mises屈服准则下,饱和软黏土的循环强度趋于不变量。循环破坏的过程可以等效为一种拟静力弹塑性循环蠕变,建立了饱和软黏土循环累积变形随静荷载、循环荷载以及循环破坏振次之间的关系式。上述结论分别从应力和变形两个方面阐述饱和软黏土的动力学特性,与试验应力状态和围压无关,可以推广到一般应力状态下。  相似文献   
57.
58.
59.
Pelagic-Benthic Coupling in the Nordic Seas: The Role of Episodic Events   总被引:3,自引:0,他引:3  
Abstract. The consequences of the following episodic phenomena for the pelagic-benthic coupling in the Nordic Seas are illustrated: (1) Advection of water masses between fjords and shelf environments, (2) freshwater run-off and vertical stability, (3) dynamics of the marginal ice zone in the central and northern Barents Sea and the Polar Ocean, (4) drift patterns of sinking particles along the North Norwegian coast, (5) advection of zooplankton into subarctic fjords and the southern Barents Sea, zooplankton overwintering and composition, and (6) transport of organic particulate matter from the Barents Sea shelf. It is shown that physical processes in the north-eastern North Atlantic and Polar Ocean can be strongly variable on time scales of days to decades. They have a significant influence on the dynamics of pelagic-benthic coupling. The physical oceanography influences the vertical and horizontal particle flux not only directly (mixing, advection, up- and down-welling), but also indirectly through its impact on the biota (for example radiation, wind, ice cover, freshwater run-off and overwintering, advection and retention of zooplankton). Understanding pelagic-benthic coupling at high latitudes depends even more on a best possible understanding of the physical oceanography and the time scales involved than elsewhere.  相似文献   
60.
Abstract. The secondary production of Spisula subtruncata (somatic production) is calculated in the framework of a benthic monitoring study in a coastal area. The temporal trends of density, biomass and growth increments are examined in the three year-classes present. These are compared to certain physical and chemical parameters.  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