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   529篇
  免费   31篇
  国内免费   2篇
测绘学   13篇
大气科学   89篇
地球物理   117篇
地质学   199篇
海洋学   30篇
天文学   98篇
综合类   2篇
自然地理   14篇
  2021年   5篇
  2020年   7篇
  2019年   7篇
  2018年   24篇
  2017年   28篇
  2016年   55篇
  2015年   30篇
  2014年   41篇
  2013年   31篇
  2012年   14篇
  2011年   23篇
  2010年   29篇
  2009年   29篇
  2008年   16篇
  2007年   17篇
  2006年   11篇
  2005年   6篇
  2004年   6篇
  2003年   8篇
  2002年   6篇
  2001年   4篇
  2000年   7篇
  1999年   2篇
  1998年   12篇
  1997年   7篇
  1996年   12篇
  1995年   6篇
  1994年   4篇
  1993年   13篇
  1992年   7篇
  1991年   7篇
  1990年   9篇
  1989年   7篇
  1988年   3篇
  1986年   6篇
  1985年   4篇
  1984年   6篇
  1983年   3篇
  1981年   3篇
  1978年   3篇
  1977年   4篇
  1976年   2篇
  1974年   2篇
  1973年   3篇
  1972年   3篇
  1971年   5篇
  1970年   3篇
  1969年   4篇
  1965年   4篇
  1963年   2篇
排序方式: 共有562条查询结果,搜索用时 15 毫秒
531.
532.
533.
534.
Effects on sediments of fish farming activity near Vrgada Island was analysed through living and total foraminiferal assemblages and concentration of major, minor and trace elements from three sediment cores. Elemental concentrations of sediments are in accordance with carbonate characteristics of the surrounding area and show mostly natural element variations between sampling locations and throughout the cores, with no significant increases due to fish farming activity. Only phosphorus concentration shows elevate values below the fish cage, assigned to fish pellets. Foraminiferal communities are dominated by epifaunal and stress tolerant species, while diversity indices point to normal marine conditions. The type of substrate and phosphorus content in sediments principally influence foraminiferal community composition, while other elemental concentrations have no perceptible effect on the assemblages. Some foraminiferal species Ammoniatepida, Ammoniabeccarii, Elphidiumcrispum, Elphidiummacellum and genus Haynesina are confirmed to be tolerant to elevated nutrient (phosphorus) content, while Ammonia parkinsoniana shows sensitivity to pollution. Postmortem processes cause decrease of foraminiferal density and species richness with core depth. All results point to negligible influence of fish farming and relatively stable environmental conditions at all sampling locations.  相似文献   
535.
Supplier selection is a complex task which assumes decision making in presence of many conflicting criteria and various parameters. If there are more than one decision maker, the problem shifts into a group context and it requires proper approach in mediating the decision making process and use of supporting multi-criteria methods and tools. This paper proposes group decision making approach for supplier selection based on analytic hierarchy process (AHP) that is combined with consensus convergence model, and two voting methods, non-preferential approval voting and preferential Borda count. Proposed approach utilized strengths of these methods thus enabling their adaption to the specific decision problem of supplier selection. An example of selecting a supplier of irrigation equipment in the company engaged in projecting, installing and maintenance of irrigation systems is used to explain and demonstrate how proposed approach can be implemented. Furthermore, this approach is viable as sufficiently general in supporting different selection processes in a field of water planning, management, and development and it can be adapted and applied on various group decision making problems.  相似文献   
536.
537.
538.
539.
Summary The three-dimensional cloud-resolving mesoscale model is used to simulate an individual Cb cloud in condition of real orography. We have conducted our numerical experiments over an area known as hail bearing clouds source. Once formed such clouds regenerate and propagate along the valley if the shallow layer of strong wind shear exists. The orographic effects on model Cb cloud are recognized through comparison of simulated cloud characteristics with those calculated for the flat terrain. Sensitivity experiments with respect to the wind shear layer depth are also conducted.Our results demonstrate the model capability to simulate well some observational Cb cloud characteristics. It is shown that the river valley is of essential importance for Cb cloud development. The most prominent features of the model cloud in this case are as follows: fast propagation along the river valley; considerable depth of the cold air nose with pronounced pulsation mechanism and intense cell regeneration at the leading edge of cold air outflow. Model and observed radar reflectivities in the vertical cross-section are in agreement. Some characteristics of surface cumulative rain precipitation are also well reproduced by the model. In contrast with the real orography case, the model cloud is more intense and it propagates freely in lateral direction for the flat terrain. The cell regeneration associated with forced updraft above the cold air nose is not pronounced in contrast with earlier considerations. Reflectivity pattern near the ground, having mainly bat-like wings, encircles much larger area with altitude compared to the case of real orography. Finally, the model cloud characteristics depend strongly on shear layer.Received June 2002; revised August 22, 2002; accepted October 1, 2002 Published online: April 10, 2003  相似文献   
540.
Global changes in the marine environment and the continuing disposal of genotoxic xenobiotics are increasing the importance of environmental pollution monitoring and of biomonitoring programs. Current approaches focus on investigations at regional and local levels in an attempt to precisely define the nature and extent of any potential environmental crisis. We have initiated, for the first time, a long-term biomonitoring program focusing on the Croatian coast of the Adriatic Sea to contribute to a more detailed understanding of marine genotoxic effects using the mussels Mytilus galloprovincialis Lam., collected along the eastern Adriatic coast over a period of five years (1998-2002), as a key test organism. The integrity of DNA in its gill homogenate was examined by the Fast Micromethod. The strand scission factor (SSF) values, as a measure of DNA integrity, DNA damage or incomplete repair have been used for the ranking of sampling sites with respect to significant genotoxic stress due to the influence or effects of genotoxic xenobiotics. The region of Split (Kastela Bay) proved to be the area with the heaviest load of genotoxic agents. The investigation of harmful effects in the ecosystem based on biomonitoring of genetic and other agents, not only on local levels but also on a wider scale, is considered as an important step in marine environmental management.  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