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   378篇
  免费   15篇
  国内免费   1篇
测绘学   14篇
大气科学   51篇
地球物理   132篇
地质学   106篇
海洋学   20篇
天文学   40篇
综合类   6篇
自然地理   25篇
  2022年   3篇
  2021年   7篇
  2020年   7篇
  2018年   6篇
  2017年   11篇
  2016年   9篇
  2015年   9篇
  2014年   15篇
  2013年   19篇
  2012年   22篇
  2011年   16篇
  2010年   18篇
  2009年   19篇
  2008年   16篇
  2007年   13篇
  2006年   13篇
  2005年   13篇
  2004年   8篇
  2003年   8篇
  2002年   5篇
  2001年   13篇
  2000年   13篇
  1999年   4篇
  1998年   6篇
  1997年   4篇
  1996年   5篇
  1995年   6篇
  1994年   6篇
  1993年   4篇
  1991年   3篇
  1990年   5篇
  1988年   5篇
  1987年   8篇
  1986年   6篇
  1984年   4篇
  1982年   8篇
  1981年   5篇
  1980年   3篇
  1979年   2篇
  1978年   4篇
  1976年   3篇
  1975年   5篇
  1971年   2篇
  1969年   2篇
  1966年   2篇
  1964年   2篇
  1957年   2篇
  1956年   3篇
  1954年   4篇
  1951年   2篇
排序方式: 共有394条查询结果,搜索用时 15 毫秒
361.
362.
363.
364.
Projections of climate impacts on crop yields simulated for different General Circulation Model (GCM) scenarios are used, in a recursively dynamic general equilibrium framework, to account for potential economy-wide impacts of climate change in Egypt. Comparing these impact projections to those obtained under a reference, business-as-usual, scenario assuming some moderate changes in the political, economic or technological spheres, indicates that global warming has potentially negative effects. The analysis is based on a global assessment of potential climate change-induced variations in world commodity production and trade. The Egyptian agricultural sector, and the non-agricultural sector to a lesser extent, are projected to be increasingly less self-sufficient. Specific potential adverse impacts are identified. The simulation results show that high-cost adaptation measures involving major changes in the agricultural system and practices may mitigate these adverse impacts. Stimulating economic development of the rural areas and creating appropriate conditions for effective diffusion and development of technologies — particularly for the agricultural sector — would seem a desirable strategy. Perhaps, more importantly, the simulation results show that the assumption of exogenously determined technological progress may be inappropriate, in which case the potential adverse impacts of a future warming of the global climate are likely to be fewer than is indicated in this study — if prevailing constraints on productivity growth in the major food and feed grains are ‘released’ by endogenous advances in technology.  相似文献   
365.
Through simultaneous measurements, it is possible to demonstrate the relation between sea swell and surface temperature as measured by a thermoradiometer onboard an aircraft. Thermodynamic measurements made on board the aircraft enable analysis of the interaction between swell and surface marine layer dynamics. The cospectral functions of vertical turbulent transfer for sensible and latent heat indicate large-scale dynamic structures which would seem to be initiated by inhomogeneities in the humidity field. A cross-spectral examination of temperature and humidity produces a structure that is common to both parameters and is caused by swell propagation. The data used here were collected during the TOSCANE-T experiment, whose aim was to validate remote sensing scatterometer techniques, by means of an instrumented aircraft designed for atmospheric research.  相似文献   
366.
Patterns of the typical groundwater quality for 13 hydrogeological units (lithofacies units) of the solid rock and for 5 stages of the contamination of groundwater by the agricultural production are derived from investigations carried out in six regions serving as examples and in evaluation of data series covering many years. The concentration values of the substances contained in water constituting the lower and upper limits of the typical width of variation are regarded as the quality of the groundwater reservoir (long retention time) and a fast runoff component of groundwater. On the basis of this model conception it is possible to determine one of the following four quantities from the other three quantities: groundwater quality, size of the groundwater reservoir, groundwater runoff with the shares of the slow component and of the fast one, removal of substances out of the root zone.  相似文献   
367.
368.
Besprechung     
Ohne Zusammenfassung  相似文献   
369.
370.
Risk-adjusted approaches for planning sustainable agricultural development   总被引:1,自引:1,他引:0  
In this paper we show that explicit treatment of risks and uncertainties in agricultural production planning may considerably alter strategies for achieving robust outcomes with regard to sustainable agricultural developments. We discuss production planning models under uncertainties and risks that may assist in planning location-specific production expansion within environmental and health risk indicators and constraints. The proposed approaches are illustrated with the example of spatially explicit livestock production allocation in China to 2030.  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