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   957篇
  免费   32篇
  国内免费   23篇
测绘学   37篇
大气科学   47篇
地球物理   180篇
地质学   608篇
海洋学   33篇
天文学   64篇
综合类   6篇
自然地理   37篇
  2023年   4篇
  2022年   34篇
  2021年   37篇
  2020年   33篇
  2019年   25篇
  2018年   78篇
  2017年   87篇
  2016年   64篇
  2015年   42篇
  2014年   66篇
  2013年   80篇
  2012年   41篇
  2011年   51篇
  2010年   37篇
  2009年   40篇
  2008年   33篇
  2007年   21篇
  2006年   24篇
  2005年   24篇
  2004年   18篇
  2003年   16篇
  2002年   16篇
  2001年   9篇
  2000年   11篇
  1999年   11篇
  1998年   3篇
  1997年   4篇
  1996年   5篇
  1995年   6篇
  1994年   7篇
  1993年   5篇
  1992年   6篇
  1991年   3篇
  1990年   5篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   7篇
  1985年   8篇
  1984年   5篇
  1983年   3篇
  1982年   8篇
  1981年   3篇
  1978年   4篇
  1976年   3篇
  1975年   2篇
  1973年   3篇
  1970年   2篇
  1969年   2篇
  1963年   1篇
排序方式: 共有1012条查询结果,搜索用时 15 毫秒
181.
A reliability based method was used to design and analyse shallow foundations using first-order Taylor series approximation. The computer program Mathcad was used to facilitate all mathematical and computional efforts. This method is an effective tool to assist the foundation designers and analyists to investigate how reliable their designs or analyses are in relation to the ultimate bearing capacity of the foundations. The approach presented in this paper provides a reliable alternative for design and analysis of shallow foundations, rather than the conventional design methods, which employs the assumptions of a specified saftey factor. Several examples were presented for design and analysis of strip footings embedded in sandy soil, and rectangular and square footings analysis embedded in clayey soils. The program input and output of each example are also presented and discussed.  相似文献   
182.
183.
The predicted relationship between water table rise and time behind a constructed underground dam is established in this paper based on a semi-physically based approach. This approach utilizes values of the most effective actual groundwater aquifer properties. Robustness of this approach was tested by applying it to a number of proposed underground dam sites in two real aquifers, in addition to a number of hypothetical cases. Results were compared with MODFLOW simulation outputs for these cases, and the comparison is found to be very encouraging.  相似文献   
184.
Theoretical and Applied Climatology - Gridded precipitation products are becoming good alternative data sources for regions with limited weather gauging stations. In this study, four climate...  相似文献   
185.
Natural Resources Research - An accurate forecasting model for the price volatility of minerals plays a vital role in future investments and decisions for mining projects and related companies. In...  相似文献   
186.
187.
INTRODUCTION Theinteractionofcomplextectonicphasesinthe IndusbasinduringtheCretaceoushasimpartedascal lopedoutlineinthesedimentarysequences.Thedevel opmentofdiversifiedsedimentaryformationsduringthe Cretaceousensuresexcellentsources(SembarandGoru formations)andreservoirs(MoghalKotandPabfor mations)forhydrocarbons.Numerousplaysandpros pectsofhydrocarbonareassociatedwiththeCretaceous system,consequentlytheIndusbasinisattractiveto petroleumexplorationcompaniesinPakistan(Sheikh andNa…  相似文献   
188.
189.
Numerical modeling of the Rideau Valley Watershed   总被引:1,自引:0,他引:1  
Using the Mike11 modeling system by the Danish Hydraulic Institute, a detailed model of the Rideau Valley Watershed was constructed. It includes 532 km of rivers and lakes, 106 basins, 122 bridges and culverts, and 20 water control structures. The model was calibrated using measured streamflow data for a time period of 5 years; additional 5 years of data was used for validation. Various methods, both qualitative and quantitative, were used to evaluate the model performance. It was found that the model can simulate the hydrological response with a reasonable to high degree of accuracy. This model is now being used for various watershed management purposes, including flood forecasting, dam safety assessment, quantification of wetland functions, and derivation of design flows.  相似文献   
190.
Abstract

Further ratification of the Kyoto Protocol by non-Annex 1 countries such as the State of Qatar will not affect the entrance into force of the Treaty; however, ratification remains an important decision due to other considerations, primarily the economic costs and benefits associated with ratification. As a member of the Organization of Petroleum Exporting Countries (OPEC), Qatar's economic position is closely allied with revenue generated from its oil and natural gas resources. Qatar expects adverse impacts from implementing the Kyoto Protocol, though the estimated magnitude varies enormously with different models. Also, the impacts depend significantly on how the implementation is done; for example, the kind of policies that other countries use. Qatar is able to counter adverse impacts by exploiting its greater share of natural gas and developing energy-intensive industries that produce nonenergy goods such as steel, petrochemicals, and chemicals. Furthermore, it is clear that clauses in the Protocol can be developed to protect OPEC interests, and if Qatar does not ratify the Protocol, it will be excluded from the subsequent rule-making processes. On balance, there are benefits to ratifying the Treaty, and there is also a strong need for extensive further research.  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