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   294篇
  免费   10篇
  国内免费   2篇
测绘学   14篇
大气科学   5篇
地球物理   65篇
地质学   162篇
海洋学   19篇
天文学   30篇
综合类   2篇
自然地理   9篇
  2023年   2篇
  2022年   7篇
  2021年   9篇
  2020年   13篇
  2019年   7篇
  2018年   20篇
  2017年   24篇
  2016年   25篇
  2015年   14篇
  2014年   25篇
  2013年   31篇
  2012年   17篇
  2011年   14篇
  2010年   15篇
  2009年   17篇
  2008年   6篇
  2007年   5篇
  2006年   4篇
  2005年   3篇
  2004年   4篇
  2003年   5篇
  2002年   3篇
  2001年   7篇
  2000年   1篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1995年   2篇
  1994年   1篇
  1993年   5篇
  1992年   1篇
  1991年   6篇
  1990年   1篇
  1987年   1篇
  1985年   1篇
  1982年   1篇
  1980年   2篇
  1979年   1篇
  1971年   1篇
排序方式: 共有306条查询结果,搜索用时 93 毫秒
301.
Relative permeability and resistivity index are important parameters for the exploration and development in a tight sandstone gas field. In the splitting method which uses permeability (K), reservoir thickness (H), and relative permeability (K), briefly referred to as the KHK splitting method, the accuracy of the relative permeability is crucial. According to the relationship between resistivity index and relative permeability of the Mesozoic Lower Safa Formation at Obaiyed Field in the Western Desert of Egypt, we improved the split method and made it more in line with the real situation by adopting Pairoys’ model which is more suitable to our study area. In this paper, we use a radial basis function (RBF) to establish the relationship between logging data and the gas production split point to point in tight sandstone gas reservoirs. To compare with the result by support vector regression (SVR), our method is better as indicated by mean absolute error values. In order to solve the problem that the relative permeability is difficult to obtain in the well logging evaluation, we also provide a convenient method and application example.  相似文献   
302.
Coal ash producing is an increasing trend because of its high energy demand worldwide. For transportation, disposal, and reuse of the industrial waste materials, geotextile tube’s dewatering technology has been widely used over the last three decades, which helps to decrease the volume of the dewatered slurry. In this study, effect of usage of polymer and fibers on dewatering characteristic of fly ash slurries was investigated. For the experimental investigation, an anionic polymer and short nylon fibers were used. As a new concept, centrifuge test is introduced as an alternative for the widely used pressure filtration test (PFT). Centrifuge test was used to evaluate final solid content of the retained sediments and change in slurry volume of fly ash. Tests were conducted on unconditioned and anionic polyacrylamide and/or fiber conditioned fly ash slurries. Centrifuge test results were compared with PFT results with respect to final solid content. It was found that fiber and/or polymer usage has remarkable effect on the dewatering rate of fly ash slurry. It was also found that final solid content of fly ash slurries was decreased by inclusion of fibers and polymer, which indicates that fiber and/or polymer usage can create more permeable soil body.  相似文献   
303.
This paper studies emergence/generation of power law in rank-order distribution of axial line length, which is a global pattern observed in real cities, due to interaction of a set of seven simple spatial rules at a local scale. These rules and their interactions form a model expected to simulate the morphological structure of free spaces in unplanned organic pedestrian small cities. Effects of each of the seven rules are discussed through repeated simulations of eight possible combinations of the rules, using a bottom-up process. The results show that the rules generate environments with statistically stable rank-order distribution of axial line length that follows the power law. It means that the axial maps of the simulated environments have a scale-free hierarchical structure such that their distributions lean toward short axial lines. It also represents dominance of local spatial structure, as the model renders a faster rate of growth at a local scale while allowing a steady growth at a global scale.  相似文献   
304.
The rapid growth of population and agricultural and industrial activities has caused an increase in demand on the Jeffara aquifers of Gabes (southeast Tunisia). In fact, the over-pumping of this aquifer system has resulted in water-level declines ranging from 0.25 to 1 m/year during the past three decades. The aim of this study is to identify favourable artificial recharge sites of this aquifer system based on the combined use of remotely sensed data, a geographic information system (GIS), the Shuttle Radar Topography Mission (SRTM) product and a multiple criteria decision making (MCDM) technique. The delineation of artificial recharge zones shows high to moderate potential for groundwater recharge (40%) in the Gabes region, with high precision of good potential proposed sites. Recharge processes need to account for natural conditions and ecosystems.  相似文献   
305.
306.
彭涛  杨建民  李俊 《海洋工程》2009,27(2):8-13
在考虑海洋工程装备在极端海况和运行海况下的载荷与受力,风载荷也是一个不可忽视的因素.目前物理模型试验仍是研究海洋工程结构物载荷与运动性能的重要手段,而深海结构物在水平漂移运动较大,如何在较大范围内得到满足试验要求的风场,是提高试验能力的重要问题.应用数值计算方法对大范围的风场模拟进行了分析,并进行了相应的物理实验,在此基础上对海洋工程试验的风场模拟提出了若干建议.  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