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   8183篇
  免费   409篇
  国内免费   36篇
测绘学   277篇
大气科学   603篇
地球物理   3177篇
地质学   2668篇
海洋学   335篇
天文学   1210篇
综合类   45篇
自然地理   313篇
  2022年   64篇
  2021年   154篇
  2020年   161篇
  2019年   122篇
  2018年   360篇
  2017年   344篇
  2016年   506篇
  2015年   367篇
  2014年   413篇
  2013年   531篇
  2012年   457篇
  2011年   396篇
  2010年   372篇
  2009年   357篇
  2008年   299篇
  2007年   238篇
  2006年   227篇
  2005年   178篇
  2004年   184篇
  2003年   168篇
  2002年   135篇
  2001年   149篇
  2000年   116篇
  1999年   85篇
  1998年   127篇
  1997年   106篇
  1996年   64篇
  1995年   94篇
  1994年   102篇
  1993年   72篇
  1992年   70篇
  1991年   65篇
  1990年   88篇
  1989年   64篇
  1988年   51篇
  1987年   54篇
  1986年   55篇
  1985年   60篇
  1984年   50篇
  1983年   57篇
  1982年   61篇
  1981年   56篇
  1980年   57篇
  1979年   55篇
  1978年   63篇
  1977年   51篇
  1975年   54篇
  1973年   66篇
  1972年   49篇
  1971年   57篇
排序方式: 共有8628条查询结果,搜索用时 15 毫秒
991.
992.

In this paper, a novelty-free software to assess an efficient CIPW Norm (± 0.006 wt.% in differences between input and output data) is presented. The package is available in the official repository for user-contributed R packages (CRAN: Comprehensive R Archive Network). The software is able to handle big data sets and considers minor and trace element compositions. The algorithm can calculate odd minerals in igneous rocks, such as cancrinite and calcite, adjust the Fe+3/Fe+2 ratio in different standard approaches, and recalculate the compositions of the rocks in an anhydrous basis (100 ± 0.003 wt.% volatile-free adjusted). Furthermore, the package calculates several petrological parameters, and the graphical outputs are displayed following IUGS scheme standards. The prime aspect of shinyNORRRM is the symbiosis of native R functions with the R package’s shiny (Web Application Framework for R) to run the norm in a user-friendly interface. shinyNORRRM can be executed in any operating system and requires no previous programming knowledge, thus promising to be the universal computational program in this matter. The output data are printed in the standard comma-separated values (*.csv) format, which is highly compatible with general spreadsheet editors. In this work, the algorithm of our program is validated using already compiled whole-rock geochemical databases.

  相似文献   
993.

Drought and water scarcity can significantly impair the sustainable development of groundwater resources, a scenario commonly found in aquifers in the Mediterranean region. Water management measures to address these drivers of groundwater depletion are highly relevant, especially considering the increasing severity of droughts under climate change. This study evaluates the potential of managed aquifer recharge (MAR) to offset the adverse effects of drought and water scarcity on groundwater storage. Los Arenales aquifer (central Spain), which was unsustainably exploited for irrigation in the second half of the twentieth century, is employed as a case study. Two neighbouring zones within this aquifer are contrasted, namely, Los Arenales (LA) and Medina del Campo (MC). The primary difference between them in terms of water resources management is the wide-scale implementation of MAR systems in LA since the early 2000s. Several groundwater statistical methods are used. Groundwater-level trend analysis and average piezometric levels show in LA a faster recovery of aquifer storage and less susceptibility to drought compared to MC. On the other hand, standardised precipitation indexes and standardised groundwater level indexes of detrended groundwater-level time series, which do not include the effects of MAR, show that LA can be more negatively affected by drought and groundwater abstraction. The sharper recovery of piezometric levels in LA when considering MAR, and bigger drought impacts observed when the effects of this measure are removed, demonstrate that MAR can effectively alleviate the impacts of water scarcity and drought, providing an adaptation solution to climate change worldwide.

  相似文献   
994.
Mathematical Geosciences - In complex geological environments, the spatial domain characterization of different ore types has been one of the most important challenges in the assessment of mineral...  相似文献   
995.
Journal of Seismology - We propose a rapid, finite-fault inversion procedure to derive first-order estimates of the coseismic slip following large Mw > 7 earthquakes in Mexico using...  相似文献   
996.
Natural Hazards - Little study has been done on the effect of the pixel neighborhood information when modeling landslide susceptibility using multiple logistic regression (MLR). The present...  相似文献   
997.
Geotechnical and Geological Engineering - This paper presents a study on Chlef sand to examine the effect of fines content (Fc), relative density (RD) and initial conditions on the compressibility...  相似文献   
998.
999.
1000.
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