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   113997篇
  免费   1398篇
  国内免费   1596篇
测绘学   3441篇
大气科学   8088篇
地球物理   22129篇
地质学   43312篇
海洋学   9226篇
天文学   22232篇
综合类   2418篇
自然地理   6145篇
  2022年   581篇
  2021年   1026篇
  2020年   1230篇
  2019年   1288篇
  2018年   6909篇
  2017年   6065篇
  2016年   5337篇
  2015年   1895篇
  2014年   2953篇
  2013年   4942篇
  2012年   3899篇
  2011年   6434篇
  2010年   5298篇
  2009年   6582篇
  2008年   5785篇
  2007年   6072篇
  2006年   3781篇
  2005年   3008篇
  2004年   3114篇
  2003年   2939篇
  2002年   2607篇
  2001年   2262篇
  2000年   2143篇
  1999年   1692篇
  1998年   1795篇
  1997年   1694篇
  1996年   1386篇
  1995年   1386篇
  1994年   1242篇
  1993年   1092篇
  1992年   1068篇
  1991年   976篇
  1990年   1099篇
  1989年   891篇
  1988年   825篇
  1987年   1015篇
  1986年   832篇
  1985年   1103篇
  1984年   1136篇
  1983年   1064篇
  1982年   1058篇
  1981年   894篇
  1980年   874篇
  1979年   764篇
  1978年   772篇
  1977年   689篇
  1976年   680篇
  1975年   648篇
  1974年   650篇
  1973年   608篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
History matching is still one of the main challenging parts of reservoir study especially in giant brown oil fields with lots of wells. In these cases, history matching with conventional manual technique needs many runs and takes months to get a match. In this work, an innovative approach was suggested for fast history matching in a real brown field. The workflow was employed based on an optimized proxy model for history matching of a field consisting of 14 active wells with multiple responses (which are production rate and pressure data) in the south part of Iran. The main important features of the proposed algorithm were defining a proxy model which is response surface method in which 21 model parameters were incorporated based on cubic centered face method. The proxy model was then optimized by one of the most famous algorithms which is genetic algorithm. Proxy model was successfully performed using 256 samples leading into p- value of 0.531 and R 2 of 0.91 dataset. As a result, the proposed workflow and algorithm showed good and acceptable results for history matching of studied real model.  相似文献   
142.
143.
144.
145.
146.
Panoramic scans of two lunar regions (Aristarchus–Herodotus and Plato craters) were obtained with a CCD camera and spectrograph to determine a range of actual color differences. The color differences expressed in color–excess (CE) units and determined as the intensity ratios for lunar features at 440 and 550 nm are mainly less than 0.1m. The color–albedo dependence is revealed only in separate clusters and is not the same in different parts of each region under consideration. This special feature of crater Aristarchus is confirmed; that is, in spite of its high albedo, the color in the crater is intermediate within the general range of color differences.  相似文献   
147.
Species of the macroalgae Caulerpa sp. are increasingly being observed in meadows of the endemic Mediterranean seagrass Posidonia oceanica, and in particular Caulerpa taxifolia, has been considered as an invasive species leading to seagrass decline. Studies have so far failed to reveal the underlying mechanisms of the success of the macroalgae, and here, we examine how biogeochemical changes of the environment associated to indigenous (Caulerpa prolifera) and non-indigenous (Caulerpa racemosa and C. taxifolia) species affect the habitat of P. oceanica. Two of the species (C. prolifera and C. racemosa) affect the sediment biogeochemical conditions by increasing organic matter pools, microbial activity, and sulfide pools of the sediments, and limited effects were found for C. taxifolia. Biomass of the macroalgae contributed to the extent of impacts, and high sulfide invasion into the seagrasses and regression of the meadow were pronounced at the location with the highest Caulerpa biomass. This suggests that Caulerpa invasion contributes to seagrass decline probably because Caulerpa thrives better than the seagrasses in the modified environment.  相似文献   
148.
149.
Doklady Earth Sciences - Speleological, geological and paleontological characteristics of the Lang Trang cave in northern Vietnam are presented. Primates Gigantopithecus blacki von Koenigswald,...  相似文献   
150.
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