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   7937篇
  免费   1561篇
  国内免费   2056篇
测绘学   777篇
大气科学   1415篇
地球物理   2035篇
地质学   4287篇
海洋学   1090篇
天文学   217篇
综合类   824篇
自然地理   909篇
  2024年   34篇
  2023年   156篇
  2022年   410篇
  2021年   452篇
  2020年   348篇
  2019年   450篇
  2018年   517篇
  2017年   438篇
  2016年   492篇
  2015年   436篇
  2014年   463篇
  2013年   519篇
  2012年   458篇
  2011年   445篇
  2010年   458篇
  2009年   444篇
  2008年   403篇
  2007年   378篇
  2006年   318篇
  2005年   300篇
  2004年   249篇
  2003年   261篇
  2002年   370篇
  2001年   391篇
  2000年   320篇
  1999年   326篇
  1998年   251篇
  1997年   229篇
  1996年   197篇
  1995年   171篇
  1994年   164篇
  1993年   139篇
  1992年   128篇
  1991年   90篇
  1990年   69篇
  1989年   65篇
  1988年   48篇
  1987年   33篇
  1986年   22篇
  1985年   23篇
  1984年   16篇
  1983年   17篇
  1982年   10篇
  1981年   12篇
  1980年   6篇
  1979年   6篇
  1978年   6篇
  1977年   3篇
  1976年   2篇
  1958年   8篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
971.
Time is a crucial factor for many remote sensing applications such as emergency response. The traditional approach requires users to spend a lot of time downloading, processing, and viewing satellite images with specialized software. Realizing interactive real‐time processing and visualization of satellite images online is our focus. This article presents an On‐Demand computing schema for remote sensing images. A processing chain model is proposed for satellite images on a private cloud computing platform designed for the China Centre for Resources Satellite Data and Application (CCRSDA). The architecture, processing flow, optimization method, fault tolerance, and user interface are described in detail. To test the efficiency and scalability of the platform, 11 processing chains were created and three load balance experiments were executed. The results from these experiments show the validity of the proposed methods and architecture.  相似文献   
972.
Under the assumption that hydrograph generation was affected by n linear reservoirs with the same value of storage coefficient k, Nash proposed the formulation of the Instantaneous Unit Hydrograph (IUH), which has been widely used in rainfall–runoff simulation and flood forecasting. However, the assumption of the parameter k having the same value in all reservoirs is obviously unphysical as it results in the estimated value of n not being integral. In this study, for parameter n integral, the different k value for each reservoir was derived using the Laplace transform and developing a general rule for the equation of the IUH of any order. The relationship between parameter k and the slope of the river channel estimated using digital elevation model (DEM) data is established, the parameter estimation procedures are given. As in most unit hydrograph studies, only isolated storm events are considered here. Seventeen flood events in three catchments were selected for the case studies. Application results show that the proposed method is slightly better than Nash's IUH with higher model efficiency and smaller absolute relative errors. This work provides a new methodology for the formulation of the IUH. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
973.

The late-Paleozoic mafic volcanic rocks occurring in the surrounding areas of the Gonghe basin are distributed in the A’nyêmaqên ophiolite zone, Zongwulong tectonic zone and Kuhai-Saishitang volcanic zone. The mafic volcanics in the A’nyêmaqên zone formed an ancient ridge-centered hotspot around the Majixueshan OIB, the Kuhai-Saishitang mafic rocks consist of E-MORB and continental rift basalts and the Zongwulong volcanic rocks are enriched N-MORB. The regionally low Nb/U and Ce/Pb ratios reflect the influence of the OIB material on the mafic magma source. From geochemistry, spatial distribution and tectonic relationship of the mafic rocks, an ancient triple-junction centered at the Majixueshan can be inferred. The existence of the Kuhai-Saishitang aulacogen may have provided a tectonic channel for the Majixueshan OIB materials metasomatizing the magma source for the Zongwulong rocks. The formation of the triple-junction and the rifting of the Zongwulong zone have separated the orogens and massifs in the region.

  相似文献   
974.
邱中华  马德强  郭兴伟 《山东国土资源》2007,23(6):2007/1/18-2007/6/28
当前,各地房地产市场活跃,房地产交易日益频繁,房地产价格一路攀升,在房地产交易中,当你用攒了半辈子的钱买了一套新房却长期拿不到土地使用证的时候,当你想进行房地产交易却因“两证”不全暗自焦急的时候,当你为办理各种房产证明不得不四处奔波的时候,就会想有没有一种措施能做到便民、省心呢?  相似文献   
975.
Delineation of phytoplankton communities in this study was based on: 1) cluster analysis by Preston's Equation (1962) and 2) analysis of the number of individuals. Results obtained by these two methods were very similar to that obtained in a previous study (Fig. 1, Gu and Guo, 1982) based on analysis of the number of planktonic species of different ecological nature. Among these three methods, that based on cluster analysis (by which some subcommunities could be recognized) proved to be the best. Contribution No. 1841 from the Institute of Oceanology, Academia Sinica.  相似文献   
976.
Based on the data obtained in the area southwest of Kyushu in the summer of 1987, the temperature-salinity distribtutions and circulation characteristics are described and the origin of the Tsushima Warm Current is analysed.  相似文献   
977.
According to practical measurement and related data, the writer discusses the main features of rivers in the Sanjiang Plain and the change of water balance with time and space, and then estimates water resources of five types, namely, runoff, ground water, soil water, and water supplied by three rivers and lakes (or reservoirs).The total volume of the above-mentioned water resources can be up to 31.5 billion m3. But they are rather unevenly distributed and the annual change is considerable, too. Up to now, only 8.3% of water resources have been utilized. According to a programme, 17.5 billion m3 will be utilized in the future in the district. Rationally exploiting water resources in the district should be combined with protection and management, and the sole criterion for judging rationality of utilization is that whether it is beneficial to economic, ecologic and social aspects.  相似文献   
978.
1 INTRODUCTION In southern high latitudes, recent observations have shown a standing mode of ACW (Antarctic Circumpolar Wave) with eastward propagation across the Southern Ocean of the Antarctic in co- varying SST (sea surface temperature) and SLP (sea le…  相似文献   
979.
1INTRODUCTION In meteorological satellite cloud images, the features of Mesoscale Convective System (MCS) are shown in white bright cloud cluster, cloud band, cloud line, vorti- calcloudsystem,etc. The MCSlife cycle and spatial size usuallyvaryfrom several hours to one day and 100km to approximately 1000km, respectively. In the last two decades, it has been proven that storm and intensive con- vective weather, such as spasmodic thunderstorm and gale, tornado and short macro-precipitati…  相似文献   
980.
根据构造控矿的观点,通过对成矿期内容矿断裂活动分析,阐述了构造活动与矿体定位的关系。  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