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   8830篇
  免费   1847篇
  国内免费   4085篇
测绘学   456篇
大气科学   777篇
地球物理   3650篇
地质学   6993篇
海洋学   1404篇
天文学   39篇
综合类   531篇
自然地理   912篇
  2024年   21篇
  2023年   147篇
  2022年   339篇
  2021年   314篇
  2020年   439篇
  2019年   631篇
  2018年   537篇
  2017年   424篇
  2016年   592篇
  2015年   560篇
  2014年   689篇
  2013年   781篇
  2012年   674篇
  2011年   759篇
  2010年   644篇
  2009年   736篇
  2008年   667篇
  2007年   686篇
  2006年   720篇
  2005年   576篇
  2004年   528篇
  2003年   434篇
  2002年   352篇
  2001年   285篇
  2000年   297篇
  1999年   292篇
  1998年   262篇
  1997年   221篇
  1996年   224篇
  1995年   165篇
  1994年   172篇
  1993年   133篇
  1992年   127篇
  1991年   81篇
  1990年   77篇
  1989年   48篇
  1988年   33篇
  1987年   28篇
  1986年   15篇
  1985年   15篇
  1984年   6篇
  1983年   4篇
  1982年   2篇
  1981年   3篇
  1979年   6篇
  1977年   9篇
  1976年   1篇
  1954年   6篇
排序方式: 共有10000条查询结果,搜索用时 1 毫秒
41.
王建平  王文富等 《海洋工程》2003,21(1):87-89,93
根据冲量相似的要求进行船舶在冲击作用下的模型试验,并将模型试验结果与理论计算及实际试验进行了对比和分析。  相似文献   
42.
针对远区台风对河口波浪动力场的影响问题,利用第三代波浪模式SWAN计算了远区台风"三巴"期间长江口波浪动力场分布,分析了陆架至河口区的波浪能量耗散和波致泥沙侵蚀的时空分布,发现波浪由外海向近岸传播过程中,波-波相互作用导致能量由高频向低频转换,周期和波长逐渐增大,近底层轨道流速增大,能量密度增高;阐明白帽破碎是维持深水区波浪能量平衡和限制波高成长的主要机制,底摩擦耗能和水深诱导的破碎耗能是长江口横沙东滩和崇明东滩邻近海域波高衰减的主要原因;提出波浪产生的底部切应力与相对水深有关,当波浪传播到浅水区时,波长和周期越大,波浪切应力越大。研究揭示了与河口相距数百公里的远区台风能够对长江口波浪动力场产生明显影响,河口水下三角洲前缘是最容易受到波浪侵蚀的区域,研究成果弥补了目前关于陆架远区台风对河口波浪动力场影响研究的不足,对深化认识远区台风对长江口动力环境、地貌演变、航运安全和滩涂保护等有重要科学意义。  相似文献   
43.
1 .IntroductionThe lifting systemis composed of pipes andtheir connectors .It is not onlythe lifting channel formanganese nodule betweenthe miningship andintermediate bin,but alsothe supporting massfor deepsea miningequipment and cables .Sothe reliability…  相似文献   
44.
于1992年4-10月在山东省青岛市黄岛前湾育苗场和胶南市红石崖镇邵家村养殖场,采用载玻片挂片和对中国对虾现场取样的方法,研究中国对虾育苗池和养成池载玻片挂 表面和对体表微型污着生物群落的组成和发展。  相似文献   
45.
High primary productivity on the Pacific coast of the Baja California Peninsula is usually related to coastal upwelling activity that injects nutrients into the euphotic zone in response to prevailing longshore winds (from the northwest to north). The upwelling process has maximum intensity from April to June, with the coastal upwelling index varying from 50 to 300 m3/s per 100 m of coastline. Along the entire coast of the peninsula, the upwelling intensity changes in accordance with local wind conditions and bottom topography. Spatial variability can also be modulated by the influence of mesoscale meanders of the California Current. We have identified the seasonal and synoptic variability of upwelling signatures on the Baja California shelf, using averaged monthly and weekly sea surface temperature (SST) distributions obtained from remote sensing imagery from the Advanced Very High Resolution Radiometer in the period from 1996 to 2001. Analysis of SST distribution and direct experimental data on temperature and nutrient concentration shows that the areas with the coldest SST anomalies were closely related to the bottom slope, shelf width, and coastline orientation relating to wind direction. We also assume that the nutrient transport into the coastal lagoons may be forced by the coupling of coastal upwelling and tidal pumping of surface waters into the lagoon system. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
46.
Decadal variability of subsurface temperature in the North Pacific has been investigated. Two dominant regions were found; the central subarctic region (CSa) and the north-eastern subtropical region (NESt). In CSa, cooling (warming) of wintertime subsurface temperature corresponds to the large (small) temperature gradient and southward (northward) shift of subsurface temperature front, associated with the increase (decrease) of positive wind stress curl and the southward (northward) shift of curl τ zero line with 2 years delay. It is suggested that the relocation of subtropical-subarctic boundary plays an important role. In NESt, importance of heat flux through the sea surface and heat divergence in the Ekman layer is also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
47.
In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis.  相似文献   
48.
Vertical variations of wave-induced radiation stress tensor   总被引:3,自引:0,他引:3  
INTRODUcrIONThe concept of radiation stress was deve1oPed by tonguet--Higgins and Stewart (1964 ),who intreduced the definition of radiation stress as the excess mornentum due to the presence ofwaves, on the basis of time-averaged laws of Newtonian fluid mechanics and the assmption ofa unifOrm velocity distribution over depth. Subequently, the theory has been applied success-fully in the investigation of phenomena such as wave set-up and set--down (Bowen et al.,l968), longshore currents …  相似文献   
49.
Variation in the sensitivity to stress of Macoma balthica was measured in several French and Dutch estuaries. For adult and juvenile Macoma balthica exposed to copper under conditions of starvation, differences in mortality rate, condition, glycogen, burrowing rate and copper content were assessed. No significant differences were observed between adults and juveniles; the influence of treatment and origin was always evident. Animals from the most southern estuaries, Loire and Gironde, near to the species's southern limit of distribution, showed, in the field, the strongest deviations for the ecophysiological traits measured, and were in the experiments the most sensitive to stress.  相似文献   
50.
用三峡及邻区(东经108°~113°,北纬29°~33°)地质资料,地震资料,现 场地应力测量资料论证三峡及邻区晚第三纪以来构造应力场稳定性及其分区特 征。  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