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   10608篇
  免费   1466篇
  国内免费   3855篇
测绘学   786篇
大气科学   1781篇
地球物理   2767篇
地质学   6361篇
海洋学   1404篇
天文学   302篇
综合类   1378篇
自然地理   1150篇
  2024年   75篇
  2023年   136篇
  2022年   158篇
  2021年   251篇
  2020年   143篇
  2019年   261篇
  2018年   284篇
  2017年   165篇
  2016年   271篇
  2015年   291篇
  2014年   492篇
  2013年   443篇
  2012年   399篇
  2011年   455篇
  2010年   297篇
  2009年   426篇
  2008年   234篇
  2007年   412篇
  2006年   496篇
  2005年   542篇
  2004年   545篇
  2003年   372篇
  2002年   445篇
  2001年   545篇
  2000年   522篇
  1999年   272篇
  1998年   151篇
  1997年   166篇
  1996年   127篇
  1995年   164篇
  1994年   151篇
  1993年   389篇
  1992年   331篇
  1991年   424篇
  1990年   407篇
  1989年   426篇
  1988年   483篇
  1987年   405篇
  1986年   290篇
  1985年   387篇
  1984年   317篇
  1983年   253篇
  1982年   200篇
  1981年   137篇
  1980年   199篇
  1976年   89篇
  1964年   95篇
  1959年   123篇
  1958年   127篇
  1957年   129篇
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
91.
两学会拟定于10月24~28日在四川成都联合召开1991年学术年会,主要就“海洋数值预报、海气相互作用、海洋环境保护、湖泊环境保护及开发治理”等内  相似文献   
92.
1955年11月,苏联科学院海洋研究所考察船“勇士号”在其第二十二航次从太平洋返航途中,曾穿过中国东海的北部,航向由琉球群岛的吐噶喇海峡指向济州岛,然后穿过日本海的朝鲜海峡。在此航程中设了十二个海洋观测站,在这些站上,除了其他的观测外,还获得了底部沉积物和底栖动物区系的资料。  相似文献   
93.
缺少密度或孔隙度测定数据的块体堆积速率的计算T.J.S.Sykes等块体堆积速率(MAR)计算已被应用于深海钻探计划(DSDP)和大洋钻探计划(ODP)岩心,以研究大洋盆地的沉积物演化,或把MAR数据分离成岩石学成分以决定方解石补偿深度(CCD)的历...  相似文献   
94.
ObservationofcloudsandsolarradiationoverthePacificOceanasrelationtoglobalclimate¥FarnParungo;ClarenceNagamoto;CeciliaM.I.R.Gi...  相似文献   
95.
AquantitativeanalysisontheEgyptianMediterraneanwaters¥M.A.SaidandF.M.Eid(ReceivedSeptember21,19931accfeptedJanuary15,1994)Abs...  相似文献   
96.
97.
On low-pass digital filters in oceanography   总被引:1,自引:0,他引:1  
-Two types of filters are widely used to remove semidirunal and diurnal tidal signals and other high frequency noises in oceanography. The first type of filters uses moving average with weights in time domain, and can be easily operated. Some data will be lost at each end of the time series, especially for the low low-pass filters. The second type of filters uses the discrete Fourier transform filter (DFTF) which operates in the frequency domain, and there are no data loss at the ends for the forward transform. However, owing to the Gibbs phenomenon and the discrete sampling (Nyquist effect) , ringing appears in the inverse transformed data, which is especially serious at each end. Thus some data at the ends are also discarded. The present study tries to find out what causes the ringing and then to seek for methods to overcome the ringing. We have found that there are two kinds of ringings, one is the Gibbs phenomenon, as defined before. The other is the "Nyquist"ringing due to sampling Nyquist critical  相似文献   
98.
Although the Yellow River Delta and Bohai Sea coastal zone are long distance and different environment with Po River Delta and Adriatic Sea coastal zone, the comparison of data of two different areas and the evolution trend of two areas are quite similar. The influence of natural climatic changes on the evolution of the deltas and coastal zones exists both in ancient and modern times. The cold/wet period occurred in 1300—1400A. D. and 1550 —1850 A.D. within this"large scale" climatie cycle, and shorter periods (10— 35 years) of cold rainy weather alternated with warm/dry period are known as "Bruckner cycles" which have influence on the evolution of the deltas and coastal zones.  相似文献   
99.
A contrasting study of the large-scale circulation features responsible for months with many typhoons and months with tew typhoons has revealed that the frequency of typhoon formation over the Northwest Pacific is related to the following conditions:Over the Northwest Pacific, a well-defined ITCZ (Intertropical Convergence Zone) extending eastward to 160°E was displaced to 20°N. At 200 mb, an extensive anomalous anticyclonic circulation prevails over the western and central Pacific. The condition characteristic of a break in the monsoon prevailed in India. The monsoon trough at 500 mb and at the surface over the Indian Peninsula was relatively weak and was accompanied by higher-than-normal rainfall in the northern part of India and lower-than-normal rainfall over the peninsula. In addition, the polar vortex tends to be weak and move to the side of the Northern Hemisphere, opposite to the North Pacific. Finally, abnormally warm water was observed over the Central and Eastern Pacific and abnormally cold  相似文献   
100.
The method developed by Wen et al. (1988 a) for deriving theoretical wind wave frequency spectrum in deep water is extended to the case of water of finite depth, in which a parameter η=H/d is introduced, where H and d represent the average wave height and water depth respectively. The derived spectra reduce to those in deep water when η=0. The case of η=1/2 corresponds to waves impending to break because of the effect of the bottom. Simplified forms of spectra are given. The theoretical results agree with the observed spectra well.  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