全文获取类型
收费全文 | 10739篇 |
免费 | 2223篇 |
国内免费 | 3982篇 |
专业分类
测绘学 | 548篇 |
大气科学 | 1774篇 |
地球物理 | 3151篇 |
地质学 | 7398篇 |
海洋学 | 1348篇 |
天文学 | 446篇 |
综合类 | 1334篇 |
自然地理 | 945篇 |
出版年
2024年 | 22篇 |
2023年 | 95篇 |
2022年 | 254篇 |
2021年 | 331篇 |
2020年 | 250篇 |
2019年 | 313篇 |
2018年 | 361篇 |
2017年 | 315篇 |
2016年 | 357篇 |
2015年 | 340篇 |
2014年 | 404篇 |
2013年 | 370篇 |
2012年 | 382篇 |
2011年 | 854篇 |
2010年 | 666篇 |
2009年 | 799篇 |
2008年 | 482篇 |
2007年 | 612篇 |
2006年 | 792篇 |
2005年 | 817篇 |
2004年 | 1344篇 |
2003年 | 943篇 |
2002年 | 696篇 |
2001年 | 553篇 |
2000年 | 457篇 |
1999年 | 460篇 |
1998年 | 517篇 |
1997年 | 461篇 |
1996年 | 355篇 |
1995年 | 323篇 |
1994年 | 275篇 |
1993年 | 462篇 |
1992年 | 393篇 |
1991年 | 204篇 |
1990年 | 97篇 |
1989年 | 124篇 |
1988年 | 72篇 |
1987年 | 99篇 |
1986年 | 55篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1978年 | 14篇 |
1977年 | 20篇 |
1976年 | 12篇 |
1940年 | 9篇 |
1937年 | 15篇 |
1933年 | 13篇 |
1924年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
21.
DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHEHEXIREGION,CHINA肖洪浪,高前兆,李福兴DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHE... 相似文献
22.
通过对辽北法库地区构造岩的观察和研究,确定了本区存在一大型推覆韧性剪切带。根据同构造侵入岩的同位素年龄,确定该韧性剪切带形成时期为海西-印支期,这与天山-兴安褶皱系最终形成时间相一致 相似文献
23.
Tidal effects on temperature front in the Yellow Sea 总被引:5,自引:0,他引:5
Temperature front (TF) is one of the important features in the Yellow Sea, which forms in spring, thrives in summer, and fades
in autumn as thermocline declines. TF intensity ⋎S
T
⋎ is defined to describe the distribution of TF. Based on the MASNUM wave-tide-circulation coupled model, temperature distribution
in the Yellow Sea was simulated with and without tidal effects. Along 36°N, distribution of TF from the simulated results
are compared with the observations, and a quantitative analysis is introduced to evaluate the tidal effects on the forming
and maintaining processes of the TF. Tidal mixing and the circulation structure adapting to it are the main causes of the
TF.
Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No.
49736190). 相似文献
24.
Hui-Rong Ji Qi-Jun Pu Yi-Hua Yan Yu-Ying Liu Zhi-Jun Chen Cheng-Ming Tan Cong-Ling Cheng De-Bang Lao Shu-Ke Li Zhi-Qiang Wang Min-Hong Yu Jian-Nong Liu Li-Kang Zhang Ji-Yong Gao National Astronomical Observatories Chinese Academy of Sciences Beijing Hebei Semiconductor Research Institute Shijiazhuang 《中国天文和天体物理学报》2005,5(4):433-441
An improved Solar Radio Spectrometer working at 1.10-2.06 GHz with much improved spectral and temporal resolution, has been accomplished by the National Astronomical Observatories and Hebei Semiconductor Research Institute, based on an old spectrometer at 1-2 GHz. The new spectrometer has a spectral resolution of 4 MHz and a temporal resolution of 5ms, with an instantaneous detectable range from 0.02 to 10 times of the quiet Sun flux. It can measure both left and right circular polarization with an accuracy of 10% in degree of polarization. Some results of preliminary observations that could not be recorded by the old spectrometer at 1-2 GHz are presented. 相似文献
25.
1:5万区域地质调查工作中,在柴达木陆块北缘首次发现古元古代变质镁铁—超镁铁质岩,获得成岩年龄为1952±15Ma,其岩石化学、地球化学特征反映出岩浆来源于亏损地幔,反映出该地区克拉通在古元古代(19亿年)发生了一次强烈的裂解(洋)事件,对于研究柴达木盆地北缘元古代结晶基底地质构造演化及进一步探讨柴达木盆地的起源及构造演化过程提供了重要地质线索。 相似文献
26.
应用地壳波浪与镶嵌构造学说对富氏谱分析法提取地壳垂直形变信息的科学性做了地质学意义上的阐释 ,并提出了根据多期形变资料提取特定波段上构造策应力的数学模型 相似文献
27.
28.
Northern Hemispheric“polar lows”,i.e.maritime,small,but fairly intense cyclonic systems have been studied formore than two decades.Recently researchers have turned their attention towards the occurrence of polar lows and othersmall-scale cyclonic disturbances on the Southern Hemisphere.In this paper a short account of our present knowledgeof Northern Hemispheric polar lows will be given,followed by some preliminary results of an investigation of the natureand occurrence of polar lows on the Southern Hemisphere. 相似文献
29.
Shi Zhi-dong Li Zhong-yuanUniversity of Science Technology of China Hefei PRC Advanced Centre for Earth Science Astronomy Third World Academy of Science 《紫金山天文台台刊》1996,(2)
Areview about K-H instability related to comet tail is presented.The effect of dust graing on KHI is theoretically analysed and relations of critical shear to excit KHI with the properties of dust grains both for sheared ion flow and for sheared dust flow re put out.Their possible application in comet tail is suggested. 相似文献
30.
PROPAGATION OF 30—60 DAY LOW FREQUENCY OSCILLATIONS AND THEIR INFLUENCE UPON THE SUBTROPICAL WESTERLIES JET STREAM DURING NORTHERN HEMISPHERE WINTER
下载免费PDF全文
![点击此处可从《Acta Meteorologica Sinica》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Based on daily ECMWF gridpoint data of two winters during 1981—1983 including an ENSOyear,propagation of low frequency oscillations(LFO)during Northern Hemisphere winters andtheir influences upon 30—60 day oscillations of the subtropical jet stream are studied with the sta-tistical methods as complex empirical orthogonal function(CEOF)and so on.Results show that inthe winter of a normal year(1981—1982),30—60 day oscillations in the subtropical zone aremainly in the northern and southern flanks of exit region of jet stream.In the ENSO year(1982—1983),they are mainly in the vicinity of entrance and exit regions of jet stream.Intraseasonalchanges of subtropical jet stream manifested themselves as latitudinal fluctuation or longitudinalprogression or regression of about 40 day period.There are marked differences between propagat-ing passages of low frequency modes responsible for changes of subtropical jet stream in the normalyear(1981—1982)and in the ENSO year(1982—1983).Changes of oscillation amplitude showobvious phases.In general,the one in late winter is stronger than that in early winter,strongestone occurs in February. 相似文献