全文获取类型
收费全文 | 406篇 |
免费 | 73篇 |
国内免费 | 309篇 |
专业分类
大气科学 | 134篇 |
地球物理 | 182篇 |
地质学 | 197篇 |
海洋学 | 111篇 |
天文学 | 86篇 |
综合类 | 8篇 |
自然地理 | 70篇 |
出版年
2024年 | 15篇 |
2023年 | 52篇 |
2022年 | 41篇 |
2021年 | 41篇 |
2020年 | 16篇 |
2019年 | 9篇 |
2018年 | 23篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 18篇 |
2014年 | 18篇 |
2013年 | 15篇 |
2012年 | 21篇 |
2011年 | 27篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 29篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 20篇 |
2002年 | 25篇 |
2001年 | 31篇 |
2000年 | 40篇 |
1999年 | 35篇 |
1998年 | 20篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1976年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有788条查询结果,搜索用时 12 毫秒
191.
Non—Acceleration theorem in a primitive equation system: I. Acceleration of zonal mean flow 总被引:5,自引:0,他引:5
Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelms thermal forcing in maintaining the mean flow in which the internal mechanical forcing associated with horizontal eddy flux of momentum plays the most important roles. Both internal forcing and external forcing are shown to be active and at the first place for the mean flow variations, whereas the forcing-induced mean meridional circulation is passive and secondary. It is also shown that the effects on mean flow of external mechanical forcing are concentrated in the lower troposphere, whereas those due to wave-mean flow interaction are more important in the upper troposphere. These act together and result in the vertically easterly shear in low latitudes and westerly shear in mid-latitudes. This verti-cal shear of mean flow is to some extent weakened by thermal forcing. 相似文献
192.
Determination on the content variation of 210Pb, 226Ra and total β radioactivity in estuary sediments of the Jiulongjiang River and the Changjiang River were made to study distributions of natural radioactive substances in the areas studied. Sources of radioactive substances were determined, and the transportation of bottom waters and sediments in the areas was searched according to the distributions. 相似文献
193.
Empirical orthogonal function(EOF) analysis was applied to a 50-year long time series of monthly mean positions of the Kuroshio path south of Japan from a regional reanalysis. Three leading EOF modes characterize the contributions from three typical paths of the Kuroshio meander: the typical large meander path, the offshore nonlarge meander path, and the nearshore non-large meander path, respectively. Accordingly, the spatial variation characteristics of oceanic anomaly fields can be depicted by... 相似文献
194.
物源分析是盆地研究的一项重要内容,在有利储层预测和油气田勘探中具有重要作用。不同物源区形成的母岩及沉积环境存在差异性,致使各物源区沉积物组分在微观特征上存在差异。选取民丰洼陷沙三中亚段沉积物特征元素比值和重矿物含量作为研究的样本,采用聚类分析方法对物源体系进行研究。首先,在对特征元素指标进行优选的基础上,通过对沉积物特征元素比值进行Q型聚类分析,精确刻画了不同物源体系的范围;其次,对沉积物重矿物含量进行R型聚类分析,恢复了不同物源区的母岩类型。研究表明:洼陷主体区主要受来自青坨子地区的永安镇三角洲和南部的东营三角洲影响。分析结果与宏观的沉积学特征一致,证明该方法可以有效地判断沉积物的物源方向。 相似文献
195.
Liu Wenlong Wu Peizhi and Chen YuweiSeismological Bureau of Annul Province Hefei China 《中国地震研究》1996,(3)
In this paper,a new method for determining the earthquake fracture feature is put forward.The generalized directional function DG is defined as the ratio of P waveamplitude spectrums recorded at station 1 and station 2 by comparisonof the recorded DG curve and the theoretical curve,the ratio of fracture lengths of a bilateral fracture in two opposite directions and the angle between station 1 and the main rupture propagating direction can be determined simultaneously.Theoretically speaking,only records of three stations distributed homogeneously are needed to determine the fracture feature of an earthquake.The main rupturing propagating direction of a strong aftershock(ML5.4)of the Tangshan earthquake(Ms7.8)has been obtained by using the new method and has been compared with the result of the earthquake source mechanism.This shows that this new method is effective. 相似文献
196.
NUMERICAL STUDY ON THE LOCAL WIND STRUCTURES FORCED BY THE COMPLEX TERRAIN OF QINGDAO AREA 总被引:1,自引:0,他引:1 下载免费PDF全文
In this paper, some 2-D features of the down- and up-slope winds and sea-land-breeze generated over the com-plex terrain of the Qingdao area and the interaction between them are numerically analysed by use of a 2-Dnon-hydrostatic mesoscale model. The simulated results in the west-east vertical cross-section show that (1) when thelarge-scale wind is a southerly gentle one, the generated easterly down-slope wind is much stronger than with an oppo-site background wind, and the down-slope wind can trigger and intensify the land breeze corresponding to the easterncoast of Jiaozhou Bay; (2) a gentle westerly background wind will reduce the eastward sea breeze and up-slope windduring the daytime due to a cold advection, but shows a little effect on the mesoscale circulation formed in the nighttime. 相似文献
197.
Wang Suyun Wu Ge Shi Zhenliang Li Qun Zhai Wenjie Gao Ajia Wu Huanying Guo Ying and Zhang XiaodongInstitute of Geophysics CSB Beijing ChinaSeismological Bureau of Liaoning Province Shenyang China 《中国地震研究》1999,(1)
This paper briefly introduces the principles and methods for compiling the "Catalog of Recent Chinese Earthquakes (1912 ~ 1990, MS≥4.7)." This new catalog is compiled by revising and supplementing the 1983 version of the Catalog of Chinese Earthquakes. 相似文献
198.
199.
200.
地震层析正作为确定地下构造的一种成象方法出现了。当视角覆盖有限,并且介质的不均匀性尺度和波长相当时,一般的射线层析方法就会失效,这在地球物理应用中是常见的。为改进成象过程,还需要其它的层析成象方法。这里,我们研究绕射层析和多源全息,并就它们对地面反射剖面(SRP),垂直地震剖面(VSP),以及井间测量中的应用进行评价。对沿震源线(source line)的线震源(line sources)和接收线(receiver line)的线接收器(line receivers),给出了二维分布的理论公式。绕线层析理论以Born或Rytov近似为基础。通过使用空间频率域覆盖的信息的考查以及数字例子来评价绕射层析和多源全息方法。类似于克希霍夫偏移,多源全息常给出被畸变的物体图象。这种畸变,在SRP情形中,产生图象的长尾,在VSP情形中,形成强烈的噪音带,并且这是由目标谱的不完全和非均一的覆盖所导至的。绕射层析的滤波作用有助于校正重构过程中的目标潜的非均一覆盖(包括重复),从而消减畸变。另一方面,多源全息更便于勾画声阻抗对比度较大的锐边界,因为现在所阐述的绕射层析方法仅限于弱非均匀性的情况。此外,多源全息有使用任意数目的震源(包括单震源)的灵活性,采样间隔不受奈奎斯特频率的限制。数字例子表明组合资料集(如地面反射资料和VSP资料的组合,或井间资料和地面资料的组合等)将改进图象质量。 相似文献