全文获取类型
收费全文 | 1151篇 |
免费 | 165篇 |
国内免费 | 172篇 |
专业分类
测绘学 | 247篇 |
大气科学 | 64篇 |
地球物理 | 264篇 |
地质学 | 437篇 |
海洋学 | 173篇 |
天文学 | 18篇 |
综合类 | 44篇 |
自然地理 | 241篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 16篇 |
2021年 | 27篇 |
2020年 | 38篇 |
2019年 | 61篇 |
2018年 | 30篇 |
2017年 | 50篇 |
2016年 | 45篇 |
2015年 | 45篇 |
2014年 | 47篇 |
2013年 | 56篇 |
2012年 | 48篇 |
2011年 | 49篇 |
2010年 | 62篇 |
2009年 | 67篇 |
2008年 | 70篇 |
2007年 | 89篇 |
2006年 | 84篇 |
2005年 | 45篇 |
2004年 | 77篇 |
2003年 | 65篇 |
2002年 | 41篇 |
2001年 | 36篇 |
2000年 | 33篇 |
1999年 | 37篇 |
1998年 | 28篇 |
1997年 | 27篇 |
1996年 | 30篇 |
1995年 | 21篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1488条查询结果,搜索用时 15 毫秒
601.
602.
603.
604.
605.
We present results from a comparative analysis of empirical and synthetic shapes for isoseismals of low intensity (I = IV–VI on the MCS scale) for six Italian earthquakes of ML = 4.5–6. Our modeling of isoseismals is based on a plane-stratified earth model and on the double–couple point source approximation to calculate seismograms in the frequency range f 1 Hz. With a minimum of parameter variation we demonstrate that the low intensity isoseismals provide information on source geometry. We strive to avoid subjectivity in isoseismal constructions by using the new Diffuse Boundary method, which visualizes isoseismals with their uncertainty. Similar results in this direction are known for large earthquakes (ML 6 or greater) with extended sources and for the higher isoseismals (I VI on the MM scale). The latter studies disregard the earth structure, use a greater number of parameters, and therefore have greater possibilities for fitting the data than our approach. 相似文献
606.
Ocean wind fields retrieved from the advanced synthetic aperture radar aboard ENVISAT 总被引:1,自引:0,他引:1
In this paper an algorithm is presented which enables high-resolution ocean surface wind fields to be retrieved from the advanced synthetic aperture radar (ASAR) data acquired by the European remote sensing satellite ENVISAT. Wind directions are extracted from wind-induced streaks that are visible in ASAR images at scales above 200 m and that are approximately in line with the mean surface wind direction. Wind speeds are derived from the normalized radar cross section (NRCS) and image geometry of the calibrated ASAR images, together with the local ASAR-retrieved wind direction. Therefore the empirical C-band model CMOD4, which describes the dependency of the NRCS on wind and image geometry, is used. CMOD4 is a semi-empirical model, which was originally developed for the scatterometer of the European remote sensing satellites ERS-1 and 2 operating at C-band with vertical polarization. Consequently, CMOD4 requires modification when applied to ASAR images that were acquired with horizontal polarization in transmitting and receiving. This is performed by considering the polarization ratio of the NRCS. To demonstrate the applicability of the algorithm, wind fields were computed from several ENVISAT ASAR images of the North Sea and compared to atmospheric model results of the German weather service.Acknowledgements The authors were supported by the German Bundesministerium für Bildung und Forschung (BMBF) in the framework of the project. A new perspective of the Ocean ENVISAT Oceanography (ENVOC). The ENVISAT ASAR data were kindly made available by the European Space Agency in the framework of the ENVISAT Project AO-ID 220, Biological and geophysical parameters from synthetic aperture radar over the ocean (BIGPASO). 相似文献
607.
棉兰老岛以东反气旋涡的Argo观测研究 总被引:1,自引:0,他引:1
报道了2003年1月至10月期间,由布放于西北太平洋中的Argo剖面浮标捕获的位于棉兰老岛以东海域的反气旋涡。该涡中心位于8.7°N、127.6°E附近,距大陆坡不远,沿等深线走向呈椭圆形分布。其长轴(NW-SE)约200km,短轴(NE-SW)长约120km。Argo浮标的漂移轨迹及其在表层及1 500db层的漂移速度场表明,该反气旋涡位于温跃层以下,中层海洋特征。在1 500db层上,涡的外围平均切向速度为11.9—14.0cm.s-1,旋转周期约为40d。温、盐度断面分布表明,该反气旋涡内的温盐结构非常复杂,可能与源自南、北半球的中层水团在涡旋内交汇并发生变性有关。 相似文献
608.
609.
Naoto Iwasaka Toshio Suga Kensuke Takeuchi Keisuke Mizuno Yasushi Takatsuki Kentaro Ando Taiyo Kobayashi Eitarou Oka Yasuko Ichikawa Motoki Miyazaki Hiroshi Matsuura Kenji Izawa Chan-Su Yang Nobuyuki Shikama Momoko Aoshima 《Journal of Oceanography》2003,59(1):119-127
We deployed two profiling floats in the region south of the Kuroshio Extension in March 2000. Temperature and salinity profiles
from a depth of 1500 × 104 Pa to the surface are reported every two and four weeks, respectively. The floats performed very well for first four months
after deployment. Later they failed in surfacing for a few months when the sea surface temperature in the region was high.
The salinity sensors seemed to suffer from some damage during their failure-in-surfacing period. Despite this trouble, the
results clearly demonstrate that the profiling float is a very useful and cost-effective tool for physical oceanographic observation
in the open sea.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
610.
精密轨道支持下的哨兵卫星TOPS模式干涉处理 总被引:1,自引:1,他引:0
哨兵卫星采用TOPS模式成像,为确保影像干涉相位偏差小于3°,方位向配准精确度需达到0.001个像素。本文论证了哨兵卫星精密轨道条件下进行几何配准即可达到较高的配准精度,满足增强谱分集进行方位向残余偏移量估计的前提条件,并基于DORIS软件实现哨兵卫星TOPS模式影像的几何配准和增强谱分集优化配准处理。地表方位向形变等信号可导致Burst干涉图之间发生相位跳变,并对增强谱分集估计几何配准残余偏移量时产生干扰,本文开展了相关的理论分析和数据处理试验,提出粗差探测方法消除相位跳变对增强谱分集配准的干扰。 相似文献