全文获取类型
收费全文 | 2016篇 |
免费 | 266篇 |
国内免费 | 732篇 |
专业分类
测绘学 | 300篇 |
大气科学 | 51篇 |
地球物理 | 425篇 |
地质学 | 1599篇 |
海洋学 | 172篇 |
天文学 | 71篇 |
综合类 | 233篇 |
自然地理 | 163篇 |
出版年
2024年 | 11篇 |
2023年 | 34篇 |
2022年 | 69篇 |
2021年 | 87篇 |
2020年 | 77篇 |
2019年 | 97篇 |
2018年 | 71篇 |
2017年 | 84篇 |
2016年 | 98篇 |
2015年 | 86篇 |
2014年 | 115篇 |
2013年 | 164篇 |
2012年 | 110篇 |
2011年 | 121篇 |
2010年 | 103篇 |
2009年 | 139篇 |
2008年 | 133篇 |
2007年 | 152篇 |
2006年 | 138篇 |
2005年 | 113篇 |
2004年 | 125篇 |
2003年 | 116篇 |
2002年 | 101篇 |
2001年 | 97篇 |
2000年 | 88篇 |
1999年 | 76篇 |
1998年 | 53篇 |
1997年 | 55篇 |
1996年 | 50篇 |
1995年 | 42篇 |
1994年 | 49篇 |
1993年 | 41篇 |
1992年 | 28篇 |
1991年 | 19篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有3014条查询结果,搜索用时 15 毫秒
171.
新疆东部基性超曲性岩常成群成带分布,明显受区域性深大断裂控制,可分为蛇绿岩套型和岩浆侵入型两种,前者包括阿尔曼太岩带和克拉美丽岩带,是蛇绿岩套的主要组成部分,前者包括阿尔曼太岩带和克拉美丽岩带,是蛇绿岩套的主要组成部分,包括喀拉通克岩带黄山岩带,为来源于上地幔的原始岩浆经分异,结晶而成,文中对这两类基性超基性岩的地质地球化学特征进行了系统研究。 相似文献
172.
中国海城地震区地壳与上地幔构造特征的研究 总被引:1,自引:0,他引:1
研究表明,海城地震区地壳与上地幔构造特征可以归纳为如下四点:1.震区所处的辽南地区,其地壳是由高速与低速相间的成层介质组成,地壳与上地幔结构不论纵向和横向都是不均匀的,且被深大断裂切割为若干块体;2.本区地壳按其界面分布特征可分为上层地壳、中层地壳和下层地壳;3.本区地壳介质在纵向及横向上均存在明显的不均一性;4.海城地震震源区位于耿庄——海城上地幔局部隆起东侧的中层地壳上部。 相似文献
173.
The second vertical derivatives of gravity and magnetic potential are widely used in geophysical prospecting because of their
better resolution. On the same basis an attempt has been made to obtain the expressions for the second vertical derivative
of the electrical potential and to compute its nature for comparison. Derivative responses over a two-layered earth and also
over an anticlinal structure have been computed and it is shown that the second vertical derivative sounding could be employed
for greater accuracy in finding out the thickness of such beds or the inclination of the sides of the anticline and its depth
when compared with normal resistivity sounding 相似文献
174.
地球数字产品的空间数学基础 总被引:4,自引:0,他引:4
在分析当前地球数字产品空间数学基础局限性的基础上,将地图投影概念由传统的曲面到平面的变换扩展为曲面到曲面的变换,提出一套适合于大型GIS和地球数字产品的“地图投影”模型的实用模型,该模型的视图采用等距离切圆柱投影,度量空间是椭球面几何系统,符合计算机环境下GIS视图与度量空间分离的特性。鉴于全球多分辨率连续可视化,精密可视化量算,三维、多维地球数据统一,标准的空间定位框架和只有在统一的空间系统内全球资源、生态环境数据才能进行精确的地理分析等四个方面的需要,从地图投影进到本模型将是方向和技术趋势。 相似文献
175.
176.
This paper focuses on the influence of the initial void ratio on the evolution of the passive earth pressure and the formation
of shear zones in a dry sand body behind a retaining wall. For the numerical simulation a rigid and very rough retaining wall
undergoing a horizontal translation against the backfill is considered. The essential mechanical properties of cohesionless
granular soil are described with a micro-polar hypoplastic model which takes into account stresses and couple stresses, pressure
dependent limit void ratios and the mean grain size as a characteristic length. Numerical investigations are carried out with
an initially medium dense and initially loose sand using a homogeneous and random distribution of the initial void ratio.
The geometry of calculated shear zones is discussed and compared with a corresponding laboratory model test. 相似文献
177.
Seismic Passive Earth Pressure Behind Non-vertical Retaining Wall Using Pseudo-dynamic Analysis 总被引:3,自引:0,他引:3
Priyanka Ghosh 《Geotechnical and Geological Engineering》2007,25(6):693-703
This paper shows a detailed study on the seismic passive earth pressure behind a non-vertical cantilever retaining wall using
pseudo-dynamic analysis. A planar failure surface has been considered behind the retaining wall. The effects of soil friction
angle, wall inclination, wall friction angle, horizontal and vertical earthquake acceleration on the passive earth pressure
have been explored. Unlike the Mononobe–Okabe method, which incorporates pseudo-static analysis, the present analysis predicts
a nonlinear variation of passive earth pressure along the wall. The results have been thoroughly compared with the existing
values in the literature. 相似文献
178.
Jin Yaqiu 《Frontiers of Earth Science》2007,1(3):284-298
This paper briefly presents the research progress of the State Major Basic Research Project 2001CB309400, “Theory and Application
for Retrieval and Fusion of Spatial and Temporal Quantitative Information from Complex Natural Environment”. Based on the
rapid advancement of synthetic aperture radar (SAR) imagery technology, information theory of fully polarimetric scattering
and applications in polarimetric SAR remote sensing are developed. To promote the modeling of passive microwave remote sensing,
the vector (polarized) radiative transfer theory (VRT) of complex natural media such as inhomogeneous, multi-layered and 3-dimensional
VRT is developed. With these theoretical progresses, data validation and retrieval algorithms for some typical events and
characteristic parameters of earth terrain surfaces, atmosphere, and oceans from operational and experimental remote sensing
satellites are studied. Employing remote sensing, radiative transfer simulation, geographic information systems (GIS), land
hydrological process, and data assimilation, the Chinese land data assimilation system (CLDAS) is established. Towards the
future development of China’s microwave meteorological satellites, employing remote sensing data of currently available SSM/I
(special sensor microwave/imager), AMSU (advanced microwave sounding unit), MTI (microwave temperature imager), etc., with
ground-based measurements, several operational algorithms and databases for atmospheric precipitation, water vapor and liquid
water in clouds, and other hydrological/hydrological applications are developed. To advance China’s SAR and InSAR (interferometric
SAR) technologies, the image processing and analysis of ERS (European remote sensing), Radarsat SAR, and Chinese SAR, etc.,
the software platforms are accomplished. Based on the researches of multi-information fusion, some simulations, identification,
and information extractions of the targets from complex background clutter scenes are studied. Some experiments of radio wave
propagation in anomalous atmospheric status are also carried out.
Translated from Advances in Earth Science, 2007, 22(2): 111–125 [译自: 地球科学进展] 相似文献
179.
In this paper, we analyze the stress change associated with the inverted volcanic source models at Mayon volcano, Philippines,
where there are gravity changes without significant deformation after the 1993 eruption. We detail the applicable data and
the associated inversion techniques and models prior to calculating the appropriate stress changes. It is determined that
the stress change associated with the central magmatic source produces compressional stress changes at a secondary source
to the northwest, prompting a change in the local water storage in the underlying fractured rock. 相似文献
180.
GIS在"数字城市"中的应用与研究 总被引:2,自引:4,他引:2
根据在“数字厦门”项目策划、建设和应用推广的实际经验,对“数字城市”的理解作了阐述,介绍了“数字厦门”的主要建设内容和应用情况,探讨了与GIS有关的问题。 相似文献