全文获取类型
收费全文 | 10111篇 |
免费 | 2273篇 |
国内免费 | 1929篇 |
专业分类
测绘学 | 1147篇 |
大气科学 | 1122篇 |
地球物理 | 3547篇 |
地质学 | 4836篇 |
海洋学 | 980篇 |
天文学 | 537篇 |
综合类 | 1160篇 |
自然地理 | 984篇 |
出版年
2024年 | 43篇 |
2023年 | 110篇 |
2022年 | 253篇 |
2021年 | 330篇 |
2020年 | 373篇 |
2019年 | 470篇 |
2018年 | 350篇 |
2017年 | 390篇 |
2016年 | 426篇 |
2015年 | 515篇 |
2014年 | 549篇 |
2013年 | 627篇 |
2012年 | 663篇 |
2011年 | 664篇 |
2010年 | 484篇 |
2009年 | 637篇 |
2008年 | 587篇 |
2007年 | 764篇 |
2006年 | 658篇 |
2005年 | 547篇 |
2004年 | 506篇 |
2003年 | 480篇 |
2002年 | 396篇 |
2001年 | 391篇 |
2000年 | 384篇 |
1999年 | 370篇 |
1998年 | 342篇 |
1997年 | 321篇 |
1996年 | 311篇 |
1995年 | 235篇 |
1994年 | 249篇 |
1993年 | 210篇 |
1992年 | 157篇 |
1991年 | 106篇 |
1990年 | 104篇 |
1989年 | 102篇 |
1988年 | 66篇 |
1987年 | 45篇 |
1986年 | 26篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1954年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
GPS-OEM在精准农业领域中的应用实例 总被引:4,自引:0,他引:4
介绍了我中心开发的内置有GPS—OEM板的农田信息采集系统,指出了GPS—OEM在精准农业领域发展潜力。 相似文献
212.
213.
During the magnetic storm of 21st March 1990, the DE-1 spacecraft encountered the auroral region at high invariant latitude
at altitudes ranging from a few thousand kilometers in the ionosphere to many earth radii in the magnetosphere. The magnetic
field perturbations interpretable as field aligned current (FAC) layers and the electrostatic turbulence possibly due to electrostatic
ion acoustic instability driven by these currents are shown. The critical drift velocity of Hot Plasma Torus (HPT) electrons
and the growth rate of ion acoustic wave as a function of electron to ion temperature ratio (T
e/Ti) for low and high current densities and energy of HPT electrons are found out. The intense FAC destabilizes the ion acoustic
wave and the resultant electrostatic turbulence creates an anomalous resistivity. The current driven resistivity produces
parallel electric field and high power dissipation. The anomalous resistivityη, potential difference along the auroral field lines Vt|, intensity of electric field turbulenceE
t| and power produced per unit volumeP are computed. It is found that the change in westward magnetic perturbation increasesJ
t|, η, Vt|, Et| andP. Hence HPT electrons are heated and accelerated due to power dissipation during magnetically active periods in the auroral
region. Concerning, applications, such HPT electrons can be used in particle accelerators like electron ring accelerator,
smokatron etc. 相似文献
214.
We approach the reconstruction of the recent structural evolution of Stromboli volcano (Italy) and the analysis of the interplay between tectonics, gravity and volcanic deformation. By tying together structural, lithostratigraphic and rock mechanics data, we establish that since 100 ka BP, the edifice has faulted and jointed mainly along NE-striking planes. Faults mostly dip to the NW with normal displacement. Taking also into account the presence of a NW-trending regional least principal stress and of tectonic earthquake hypocenters inside the cone, we suggest that this fracturing can be related to the transmission of tectonic forces from the basement to the cone. Dyking concentrated along a main NE-trending weakness zone (NEZ) across the volcano summit, resembling a volcanic rift, whose geometry is governed by the tectonic field. In the past 13 ka, Stromboli experienced a reorganisation of the strain field, which was linked with the development of four sector collapses affecting the NW flank, alternating with growth phases. The tectonic strain field interplayed with dyking and fracturing related to unbuttressing along the collapse shoulders. We propose that tectonics control the geometry of dykes inside the cone and that these, in turn, contribute to destabilise the cone flanks. 相似文献
215.
Cretaceous deformation history of the middle Tan-Lu fault zone in Shandong Province, eastern China 总被引:13,自引:0,他引:13
Based on field analysis of fault-slip data from different rock units of the Cretaceous basins along the middle part of the Tan-Lu fault zone (Shandong Province, eastern China), we document polyphase tectonic stress fields and address the changes in sense of motion of the Tan-Lu fault zone during the Cretaceous. The Cretaceous deformation history of the Tan-Lu fault zone can be divided into four main stages. The first stage, during the earliest Cretaceous, was dominated by N-S extension responsible for the formation of the Jiaolai basin. We interpret this extension to be related to dextral strike-slip pull-apart opening guided by the Tan-Lu fault zone. The second stage, during the middle Early Cretaceous, was overwhelmingly rift-dominated and characterized by widespread silicic to intermediate volcanism, normal faulting and basin subsidence. It was at this stage that the Tan-Lu-parallel Yi-Shu Rift was initiated by E-W to WNW-ESE extension. The tectonic regime then changed during the late Early Cretaceous to NW-SE-oriented transpression, causing inversion of the Early Cretaceous rift basin and sinistral slip along the Tan-Lu fault zone. During the Late Cretaceous, dextral activation of the Tan-Lu fault zone resulted in pull-apart opening of the Zhucheng basin, which was subsequently deformed by NE-SW compression. This deformation chronology of the Tan-Lu fault zone and the associated Cretaceous basins allow us to constrain the regional kinematic models as related to subduction along the eastern margin of Asia, or related to collision in the Tibet region. 相似文献
216.
217.
Application of Weights of Evidence to Mineral Potential Mapping of Yujiacun Ore Field in Northwest Yunnan Province, China 总被引:1,自引:0,他引:1
ZHAO Pengda 《中国地质大学学报(英文版)》2003,14(3):269-273
The multivariate information conprehensive processing technique is especially important at present to the digital mineral prospecting. However, the GIS-based weights of evidence have provided us with powerful tool for the quantitative assessment of mineral resource potential. In this paper, the mineralization model is established, based on the achievements made by previous researchers, to mend such deficiencies ad few references on ore fields in Yujiacun, Yunnan Province and the shortage of quantitative prediction and assessment of mineral resources. In addition, the weights of evidence are used to make a systematic quantitative prediction and assessment of mineral resources there, so that 2 mineral prospecting target areas of grade Ⅰ and 8 mineral prospecting target areas of grade Ⅱ are delineated, providing the further mineral resource exploration with the basis for the selection of mineral deposits. 相似文献
218.
219.
220.