全文获取类型
收费全文 | 30171篇 |
免费 | 5531篇 |
国内免费 | 8344篇 |
专业分类
测绘学 | 3555篇 |
大气科学 | 5115篇 |
地球物理 | 5900篇 |
地质学 | 16044篇 |
海洋学 | 4389篇 |
天文学 | 1424篇 |
综合类 | 2630篇 |
自然地理 | 4989篇 |
出版年
2024年 | 115篇 |
2023年 | 439篇 |
2022年 | 1096篇 |
2021年 | 1351篇 |
2020年 | 1500篇 |
2019年 | 1871篇 |
2018年 | 1365篇 |
2017年 | 1529篇 |
2016年 | 1591篇 |
2015年 | 1804篇 |
2014年 | 1971篇 |
2013年 | 2047篇 |
2012年 | 2115篇 |
2011年 | 2136篇 |
2010年 | 1751篇 |
2009年 | 1906篇 |
2008年 | 2017篇 |
2007年 | 2218篇 |
2006年 | 2174篇 |
2005年 | 1829篇 |
2004年 | 1574篇 |
2003年 | 1355篇 |
2002年 | 1192篇 |
2001年 | 1005篇 |
2000年 | 1038篇 |
1999年 | 960篇 |
1998年 | 795篇 |
1997年 | 622篇 |
1996年 | 527篇 |
1995年 | 429篇 |
1994年 | 392篇 |
1993年 | 332篇 |
1992年 | 301篇 |
1991年 | 195篇 |
1990年 | 105篇 |
1989年 | 118篇 |
1988年 | 85篇 |
1987年 | 56篇 |
1986年 | 44篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1954年 | 7篇 |
1877年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
~(40)Ar/~(39)Ar dating of shear deformation of the Xianshuihe fault zone in west Sichuan and its tectonic significance 总被引:6,自引:1,他引:6
ZHANG Yueqiao CHEN Wen & YANG Nong . Institute of Geomechanics Chinese Academy of Geological Sciences Beijing China . Institute of Geology Chinese Academy of Geological Sciences Beijing China . Institute of Geology Geophysics Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2004,47(9)
TheNW-SEstrikingXianshuihefaultzoneslicesthesoutheasternTibetanPlateauandconnectssoutheastwardwiththeAnninghe-Zemuhe-Xiaojiangfaultzone,whichformahuge,activesinistralstrike-slipfaultzone(fig.1).ThisfaultzoneisanimportantseismicfaultineastTibet[1-5].EarthquakegeologystudiesandoffsetpatternsofyounggeologicalfeatureshaveshownthatlateQuaternarysinistralsliprateoftheXianshuihefaultzonereaches13mm/a[1,2].TheXianshuhefaultzoneconsistsoftwomainbranches,theDaofufaultbranchinthewestandtheXianshuih… 相似文献
992.
YAN Shouxun Laboratory of Remote Sensing Information Sciences Institute of Remote Sensing Applications Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2004,47(9)
To examine the application potential of hyperspectral remote sensing techniques in classifying very low-grade metamorphic belts, the composition of clay minerals and the cyrstallinity of illite from mudstones were measured using XRD and VIS-SWIR (400-2500 nm) reflectance spectroscopy. Based on the illite cyrstallinity, Kubler Index (KI), the Early Triassic LuoLou Group and the Middle Triassic lower Baifeng Formation were classified as the lower Epizone with KI△2θ° ranging from 0.22 to 0.25, the upper Baifeng Formation as upper anchizone with KI△2θ°ranging from 0.26 to 0.33, and the Hekou Formation as lower anchizone with KI△2θ° ranging from 0.38 to 0.40. According to a KI△2θ° value of 0.43, it is possible that there may exist a local diagenetic zone in the upper strata. The illite cyrstallinity Kubler index and the metamorphic grade increase from the bottom to the top of the stratigraphic sequence. The metamorphic grade boundaries nearly match the stratigraphic boundaries, indicating a burial metamorphism nature for the stratigraphic sequence. From the bottom to the top of the sequence, the spectral absorption band center of clay minerals from fresh rocks is around 2200 nm. The absorption band centers change towards shorter wavelengths: the Luolou Group being at 2220 nm, the Baifeng Formation at 2217-2213 nm, the lower member of the Hekou Formation at 2214-2206 nm, and the upper member of the Hekou Formation at 2205-2197 nm. The spectral absorption band center of illite shows the same change pattern. These results indicate that very low-grade metamorphic belts can be subdivided using spectral indices of clay minerals, which are measured by using field portable spectroradiometers. However, it may not work well with satellite and airborne sensors. 相似文献
993.
Preliminary Study on Cenozoic Group and Fault Activity in the Sea Area Near the Yangtze River Mouth 总被引:2,自引:0,他引:2
By shallow seismic prospecting, the Cenozoic Group in the sea area near the Yangtze Rver Mouth can be divided into five seismic sequences. They correspond to the Quaternary,Pliocene, Upper Miocene, Lower Miocene and Eocene respectively. The Quaternary System covers all the detecting area. The Tertiary System overlaps and thins out from NE to SW. The sedimentary basement mainly consists of volcanic rock (J3) and acidic rock (r35). Paleogene or Late Cretaceous basins are not found there. The faults that have been detected are all normal faults. They can be divided into three groups (NE, NW, near EW) by their trend. The NE and NW-trending faults are predominant, and agree with aeromagnetic anomaly. Their length and displacement are larger than that of the EW-trending faults. The activity of the NEtrending faults is different in different segments. The SW segment is a Quaternary fault, the middle segment is a Neogene fault, The NE is Paleogene. But the segment of the NW-trending fault is not obvious. The average vertical displacement rate is about 0.015mm/a. 相似文献
994.
Zhang Xiaoliang 《中国地震研究》2004,18(2):161-170
On the basis of Discontinuous Deformation Analysis (DDA), and considering the moderate intrusion of specific block boundaries to different extents, the first-order block motion model is established for the northeastern margin of Qinghai-Xizang(Tibet) block and the kinematical model for depicting deformation of small regions as well by using GPS observations of three periods (1991, 1999 and 2001). By simulating, we obtained the motion features of the firstorder blocks between the large WWN faults on the sides of the studied region, the distribution features of the principal strain rate field and the inhomogeneous motion features with spacetime of the faults in the northern boundary of the Qinghai-Xizang (Tibet) block. 相似文献
995.
As a result of the left-lateral strike-slipping of the Altyn Tagh fault in Neotectonic period, a contra-rotational structure, namely the Zhaobishan vortex structure, has developed at the juncture of the main Altyn Tagh fault and the northern fringe fault of the Qilian Mountains.Preliminary analysis on the deformation and evolution of the Zhaobishan vortex structure. In combination with the previous data, suggests that the tectonic transform between the Altyn Tagh fault and the northern fringe fault of the Qilian Mountains attributes to the deformation of the rotational structure. The existence of a series of rotational structures along the Altyn Tagh fault and on the northeastern edge of the Qinghai-Xizang(Tibet) plateau indicate that as the substance in the northern Qinghal-Xizang (Tibet) plateau moves clockwise around the eastern tectonic knot of the Himalayas, rotational structures become the principal mode on the northern marginal zone of the Plateau of transforming and absorbing tectonic deformation. 相似文献
996.
997.
山西省主要河流流域面雨量预报业务流程 总被引:3,自引:1,他引:3
以T213、HLAFS模式、MM5中尺度模式输出的格点资料以及日本降水量格点资料为基础,将影响山西降水的天气动力模型归纳为诊断模型,从中引出多个能够全面反映降水模型特征的综合物理因子;根据各种数值模式输出的降水量预报性能和质量优劣特点,依据数值模式的形势场预报优于要素场预报的现实,构造在不同环流形势背景下,启动不同预报方程的面雨量预报业务流程,有效地遏止了在环流形势调整时预报输出不能快速响应的弱点,提高了点和面雨量预报的准确度。 相似文献
998.
本文分析了天山山区近40 a来年降水变化的基本特征,并与南疆、北疆进行了比较,所得的主要结果如下:(1)天山山区在年降水量干湿变化阶段上与北疆的相似性强于南疆。(2)年降水量的空间分布的同步变化性以北疆为最好,南疆最差,天山山区居中,而年降水量的空间分布的反向变化性,以天山山区为最大,北疆最小,南疆居中。(3)天山山区与南疆从60年代到90年代,年降水均表现出了持续的增加的趋势,北疆年降水从60年代到90年代,除70年代外,不断增多。 相似文献
999.
1000.
通过对阿勒泰地区1991~2000年西部区域性偏东大风天气的气候特征、环流形势及地形进行分析,归结出产生西部区域性偏东大风天气的成因及预报指标。 相似文献