全文获取类型
收费全文 | 3009篇 |
免费 | 527篇 |
国内免费 | 704篇 |
专业分类
测绘学 | 134篇 |
大气科学 | 658篇 |
地球物理 | 707篇 |
地质学 | 1511篇 |
海洋学 | 374篇 |
天文学 | 220篇 |
综合类 | 317篇 |
自然地理 | 319篇 |
出版年
2024年 | 8篇 |
2023年 | 44篇 |
2022年 | 119篇 |
2021年 | 146篇 |
2020年 | 131篇 |
2019年 | 109篇 |
2018年 | 148篇 |
2017年 | 161篇 |
2016年 | 174篇 |
2015年 | 134篇 |
2014年 | 192篇 |
2013年 | 160篇 |
2012年 | 135篇 |
2011年 | 153篇 |
2010年 | 165篇 |
2009年 | 161篇 |
2008年 | 130篇 |
2007年 | 133篇 |
2006年 | 97篇 |
2005年 | 94篇 |
2004年 | 100篇 |
2003年 | 87篇 |
2002年 | 94篇 |
2001年 | 96篇 |
2000年 | 103篇 |
1999年 | 155篇 |
1998年 | 115篇 |
1997年 | 125篇 |
1996年 | 119篇 |
1995年 | 94篇 |
1994年 | 98篇 |
1993年 | 70篇 |
1992年 | 82篇 |
1991年 | 55篇 |
1990年 | 43篇 |
1989年 | 50篇 |
1988年 | 38篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 22篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1965年 | 1篇 |
1964年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有4240条查询结果,搜索用时 31 毫秒
51.
Wang Tan K. McIntosh Kirk Nakamura Yosio Liu Char-Shine Chen How-Wei 《Marine Geophysical Researches》2001,22(4):265-287
A wide-angle seismic survey, combining ocean-bottom seismometers (OBS) and multi-channel seismic (MCS) profiling, was implemented
in the southwestern Ryukyu subduction zone during August and September 1995. In this paper, we present the data analysis of
eight OBSs and the corresponding MCS line along profile EW9509-1 from this experiment. Seismic data modeling includes identification
of refracted and reflected arrivals, initial model building from velocity analysis of the MCS data, and simultaneous and layer-stripping
inversions of the OBS and MCS arrivals. The velocity-interface structure constructed along profile EW9509-1 shows that the
northward subduction of the Philippine Sea Plate has resulted in a northward thickening of the sediments of the Ryukyu Trench
and the Yaeyama accretionary wedge north of the trench. The boundary between the subducting oceanic crust and the overriding
continental crust (represented by a velocity contour of 6.75 km/s) and a sudden increase of the subducting angle (from 5 degrees
to 25 degrees) are well imaged below the Nanao Basin. Furthermore, velocity undulation and interface variation are found within
the upper crust of the Ryukyu Arc. Therefore, the strongest compression due to subduction and a break-off of the slab may
have occurred and induced the high seismicity in the forearc region.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
52.
南海西沙西南海域表层沉积物特征 总被引:3,自引:1,他引:3
西沙西南海域表层沉积物样品矿物成分,地球化学,微体古生物分析测试结果表明:沉积物可分为7种类型,沉积环境主要是陆坡,部分为深海平原,海洋生物,海洋化学以及火山物质的沉积起到了积极的作用,陆源物质的影响较小,它们主要来源于北部大陆和南部岛礁等物源区。 相似文献
53.
本文根据1949~1989年热带气旋历史资料,对影响东海的热带气旋进行了统计分析,结果表明,热带气旋在东海的活动相当频繁,特别是7、8、9三个月;热带气旋逐年出现个数有明显的年际波动和季节性变化;进入东海的热带气旋大致分为七类路径,不同路径的热带气旋对东海沿岸地区造成不同程度的危害,其灾情以具体实例作了阐述。 相似文献
54.
Treatment with metallic copper for the removal of elemental sulfur from bitumen extracted from sedimentary rocks or petroleum is the most widely used method. Little attention has been paid, however, to its disadvantages. It was observed that copper can interact with some polar organic substances during conventional sulfur removal, which can strongly influence the quantitative and qualitative determination of bitumen, as has been confirmed by interaction of long-chain fatty acids with copper. The copper soap generated was analyzed by element analysis, inductively coupled plasma optical emission spectrometry (ICP-OES), thermal analysis (TG-DSC) and Fourier Transform Infrared spectroscopy (FFIR). Mechanism of the interaction was investigated and elucidated. Our experimental results would necessitate improvement of the present method for sulfur removal and/or a search for a new one. 相似文献
55.
56.
We propose an information-structure-analysis (ISA) method to quantify the correlations between quantitative and qualitative variables as well as within each type of variable. This method is applied to the evaluation of mineral resources in the western Zheijiang Province of China. The district contains a number of silver-bearing Fe–Cu–Pb–Zn mineral deposits near igneous complexes and FeCuPbZn zones away from the complexes. Silver anomalies occur not only in the known Fe–Cu–Zn–Pb deposits, but also in the country rock, suggesting the possible existence of silver deposits far from the igneous complexes.The tonnage distribution of silver is modeled by Monte Carlo simulation. This simulation is conducted on the basis of the correlations between silver (Ag) and lead (Pb), since no known data on silver is available. The known tonnage distribution of lead in 11 control cells was used to approximate the tonnage distribution of silver in the Monte Carlo simulation. With ISA and Monte Carlo methods, the total amount of potential polymetallic resources in 49 cells in the western Zhejiang Provice is predicted. Significantly, a deposit with about 24 tonnes of silver has been found within our exploration target area. 相似文献
57.
Tan KC 《GeoJournal》1993,29(2):155-162
China's 12,000 designated towns and more than 40,000 rural market towns have experienced a major transformation since the institution of rural reforms in the late 1970s. Rural industrialization based on the concept of leaving the soil but not the village, entering the factory but not the town has contributed to the revitalization of many small towns. But this rural urbanization has also brought about a number of problems in the countryside, leading many to propose the adoption of the concept ofleaving the soil and the village as another basis of China's small town urbanization. This essay attempts to examine this transformation, particularly the recent criticism and adjustment made to the small town urbanization program. 相似文献
58.
59.
北京云蒙山地区花岗岩穹隆及伸展构造的探讨 总被引:9,自引:0,他引:9
北京云蒙山花岗岩为一中生代侵入的花岗岩穹隆,花岗岩穹隆的叶理普遍发育,叶理轨迹基本平行于穹隆的外部边界,并显示出从核部到边部逐渐增强,东南侧明显强于西北侧的特点。变形构造研究显示,花岗岩穹隆的边部及围岩中普遍存在不同层次及不同运动方向的伸展构造。东南侧以具河防口-水峪伸展型韧性剪切带为特征,剪切运动标志显示为从NW-SE的正剪切运动,有限应变分析估算其剪切位移量在10km以上,剪切带上部被河防口正 相似文献
60.
本文建立了国土资源评价的指标系统,应用“三角形法”进行了综合评价,高度概括了区域国土资源的宏观特征。 相似文献