全文获取类型
收费全文 | 13827篇 |
免费 | 3606篇 |
国内免费 | 6785篇 |
专业分类
测绘学 | 36篇 |
大气科学 | 3篇 |
地球物理 | 536篇 |
地质学 | 21587篇 |
海洋学 | 675篇 |
天文学 | 1篇 |
综合类 | 1084篇 |
自然地理 | 296篇 |
出版年
2024年 | 90篇 |
2023年 | 334篇 |
2022年 | 534篇 |
2021年 | 693篇 |
2020年 | 609篇 |
2019年 | 717篇 |
2018年 | 673篇 |
2017年 | 764篇 |
2016年 | 923篇 |
2015年 | 898篇 |
2014年 | 1254篇 |
2013年 | 1038篇 |
2012年 | 1295篇 |
2011年 | 1211篇 |
2010年 | 1102篇 |
2009年 | 996篇 |
2008年 | 914篇 |
2007年 | 975篇 |
2006年 | 861篇 |
2005年 | 834篇 |
2004年 | 770篇 |
2003年 | 705篇 |
2002年 | 652篇 |
2001年 | 699篇 |
2000年 | 682篇 |
1999年 | 624篇 |
1998年 | 581篇 |
1997年 | 535篇 |
1996年 | 503篇 |
1995年 | 408篇 |
1994年 | 341篇 |
1993年 | 257篇 |
1992年 | 219篇 |
1991年 | 169篇 |
1990年 | 96篇 |
1989年 | 93篇 |
1988年 | 65篇 |
1987年 | 41篇 |
1986年 | 34篇 |
1985年 | 13篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Richard N. Hey Gary J. Massoth Robert C. Vrijenhoek Peter A. Rona John Lupton David A. Butterfield 《Marine Geophysical Researches》2006,27(2):137-153
Earth’s fastest present seafloor spreading occurs along the East Pacific Rise near 31°–32° S. Two of the major hydrothermal
plume areas discovered during a 1998 multidisciplinary geophysical/hydrothermal investigation of these mid-ocean ridge axes
were explored during a 1999 Alvin expedition. Both occur in recently eruptive areas where shallow collapse structures mark
the neovolcanic axis. The 31° S vent area occurs in a broad linear zone of collapses and fractures coalescing into an axial
summit trough. The 32° S vent area has been volcanically repaved by a more recent eruption, with non-linear collapses that
have not yet coalesced. Both sites occur in highly inflated areas, near local inflation peaks, which is the best segment-scale
predictor of hydrothermal activity at these superfast spreading rates (150 mm/yr). 相似文献
102.
103.
104.
Baraza J. Ercilla G. Farrán M. Casamor J. L. Sorribas J. Flores J. A. Sierro F. Wersteeg W. 《Marine Geophysical Researches》1997,19(2):115-135
Multibeam bathymetric and ultra high-resolution seismic data reveal that the distal course of the Equatorial Atlantic Mid-Ocean Channel (EAMOC) extends further east and south than was previously known, and is controlled by the presence of morphologic highs related to the Fernando de Noronha Fracture Zone. Distal course of the EAMOC is buried by sediments, and does not have bathymetric expression on the seafloor. The channel fill consists of three seismic sequences, suggesting that the recent geological evolution of the channel is composed of successive phases of decreasing sedimentary activity that finally resulted in its complete burial. Tectonic and volcanic activity related to the Fernando de Noronha Fracture Zone and Ridge, together with the effect of strong pulses of the Antarctic bottom water current during the upper Pliocene are suggested to have contributed to the progressive burial and the final abandonment of the EAMOC. 相似文献
105.
The major and minor element contents in the sediment core H9 from the hydrothermal fields of the Okinawa Trough show a sharp change at the depth of 80 cm. The elements enriched in the upper 80 cm core are those enriched in the hydrothermal deposits and in the surface sediments recovered from the hydrothermal fields in the trough, which indicates the input of hydrothermal materials. Comparing with other hydrothermal sediments from Mid-ocean Ridges or the Lau Basin, the degree of the enrichment of elements iron, copper,cobalt, and nickel is relatively low. However, the enrichment of elements manganese, lead, arsenic, antimony and mercury is remarkable. The average contents of these elements in the upper 80 cm core sediments are three to six times those in the lower section, and 3~12 times those in the surface sediments which are not influenced by hydrothermal activities. Hydrothermal activities have contributed significant manganese, lead, arsenic, antimony and mercury to the sediments, and these elements are distinct indicators for the hydrothermal activity in the Okinawa Trough. The significant enrichment of these elements in Core H9 upward from the depth 80 cm indicates the start or the significant enhancing of the hydrothermal activity in this area at about 5 740 aB.P. The average accumulation rate of manganese during this period is about 40 461 μg/(cm2·ka), which is similar to the hydrothermal sediments in the Lau Basin or the East Pacific Rise. 相似文献
106.
本文以粤西水东湾表层沉积物样品的粒度分布为基本数据,使用对应分析方法并结合地形与波流特征,分析了海湾动力沉积环境。分析结果表明,海湾现代沉积环境可划分为4个动力沉积区。 相似文献
107.
水成沉积与风成沉积及古土壤的磁组构特征 总被引:14,自引:2,他引:14
晚第四纪水成沉积、风成沉积、古土壤等的磁组构研究表明,不同成因的沉积物具有明显不同的磁组构特征。一般地,水成沉积的体积磁化率K受物源和水动力因素控制,P和F均>1.02,q<0.5;风成沉积的K受物源控制,内陆黄土的K明显高于沿海黄土及海岸风沙K,P和F均<1.02,q的平均值>0.55;古土壤的K受母质沉积类型和成土环境的氧化还原条件控制,内陆古土壤的K偏高,沿海古土壤的K偏低,内陆古土壤的K远高于沿海古土壤的K,P和F均<1.02,q的平均值在0.5左右。运用典型沉积的磁组构特征对比分析未知沉积物,可以得到未知沉积物的物源、沉积过程和环境信息。 相似文献
108.
109.
本文对福清湾北部及其以东近岸海域的地质地貌,潮流和波浪等沉积环境因素,以及对沉积物和悬浮泥沙的粒度,矿物特征进行研究,认为福清湾为溺谷型的半封闭潮汐汊道海湾存在着较大的潮差和潮流流速,沉积物沿潮流方向呈东粗西细和岸边细、向海变粗的潮流分异特征,潮流控制着沉积物的布局,而属于潮控的浅海沉积环境。 相似文献
110.
渤海南部表层沉积的相特征 总被引:1,自引:0,他引:1
通过海上调查及实验室分析,查明渤海南部表层沉积物在结构类型、矿物组合、生物组分及沉积构造等相特征方面具有明显的分区性。渤海南部存在五种沉积相:黄河水下三角洲相、陆架盆地相、海湾相、潮流浅滩相及古滨岸相。黄河水下三角洲相从河口延至水深15—20米处,沉积速率很高,沉积物富含碎屑云母及CaCo_3。陆架盆地相的沉积为粉砂质粘土,具有生物扰动构造。 相似文献