全文获取类型
收费全文 | 214篇 |
免费 | 31篇 |
国内免费 | 33篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 7篇 |
地球物理 | 36篇 |
地质学 | 107篇 |
海洋学 | 59篇 |
天文学 | 5篇 |
综合类 | 11篇 |
自然地理 | 50篇 |
出版年
2022年 | 8篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 16篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 15篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
排序方式: 共有278条查询结果,搜索用时 15 毫秒
261.
262.
作者曾在“<史记历术甲子篇>探讨”一文中分析了<甲子篇>的数学逻辑,提出完算完整的<甲子篇>历谱的方法。按照这种方法,现用计算机排算出一个76年周期的<甲子篇>四分法历谱以及同一时期的<太初历>八十一分法历谱,并与江曰桢、陈垣的历谱进行比较。 相似文献
263.
北部湾临港工业圈的布局构想 总被引:1,自引:0,他引:1
许进 《广东海洋大学学报》2005,25(2):6-10
现代临港工业要求港口的区位条件、海陆运输条件良好,腹地广阔,依托城市的工业基础良好。环北部湾海岸线长,港口资源丰富,具有发展临港工业的优势。环北部湾在选择发展临港工业方面竞争多于合作,需要通过各地政府协调,培育“环北部湾”意识,制订临港工业发展规划,扩大开发和开放,科学合理布局海洋油气业、燃气发电及滨海电力业、重化工业、船舶制造业、海水产品加工业等产业,促进环北部湾临港工业的发展。 相似文献
264.
“三苗日食”的可能年代 总被引:1,自引:0,他引:1
史载上古禹时日妖宵出被解释为日落时发生的日食。分析了相关史料、该日食的各种可能年代及其戌地球自转长期变化的关系。 相似文献
265.
In the deep subsurface of the northeast German basin products of extensive volcanism are present that formed during the waning
phase of the Variscan orogeny (Permian–Carboniferous boundary). Large volumes (≥48,000 km3) of dominantly felsic magma were emplaced in the northern foreland of the Variscan mountains in a terrestrial semi-arid environment.
Most of these units were inferred by previous authors to represent the products of explosive volcanic eruptions such as ignimbrites.
However, a detailed analysis of the volcanic texture and lithofacies association shows that most units are best interpreted
as coherent lavas emplaced either as extrusive units or as shallow intrusions, with important implications for the reconstruction
of the paleo-environment. This study shows that detailed textural examination of drill cores provide important observations,
which can be applied as criteria for the interpretation of the mode of volcanic eruptions. Furthermore, phenocryst logging
and geochemical fingerprinting based on immobile element ratios can be employed for the classification and discrimination
of individual emplacement units. 相似文献
266.
Drying of masonry specimens was monitored by means of a two-dimensional (2D) magnetic resonance imaging (MRI) technique. The
external surfaces stayed wet for longer if NaCl was present instead of pure water only. This corroborates many practical observations
that salts aggravate dampness in masonry. A slower evaporation process and not hygroscopicity was the cause. That suggests
that salt-induced dampness may, in general, arise simply from changes in the drying process of masonry materials. That also
implies that the height and depth at which crystallization occurs in walls may depend on the relative equilibrium humidity
(RHeq) and other properties of salts that influence drying of porous materials. Evaporation rates of free surfaces of pure
water and saturated NaCl solution were measured by a gravimetric technique. The results indicate that slow drying of salt-contaminated
materials is not due only to the lower RHeq of salt solutions. The effective surface of evaporation is likely to be reduced
perhaps due to blocking of pores by salt crystals. Final salt-distribution maps of the specimens show that: (a) salts may
affect the inner materials of the masonry, even in evaporation-induced processes that lead crystallization to occur predominantly
on the external surface; (b) distinct internal distribution patterns occur if masonry composition varies.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
267.
苏北浅滩钙结核的特征及其环境指示意义 总被引:1,自引:0,他引:1
对采自苏北浅滩的钙结核样品进行了岩石学、矿物学和碳氧同位素的分析。样品富含石英和长石砂屑,碳酸钙胶结,其碳和氧同位素组成分别为-8.38‰~-8.19‰V-PDB及-5.23‰~-5.03‰V-PDB。根据样品的氧同位素组成,利用碳酸盐-水体系氧同位素方程,结合现今底层水温度,并考虑可能存在的温度变化,计算得到古沉淀流体的δ18 O水范围为-4.72‰~-4.52‰VSMOW,较正常海水偏负,认为钙结核的形成可能受到了淡水影响。根据结核中碎屑矿物的成分及其成熟度,判断其包含的碎屑矿物源自古黄河,认为这些结核样品可能形成于海陆交互环境,形成时间约为7~6.5ka BP左右,当时古海平面高度比现今低10m左右,古黄河河道可能位于苏北浅滩附近。 相似文献
268.
西藏北部拉萨地块那曲地区约113Ma安山岩岩石成因与意义 总被引:3,自引:2,他引:1
西藏北部拉萨地块广泛分布着早白垩世岩浆岩,由于缺少高质量的年代学和地球化学数据,其岩浆源区和岩石成因迄今未能很好约束。本文报道了北部拉萨地块那曲地区安山岩的锆石U-Pb定年、地球化学和Sr-Nd-Hf同位素数据。那曲安山岩锆石U-Pb年龄为112.7±0.7Ma。岩石为高钾钙碱性系列,富集大离子亲石元素、Th、U和轻稀土元素[(La/Yb)N=6.62~11.68],亏损Nb、Ta、P和Ti等高场强元素。样品具有较高的(87Sr/86Sr)i值(0.7100~0.7126)、负的全岩εNd(t)值(-10.5~-7.8)和负的锆石εHf(t)值(-9.9~-4.7),对应于古老的Nd同位素二阶段模式年龄(1.5~1.8Ga)和锆石Hf同位素地幔模式年龄(1.0~1.6Ga)。综合岩石学、地球化学和区域构造背景研究认为,那曲地区安山岩形成于南向俯冲的班公湖-怒江洋壳岩石圈板片断离的背景,很可能是受早期流体/沉积物熔体交代富集的安多微陆块古老岩石圈地幔物质部分熔融的产物,并经历了不同程度的分离结晶。 相似文献
269.
Eastern Ancient Terrane of the North China Craton 总被引:2,自引:0,他引:2
WAN Yusheng LIU Shoujie Alfred KRONER DONG Chunyan XIE Hangqiang XIE Shiwen BAI Wenqian REN Peng MA Mingzhu LIU Dunyi 《《地质学报》英文版》2016,90(4):1082-1096
Based on the spatial distribution of ancient rocks and zircons, three ancient terranes older than ca. 2.6 Ga have recently been identified in the North China Craton, namely the Eastern, Southern, and Central Ancient Terranes. The Eastern Ancient Terrane is the best studied and understood of the three ancient terranes. It has a long geological history back to ca. 3.8 Ga ago and includes the areas of Anshan-Benxi, eastern Hebei, eastern Shandong and western Shandong. In Anshan-Benxi, several different types of 3.8 Ga rocks were discovered together with 3.1-3.7 Ga rocks, whereas 2.9-3.0 Ga K-rich granites and 2.5 Ga syenogranite occur on larger scales. In eastern Hebei, 3.0-3.4 Ga rocks and older detrital and xenocrystic zircons were identified. In eastern Shandong, there are a large volumes of 2.7 Ga and 2.9 Ga rocks. In western Shandong, early Neoarchean(2.6-2.7 Ga) intrusive and supracrustal rocks are widely distributed. Whole-rock Nd and zircon Hf isotope data suggest that both mantle additions and crustal recycling played important roles within the Eastern Ancient Terrane during almost every tectono-magmatic event. Most BIFs in the North China Craton are late Neoarchean in age and are distributed on continental crust along the western margin of the Eastern Ancient Terrane, probably suggesting that a stable environment was one of the key factors for the formation of large-scale BIFs. 相似文献
270.
Response and Feedback of Marine Carbon Sink to Climate Change 总被引:1,自引:0,他引:1
The response and feedback of ocean carbon sequestration to climate changes is a international hot topic and requires large spatial/temporal scale, collaborative and multi-disciplinary research. In the first conference of GRC Ocean biogeochemistry, scientists focus on three biologically-driven ocean carbon pumps (Biological Pump, BP; Microbial Carbon Pump, MCP; Carbonate Counter Pump, CCP) and their environmental and climate consequences. As a sister meeting in China, we organized the session to show the efforts and progress of ocean carbon sequestration of Chinese scientists. The microbial ecological processes of phytoplankton, bacteria, archaea and viruses and interactions between them were highlighted in the session. Use coral reefs in the South China Sea as an example, the presenters and the participants come to an agreement that interdisciplinary collaborations are needed to ensure a comprehensive understanding of the interactions between microbes and their geochemical environment and the consequences of microbial processing of carbon on outgassing of CO2 and carbon sequestration. The session also have presentations focusing on paleo-environmental reconstruction for carbon sinks as well as their paleo-ecological effects in ancient oceans with time spanning from the 1.8~0.8 Ga Proterozoic to the 2.5 Ma Quaternary. These talks provide specific geological cases for the oceanic carbon sink research and convey the emerging geological view of paleooceanic carbon sinks to the research community of modern ocean carbon sinks. As a summary, the discussion in this session of biological pump, microbial carbon pump and carbonate counter pump shows the latest research progress and future development trend in this field. 相似文献