全文获取类型
收费全文 | 180篇 |
免费 | 28篇 |
国内免费 | 47篇 |
专业分类
测绘学 | 20篇 |
大气科学 | 20篇 |
地球物理 | 23篇 |
地质学 | 89篇 |
海洋学 | 56篇 |
天文学 | 12篇 |
综合类 | 10篇 |
自然地理 | 25篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 14篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 21篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 11篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有255条查询结果,搜索用时 15 毫秒
151.
CHENG Li-bin LE Gui-ming LU Yang-ping CHEN Min-hao LI Peng YIN Zhi-qiang 《Chinese Astronomy and Astrophysics》2014
The solar flares, the speeds of shocks propagated in the solar-terrestrial space and driven by coronal mass ejections (CMEs), the heliographic longitudes and Carrington longitudes of source regions, and the geomagnetic storms, which are accompanied by the super solar proton events with a peak ?ux equal to or exceeding 10 000 pfu, have been studied by using the data of ground-based and space observations. The results show that the heliographic longitudes of source regions of super solar proton events distributed in the range from E30? to W75°. The Carrington longitudes of source regions of super solar proton events distributed in the two longitudinal belts, 130°∼220° and 260°∼320°, respectively. All super solar proton events were accompanied by major solar flares and fast CMEs. The averaged speeds of shocks propagated from the sun to the Earth were greater than 1 200 km/s. Eight super solar proton events were followed by major geomagnetic storms (Dst≤−100 nT), except that one super solar proton event was followed by a geomagnetic storm with the geomagnetic activity index Dst=−96 nT, a little smaller than that of major geomagnetic storms. 相似文献
152.
LI Peng LE Gui-ming CHEN Yu-lin CHEN Min-hao LU Yang-ping YIN Zhi-qiang 《Chinese Astronomy and Astrophysics》2014
Based on the observational data of sunspots, the relation between the amplitude of solar cycle and the total area of all active regions occurred in a solar cycle has been investigated. The result shows that the amplitude of solar cycle has a good correlation with the total area of all active regions occurred in the solar cycle. The relation between the amplitude of solar cycle and the area of the largest active region during a solar cycle has also been investigated. The result shows that the amplitude of solar cycle has a poor correlation with the area of the largest active region during a solar cycle, and there is no fixed relation between the peak time of a solar cycle and the time when the largest active region occurred in the solar cycle. 相似文献
153.
154.
155.
右江褶皱带东南缘西大明山矿集区燕山期长英质岩浆锆石SHRIMP原位氧同位素组成与地质意义 总被引:1,自引:1,他引:0
右江褶皱带晚白垩世岩浆岩的物质来源和成因机制及其相关的大规模Sn-W多金属成矿作用是目前研究的热点和前沿问题之一。本文在已获得锆石U-Pb年龄及Hf同位素基础上,对广西西大明山地区酸性岩浆进行了锆石SHRIMP氧同位素研究。石英斑岩δ~(18)O_(Zrn)值为5.31‰~9.31‰(平均值为7.61±2.17‰)、绢英岩化黑云母花岗岩δ~(18)O_(Zrn)值为7.11‰~9.79‰(平均值为8.36±1.33‰)、细粒黑云母花岗岩δ~(18)O_(Zrn)值为5.06‰~9.27‰(平均值为7.73±2.23‰)、中粒黑云母花岗岩δ~(18)O_(Zrn)值为5.06‰~9.27‰(平均值为7.73±2.23‰)二长花岗岩δ~(18)O_(Zrn)值为5.48‰~10.99‰(平均值为7.55±2.77‰)。测试结果显示广西西大明山地区酸性岩浆锆石氧同位素普遍具有双峰式分布特征且Hf-O同位素组成构成负相关性,暗示地壳组份和富集地幔两端元混合的特征。Hf-O同位素特征指示酸性岩浆岩源主要来自古老的地壳,并混有部分幔源物质。地幔物质的存在暗示了同时期来自地幔的物质不仅参与右江褶皱带晚白垩世岩浆作用的形成,可能为的地壳部分熔融,花岗岩岩浆的形成提供了热能。西大明山地区酸性岩浆具有高δ~(18)O_(Zrn)值和低ε_(Hf)(t)值且低Ce(Ⅳ)/Ce(Ⅲ)比值(即低氧逸度),显示出有利于形成大型以Pb-Zn为主的矽卡岩型矿床特征。本文研究结果表明,锆石O-Hf同位素综合研究能限定幔源岩浆参与花岗岩形成中的作用能帮助更加准确的限定岩浆源区。同时锆石氧同位素可以作为成矿规律研究的有效途径之一。 相似文献
156.
渌井矿床是广西西大明山地区内一个典型的脉状铅锌矿床,矿体赋存于寒武纪地层中,主要受断裂构造控制。本文在详细野外调查的基础上,通过对其流体包裹体、硫化物矿物化学和硫同位素的系统测定和分析,探讨了成矿流体性质和矿质来源。流体包裹体研究表明,渌井矿床主成矿阶段流体包裹体类型以富液相的气液两相包裹体和纯液相包裹体为主,主成矿期包裹体均一温度为237~281℃(平均值为256℃),对应盐度为3.54%~12.69%(均值为8.39%)。硫化物电子探针分析结果显示,闪锌矿以富集Fe、Cd、In而贫Mn、Ga、Ge等元素为特征,多属于形成温度偏高的含铁闪锌矿类型。硫化物硫同位素研究显示,δ34S值总体变化范围为-1.9‰~4.4‰,呈塔式分布,均值为1.7‰,位于零值附近,暗示渌井矿床硫化物的硫主要来源于岩浆。综合矿床地质、流体包裹体、硫化物矿物化学及硫同位素特征可知,渌井矿床应归属于热液脉型铅锌矿床范畴,在成因上与本区深部的隐伏岩体具有密切的联系,成矿时代可能为燕山晚期。 相似文献
157.
158.
应用1958-2012年河北21个基准站和基本站逐日降水观测资料,分析了河北汛期暴雨的气候分布特征、年际、年代际变化以及趋势变化特征。结果表明,汛期暴雨分布呈现东部、南部多,向西北部递减的特征。最大暴雨量中心在河北东部、燕山南麓的唐山、秦皇岛地区。从年际和年代际尺度分析,暴雨量、频次、强度都存在2-3 a的年际变化周期信号,暴雨量和频次在20世纪80年代以后存在15-20 a的年代际周期信号。汛期暴雨量、暴雨频次时间序列整体呈现下降趋势,特别是21世纪以来,河北暴雨量和暴雨频次下降趋势更为明显,暴雨强度在近50 a变化幅度不大。在空间分布上,暴雨量、暴雨频次和暴雨强度三个特征量在年代际变化中整体都呈现东退南缩的特征。从趋势分析看来,大部分站点汛期暴雨量、频次、强度都呈现下降趋势。 相似文献
159.
Justin FILIBERTO Donald S. MUSSELWHITE Juliane GROSS Katherine BURGESS Loan LE Allan H. TREIMAN 《Meteoritics & planetary science》2010,45(8):1258-1270
Abstract– Northwest Africa (NWA) 1068 is one of the few olivine‐phyric shergottites (e.g., NWA 1068, Larkman Nunatak [LAR] 06319, and Roberts Massif [RBT] 04262) that is not depleted in light rare earth elements (LREE). Its REE pattern is similar to that of the basaltic shergottite Shergotty, suggesting a possible connection between the olivine‐phyric and the basaltic shergottites. To test this possible link, we have investigated the high‐pressure near‐liquidus phase equilibria for the NWA 1068 meteorite bulk composition. Our results show that the NWA 1068 bulk composition does not represent an unmodified mantle‐derived melt; the olivine and pyroxene in our near‐liquidus experiments are more magnesian than in the rock itself, which suggests that NWA 1068 contains cumulate minerals (extra olivine). We have then used these experimental results combined with the pyroxene compositions in NWA 1068 to constrain the possible high‐pressure crystallization history of the parental magma. These results suggest that NWA 1068 had a complex polybaric history. Finally, we have calculated a model parental magma composition for the NWA 1068 meteorite. The calculated parental magma is an evolved basaltic composition which is too ferroan to be a primitive melt directly derived from the mantle. We suggest that it ponded and crystallized at approximately the base of the crust. This provided an opportunity for the magma to become contaminated by an “enriched” crustal component prior to crystallization. The results and modeling from these experiments are applicable not only to the NWA 1068 meteorite, but also to LAR 06319 and possibly any other enriched olivine‐phyric shergottite. 相似文献
160.
ALEXIS Alain LE BRAS Gilbert Researcher Laboratoire de Genie Civil de Names Saint-Nazaire IUT de Saint-Nazaire Saint Nazaire France PHD Student Laboratoire de Genie Civil de Names Saint-Nazaire IUT de Saint-Nazaire Saint Nazaire France Tel. 《国际泥沙研究》2000,(3)
I INTRODUCTIONHigh water coment soils are often at the centre of delicate industrial and environmental problems,particularly concerning the behaviour of port or estuary mud, and deposits at sea.In soil mechanics, an understanding of the behaviour of soils is based upon the concept of effectivestress proposed by Terzaghi (1936) and defined by the difference betWeen the total stress and the porepressure. Theoretical studies (Aleds et al., 1992) highlight the effective stress as the main co… 相似文献