全文获取类型
收费全文 | 240篇 |
免费 | 11篇 |
国内免费 | 52篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 12篇 |
地球物理 | 29篇 |
地质学 | 236篇 |
海洋学 | 3篇 |
天文学 | 12篇 |
综合类 | 5篇 |
自然地理 | 3篇 |
出版年
2022年 | 8篇 |
2021年 | 2篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 7篇 |
2015年 | 16篇 |
2014年 | 7篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 17篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 6篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 9篇 |
2002年 | 5篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1971年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有303条查询结果,搜索用时 203 毫秒
91.
92.
93.
The Rajahmundry Trap Basalts(RTB) are erupted through fault-controlled fissures in the Krishna-Godavari Basin(K-G Basin) of Godavari Triple Junction,occurring as a unique outcrop sandwiched between Cretaceous and Tertiary sediments along the east coast of India.Detailed geochemical studies have revealed that RTB are mid-Ti(1.74-1.92) to high-Ti(2.04-2.81) basalts with a distinct quartz tholeiitic parentage.MgO(6.2-13.12 wt.%),Mg#(29-50) and Zr(109-202 ppm) suggest that these basalts evolved by fractional crystallization during the ascent of the parent magma along deep-seated fractures.Moderate to high fractionation of HREE,as indicated by(Gd/Yb)N ratios(1.71-2.31) of RTB,suggest their generation through 3-5%melting of a Fe-rich mantle corresponding to the stability fields of spinel and garnet peridotite at depths of 60-100 km.Low K2O/P2O5(0.26-1.26),high TiO2/P2O5(6.74-16.79),La/Nb(0.89-1.45),Nb/Th > 8(8.35-13),negative anomalies at Rb reflect minimum contamination by granitic continental crust.(Nb/La)PM ratios(0.66-1.1) of RTB are attributed to endogenic contamination resulted through recycling of subducted oceanic slab into the mantle.Pronounced Ba enrichment with relative depletion in Rb indicates assimilation of Infra- and Inter-trappean sediments of estuarine to shallow marine character.Geochemical compositions such as Al2O3/TiO2(3.88-6.83),medium to high TiO2(1.74-2.81 wt.%).positive Nb anomalies and LREE enrichment of these RTB attest to their mantle plume origin and indicate the generation of parent magma from a plume-related enriched mantle source with EM 1signature.Ba/Th(46-247),Ba/La(3.96-28.51) and Th/Nb(0.08-0.13) ratios suggest that the source enrichment process was marked by recycling of subduction-processed oceanic crust and lithospheric components into the mantle.Zr/Hf(37-41) and Zr/Ba(0.51-3.24) indicate involvement of an asthenospheric mantle source.The Rajahmundry basalts show affinity towards FOZO(focal zone mantle) and PSCL(post-Archaean subcontinental lithosphere) which reflect mixing between asthenospheric and lithospheric mantle components in their source.Origin of RTB magma is attributed to plume-lithosphere interaction and the upward movement of melt is facilitated by intrabasinal deep-seated faults in the K-G Basin. 相似文献
94.
G. Resmi Santosh G. Thampi S. Chandrakaran 《Journal of the Geological Society of India》2011,77(1):42-46
Clay liners are widely used as barriers to arrest the migration of pollutants. These liners are subjected to leaching of various
chemicals and hazardous wastes. Migration of heavy metals through the liner material may lead to changes in the soil properties
and this, in turn, may affect the performance of liners. In this paper, the change in index and engineering properties of
clayey soil due to migration of lead is presented. Pronounced changes in soil properties are noticed when the soil is contaminated
with high concentrations of lead. The findings from the present study are important while designing liners in landfills used
for containment of pollution due to heavy metals and hazardous wastes. 相似文献
95.
Hong-Fu Zhang Ji-Feng Ying Yan-Jie Tang Xian-Hua Li Chuang Feng M. Santosh 《Gondwana Research》2011,19(2):446-459
The Archean lithospheric root of the North China Craton (NCC) has been considerably eroded and modified by Phanerozoic magmatic processes. Here we investigate the decratonization of the NCC through U–Pb and Hf isotopic analyses of zircons from Cenozoic basalts in the Liaodong Peninsula using ion-probe and MC-ICPMS techniques. The U–Pb zircon geochronology identifies three zircon populations: Precambrian, Paleozoic and Mesozoic. The Precambrian zircons yield 207Pb/206Pb ages of 2275–2567 Ma with a peak at around 2.5 Ga. They define a U–Pb discordia with upper intercept ages of 2447 ± 50 Ma to 2556 ± 50 Ma and a wide range of Hf TDM ages with a mode at 2.7–2.8 Ga. Our results clearly demonstrate the presence of an Archean lower crust in the Liaodong region. The Paleozoic zircons from the Liaodong region lack the clear internal zoning and are subhedral to rounded in shape, and yield a narrow 206Pb/238U concordant ages of 419–487 Ma with a weighted mean age of 462 ± 16 Ma. The Mesozoic zircons predominantly show crystallization in the early Cretaceous and yield a relatively large range in 206Pb/238U ages from 100 to 138 Ma (n = 53) with a peak around 120 Ma. Three samples give indistinguishable weighted mean 206Pb/238U ages of 120 ± 5 Ma, 120 ± 4 Ma and 121 ± 2 Ma. These early Cretaceous zircons have enriched Hf isotope compositions with εHf(t) values from ?26 to ?16. Our results provide important constraints on episodic magmatism during the Phanerozoic in the Liaodong region, which led to substantial reactivation of the Archean basement of the North China Craton. 相似文献
96.
Sung Won Kim Sanghoon Kwon Hee Jae Koh Keewook Yi Youn-Joong Jeong M. Santosh 《Gondwana Research》2011,20(4):865-889
This study presents sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages, and whole-rock chemical and isotopic (Sr-Nd) compositions of representative Triassic plutons from South Korea. The plutons from the Gyeonggi massif (Hongseong, Namyang, Yangpyeong and Odesan), the central Okcheon belt (Baeknok and Yongsan), and the Yeongnam massif (Sangju, Gimcheon, Hamyang and Macheon) yield zircon U–Pb ages of ca. 232–226 Ma, 227–226 Ma, and 240–228 Ma, respectively. Among the Triassic plutonic suite in South Korea, those within the Gyeonggi massif are dominated by granite, syenite, monzonite, monzodiorite and gabbro. Plutons within the Okcheon belt are mainly by granite to quartz monzodiorite. The Yeongnam massif mainly incorporates granite to granodiorite and minor monzodiorite intrusions. The geochemical signatures of the Triassic plutons are characterized by Ta–Nb troughs, depletion of P and Ti, and enrichment of LILE. Most plutons except Macheon monzodioritic pluton show high initial 87Sr/86Sr ratios (0.708248–0.714678) and strongly negative εNd(T) (− 20.3 to − 7.7) values, suggesting contribution from middle to upper crust. In contrast, the Macheon monzodioritic pluton in the Yeongnam massif shows relatively low initial 87Sr/86Sr ratios (0.706547-0.706629) and negative εNd(T) (− 4.43 to − 3.62) values. The Middle Triassic syenite–monzonite–granite–gabbro series in and around the Gyeonggi massif possess high-K calc-alkaline and shoshonitic affinity suggesting a post-collisional magmatic event following the Permo–Triassic collision between the North and South China blocks. The Triassic plutons in the Yeongnam massif and the Okcheon belt, together with a Permian Yeongdeok pluton in the Gyeongsang basin, show features typical of high- to medium-K calc-alkaline magmatism with LREE and LILE enrichments. This together with a depletion of Y and HREE suggests their formation in a subduction setting. Our results provide robust evidence to consider the Gyeonggi massif as an extension of the Qinling–Dabie–Sulu belt between the North and South China blocks in central China. The Okcheon belt and Yeongnam massif in South Korea, together with the continental margin of South China, are marked by a common Permian to Triassic magmatic episode, probably related to the paleo-Pacific slab subduction. 相似文献
97.
A rapid change in climate patterns potentially driven by global warming is considered to be greatest threats to agriculture. However, little is known about how the change in climate concretely affects agricultural production especially in Nepal with respect to seasons and regions of different altitudes. To examine this issue, we seek to empirically identify the impact of climatic variation on agricultural yield and its variability by utilizing the data of rice, wheat and climate variables in the central region of Nepal. The main focus is on whether the impacts vary across seasons, altitudes and the types of crops. For this purpose, we employ a stochastic production function approach by controlling a novel set of season-wise climatic and geographical variables. The result shows that an increase in the variance of both temperature and rainfall has adverse effects on crop productions in general. On the other hand, a change in the mean levels of the temperature and rainfall induces heterogeneous impacts, which can be considered beneficial, harmful or negligible, depending on the altitudes and the kinds of crops. These results imply that adaptation strategies must be tailor-made in Nepalese agriculture, considering growing seasons, altitudes and the types of crops. 相似文献
98.
This paper introduces a concept of ‘effective length’ in hillslopes to define the effective area influencing the runoff‐producing saturated zones of a hillslope or catchment. This effective area of a catchment usually is less than that given by its physical boundaries, particularly in regions where the total potential evaporation exceeds total rainfall on an annual basis. In this paper, expressions for effective lengths in hillslopes with different scale, shape and soil properties are derived for given climatic conditions. The influence of these variables on effective length is investigated. It is shown that, for a given rainfall frequency and soil parameters, the effective length changes with the planform geometry and profile shape of a hillslope; it is also a function of the ratio of available travel opportunity time to the hillslope's scale response time. The application of the concept to three natural catchments, subdivided into a number of simple hillslopes, is described. It is shown that, for these three test catchments and over 24 years of record, rarely would the entire catchment areas contribute to flow at the respective outlets. The implications of the concept of effective length for several land‐use practices, such as clearing for forest for greater water yield, and planting trees for salinity control, are discussed. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
99.
Santosh Sapkota Saurav Sarup Khadka Gautam Sabin Karki Monika Adhikari Binod Mishra Roshan Kumar Klausner Virginia Dhungana Beni Madhav 《Geomagnetism and Aeronomy》2022,62(1-2):125-137
Geomagnetism and Aeronomy - Electrodynamical coupling between the solar wind’s plasma and the Earth’s magnetosphere creates geomagnetic disturbances recorded on the ground. This work... 相似文献
100.
正Following the publication of Part Ⅰ of the series on"Frontiers in early Earth history and primordial life"(Maruyama and Santosh,2017),we present the second part in this volume compiling state-of-the-art research focusing on issues related to the early evolutionary history of the Earth and life.The first paper by Imaeda and Ebisuzaki(2018)on"Single planet formation regime in the high-ionization environment: 相似文献