全文获取类型
收费全文 | 350篇 |
免费 | 11篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 28篇 |
大气科学 | 31篇 |
地球物理 | 55篇 |
地质学 | 171篇 |
海洋学 | 23篇 |
天文学 | 45篇 |
综合类 | 7篇 |
自然地理 | 7篇 |
出版年
2024年 | 1篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 32篇 |
2017年 | 25篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 28篇 |
2012年 | 23篇 |
2011年 | 24篇 |
2010年 | 20篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 2篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有367条查询结果,搜索用时 218 毫秒
161.
The variations in CaCO3 and organic carbon and their inter-relationship in a core from the southeastern Arabian Sea (water depth 2,212 m) have been
used to demarcate the Holocene/Pleistocene boundary; an increased terrigenous deposition during Late Pleistocene has been
inferred. The higher contents of organic carbon and sulfide sulfur and their negative relationship clearly establish the existence
of a reducing environment below 65 cm subbottom depth. The occurrence of pyrite framboids and crystals, present only on the
surface of fecal pellets (80–85 cm), has been discussed in terms of significance of reducing microenvironment. 相似文献
162.
Satya Narayan Soumyashree Debasis Sahoo Ujjawal Kumar Vipin Kumar Pathak T. J. Majumdar 《国际地球制图》2017,32(4):351-366
The present study deals with classical problem of edge detection in potential field data over complex tectonic regime for both shallower and deeper sources, simultaneously. Balanced horizontal derivative (BHD) technique is a latest edge detection concept which delineates edges using balancing of amplitude responses for both shallower and deeper sources. The BHD technique has been validated by comparing with total horizontal derivative (THD) technique. Initially, three different synthetic models have been generated with spherical, cylindrical and vertical prismatic objects at different depths and corresponding gravity responses have been enhanced using BHD and THD techniques. Structural features have been delineated from EIGEN6C4 free-air gravity data using THD and BHD techniques over a part of the Bay of Bengal. Major lineaments have been identified in N–S direction followed by those identified along the NE–SW, NW–SE and E–W directions. Both studies of synthetic models and real gravity data reveal that BHD is an advanced technique than THD. 相似文献
163.
P. Vivekananda Rao M. B. K. Sarma B. V. N. S. Prakash Rao 《Journal of Astrophysics and Astronomy》1994,15(2):165-178
Light curves of the long period RS CVn type eclipsing binary RZ Eri, obtained during the period 1976–1979 with the 1.2 m telescope of the Japal-Rangapur Observatory are analysed, using Wilson-Devinney method, by fixing the two parametersT h (7400°K) andq(0.963), resulting in the following absolute elements:A = 72.5 ± 1.4R ⊙,R h = 2.84 ± 0.12R ⊙,R c = 6.94 ± 0.20R ⊙,M bol,h = 1.35 ± 0.28,M bol ,c= 1.41 ± 0.28,m h = 1.69 ± 0.6m ⊙ andmc= 1.63 ± 0.13m ⊙. The presence of humps and dips of varying amplitudes at a few phases in the normal UBV light curves is explained as due to residual distortion wave. The derived (B-V) and (U-B) colours of both the components appear to have been reddened to an extent of 0 m .20 in (B-V) and 0 m .16 in (U-B) colours. This reddening is attributed to the presence of an envelope around the system, the material of which might have come from the loss of mass experienced by the evolving cooler component. Taking into consideration the dereddened colours and temperatures of the components, spectral types ofF0 IV for the primary and G 5–8 III–IV for the secondary component were derived. The fractional radii of 0.039 and 0.096 of the two components, when compared with the radii of their critical Roche lobes of 0.378 and 0.372 suggest that these components are well within their critical sizes. From the position of the components on the. isochrones and the evolutionary tracks of stars of Pop I composition computed by Maeder & Meynet, it is concluded that the evolution of the components of RZ Eri is abnormal. This system is found to be situated at a distance of 185 pc, with an age of about 2.5 × 109 yrs. 相似文献
164.
Thomas Oommen Debasmita Misra Navin K. C. Twarakavi Anupma Prakash Bhaskar Sahoo Sukumar Bandopadhyay 《Mathematical Geosciences》2008,40(4):409-424
Accurate thematic classification is one of the most commonly desired outputs from remote sensing images. Recent research efforts
to improve the reliability and accuracy of image classification have led to the introduction of the Support Vector Classification
(SVC) scheme. SVC is a new generation of supervised learning method based on the principle of statistical learning theory,
which is designed to decrease uncertainty in the model structure and the fitness of data. We have presented a comparative
analysis of SVC with the Maximum Likelihood Classification (MLC) method, which is the most popular conventional supervised
classification technique. SVC is an optimization technique in which the classification accuracy heavily relies on identifying
the optimal parameters. Using a case study, we verify a method to obtain these optimal parameters such that SVC can be applied
efficiently. We use multispectral and hyperspectral images to develop thematic classes of known lithologic units in order
to compare the classification accuracy of both the methods. We have varied the training to testing data proportions to assess
the relative robustness and the optimal training sample requirement of both the methods to achieve comparable levels of accuracy.
The results of our study illustrated that SVC improved the classification accuracy, was robust and did not suffer from dimensionality
issues such as the Hughes Effect. 相似文献
165.
Rangli Rangliot is an integral part of lesser Himalaya. The area around Rangli Rangliot consists of garnetstaurolite-mica schist and it is characterized by mineral assemblage garnet-biotite-muscovite-staurolite-quartz± plagioclase. Different reaction textures are of particular interest as they reflect discontinuous or continuous reactions under changing physical conditions. The relative XMg in the minerals varies in the order: muscovite> biotite> staurolite> garnet, and the XMn decreases in the order: garnet>staurolite>biotite>muscovite. The P-T evolution of the garnet-staurolite-mica schist has been constrained through the use of internally consistent TWEEQU programme and Perple_X software in the KFMASH model system. The combination of these two approaches demonstrates that the garnet-staurolite-mica schist experienced peak pressure and temperature at 5.8 kbar and 590 °C. The proposed clockwise P-T path implies that rocks from the study area could have resulted from thickened continental crust undergoing decompression. 相似文献
166.
S.K. Pal T.J. Majumdar Vipin Kumar Pathak Satya Narayan Ujjawal Kumar Om Prakash Goswami 《国际地球制图》2016,31(7):783-802
High-resolution EIGEN6C4 and EGM2008 Bouguer gravity data of 2190 degree spherical harmonic over the Singhbhum-Orissa Craton, India, have been generated from the International Centre for Global Earth Models. The Bouguer gravity anomaly difference maps of (i) in situ and EIGEN6C4, (ii) in situ and EGM2008 and iii) EIGEN6C4 and EGM2008 of the study area are compared. It reveals that EIGEN6C4 has lesser systematic error than EGM2008. However, from different profile plots of Bouguer gravity, east–west horizontal derivative and north–south horizontal derivative anomalies of the in situ, EIGEN6C4 and EGM2008, it is observed that most of the signatures of lithounits and geological structural elements are delineated very well by EGM2008 and match 94–98% with those of EIGEN6C4. Further, the Bouguer gravity, east–west horizontal derivative and north–south horizontal derivative anomalies of EGM2008 data over the study area have been used effectively for identifying various lithounits and geological structural elements. 相似文献
167.
168.
169.
170.
Geo-hydrological database modeling for integrated multiple hazards and risk assessment in Lesser Himalaya: a GIS-based case study 总被引:1,自引:1,他引:0
The main objective of the study was to assess the integrated multiple hydrological hazards and their environmental and socio-economic risks in Himalaya through geographical information system (GIS) and database management system (DBMS). The Dabka Watershed constitutes a part of the Kosi Basin in the Kumaun Lesser Himalaya has been selected for the case illustration. The Dabka DBMS is constituted of three GIS modules, that is, geo-informatics, hydro-informatics and hazard-informatics. Through the integration and superimposing of these modules prepared Hydrological Hazard Index to identify the level of vulnerability for existing hydrological hazards and their socio-economic and environmental risks. The results suggested that geo-environmentally most stressed barren land areas have high rate of runoff, flood magnitude, erosion sediment load and denudation during rainy season particularly in the month of August (i.e., respectively, 84.56 l/s/km2, 871.80 l/s/km2, 78.60 t/km2 and 1.21 mm/year), which accelerates high hazards and their socio-economic and environmental risks, whereas geo-environmentally least stressed dense forest areas experience low rate of stream runoff, flood magnitude, erosion sediment load and denudation in the same season and month (i.e., respectively, 20.67 l/s/km2, 58.12 l/s/km2, 19.50 t/km2 and 0.20 mm/year) comparatively have low hazards and their socio-economic and environmental risks. The other frazzled geo-environment that also found highly vulnerable for natural hazards and their risks is agricultural land due to high stream runoff, flood magnitude, erosion sediment load and denudation rates (i.e., respectively, 53.15 l/s/km2, 217.95 l/s/km2, 90.00 t/km2 and .92 mm/year). This makes it necessary to take up an integrated and comprehensive sustainable land use policy for the entire Himalaya region based on the scientific interpretation of the crucial linkages between land use and hydrological hazards, that is, floods, erosion, landslides during rainy season and drought due to dry-up of natural springs and streams during summer season. The study would help the village, district and state development authority to formulate decision support system for alternate planning and management for the Himalaya region. 相似文献