全文获取类型
收费全文 | 244篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 16篇 |
地球物理 | 37篇 |
地质学 | 102篇 |
海洋学 | 16篇 |
天文学 | 57篇 |
自然地理 | 7篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2001年 | 1篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1982年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有259条查询结果,搜索用时 15 毫秒
101.
R. K. Anand 《Astrophysics and Space Science》2012,342(2):377-388
Generalized forms of jump relations are obtained for one dimensional shock waves propagating in a non-ideal gas which reduce to Rankine-Hugoniot conditions for shocks in idea gas when non-idealness parameter becomes zero. The equation of state for non-ideal gas is considered as given by Landau and Lifshitz. The jump relations for pressure, density, temperature, particle velocity, and change in entropy across the shock are derived in terms of upstream Mach number. Finally, the useful forms of the shock jump relations for weak and strong shocks, respectively, are obtained in terms of the non-idealness parameter. It is observed that the shock waves may arise in flow of real fluids where upstream Mach number is less than unity. 相似文献
102.
S.Z. Weider B.J. Kellett B.M. Swinyard I.A. Crawford K.H. Joy M. Grande C.J. Howe J. Huovelin S. Narendranath L. Alha M. Anand P.S. Athiray N. Bhandari J.A. Carter A.C. Cook L.C. d'Uston V.A. Fernandes O. Gasnault M. Wieczorek 《Planetary and Space Science》2012,60(1):217-228
We present X-ray fluorescence observations of the lunar surface, made by the Chandrayaan-1 X-ray Spectrometer during two solar flare events early in the mission (12th December 2008 and 10th January 2009). Modelling of the X-ray spectra with an abundance algorithm allows quantitative estimates of the MgO/SiO2 and Al2O3/SiO2 ratios to be made for the two regions, which are in mainly basaltic areas of the lunar nearside. One of these ground tracks includes the Apollo 14 landing site on the Fra Mauro Formation. Within the 1σ errors provided, the results are inside the range of basaltic samples from the Apollo and Luna collections. The Apollo 14 soil composition is in agreement with the results from the January flare at the 1σ uncertainty level. Discrepancies are observed between our results and compositions derived for the same areas by the Lunar Prospector gamma-ray spectrometer; some possible reasons for this are discussed. 相似文献
103.
Abhay Anand Bourai Sunita Aswal Anoop Dangwal Mukesh Rawat Mukesh Prasad Nagendra Prasad Naithani Veena Joshi Rakesh Chand Ramola 《Acta Geophysica》2013,61(4):950-957
Radon in the Earth’s crust or soil matrix is free to move only if its atoms find their way into pores or capillaries of the matrix. 222Rn atoms from solid mineral grains get into air, filling pores through emanation process. Then 222Rn enters into the atmosphere from air-filled pores by exhalation process. The estimation of radon flux from soil surface is an important parameter for determining the source term for radon concentration modeling. In the present investigation, radon fluxes and soil-gas radon concentration have been measured along and around the Main Central Thrust (MCT) in Uttarkashi district of Garhwal Himalaya, India, by using Scintillation Radon Monitor (SRM) and RAD7 devices, respectively. The soil radon gas concentration measured by RAD7 with soil probe at the constant depth was found to vary from 12 ± 3 to 2330 ± 48 Bq·m?3 with geometrical mean value of 302 ± 84 Bq·m?3. Th significance of this work is its usefulness from radiation protection point of view. 相似文献
104.
Stephen J. Barnes L. A. Fisher R. Anand T. Uemoto 《Australian Journal of Earth Sciences》2013,60(2):269-285
Large, high-quality multi-element geochemical datasets are becoming widely available in the exploration industry, and afford excellent opportunities to investigate geochemical processes. A dataset of over 2500 analyses of unweathered and variably weathered mafic and ultramafic rocks for over 50 elements has been collected by Gold Fields Ltd. in the auriferous Agnew-Lawlers area of the eastern Yilgarn Craton of Western Australia. This dataset is used to investigate changes in element abundances and inter-element ratios through varying degrees and styles of weathering in an area of thick regolith characterised by deep in situ weathering. Systematic interrogation of the data, using lithostratigraphic controls derived from regional mapping and geophysics, reveals that a suite of elements, including Ti, Al, Zr, Th, La, Sc and Nb, and to a lesser extent Cr and Ni, behave as essentially immobile components during saprolite formation. In some cases diagnostic element ratios persist into siliceous duricrust. Ratios of these elements are used as reliable discriminants of bedrock type, and delineate features such as cryptic layering within fractionated sills and subtle geochemical variants in a sequence of tholeiitic and komatiitic basalts. Mapping on the basis of discriminant element ratios greatly extends previous trace-element ratio-based schemes for rock type discrimination. The potential to determine several of these elements with adequate precision and accuracy using portable XRF technology opens a potentially useful technique for rapid geochemical bedrock mapping in residual terrains. 相似文献
105.
Numerical and multivariate stochastic approaches to characterize flow in a constructed wetland basin 总被引:1,自引:1,他引:0
Xiaohua Wei Anand K. Plappally Alfred B. O. Soboyejo Bin Dong Zhi Mao Larry C. Brown 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(4):545-556
Reduction in specific and viscous dissipation rate in surface waters by flow control and contaminant removal are the goals
of constructed wetlands. A two-dimensional simulation study on surface flow through a constructed wetland in Guilin, China
is performed. The flow through the wetland is modeled and dynamically simulated by distinct case studies by varying both inlet
width and inflow rate. Nonlinear increase in peak dynamic pressure and specific dissipation rates as a function of increasing
inflow rate is reported for the different cases studied. The results of the numerical models confirm an increase in viscous
dissipation, shear stress and dynamic pressure within the wetland with increase in inflow rate. These modeling results are
used as inputs for performing a statistical data analysis. Further, a multivariate stochastic statistical framework has been
proposed for the prediction of dissipation as a function of variables including inflow rate, inlet geometry and wall shear
stress. Multivariate and variance analysis is performed to validate the appropriateness of the theoretical models proposed.
Results provide simplified meaningful suggestions to constructed wetland design and related applications. 相似文献
106.
When a piezocone (CPTU) penetrates the ground, pore pressures are set up due to the stress changes. Pore pressure dissipation occurs in the subsequent consolidation process in a manner dependent on the initial stress distribution. The process of analysis can be used to interpret the consolidation parameters from CPTU data based on strain path approach. For the two approaches to the CPTU analysis, the Houlsby and Teh method used an elastic-plastic model, while the Levadoux and Baligh solution used parameters specifically appropriate for Boston Blue Clay. This article discusses a comparison between the two theoretical predictions and field CPTU measurements deployed in Jiangsu (China) Quaternary clays. The values of the coefficient of consolidation calculated from the two methods are then compared with high-quality laboratory tests. Both theoretical predictions provide good agreement for the shape of the dissipation curve, but the predicted c h values are different and thought should indeed be given to the use of an appropriate value of G/s u. 相似文献
107.
Vrishali?DeosthaliEmail author Anand?N.?Akmanchi 《Journal of the Indian Society of Remote Sensing》2006,34(3):279-288
Estimation of crop production in advance of the harvest has been an intensively researched field in agriculture. Spectral
parameters derived from the spectral growth profile being indicator of growth and development characteristics of the crop
have a direct utility in crop-yield modeling. The present study is undertaken in a mixed cropping area of Karveer taluka,
Kolhapur district, Maharashtra, to assess feasibility of multi-date moderately coarse WiFS data in developing spectral growth
curves following Badhwar model (1980) for summer groundnut and paddy. The analysis highlighted potential of moderately coarse
resolution WiFS data in discriminating the crops grown in fragmented conditions, provided detailed and adequate ground truth
is used. The regression models using spectral parameters explained 94 % variation in paddy yield. However, model using ground
information as peak LAI in addition to spectral variables, could explain 91 % variation in groundnut yield; thus for prediction
of low-yielding and poorly managed crop a convergent model is essential. Vegetative growth rate during the pre-heading phase
and total growing season absorbed photosynthetically active radiation (APAR) indicated by the area under the curve are the
main predictors. 相似文献
108.
Jianhua Shao George Kuk Suchith Anand Jeremy G. Morley Mike J. Jackson Tyler Mitchell 《Transactions in GIS》2012,16(4):581-597
Over the last decade, there has been a tremendous growth and exploitation of open source geospatial software and technologies. A combination of factors is driving this momentum, including the contributions made by hundreds of developers and the leading role played by the Open Source Geospatial Foundation (OSGeo), aiming primarily to support and promote the collaborative development of open source geospatial technologies and data. This article seeks to map out the social history of collaborative activities within the OSGeo ecosystem. We used the archival logs of developers' contributions, specifically looking for boundary spanning activities where contributions crossed multiple projects. The analysis and visualization of these activities allow us to have a better understanding of the role of boundary spanning in the resourcing of each project, the incubation mechanism advocated by OSGeo, and the significance of the social interrelatedness among projects. The data consisted of the subversion (SVN) commit history made by individual developers in the programming code repository. We applied several network analytical and visualization techniques to explore the data. Our findings indicate that more than one in seven developers spanned multiple projects which potentially had the effects of shaping the projects' directions, and increased knowledge flow and innovation. In addition, the OSGeo's incubation mechanism provided an important encouragement for boundary spanning and increased knowledge sharing. By studying the social history of contributions, further tools can be developed in future to assist tracking of the social history, and make developers mindful of the significance of the interdependence among projects and hence continuously contribute to the health of the OSGeo ecosystem. 相似文献
109.
The great 1950 Assam Earthquake revisited: Field evidences of liquefaction and search for paleoseismic events 总被引:1,自引:0,他引:1
D.V. Reddy P. Nagabhushanam Devender Kumar B.S. Sukhija P.J. Thomas Anand K. Pandey R.N. Sahoo G.V. Ravi Prasad K. Datta 《Tectonophysics》2009,474(3-4):463-472
Extensive field investigations were carried out for the first time in the meizoseismal area of the great 1950 Assam Earthquake aimed at exploring the paleoseismic history of the NE Indian region through documentation of liquefaction features and radiocarbon (14C) dating. Trenching at more than a dozen locations along the Burhi Dihing River valley and within the alluvial fans adjoining the Brahmaputra and Dibang Rivers resulted in the identification of more than a dozen very prominent liquefaction features (sand dykes, sills, sand blows etc.) as evidences of large to great earthquakes. 14C dating of the organic material associated with some of the features indicates a paleoseismic record of about 500 yrs archived by the sediments in this region. Compelling geological evidence(s) of the great 1950 earthquake are well constrained by 14C dating. Out of the two historically reported seismic events (1548 AD and 1697 AD) from this region, 14C dating could constrain the 1548 AD event though not distinctly. Further studies using combined 14C and OSL dating may better constrain the seismo-chronology of the study region. 相似文献
110.
Banerjee Meenakshi Dutta Upama Anand R. Atlas Zachary D. 《Mineralogy and Petrology》2019,113(5):625-649
Mineralogy and Petrology - Coronae between olivine and plagioclase are a common replacement texture in mafic rocks by magmatic and metamorphic processes. Mafic dykes from Palghat Cauvery Shear Zone... 相似文献