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21.
An extensive meteorological dataset obtained from the plumevalidation experiment conducted by the Electric Power Research Institute (EPRI) atKincaid during 1980–1981 is analysed for studying the characteristic differences in thesurface-layer parameters in strong and weak wind stable conditions. The surface-layerparameters are computed using the similarity functions m and h proposed byBeljaars and Holtslag. The weak winds are characterized using the geostrophic wind speedas well as the wind speed at the 10-m level. The surface fluxes are found to be finitein weak wind conditions.Empirical formulations for the eddy diffusivities of momentum(KM) and heat (KH), and drag (CD) and heat exchange (CH) coefficients, as powerlaw functions of the bulk Richardson number (RiB), are proposed under both strong andweak wind conditions. Results are close to those based on observations taken from the IndianInstitute of Technology low wind diffusion experiment, the Land surface processes experiment,the Hanford diffusion experiment, the Cabauw field experiment and the Cooperative Atmospheric SurfaceExchange Study 1999 (CASES-99) experiment. In addition, the fluxes obtained fromthe proposed empirical relations are in good agreement with those based on similarity theory as wellas the turbulence measurements taken from the CASES-99 experiment. 相似文献
22.
Carbonate ooids, notionally incompatible with an euxinic environment, and some curious reticulate tubular structures with fibrous carbonate walls are described from intraclasts occurring in Proterozoic black shales containing the pyrite deposit at Amjhor. While some of the tubes are visibly due to coalescence of ooids, others are interpreted as worm burrows on the basis of their strata-transgressive orientation, branching nature and larger diameter than those of the ooids.All stages of pyritization of ooids and tube-cores, displaying truncation of the growth-fabric of calcite grains by growing pyrite crystals, point to a late- or post-diagenetic age of pyritization. The clasts containing ooids and tubes are believed to have been transported from a shallow-bank and/or a nearshore environment into a lagoonal, euxinic basin. An environmental model, consistent with the observed data, is proposed to account for the ooid—black shale association. 相似文献
23.
The observations in weak wind stable conditions are scarce. The present study examines the observations from the Land Surface
Processes Experiment (LASPEX) conducted at Anand, (Gujarat, India) during the year 1997–1998 to study the characteristics
of surface layer under weak wind stable conditions. The observed surface fluxes are compared with those computed using Monin-Obukhov
(M-O) similarity theory. The upper air observations and regional climatology are used to justify the persistence of weak wind
conditions at Anand. The frequency of occurrence of weak wind stable conditions is observed to be around 67%. In 86% of the
cases under weak wind conditions, bulk Richardson number (RiB) is found to be larger than 0.2. The magnitude of surface fluxes computed from M-O similarity theory is shown to be smaller
in comparison to those based on the observations in weak wind stable conditions. Surface fluxes computed using the empirical
relations for the eddy diffusivities and drag and heat exchange coefficients are found to be comparable with those based on
M-O similarity theory however these fluxes are under-predicted in comparison to the observations. The traditional M-O similarity
theory is not able to simulate the observed fluxes well in weak wind stable conditions at Anand. 相似文献
24.
Natural Hazards - Ionospheric effects like scintillations and anomalous variations in total electron content (TEC) monitored with Global Positioning System (GPS) satellites of L1 frequency over... 相似文献
25.
Some aspects of South Asia's groundwater irrigation economy: analyses from a survey in India, Pakistan, Nepal Terai and Bangladesh 总被引:4,自引:2,他引:2
Since 1960, South Asia has emerged as the largest user of groundwater in irrigation in the world. Yet, little is known about this burgeoning economy, now the mainstay of the region's agriculture, food security and livelihoods. Results from the first socio-economic survey of its kind, involving 2,629 well-owners from 278 villages from India, Pakistan, Nepal Terai and Bangladesh, show that groundwater is used in over 75% of the irrigated areas in the sample villages, far more than secondary estimates suggest. Thanks to the pervasive use of groundwater in irrigation, rain-fed farming regions are a rarity although rain-fed plots within villages abound. Groundwater irrigation is quintessentially supplemental and used mostly on water-economical inferior cereals and pulses, while a water-intensive wheat and rice system dominates canal areas. Subsidies on electricity and canal irrigation shape the sub-continental irrigation economy, but it is the diesel pump that drives it. Pervasive markets in tubewell irrigation services enhance irrigation access to the poor. Most farmers interviewed reported resource depletion and deterioration, but expressed more concern over the high cost and poor reliability of energy supply for groundwater irrigation, which has become the fulcrum of their survival strategy.
相似文献
Tushaar ShahEmail: Phone: +91-2692-229311-13Fax: +91-2692-229310 |
26.
Aditi Kulshrestha Deewan Singh Bisht Jamson Masih David Massey Suresh Tiwari Ajay Taneja 《Journal of Atmospheric Chemistry》2009,62(2):121-138
This paper deals with the atmospheric concentrations of PM5 and PM2.5 particulate matter and its water soluble constituents along with the size distribution of ions and spatial variation at three
different residential environments in a semiarid region in India. Samples were collected from the indoors and outdoors of
urban, rural and roadside sites of Agra during October 2007–March 2008. The mean concentrations of PM2.5 indoors and outdoors were 178 μgm−3 and 195 μgm−3 while the mean concentrations of PM5 indoors and outdoors were 231.8 μgm−3 and 265.2 μgm−3 respectively. Out of the total aerosol mass, water soluble constituents contributed an average of 80% (33% anions, 50% cations)
in PM5 and 70% (29% anions, 43% cations) in PM2.5. The indoor–outdoor ratio of water soluble components suggested additional aerosol indoor sources at rural and roadside sites.
Indoor–outdoor correlations were also determined which show poor relationships among concentrations of aerosol ions at all
three sites. Univariate Pearson correlation coefficients among water soluble aerosols were determined to evaluate the relationship
between aerosol ions in indoor and outdoor air. 相似文献
27.
28.
M. Mookherjee M. D. Welch L. Le Pollès S. A. T. Redfern D. E. Harlov 《Physics and Chemistry of Minerals》2005,32(2):126-131
The behaviour of the ammonium ion in synthetic buddingtonite, N(D,H)4AlSi3O8, has been studied by infrared (IR) spectroscopy from 20 K to 298 K and by 2H NMR spectroscopy from 120 K to 298 K. IR spectra were collected from 500 to 3500 cm–1. Static 2H NMR spectra collected at 298 K and 120 K are very similar, consisting of a single sharp isotropic resonance, indicating complete averaging of quadrupolar interactions and implying that at these temperatures the ammonium ion is in rapid (<1 s) randomised motion within the M-site cavity of the feldspar framework. NMR spectroscopy indicates that the splitting of the internal modes of the ammonium ion observed by IR spectroscopy is not due to freezing in of the ammonium ion. This observation rules out the formation of a preferred N–H...O hydrogen bond, with precession of the ion about it, as proposed by Kimball and Megaw (1978), because any N–H...O hydrogen bond must be very weak and transient in nature. Contraction of the cavity site upon cooling imposes a distortion upon the ammonium ion that affects vibrational modes. This distortion does not affect the motion of the ammonium ion as observed on the NMR time-scale. 相似文献
29.
Groundwater socio-ecology and governance: a review of institutions and policies in selected countries 总被引:7,自引:6,他引:1
Groundwater is crucial for the livelihoods and food security of millions of people, and yet, knowledge formation in the field of groundwater has remained asymmetrical. While, scientific knowledge in the discipline (hydrology and hydrogeology) has advanced remarkably, relatively little is known about the socio-economic impacts and institutions that govern groundwater use. This paper therefore has two objectives. The first is to provide a balanced view of the plus and the down side of groundwater use, especially in agriculture. In doing so, examples are drawn from countries such as India, Pakistan, Bangladesh, China, Spain and Mexico—all of which make very intensive use of groundwater. Second, institutions and policies that influence groundwater use are analyzed in order to understand how groundwater is governed in these countries and whether successful models of governance could be replicated elsewhere. Finally, the authors argue that there is a need for a paradigm shift in the way groundwater is presently perceived and managed—from management to governance mode. In this attempt, a number of instruments such as direct regulation, indirect policy levers, livelihood adaptation and peoples participation will have to be deployed simultaneously in a quest for better governance.
相似文献
Tushaar ShahEmail: |
30.
M. Zhang G. J. Redhammer E. K. H. Salje M. Mookherjee 《Physics and Chemistry of Minerals》2002,29(9):609-616
Synthetic aegirine LiFeSi2O6 and NaFeSi2O6 were characterized using infrared spectroscopy in the frequency range 50–2000 cm−1, and at temperatures between 20 and 300 K. For the C2/c phase of LiFeSi2O6, 25 of the 27 predicted infrared bands and 26 of 30 predicted Raman bands are recorded at room temperature. NaFeSi2O6 (with symmetry C2/c) shows 25 infrared and 26 Raman bands. On cooling, the C2/c–P21/c structural phase transition of LiFeSi2O6 is characterized by the appearance of 13 additional recorded peaks. This observation indicates the enlargement of the unit
cell at the transition point. The appearance of an extra band near 688 cm−1 in the monoclinic P21/c phase, which is due to the Si–O–Si vibration in the Si2O6 chains, indicates that there are two non-equivalent Si sites with different Si–O bond lengths. Most significant spectral
changes appear in the far-infrared region, where Li–O and Fe–O vibrations are mainly located. Infrared bands between 300 and
330 cm−1 show unusually dramatic changes at temperatures far below the transition. Compared with the infrared data of NaFeSi2O6 measured at low temperatures, the change in LiFeSi2O6 is interpreted as the consequence of mode crossing in the frequency region. A generalized Landau theory was used to analyze
the order parameter of the C2/c–P21/c phase transition, and the results suggest that the transition is close to tricritical.
Received: 21 January 2002 / Accepted: 22 July 2002 相似文献