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61.
A. A. Deshpande R. Ramachandran G. Srinivasan 《Journal of Astrophysics and Astronomy》1995,16(1):53-67
A detailed statistical analysis of pulsarcurrent is presented. The conclusions reached are the following: (1) The birthrate of pulsars is about one in 75 ± 15 years. (2)
There is evidence forinjection of pulsars into the population of solitary pulsars. Such an injection is particularly pronounced in the magnetic field range
12 < logB < 12.6. (3) This is interpreted as due torecycled pulsars being released into the population. (4) We tentatively conclude that as much as 10 – 15% of all pulsars may have been born
and processed in binary systems. 相似文献
62.
The continuum spectrum of OJ 287, like most other BL Lac objects, is featureless- no emission or absorption lines are observed. However, OJ 287 shows variations at different timescales in flux and polarization at various wavelength bands. Using the available variability data one can estimate the sizes of the emission regions in the source from light travel time arguments. We assume the emission mechanism to be synchrotron radiation by high energy electrons with single power law energy distribution. Theoretical synchrotron spectrum in the frequency range 1011–1017
H
z
is compared with the observed spectral shape, obtained from new multifrequency quasi-simultaneous observations, to estimate the lower and upper cut off frequencies. These frequencies are used to obtain theoretical values of the variability timescales and magnetic field in the emission region. We obtain a value of 0.93 G for the magnetic field and 5.184×104
sec for the cooling time from the quiescent continuum spectrum. The shock-in-jet model explains the spectrum where shocks accelerate the particles and amplify the magnetic field in the jet. This timescale is compared with the one obtained from observed short timescale variability (20 minutes) with proper beaming correction. The short timescale variations (200 minutes in the source frame), possibly caused by an additional, flaring, component of the source, are also used to calculate compressed magnetic field. The observed and theoretically estimated variability timescales and the shape of the spectrum suggest that there are more than one emission components in OJ 287. 相似文献
63.
Narkhedkar S. G. Morwal S. B. Padmakumari B. Deshpande C. G. Kothawale D. R. Maheskumar R. S. Kulkarni J. R. 《Climate Dynamics》2015,45(5-6):1493-1512
Climate Dynamics - Rainfall mechanism over the rain-shadow region of north peninsular India during the summer monsoon season has been investigated using dynamic, thermodynamic, cloud microphysics... 相似文献
64.
65.
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
66.
Anne J. Jefferson Aditi S. Bhaskar Kristina G. Hopkins Rosemary Fanelli Pedro M. Avellaneda Sara K. McMillan 《水文研究》2017,31(23):4056-4080
Deleterious effects of urban stormwater are widely recognized. In several countries, regulations have been put into place to improve the conditions of receiving water bodies, but planning and engineering of stormwater control is typically carried out at smaller scales. Quantifying cumulative effectiveness of many stormwater control measures on a watershed scale is critical to understanding how small‐scale practices translate to urban river health. We review 100 empirical and modelling studies of stormwater management effectiveness at the watershed scale in diverse physiographic settings. Effects of networks with stormwater control measures (SCMs) that promote infiltration and harvest have been more intensively studied than have detention‐based SCM networks. Studies of peak flows and flow volumes are common, whereas baseflow, groundwater recharge, and evapotranspiration have received comparatively little attention. Export of nutrients and suspended sediments have been the primary water quality focus in the United States, whereas metals, particularly those associated with sediments, have received greater attention in Europe and Australia. Often, quantifying cumulative effects of stormwater management is complicated by needing to separate its signal from the signal of urbanization itself, innate watershed characteristics that lead to a range of hydrologic and water quality responses, and the varying functions of multiple types of SCMs. Biases in geographic distribution of study areas, and size and impervious surface cover of watersheds studied also limit our understanding of responses. We propose hysteretic trajectories for how watershed function responds to increasing imperviousness and stormwater management. Even where impervious area is treated with SCMs, watershed function may not be restored to its predevelopment condition because of the lack of treatment of all stormwater generated from impervious surfaces; non‐additive effects of individual SCMs; and persistence of urban effects beyond impervious surfaces. In most cases, pollutant load decreases largely result from run‐off reductions rather than lowered solute or particulate concentrations. Understanding interactions between natural and built landscapes, including stormwater management strategies, is critical for successfully managing detrimental impacts of stormwater at the watershed scale. 相似文献
67.
P. R. Rakhecha N. R. Deshpande A. K. Kulkarni B. N. Mandal R. B. Sangam 《Theoretical and Applied Climatology》1995,52(3-4):219-229
Summary The Almatti dam is the major engineering feature in the development of water resources in the Upper Krishna river forming a storage reservoir of 6425 million m3 at spillway crest level. In this paper, the design storm rainfalls for different return periods and also the Probable Maximum Precipitation (PMP) for the catchment above Almatti dam have been estimated to review the adequacy of the flood spillway design for the dam. The design storm rainfalls of various return periods have been computed from a statistical analysis of point and areal time series of annual maximum rainfall. In evaluating the PMP, the maximum observed rainfall obtained by Depth Duration method were maximized as the orography of the Western Ghats plays profound influence over the catchment. It was found that (area 35925 km2) the highest areal rainfalls over the catchment were 14.0 cm, 21.5 cm and 24.6 cm in 1, 2 and 3-day durations, respectively. These are scaled up by a factor of 1.23 to obtain the PMP rainfalls. The areal PMP estimates for the upper Krishna River (UKR) catchment above Almatti dam have been found to be 18.0 cm, 27.0 cm and 31.0 cm, respectively.With 6 Figures 相似文献
68.
Madhuri?Khambete Aditi?DivekarEmail author 《Journal of the Indian Society of Remote Sensing》2014,42(1):249-255
Remote sensing offers a wide variety of image data with different characteristics in terms of spatial and spectral resolutions. For optical sensor systems, imaging systems have a trade-off between high spatial and high spectral resolution, and no single system offers both. Hence, in the remote sensing application, an image with ‘greater quality’ often means higher spatial and higher spectral resolution. It is, therefore, necessary and very useful to merge images with higher spectral information and higher spatial information. Pansharpening combines spatial information from the high-resolution panchromatic image and color information from multispectral bands to create a high-resolution color image. Here we propose Discrete Cosine Transform (DCT) based pansharpening algorithm using Adaptive Linear model which preserves spectral information from Multispectral image and retains spatial resolution of Panchromatic image. 相似文献
69.
Kopparapu Vijaya Kumar Chakradhar Chavan Sariput Sawant K. Naga Raju Prachiti Kanakdande Sangita Patode Krishna Deshpande S. K. G. Krishnamacharyulu T. Vaideswaran V. Balaram 《Contributions to Mineralogy and Petrology》2010,159(6):839-862
Spatial and temporal variations in the geochemistry of an extrusive basaltic section of Deccan traps record progressive changes
in mantle melting and crustal filtration and are relevant to understand continental flood basalt (CFB) magmatism. In the present
work we have carried out detailed field, petrographic, density and magnetic susceptibility, and geochemical investigations
on a small, semi-continuous extrusive section in the eastern Deccan Volcanic Province (DVP) to understand the role of shallow
magma chambers in CFB magmatism. Four formations, Ajanta, Chikhli, Buldhana and Karanja crop out in the Gangakhed–Ambajogai
area with increasing elevation. Our studies indicate that: (1) the Karanja Formation represents a major magma addition, as
indicated by abrupt change in texture, increases in MgO, CaO, Ni, Cr, and Sr, and drastic decreases in Al2O3, Na2O, K2O, Rb, Ba, REE, bulk-rock density and magnetic susceptibility; (2) assimilation fractional crystallization, crystal-laden
magmas, and accessory cumulus phases influence the trace element chemistry of Deccan basalts; (3) the predicted cumulate sequence
of olivine gabbro–leucogabbro–oxide-apatite gabbro is supported by the observed layered series in a shallow magma chamber
within the DVP; (4) the initial magma was saturated with olivine, plagioclase, and augite, and final the pressure of equilibration
for the Gangakhed–Ambajogai section basalts is ~2 kbar (~6 km depth); (5) petrophysical parameters act as proxies for magmatic
processes; (6) a small layer of oxide-rich basalts may represent the latest erupted pulse in a given magmatic cycle in the
DVP; (7) parental basalts to some of the red boles, considered as formation boundaries, might represent small degree partial
melts of the mantle; (8) SW Deccan basaltic-types continue into the eastern DVP; and (9) in addition to the magma chamber
processes, dynamic melting of the mantle may have controlled DVP geochemistry. The present study underscores the importance
of mapping specific stratigraphic intervals in limited areas to understand mantle and magma chamber processes relevant to
CFB magmatism. 相似文献
70.
Jyoti Shah Deepak C. Srivastava Vipul Rastogi Rajit Ghosh Aditi Pal 《Journal of the Geological Society of India》2010,75(1):89-97
Most of the existing methods of strain analysis can estimate strain in a single form of distorted brachiopod, or trilobite
provided independent evidence, such as the association of the fossil with cleavage and/or stretching lineation is available
for inferring the direction of maximum principal strain. This article proposes a simple computer graphics based method and
its MATLAB code that determine the minimum amount of strain in a single distorted fossil form even if data for inferring the
maximum principal strain direction are lacking. Our method is a rapid computer-graphics alternative to some of the existing
analytical methods.
In a distorted fossil form of original bilateral symmetry, the relative senses of angular shears along the hinge line and
the median line are mutually opposite to each other. It follows, therefore, that the maximum principal strain direction lies
within the acute angle between the hinge and the median lines in the plane of the fossil. Using this principle, our method
performs several simulations such that each simulation retrodeforms the distorted fossil by assuming a particular orientation,
lying within the acute angle between the hinge line and the median line, as the potential direction of the maximum principal
strain. Each simulation of retrodeformation yields a potential strain ratio. The distribution of all the potential strain
ratios, obtained by assuming different orientations as the potential directions of the maximum strain, is typically a parabola-like
curve with a distinct vertex that corresponds to the minimum amount of strain in the distorted fossil. An entirely computer
graphical approach is somewhat time-intensive because it involves a large number of retrodeformational simulations. We, therefore,
give a MATLAB code, namely, the Minstrain, that rapidly retrodeforms the fossil and determines the minimum strain with precision. 相似文献