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31.
Benthic macroinvertebrates and fish species were collected at monthly intervals during a 12‐month period, from 3 areas of the lower Rakaia River. The composition and abundance of the benthos and stomach contents of the fish were analysed for seasonal trends, food niche breadth and overlap between pairs of fish species, and overlap between the benthos and the diet of each fish species. The diets of bluegilled bully (Gobiomorphus hubbsi), upland bully (G. breviceps), juvenile longfinned eel (Anguilla dieffenbachii), Galaxias brevipinnis, G. paucispondylus, and juvenile brown trout (Salmo trutta) were similar to the proportions of prey species in the benthos. Deleatidium and chironomid larvae dominated the benthos in all seasons and formed the majority of food items in the diet of these species. Food niche overlap between these species was high, indicating potential competition, but preferred habitat and feeding habit differences plus low fish population density and abundance of main prey items probably eliminate the occurrence of any serious competition. The diet of the other fish species differed from this pattern. The common bully (Gobiomorphus cotidianus) ate proportionally more chironomid larvae and fish eggs than occurred in the benthos; torrentfish (Cheimarrichthys fosteri) ate proportionally more chironomid larvae than occurred in the benthos; and quinnat salmon (Oncorhynchus tshawytscha) depended largely upon prey species of terrestial origin, such as adult Deleatidium and dipterans. 相似文献
32.
Thedietsofthealpinegalaxias(Galaxias paucispondylus Stokell, 1938) and the longjawed galaxias (G. prognathus Stokell, 1940) were studied in Deep Creek, a high‐country stream in the central South Island of New Zealand. Both species are small, slender fish with entirely freshwater life cycles. Their diets were very similar and consisted of aquatic invertebrates, dominated by the larvae of Deleatidium spp. (Ephemeroptera), Hydrobiosis spp. (Trichoptera), and Chironomidae (Diptera). Although diets partly reflected what was available in the stream, both fish selected soft‐bodied prey in preference to cased or harder shelled prey. Both species are probably nocturnal feeders. 相似文献
33.
CHU Duo PUBU Tundrop NORBU Ghancan SAGAR Bajrachary MANDIRA Shresth GUO Jianping 《Acta Meteorologica Sinica》2011,25(6):734-741
Measuring rainfall from space appears to be the only cost effective and viable means in estimating regional precipitation
over the Tibet, and the satellite rainfall products are essential to hydrological and agricultural modeling. A long-standing
problem in the meteorological and hydrological studies is that there is only a sparse raingauge network representing the spatial
distribution of precipitation and its quantity on small scales over the Tibet. Therefore, satellite derived quantitative precipitation
estimates are extremely useful for obtaining rainfall patterns that can be used by hydrological models to produce forecasts
of river discharge and to delineate the flood hazard area. In this paper, validation of the US National Oceanic and Atmospheric
Administration (NOAA) Climate Prediction Center (CPC) RFE (rainfall estimate) 2.0 data was made by using daily rainfall observations
at 11 weather stations over different climate zones from southeast to northwest of the Tibet during the rainy season from
1 June to 30 September 2005 and 2006. Analysis on the time series of daily rainfall of RFE-CPC and observed data in different
climate zones reveals that the mean correlation coefficients between satellite estimated and observed rainfall is 0.74. Only
at Pali and Nielamu stations located in the southern brink of the Tibet along the Himalayan Mountains, are the correlation
coefficients less than 0.62. In addition, continuous validations show that the RFE performed well in different climate zones,
with considerably low mean error (ME) and root mean square error (RMSE) scores except at Nielamu station along the Himalayan
range. Likewise, for the dichotomous validation, at most stations over the Tibet, the probability of detection (POD) values
is above 73% while the false alarm rate (FAR) is between 1% and 12%. Overall, NOAA CPC RFE 2.0 products performed well in
the estimation and monitoring of rainfall over the Tibet and can be used to analyze the precipitation pattern, produce discharge
forecast, and delineate the flood hazard area. 相似文献
34.
35.
Ambuj D. Sagar 《Climatic change》2000,45(3-4):511-527
The need to develop a framework for allocatingnational GHG emissions based on rights to theatmosphere is increasingly pressing since aresolution of the issues surrounding these rights arelikely to be a precondition not only for moving beyondthe Kyoto Protocol, but even for effectiveimplementation of its Articles. This paper exploressome possible variations of a framework that isderived from the principles of the Climate Convention. It takes into account differences among countries interms of their current and historical greenhouse gasemissions, the attributes that contribute to thesedifferences, and the capabilities for contributing tothe achievement of the Convention's objectives. Furthermore, it is suggested that such a frameworkshould be designed so as to decouple the allocationissue from the deliberations over a suitable GHGconcentration stabilization target or global emissionscap. Such an approach could help achieve results inthe short to mid term without waiting for resolutionof the complex debate on the desirable level ofstabilization of greenhouse gas concentrations in theatmosphere.Sample explorations with carbon dioxide emissions dataindicate that the framework presented here can beparticularly favorable to the least-developedcountries. This is appropriate since these countrieshave not contributed substantially to the enhancedgreenhouse effect, but may be quite vulnerable to theimpacts of a changing climate, and lack thecapabilities to mitigate adverse impacts or adapt asneeded. Equally importantly, the framework alsodifferentiates between industrialized countries on thebasis of their current income and historicalemissions. The implementation of such a framework inconjunction with an emissions trading scheme may offeran appropriate path towards meeting the objectives ofthe Climate Convention. 相似文献
36.
A collaborative programme searching for mmag pulsations in chemically peculiar stars in the northern hemisphere was initiated
in 1997 between Nainital, India, and Cape Town, South Africa. It was therefore named as theNainital-Cape Survey programme. The detection limits imposed by the observing conditions (including atmospheric noise and telescope size) at both
Manora Peak and Devasthal sites are described. The scintillation noise on the best photometric nights is≈ 0.1 to 0.2 mmag for these sites. Both places allow one to detect few mmag variation in bright stars(B ≤ 12 mag), and are therefore particularly well-suited for carrying out the proposed survey work. The main characteristics of
the three-channel photometer developed at ARIES for carrying out the observations are also presented. This excellent instrument
has been used extensively since 1999 at the f/13 Cassegrain focus of ARIES’ 104 cm telescope. In particular, it allowed the
survey to result in the discovery of δ Scuti like pulsations in four Am stars, in one rapidly oscillating Ap star, and in
a number of probable variables so far. The future prospects are then presented, which regard the acquisition of a high speed
time series CCD photometer, a project to build a 3-metre class telescope at Devasthal, and collaborative observations with
Indian and foreign astronomical sites. 相似文献
37.
Rongxing Li Sagar Deshpande Xutong Niu Feng Zhou Kaichang Di Bo Wu 《Marine Geodesy》2013,36(3):143-159
This paper investigates the geopositioning accuracy achievable from integrating IKONOS and QuickBird satellite stereo image pairs with aerial images acquired over a region at Tampa Bay, Florida. The results showed that the accuracy is related to a few factors of imaging geometry. For example, the geopositioning accuracy of a stereo pair of IKONOS or QuickBird images can be improved by integrating a set of aerial images, even just a single aerial image or a stereo pair of aerial images. Shorelines derived from the IKONOS and QuickBird stereo images, particularly the vertical positions, are compared with the corresponding observations of water-penetrating LiDAR and water gauge stations and proved that differences are within the limit of the geopositioning uncertainty of the satellite images. 相似文献
38.
Ram Sagar 《Journal of Astrophysics and Astronomy》1997,18(4):295-301
The Galactic globular clusters are believed to be among the most ancient objects for which reliable ages can be determined.
As the Universe can not be younger than the oldest object it contains, the oldest Galactic globular clusters provide one of
the few most important constraints that one can have on cosmological models. Latest estimates indicate that the absolute age
of the oldest globular clusters is 14 ± 3 Gyr. The calibration of absolute ages is still subject to observational and theoretical
uncertainties at the ≈ 20% level, and represents a major limitation on our ability to test cosmological models. However, relative
ages are starting to be much better known due to the super colour-magnitude diagrams that have been obtained through the use
of CCD detectors on large telescopes and the Hubble Space Telescope. The available data are consistent with the majority of
Galactic globular clusters being virtually coeval but with a minority having significantly lower ages. The existence of “prehistoric”
clusters with ages of around 50 Gyr, as hypothesised in the quasi-steady state cosmology, should be readily recognised. 相似文献
39.
40.
Biman J. Medhi Maheswar G. J. C. Pandey T. S. Kumar Ram Sagar 《Monthly notices of the Royal Astronomical Society》2008,388(1):105-116
We present new B , V and R linear polarimetric observations for 61 stars towards the region of the young open cluster NGC 654. In this study we found evidence for the presence of at least two layers of dust along the line of sight to the cluster. The distances to the two dust layers are estimated to be ∼200 pc and ∼1 kpc which are located much closer to the Sun than the cluster (∼2.4 kpc). Both the dust layers have their local magnetic field orientation nearly parallel to the direction of the Galactic plane. The foreground dust layer is found to have a ring morphology with the central hole coinciding with the centre of the cluster. The foreground dust grains are suggested to be mainly responsible for both the observed differential reddening and the polarization towards the cluster. 相似文献