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994.
A geospatial approach to assessing land change in the built-up landscape of Wa Municipality of Ghana
《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2012,112(2):121-135
ABSTRACTUrban landscapes are changing in response to changes in socio-economic conditions. Land change scientists seek to understand these land dynamics in the coupled human-environment system of urban landscapes. This study assessed land change in the built-up area of Wa Municipality between 1986 and 2016 using Landsat images. We used the Support Vector Machine algorithm for classifying the images. We recorded image classification accuracies of 97%, 95%, 92% and 96% for the 1986, 1996, 2006 and 2016 classified images, respectively. Our study finds that over the 1986–2016 period, agricultural land and bare land transitioned to build-up land by 9.23% and 3.79%, respectively, as compared to 2.79% for vegetation and 0.05% for water. Our in-municipal level analysis thus shows that urban landscapes could expand more sustainably by targeting other dominant land categories instead of the vegetation cover. The findings in this paper could serve as a spatial model for planning and reducing the unintended socio-ecological impacts of expansion in the built-up area. 相似文献
995.
Oleksandr Kit 《Applied geography (Sevenoaks, England)》2012,32(2):660-667
This paper outlines a methodology to identify informal settlements out of high resolution satellite imagery using the concept of lacunarity. Principal component analysis and line detection algorithms were applied alternatively to obtain a high resolution binary representation of the city of Hyderabad, India and used to calculate lacunarity values over a 60 × 60 m grid. A number of ground truthing areas were used to classify the resulting datasets and to identify lacunarity ranges which are typical for settlement types that combine high density housing and small dwelling size - features characteristic for urban slums in India. It was discovered that the line detection algorithm is advantageous over principal component analysis in providing suitable binary datasets for lacunarity analysis as it is less sensitive to spectral variability within mosaicked imagery. The resulting slum location map constitutes an efficient tool in identifying particularly overcrowded areas of the city and can be used as a reliable source in vulnerability and resilience assessments at a later stage. The proposed methodology allows for rapid analysis and comparison of multi-temporal data and can be applied on many developing urban agglomerations around the world. 相似文献
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997.
Spectral observations of 10 FBS blue stellar objects (BSO) with the OHP 1.93-m and BAO 2.6.m telescopes are reported, and
overall progress in all the spectral observations and classifications of FBS BSO over 1987–2000 and in the classification
of these objects based on all the accessible sources-- in all, 753 out of 1103 objects-- is discussed. Representative slit
spectra for the major types of objects are presented and compared with digitized low dispersion spectra from the DFBS. The
nature of the FBS objects is examined in terms of advances in the spectral studies. Two-color diagrams are constructed from
the SDSS data and are used to find the regions occupied by the various types for further identification of objects of unknown
type.
Translated from Astrofizika, Vol. 52, No. 1, pp. 85–97 (February 2009). 相似文献
998.
The results of morphological and spectral study of the galaxies Kaz 5, Kaz 92, and Kaz 390 are presented. The observations
were made on the 2.6-m telescope at the Byurakan Observatory with the VAGR microlenses spectrograph. Isophotes of the images
of the galaxies are constructed in the Hα, [NII] λλ6584 , 6548, and [SII] λλ6731, 6717 emission lines and in the continuum. The masses of Kaz 5 and Kaz 92 are determined to be 8.6 × 108 M⊙ and 6.1 × 109 M⊙ , respectively. The mass of the gaseous component in the centers of regions I and IV of Kaz 390, which encompass a 1 pixel
area, are also determined. The morphological structure of the central region of Kaz 5 in the observed spectral range, λλ6400–6800?, differs completely from the structure of the same part of the galaxy observed with the 6-m and 2.5-m telescopes. It is shown
that these differences in the structure in images of Kaz 5 are mostly explained by the comparatively low resolution of the
telescope in combination with the VAGR spectrograph. Absorbing matter also contributes to this effect. It is also shown that
a “deficit” of nitrogen has been observed in the region of Kaz 390 studied here (a circle of diameter 40″).
Translated from Astrofizika, Vol. 52, No. 1, pp. 63–74 (February 2009). 相似文献
999.
We revisit calculations of the cosmogenic production rates for several long-lived isotopes that are potential sources of background in searching for rare physics processes such as the detection of dark matter and neutrinoless double-beta decay. Using updated cosmic-ray neutron flux measurements, we use TALYS 1.0 to investigate the cosmogenic activation of stable isotopes of several detector targets and find that the cosmogenic isotopes produced inside the target materials and cryostat can result in large backgrounds for dark matter searches and neutrinoless double-beta decay. We use previously published low-background HPGe data to constrain the production of 3H on the surface and the upper limit is consistent with our calculation. We note that cosmogenic production of several isotopes in various targets can generate potential backgrounds for dark matter detection and neutrinoless double-beta decay with a massive detector, thus great care should be taken to limit and/or deal with the cosmogenic activation of the targets. 相似文献
1000.
Jacqueline H. Carrillo Scott E. Emert D. Eli Sherman Pierre Herckes Jeffrey L. Collett Jr. 《Atmospheric Research》2008,87(3-4):259
A new, relatively low cost instrument has been developed to detect the presence of fog or cloud for fog/cloud sampling applications. The instrument uses attenuation of an 880 nm light emitting diode signal to detect cloud/fog drops in the optical path between a sending and receiving arm. Laboratory and field testing under a variety of conditions and fog types were carried out to determine the ability of the optical fog detector (OFD) to accurately detect cloud/fog presence as well as to provide some measure of liquid water content. Results indicated that the OFD provided a reliable estimate of fog presence as well as a reasonable estimate of liquid water content (LWC) under several different conditions. The OFD does appear to have an interference from rain, resulting in an overestimation of LWC during rainfall. This may occasionally give a false positive indication of fog presence. 相似文献