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951.
本文以遥感正射影像图的制作为例,简要介绍了卫星影像图的来源和特性,描述了正射影像图制作中的纠正、配准与融合流程及原理,概括地说明了影像图的几何镶嵌、色调调整、去重叠等数字处理过程。 相似文献
952.
Hydrated magnesium sulfate salts have been proposed as major components of the disrupted, reddish terrains on the surface of Europa. This is based on near-infrared reflectance spectra which contain distorted and asymmetric water absorption features typical of moderately hydrated materials such as hexahydrite (MgSO4⋅6H2O) and epsomite (MgSO4⋅7H2O). Hydrated magnesium sulfates having many waters of hydration could produce improved spectral matches. Here we present cryogenic laboratory spectra of highly hydrated sulfur-bearing salts, including hexahydrite, epsomite, bloedite (Na2Mg(SO4)2⋅4H2O), mirabilite (Na2SO4⋅10H2O), sodium sulfide nonahydrate (Na2S⋅9H2O), supersaturated MgSO4, NaHCO3, and Na2SO4 brines, and magnesium sulfate dodecahydrate (MgSO4⋅12H2O). All have been measured under conditions of pressure and temperature appropriate to the surface environment of Europa. Novel methods for preparation, verification and analysis of MgSO4⋅12H2O, which is not stable at standard temperature and pressure (STP), are described. At 100 K, all of these materials exhibit distorted and asymmetric absorption features similar to those in the Europa observations, as well as several weaker, narrow absorptions having widths ranging from 15 to 80 nm. While the agreement with Galileo NIMS observations of dark terrains on Europa is indeed better for highly hydrated salts than for salts of lower hydration states, we conclude that none of these materials alone can account for all of the observed spectral character. As previously suggested, Europa's reddish material appears to be a complex mixture of sulfate hydrates and other materials. 相似文献
953.
J.G Luhmann 《Planetary and Space Science》2003,51(6):387-392
The MIMI CHEMS Instrument on the Cassini Orbiter detected Jovian pickup ions almost an AU upstream of Jupiter during the 2001 flyby. The clue to their planetary origin is the presence of singly ionized sulfur ions in quantities exceeding those expected from the interstellar gas entering the heliosphere (Nature 415 (2002) 994). Earlier modeling of the extended Jovian neutral gas disk suggested how the combination of the orbiting, localized Jovian source and interplanetary ionization processes should combine to produce a distinctive reservoir for heliospheric pickup ion production, different from its interstellar gas counterpart. Here the expected characteristics of pickup ions from the Jovian source are considered using a simplified model. The results provide an idea of the signatures in physical and phase space that reflect both the initial velocities and directionalities of the parent neutral population. Long-term measurements can easily test for these attributes given sufficient spatial and ion energy coverage. 相似文献
954.
In this paper, a new retrieval method, i.e., the Statistical-Physical Retrieval Method (STPRM) has been developed. It is a
combination of both statistical and physical method. On this basis, a retrieval system of temperature-humidity profiles and
cloud parameters has been developed. By use of the developed TOVS STPRM the distribution of atmospheric temperature, humidity
and geopotential height on isobaric surface can be obtained. In comparison with the statistical method and physical method,
the TOVS STPRM system not only has the advantage of convenience in use, quickness in data processing and accuracy in retrieval
result, but also can display cloud evolution on screen. 相似文献
955.
The need for the use of general empirical mathematical models for satellite sensor modeling and 3D geo-positioning has increased recently, mainly because of the absence of the satellite sensor information of some of the high-resolution satellites. In addition, empirical mathematical models can be applied to different satellite sensors since they are time independent mathematical models and do not require specialized commercial software packages. This paper discusses the applicability of the empirical mathematical models presented by the 3D affine model and the 3D polynomial models for satellite sensor modeling and 3D geo-positioning. The objectives of the paper are to demonstrate that (a) the 3D affine model and its modifications of the 3D polynomial models are applicable to different satellite sensors and different types of terrain, and (b) under some conditions, the empirical models can produce accuracies close to those from rigorous mathematical models. 相似文献
956.
957.
G. Bourda 《Journal of Geodesy》2008,82(4-5):295-305
The temporal variations of the Earth’s gravity field, nowadays routinely determined from satellite laser ranging (SLR) and
GRACE (Gravity Recovery And Climate Experiment), are related to changes in the Earth’s rotation rate through the Earth’s inertia
tensor. We study this connection from actual data by comparing the traditional length-of-day (LOD) measurements provided by
the International Earth Rotation and Reference Systems Service (IERS) to the variations of the degree-2 and order-0 Stokes
coefficient of the gravity field determined from fitting the orbits of the LAGEOS-1 and −2 satellites since 1985. The two
series show a good correlation (0.62) and similar annual and semi-annual signals, indicating that the gravity-field-derived
LOD is valuable. Our analysis also provides evidence for additional signals common to both series, especially at a period
near 120 days, which could be due to hydrological effects. 相似文献
958.
F. Wild-Pfeiffer 《Journal of Geodesy》2008,82(10):637-653
Topographic and isostatic mass anomalies affect the external gravity field of the Earth. Therefore, these effects also exist
in the gravity gradients observed, e.g., by the satellite gravity gradiometry mission GOCE (Gravity and Steady-State Ocean Circulation Experiment). The downward continuation of the gravitational signals is rather difficult because of the high-frequency behaviour
of the combined topographic and isostatic effects. Thus, it is preferable to smooth the gravity field by some topographic-isostatic
reduction. In this paper the focus is on the modelling of masses in the space domain, which can be subdivided into different
mass elements and evaluated with analytical, semi-analytical and numerical methods. Five alternative mass elements are reviewed
and discussed: the tesseroid, the point mass, the prism, the mass layer and the mass line. The formulae for the potential,
the attraction components and the Marussi tensor of second-order potential derivatives are provided. The formulae for different
mass elements and computation methods are checked by assuming a synthetic topography of constant height over a spherical cap
and the position of the computation point on the polar axis. For this special situation an exact analytical solution for the
tesseroid exists and a comparison between the analytical solution of a spherical cap and the modelling of different mass elements
is possible. A comparison of the computation times shows that modelling by tesseroids with different methods produces the
most accurate results in an acceptable computation time. As a numerical example, the Marussi tensor of the topographic effect
is computed globally using tesseroids calculated by Gauss–Legendre cubature (3D) on the basis of a digital height model. The
order of magnitude in the radial-radial component is about ± 8 E.U.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
959.
全球开放DEM数据为数字地形分析提供了重要数据源。与已有的全球开放DEM数据相比,资源三号卫星具有更高的空间分辨率、更大的覆盖范围和更好的现势性。将资源三号卫星生成的DEM数据与全球开放DEM数据进行误差对比则为基于资源三号卫星的全球DEM数据研制提供科学依据。本文以山西省中部太原市为研究区,基于高精度激光点云数据生成DEM为参考数据,对资源三号卫星影像生成的DEM数据与全球典型的开放DEM数据(AW3D30、SRTM1和ASTER GDEM)的误差进行了对比分析,并获得了其在不同坡度等级下绝对误差与相对误差的平均值、平均绝对值、均方根值和标准偏差值。研究结果表明:①4种DEM数据的误差分布均具有较好的对称性。同时,平均误差接近于0 m,SRTM1和ASTER GDEM数据更是如此。因此均方根误差值与标准偏差值近似一致;②资源三号DEM具有最高的精度,误差最小(均方根误差4.6 m)。其次为AW3D30数据(均方根误差5.6 m)和SRTM1数据(均方根误差8.8 m)。ASTER GDEM数据误差最大(均方根误差12.6 m),精度最差;③资源三号DEM、SRTM1和ASTER GDEM数据的误差均随坡度的变大而增大,而AW3D30数据误差随着坡度增加呈现先减小后增大的趋势。总体上,与其他3种DEM数据相比,资源三号DEM在所有坡度范围均具有最小的误差值。 相似文献
960.
针对北斗频间卫星钟差偏差现有估计方法的不足,提出一种估计方法。该方法不仅顾及频间卫星钟差偏差的变化部分也顾及了其常数部分。采用10个观测站数据,验证了本文提出的算法,分析了北斗频间卫星钟差偏差的特性。在短期内,北斗频间卫星钟差偏差常数部分具有稳定性。对采用新算法计算得到的北斗频间卫星钟差偏差进行了模型化,结果表明,每颗卫星对应的频间钟差偏差可以利用10个参数予以高精度表示,对应精度可以达到厘米级。当采用第1天的模型参数进行第2天频间卫星钟差偏差值计算时,可实现厘米级结果。基于北斗频间卫星钟差偏差的稳定性与可模型化性,提出了高精度北斗卫星钟差服务策略,为我国高精度北斗卫星钟差服务提供参考。 相似文献