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451.
Li Chao 《Mathematical Geology》1998,30(1):43-56
A multidimensional version of the time varying periodogram has been developed. The estimation method based on the multidimensional time-varying periodogram has been applied to a nonstationary multidimensional storm model. This work proposes that the multidimensional time varying periodogram is capable of estimating nonstationary spectral density functions in space and time. 相似文献
452.
阿拉斯加巴罗AB—67钻孔岩芯的沉积环境分析 总被引:3,自引:0,他引:3
巴罗AB-67钻孔岩芯的48个样品被进行了25个项目的粒度分析和44个项目的地球化学分析。本文对这些数据进行了Q型因子分析,并得到了4个主因子。研究表明,这4个因子分别代表了沉积环境的四项指标,它们分别为沉积速率,降水,海平面和温度。从岩芯顶部5个样品与巴罗气象台观测记录研究了古温度和古降水的转换函数,从^210Pb测年和几个环境事件确定了沉积速率的转换函数。 相似文献
453.
Variations in the crustal structure beneath western Turkey 总被引:6,自引:0,他引:6
Paul Saunders Keith Priestley & Tuncay Taymaz 《Geophysical Journal International》1998,134(2):373-389
454.
Ghassem Habibagahi 《Soil Dynamics and Earthquake Engineering》1998,17(1):53-56
Estimation of the magnitude of reservoir induced seismicity is essential for seismic risk analysis of dam sites. Different geological and empirical methods dealing with the mechanism or magnitude of such earthquakes are available in the literature. In this study, a method based on an artificial neural network utilizing radial basis functions (RBF network) was employed to analyze the problem. The network has only two input neurons, one representing the maximum depth of the reservoir and the other being a comprehensive parameter representing reservoir geometry. Magnitudes of the induced earthquakes predicted using the RBF network were compared with the actual recorded data. Compared with the conventional statistical approach, the proposed method gives a better prediction, both in terms of coefficients of correlation and error rates. 相似文献
455.
从横向均匀介质满足的基本方程出发,得到视电阻率核函数的一阶非线性微分方程,通过方程求解,并利用滤波系数法容易得到电阻率随深度任意变化的视电阻率问题。当各层介质电性结构随深度呈指数变化时,还可得到各层之间核函数的递推关系,这对实际介质的正反演问题都有重要意义和应用价值。 相似文献
456.
An analytical form for the source function is formulated by comparing the fetch-limited approximation of the Ocean Wave Transport
equation and the empirical equation for the fetch-dependent wave forecast nomograms. The source function thus generated has
been utilised in the numerical model based on Toba’s formulation of wave transport equation and tested for the seas around
the Indian subcontinent (5°S to 25°N latitude; 45°E to 100°E longitude). The grid averaged hindcast wave heights are found
to be moderately matching with the GEOSAT altimeter measured significant wave heights of the 1987–1989 period, particularly
for waves higher than 1 meter. 相似文献
457.
本文用样条函数法实现了二维位场的向上延拓和向下延拓,向上延拓用样条函数法计算泊松积分,向下延拓用样条函数法求解第一类Fredholm积分方程。模型和实例计算表明,本文方法正确可行且精度高。 相似文献
458.
Neil Trentham 《Monthly notices of the Royal Astronomical Society》1998,293(1):71-88
We present the luminosity function and measurements of the scalelengths, colours and radial distribution of dwarf galaxies in the Coma cluster down to R =24. Our survey area is 674 arcmin2 ; this is the deepest and most detailed survey covering such a large area.
Our measurements agree with those of most previous authors at bright and intermediate magnitudes. The new results are as follows.
(1) Galaxies in the Coma cluster have a luminosity function φ( L )∝ Lα that is steep (α∼−1.7) for −15< MR <−11, and is shallower brighter than this. The curvature in the luminosity function at MR ∼−15 is statistically significant.
(2) The galaxies that contribute most strongly to the luminosity function at −14< MR <−12 have colours and scalelengths that are consistent with those of local dwarf spheroidal galaxies placed at the distance of Coma.
(3) These galaxies with −14< MR <−12 have a colour distribution that is very strongly peaked at B − R =1.3. This is suggestive of a substantial degree of homogeneity in their star formation histories and metallicities.
(4) These galaxies with −14< MR <−12 also appear to be more confined to the cluster core ( r ∼200 kpc) than the brighter galaxies. Alternatively, this observation may be explained in part or whole by the presence of an anomalously high number of background galaxies behind the cluster core. Velocity measurements of these galaxies would distinguish between these two possibilities. 相似文献
Our measurements agree with those of most previous authors at bright and intermediate magnitudes. The new results are as follows.
(1) Galaxies in the Coma cluster have a luminosity function φ( L )∝ L
(2) The galaxies that contribute most strongly to the luminosity function at −14< M
(3) These galaxies with −14< M
(4) These galaxies with −14< M
459.
Neil Trentham 《Monthly notices of the Royal Astronomical Society》1998,294(2):193-200
We present the results from a CCD survey of the B -band luminosity function of nine clusters of galaxies, and compare them to published photographic luminosity functions of nearby poor clusters like Virgo and Fornax, and also to the field luminosity function. We derive a composite luminosity function by taking the weighted mean of all the individual cluster luminosity functions; this composite luminosity function is steep at bright and faint magnitudes and is shallow in-between.
All clusters have luminosity functions consistent with this single composite function. This is true both for rich clusters like Coma and for poor clusters like Virgo.
This same composite function is also individually consistent with the deep field luminosity functions found by Cowie et al. and Ellis et al., and also with the faint end of the Las Campanas Redshift Survey R -band luminosity function, shifted by 1.5 mag. A comparison with the Loveday et al. field luminosity function, which is well determined at the bright end, shows that the composite function, which fits the field data well fainter than MB =−19, drops too steeply between M B =−19 and −22 to fit the field data there. 相似文献
All clusters have luminosity functions consistent with this single composite function. This is true both for rich clusters like Coma and for poor clusters like Virgo.
This same composite function is also individually consistent with the deep field luminosity functions found by Cowie et al. and Ellis et al., and also with the faint end of the Las Campanas Redshift Survey R -band luminosity function, shifted by 1.5 mag. A comparison with the Loveday et al. field luminosity function, which is well determined at the bright end, shows that the composite function, which fits the field data well fainter than M
460.
Pippa Goldschmidt & Lance Miller 《Monthly notices of the Royal Astronomical Society》1998,293(1):107-112
The recently finished Edinburgh UVX quasar survey at B <18 is used together with other complete samples to estimate the shape and evolution of the optical luminosity function in the redshift range 0.3< z <2.2. There is a significantly higher space density of quasars at high luminosity and low redshift than previously found in the PG sample of Schmidt & Green, with the result that the shape of the luminosity function at low redshifts ( z <1) is seen to be consistent with a single power law. At higher redshifts the slope of the power law at high luminosities appears to steepen significantly. There does not appear to be any consistent break feature which could be used as a tracer of luminosity evolution in the population. 相似文献