全文获取类型
| 收费全文 | 6022篇 |
| 免费 | 18篇 |
| 国内免费 | 12篇 |
专业分类
| 测绘学 | 30篇 |
| 大气科学 | 1089篇 |
| 地球物理 | 1432篇 |
| 地质学 | 3306篇 |
| 海洋学 | 63篇 |
| 天文学 | 67篇 |
| 综合类 | 5篇 |
| 自然地理 | 60篇 |
出版年
| 2013年 | 73篇 |
| 2009年 | 46篇 |
| 2006年 | 38篇 |
| 1997年 | 44篇 |
| 1996年 | 81篇 |
| 1995年 | 49篇 |
| 1994年 | 44篇 |
| 1993年 | 64篇 |
| 1992年 | 157篇 |
| 1991年 | 163篇 |
| 1990年 | 150篇 |
| 1989年 | 137篇 |
| 1988年 | 140篇 |
| 1987年 | 175篇 |
| 1986年 | 137篇 |
| 1985年 | 118篇 |
| 1984年 | 165篇 |
| 1983年 | 182篇 |
| 1982年 | 191篇 |
| 1981年 | 195篇 |
| 1980年 | 161篇 |
| 1979年 | 194篇 |
| 1978年 | 170篇 |
| 1977年 | 158篇 |
| 1976年 | 117篇 |
| 1975年 | 143篇 |
| 1974年 | 134篇 |
| 1973年 | 148篇 |
| 1972年 | 139篇 |
| 1971年 | 143篇 |
| 1970年 | 152篇 |
| 1969年 | 102篇 |
| 1968年 | 137篇 |
| 1967年 | 131篇 |
| 1966年 | 89篇 |
| 1965年 | 96篇 |
| 1964年 | 108篇 |
| 1963年 | 44篇 |
| 1962年 | 94篇 |
| 1960年 | 110篇 |
| 1959年 | 38篇 |
| 1957年 | 47篇 |
| 1956年 | 41篇 |
| 1955年 | 46篇 |
| 1954年 | 68篇 |
| 1953年 | 41篇 |
| 1952年 | 58篇 |
| 1951年 | 40篇 |
| 1950年 | 63篇 |
| 1949年 | 46篇 |
排序方式： 共有6052条查询结果，搜索用时 46 毫秒
1.
2.
3.
4.
5.
6.
Prediction of Stellar Atmospheric Parameters using Instance-Based Machine Learning and Genetic Algorithms 总被引：1，自引：0，他引：1
In this article we present a method for the automated prediction of stellar atmospheric parameters from spectral indices.
This method uses a genetic algorithm (GA) for the selection of relevant spectral indices and prototypical stars and predicts
their properties, using the k-nearest neighbors method (KNN). We have applied the method to predict the effective temperature,
surface gravity, metallicity, luminosity class and spectral class of stars from spectral indices. Our experimental results
show that the feature selection performed by the genetic algorithm reduces the running time of KNN up to 92%, and the predictive
accuracy error up to 35%.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Gianluca Loffredo Filippo Frontera Damiano Pellicciotta Alessandro Pisa Vito Carassiti Stefano Chiozzi Federico Evangelisti Luca Landi Michele Melchiorri Stefano Squerzanti 《Experimental Astronomy》2005,20(1-3):413-420
We will report on the current configuration of the X-ray facility of the University of Ferrara recently used to perform reflectivity tests of mosaic crystals and to calibrate the experiment JEM–X aboard Integral. The facility is now located in the technological campus of the University of Ferrara in a new building (named LARIX laboratory= ̳LARge ̳Italian ̳X-ray facility) that includes a tunnel 100 m long with, on the sides, two large experimental rooms. The facility is being improved for determining the optical axis of mosaic crystals in Laue configuration, for calibrating Laue lenses and hard X-ray mirror prototypes. 相似文献
8.
9.
10.
Dr M. J. Wooller D. L. Swain K. J. Ficken A. D. Q. Agnew F. A. Street-Perrott G. Eglinton 《第四纪科学杂志》2003,18(1):3-15
Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755‐cm‐long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon‐isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C4 photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C4 grass taxa were present at the LGM and that the majority followed the cold‐tolerant NADP‐MEC4 subpathway. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献