全文获取类型
收费全文 | 59584篇 |
免费 | 1281篇 |
国内免费 | 1225篇 |
专业分类
测绘学 | 1425篇 |
大气科学 | 4552篇 |
地球物理 | 12111篇 |
地质学 | 21541篇 |
海洋学 | 5123篇 |
天文学 | 13071篇 |
综合类 | 283篇 |
自然地理 | 3984篇 |
出版年
2022年 | 368篇 |
2021年 | 602篇 |
2020年 | 636篇 |
2019年 | 680篇 |
2018年 | 1306篇 |
2017年 | 1240篇 |
2016年 | 1516篇 |
2015年 | 1082篇 |
2014年 | 1545篇 |
2013年 | 2898篇 |
2012年 | 1933篇 |
2011年 | 2605篇 |
2010年 | 2310篇 |
2009年 | 2991篇 |
2008年 | 2571篇 |
2007年 | 2619篇 |
2006年 | 2483篇 |
2005年 | 1890篇 |
2004年 | 1835篇 |
2003年 | 1710篇 |
2002年 | 1637篇 |
2001年 | 1422篇 |
2000年 | 1353篇 |
1999年 | 1162篇 |
1998年 | 1214篇 |
1997年 | 1159篇 |
1996年 | 961篇 |
1995年 | 907篇 |
1994年 | 813篇 |
1993年 | 726篇 |
1992年 | 693篇 |
1991年 | 639篇 |
1990年 | 721篇 |
1989年 | 610篇 |
1988年 | 576篇 |
1987年 | 718篇 |
1986年 | 581篇 |
1985年 | 745篇 |
1984年 | 876篇 |
1983年 | 793篇 |
1982年 | 750篇 |
1981年 | 695篇 |
1980年 | 701篇 |
1979年 | 620篇 |
1978年 | 637篇 |
1977年 | 581篇 |
1976年 | 556篇 |
1975年 | 552篇 |
1974年 | 530篇 |
1973年 | 547篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The wadic project: A comprehensive field evaluation of directional wave instrumentation 总被引:1,自引:0,他引:1
J. Allender T. Audunson S. F. Barstow S. Bjerken H. E. Krogstad P. Steinbakke L. Vartdal L. E. Borgman C. Graham 《Ocean Engineering》1989,16(5-6)
The results of a comprehensive field trial of nearly all commercially available directional wave measurement systems at the Edda field in the North Sea during winter 1985-86 are presented. The results summarize the accuracy of the principal engineering wave parameters from each system and the dependence on sea state. Limiting factors on system performance and operational problems are also included in the assessment. Overall experience has been good with systems utilizing widely different measurement principles returning consistent results. 相似文献
82.
The authors describe the effect of copper pollution on the mitochondria from various areas of the Torpedo marmorata central nervous system. A high percentage of swollen mitochondria has been observed in neurons from animals experimentally exposed to high level of copper (4 ppm). The correlation with age pigment granules is discussed. 相似文献
83.
In this paper the peculiarities of compiled oceanographic data sets, which consist primarily in the presence of some characteristic information as well as in the planned incomplete filling of the files with observations, are discussed. A number of special ways are suggested which essentially improve the packing density of computerized data without applying special archiving algorithms. The effectiveness of these methods has been tested by treating thein situ hydrological/chemical data file compiled in the Black Sea in 1988.Translated by Vladimir A. Puchkin. 相似文献
84.
85.
Thomas L. Duvall Jr. 《Solar physics》1982,76(1):137-143
The equatorial photospheric rotation rate has been observed on 14 days in 1978–1980. The resulting rotation rate, = 14.14±0.04°/day, is 2% slower than the rate as observed for long-lived sunspots.Stationed at Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation. 相似文献
86.
The spreading angle of a number of light and dark Martian streaks is determined from selected Mariner 9 images. The resulting frequency distributions of spreading half-angles have maxima at ~5° for light, and ~7° for dark streaks; however the dark streaks have a secondary maximum spreading angle at ~14°. The smaller values, which include most streaks, are interpreted as crater-wake spreading phenomena. The larger value, found in only a few dark streaks or “tails,” may result from atmospheric diffusion and subsequent deposition of material from isolated sources such as vents or blowouts. An atmospheric diffusion-deposition analysis is presented, assuming this streak origin, from which it is possible to deduce the eddy diffusivity, K, in Mars' boudary layer. Calculated K values are found to agree with various theoretical estimates. They lie in the range 107 and 109 cm2 sec?1 and exhibit the proper scale dependence. Thus it appears that, in addition to streak-derived wind direction patterns and speed information, it is possible in a few cases to derive information on Mars' boundary-layer turbulence from streak-spreading measurements. 相似文献
87.
88.
89.
Lithology and Mineral Resources - The chemical composition and Nd isotope systematics were obtained for mudrocks (mudstones) from sections of the Siberian hypostratotype of the Riphean and Vendian... 相似文献
90.