全文获取类型
收费全文 | 458篇 |
免费 | 27篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 20篇 |
地球物理 | 115篇 |
地质学 | 212篇 |
海洋学 | 23篇 |
天文学 | 94篇 |
综合类 | 2篇 |
自然地理 | 17篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 29篇 |
2015年 | 21篇 |
2014年 | 35篇 |
2013年 | 66篇 |
2012年 | 14篇 |
2011年 | 25篇 |
2010年 | 35篇 |
2009年 | 22篇 |
2008年 | 19篇 |
2007年 | 5篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 13篇 |
1996年 | 4篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 7篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1935年 | 1篇 |
排序方式: 共有487条查询结果,搜索用时 187 毫秒
51.
Y. Öhman 《Astrophysics and Space Science》1978,55(1):39-47
A report is given of some laboratory experiments on the thermal emission of glowing iron flakes. Clear effects of polarization are found sometimes in flakes of small size, indicating polarization of a kind similar to that appearing in the thermal emission from narrow metallic filaments. Sudden flashes of light appear in the thermal emission from flakes produced in a grinding wheel. At the same time the flake splits into two parts. It is suggested that the flash is due to tribo-thermoluminescence. It seems possible that the infrared radiation of the solar corona may contain a faintly polarized component due to thermal emission from dust particles.Paper dedicated to Professor Hannes. Alfvén on the occasion of his 70th birthday, 30 May, 1978. 相似文献
52.
Atila Özgüç 《Astrophysics and Space Science》1989,162(1):123-127
In the present paper, the time series of 1–8 Å X-ray index for the time interval between January 1977 to September 1981 has been analyzed by carrying out power spectrum using Discrete Fourier Transform. The 78-day periodicity which is one-half of the period found from various solar parameters of cycles 20 and 21 by various authors, was found. This periodicity is thought to be related to the 152-day periodicity. 相似文献
53.
Öivind Hauge 《Solar physics》1972,22(2):263-275
Photoelectric measurements of photospheric velocity fields have been carried out with the Sacramento Peak Doppler Zeeman Analyzer. Emphasis was given to long periods and low spatial wavenumbers in deep photospheric layers, where the 5-min oscillations are less dominant.Multiple or double peaks cannot be detected in power spectra of the 5-min oscillations, provided that a sufficient number of physically independent points on the solar surface are observed.The most frequent wave-numbers in the spectra of 5-min oscillations (as well as of the low frequency field) agree with those derived from a model assuming statistically independent oscillators of 10 to 20 diameter. These two velocity fields are anti-correlated spatially.Kinetic power in the 20-to-50-min range of periods is closely linked to brightness changes in the same layer, an increase of brightness lagging about 250 sec behind rising motion. Granules can be excluded as a possible source for the appearance of low frequency flow patterns. Different explanations are suggested.On leave from Fraunhofer Institut, Freiburg, Germany. 相似文献
54.
Book reviewed in this article:
Bradley, R. S. (ed.) 1991: Global Changes of the Past. 514 pp. Office for Interdisciplinary Earth Studies, Boulder, Colorado 相似文献
Bradley, R. S. (ed.) 1991: Global Changes of the Past. 514 pp. Office for Interdisciplinary Earth Studies, Boulder, Colorado 相似文献
55.
56.
57.
Günay Erpul Donald Gabriels Melis Özge Pınar Çağlar Sagun Wim Cornelis 《地球表面变化过程与地形》2021,46(14):2870-2883
The effects of wind-driven rain (WDR) on sand detachment were studied under various raindrop obliquities. Results suggested a significant reduction in compressive stress on sand surfaces for a two-dimensional experimental set-up in a wind tunnel. During experiments, sand particles in splash cups were exposed to both wind-free rain (WFR) and WDR driven by horizontal winds of 6.4, 8.9 and 12.8 m s−1 and rainfall intensities of 50, 60, 75 and 90-mm h−1 to assess the sand detachment rate (D, in g m−2 s−1). The effects of sand moisture state (dry and wet) on the detachment of different-sized particles (0.20–0.50 and 0.50–2.00 mm, respectively) were also tested. Factorial analysis of variance showed that shear and compressive stress components evaluated by horizontal and vertical kinetic energy flux terms (KEx and KEy, respectively, in J m−2 s−1) along with their vector sum (KEr, in J m−2 s−1) explained the variation in D. Neither sand size nor sand moisture was statistically significant alone although binary interactions of KEr, KEx and KEy with the sand size and three-way interaction of KEx, sand size and moisture were statistically significant. These results can be explained by size-dependent variation in sand compressibility and surface friction related to the total stress field developed by a given partition of shear and compressive stresses of wind-driven oblique raindrops (KEx/KEy). Further analysis of the variation of the unit sand detachment rate (Du = D/KEr = g J−1) with rain inclination (α, in degrees) better revealed the effect of WDR obliquity on Du that further changed with sand size class and moisture state. Finally, the difference in the resulting stress field differentiable by the oblique raindrop trajectories of the experiment over sand surface significantly affected the non-cohesive particle detachment rates, to some extent interacted with size-dependent compressibility and interface shear strength of sand grains. 相似文献
58.
59.
Field and laboratory studies of the sulphide-bearing tailings at Laver, northern Sweden, show that the present release of
metals from the tailings is low, especially with regard to Cu. A large part of the Cu released by sulphide oxidation is enriched
in a distinct zone just below the oxidation front. The enrichment zone occurs almost all over the tailings area except in
areas with a shallow groundwater table. The Cu enrichment is caused by formation of covellite and adsorption onto mineral
surfaces. The transport of Zn, Co, Cd, Ni and S seems to be controlled mainly by adsorption. No secondary zone or secondary
minerals containing these metals have been found. Just below the groundwater table, metals are released into solution when
the enrichment zone reaches the groundwater due to the low pH. An increased release of metals, especially Cu, can be expected
in the future, since the enrichment zone is moving towards the groundwater table.
Received: 4 December 1997 · Accepted: 17 December 1998 相似文献
60.
Ömer Emre Tamer Y. Duman Selim Özalp Fuat Şaroğlu Şeyda Olgun Hasan Elmacı Tolga Çan 《Bulletin of Earthquake Engineering》2018,16(8):3229-3275
We have updated the active fault map of Turkey and built its database within GIS environment. In the study, four distinct active fault types, classified according to geochronological criteria and character, were delineated on the 1:25,000 base map of Turkey. 176 fault segments not included in the former active fault map of Turkey, have been identified and documented. We infer that there are 485 single fault segments which are substantially potential seismic sources. In total 1964 active-fault base-maps were transferred into the GIS environment. Each fault was attributed with key parameters such as class, activity, type, length, trend, and attitude of fault plane. The fault parameters are also supported by slip-rate and seismogenic depth inferred from available GPS, seismological and paleoseismological data. Additionally, expected maximum magnitude for each fault segment was estimated by empirical equations. We present the database in a parametric catalogue of fault segments to be of interest in earthquake engineering and seismotectonics. The study provides essential geological and seismological inputs for regional seismic hazard analysis of all over Turkey and its vicinity. 相似文献