全文获取类型
收费全文 | 621篇 |
免费 | 16篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 26篇 |
地球物理 | 115篇 |
地质学 | 249篇 |
海洋学 | 41篇 |
天文学 | 154篇 |
综合类 | 2篇 |
自然地理 | 47篇 |
出版年
2021年 | 8篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 30篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 30篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 28篇 |
2006年 | 11篇 |
2005年 | 14篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 22篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 5篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 15篇 |
1974年 | 13篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1970年 | 4篇 |
1967年 | 4篇 |
1890年 | 3篇 |
排序方式: 共有641条查询结果,搜索用时 15 毫秒
61.
62.
T. H. Green 《Contributions to Mineralogy and Petrology》1977,65(1):59-67
Melting experiments on a model pelitic composition yield low-spessartine garnet as an important residual phase at pressures above 7 kb. The K
D
values for distribution of iron and magnesium between coexisting garnet and liquid in the pelitic composition are mainly sensitive to temperature, but also have a small pressure dependence. At temperatures above 950 ° C garnet has a higher
value than coexisting liquid, but below 950 ° C the garnet
value is lower than that of the coexisting liquid. Thus at temperatures below 950 ° C silicic magmas may fractionate garnet and produce more magnesian derivative liquids.Reconnaissance experiments with added MnO content in the model pelite demonstrate that spessartine-rich garnets are stable in silicic liquids to pressures as low as 3 kb. The MnO and CaO contents of the experimentally crystallized garnets show an antipathetic relation. Also, the grossular content of near-liquidus garnets crystallizing from a range of compositions increases with increasing pressure. The spessartine and grossular contents of most natural garnets in eastern Australian granitic rocks suggest that these garnets formed at pressures greater than 5 kb. Increased spessartine content allows crystallization of garnet in equilibrium with a silicic magma well within the pressure limit of stability of cordierite, provided the garnet contains 10 mol.% spessartine. Thus the depth range over which garnet and cordierite may coexist in a silicic melt is broadened, subject to the availability of MnO. The effect of increased Mn content on the low-pressure stability limit of garnet may also explain the lack of resorption of some garnets in granitic magmas, as these magmas rise to shallower levels. These euhedral garnets characteristically show zoning from an Mn-poor core (typically <4 % MnO) to an Mn-richer rim (typically >4 % MnO) and may reflect continued growth of the garnet in a low pressure regime, stabilized by Mn concentrated in the residual liquid fractions of the crystallizing magma. 相似文献
63.
64.
65.
Clear evidence exists for a cordierite breakdown reaction to amphibole-kyanite-quartz in high-grade metamorphic rocks of the Arunta Complex, Australia. Using the natural minerals this reaction has been duplicated experimentally. It proceeds over a divariant band with a slope of 12±4 bars/°C, occurring between 8 and 10.4 kb at 750° C and between 9.5 and 11.3 kb at 850°C. The reaction is cut off at low temperature by the appearance of talc and at high temperature by the appearance of orthopyroxene. The maximum pressure stability of the amphibole-kyanite-quartz assemblage is about 20 kb. These data suggest that the natural rock was subjected to pressures of at least 8 kb at 750–850° C for high water fugacities. Other experimental data on the hydration of hypersthene and cordierite-hypersthene stability, point to a temperature below 820° C and an upper pressure limit of 9.5 kb at 750–820°C. Experiments at \(P_{{\text{H}}_{\text{2}} {\text{O}}}\) total indicate that the breakdown of cordierite to amphibole-kyanite-quartz is a hydration reaction, and occurred in the natural rock as a result of an increase of water fugacity at constant total pressure (8–9.5 kb) and temperature (750–820°C). 相似文献
66.
Talc-garnet-kyanite-quartz schist occurs in an eclogite-bearing terrane in the Precambrian of Western Tasmania. It is argued that this rock was formed at a pressure of ? 10 kb and a temperature of 600°±20° C. Chemical zoning in the garnet and talc preserves evidence of increasing temperature during growth of the major minerals. 相似文献
67.
Julian C. Green 《水文研究》2005,19(6):1245-1259
Aquatic macrophytes are often the dominant factor influencing flow conditions within the channels they occupy. Existing knowledge of how stream plants affect the flow is outlined, and the different scales at which vegetation resistance operates are proposed. Resistance is shown to be a function of the size of the plants, their structural properties, location in the channel, and the local flow conditions. Current models to calculate this composite resistance effect are assessed in the light of theoretical considerations of the nature of vegetation resistance. New theory is also presented, which demonstrates the non‐linear relationship between channel resistance and the proportion of the channel occupied by vegetation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
68.
L.N. Baransky S.P. Belokris U.E. Borovkov C.A. Green 《Planetary and Space Science》1990,38(12):1573-1576
It has previously been shown that application of the “gradient method” to simultaneous recordings of geomagnetic pulsation fields at two stations on a meridian can determine the resonant frequency of a magnetic field line, and that the distribution of resonant frequencies along the meridian can be calculated from three stations. It is shown here that if the D-component spectrum of the pulsations is taken to be a representation of the driving wave, the same information can be derived from one and two station measurements, respectively, albeit with some slight loss of accuracy. It is also suggested that the empirical method of inferring the intensity of the interplanetary magnetic field from the measurement of the period of ground magnetic pulsations would be more accurate if D-component observations only were used. 相似文献
69.
70.
Bi-Qing For Elizabeth M. Green Gilles Fontaine Scott Shaw 《Astrophysics and Space Science》2010,328(1-2):87-90
In this paper, we report a rare reflection effect eclipsing sdB+dM binary, 2M?1533+3759. It is the seventh eclipsing sdB+dM binary that has been discovered to date. This system has an orbital period of 0.16177042 day and a velocity semi-amplitude of 71.1 km?s?1. Using a grid of zero-metallicity NLTE model atmospheres, we derived T eff=29250 K, log?g=5.58 and [He/H]=?2.37 from spectra taken near the reflection effection minimum. Lightcurve modeling resulted in a system mass ratio of 0.301 and an orbital inclination angle of 86.6°. The derived primary mass for 2M?1533+3759, 0.376±0.055 M ⊙, is significantly lower than the canonical mass (0.48 M ⊙) found for most previously investigated sdB stars. This implies an initial progenitor mass >1.8 M ⊙, at least a main sequence A star and perhaps even one massive enough to undergo non-degenerate helium ignition. 相似文献