全文获取类型
收费全文 | 319篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 15篇 |
地球物理 | 79篇 |
地质学 | 78篇 |
海洋学 | 43篇 |
天文学 | 72篇 |
综合类 | 1篇 |
自然地理 | 36篇 |
出版年
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 21篇 |
2012年 | 13篇 |
2011年 | 14篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 12篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1965年 | 1篇 |
1928年 | 1篇 |
1922年 | 1篇 |
1912年 | 1篇 |
排序方式: 共有333条查询结果,搜索用时 15 毫秒
61.
The outer slope of the eastern reefs of Mauritius shows: from 0 to 15 m depth, a spurs-and-grooves zone of coral morphogenesis, sometimes replaced by a flagstone of coral morphogenesis (down to 20 m) or a spurs-and-grooves zone of volcanic morphogenesis; from 20 to 50 m, a volcanic flagstone with a thin coral-built layer and a buttresses-and-valleys zone of volcanic morphogenesis. The living cover of the upper part (0–15 m) is also quite similar to the cover of the leeward side. On the contrary, the volcanic basement in the lower part is poorly covered by reef-building organisms, while soft or slightly calcified algae are of widespread occurrence. 相似文献
62.
63.
An experiment is described showing that an optical scintillation instrument gives reliable values of heat and momentum fluxes in the surface layer, subject to the usual restrictions of homogeneity and steady state. This instrument measures the turbulence inner scale and refractive-index structure parameter, which are used to obtain the fluxes from Monin-Obukhov similarity relationships. The instrument gives space-averaged values over a propagation path that can range in length from tens to hundreds of meters. The history of the use of optical propagation to estimate fluxes is reviewed. 相似文献
64.
65.
Ohne Zusammenfassung 相似文献
66.
Laboratory investigations were conducted on the formation of NaF° ion-pairs at the ionic strength of seawater using specific ion electrodes. Sodium and fluoride ion electrodes produced results which are consistent with the ion-pairing model for these ionic interactions. The stoichiometric association constant for NaF°, , was determined at 15, 25, and 35°C. It was assumed that was a function of temperature, pressure, and ionic strength but not of solution composition. The value for at 25°C and I = 0.7 m is 0.045 ± 0.006. increased with decreasing temperature. This result was used to recompute values of and accounting for the presence of NaF° ion-pairs. The value for indicates that 1.1% of the fluoride in seawater is ion-paired with sodium at 25°C and 35‰ salinity. This fraction increases to approximately 2% at the lower temperatures found in the deep ocean. The percentage of free fluoride in natural seawater was measured at 15, 25, and 35°C to verify the speciation calculated from equilibrium constants. 相似文献
67.
68.
69.
The oxidation and reduction that occur during early diagenesis of sediments has been studied in the interstitial waters of
a rapidly accumulating sedimentary sequence from the Mediterranean margin of Spain. A series of reactions that are mediated
by progressively lower free energy derived from oxidation of organic matter is evident in the sedimentary sequence. Iron and
manganese are rapidly reduced. Phosphate and alkalinity maxima at a subbottom depth of 15 m indicate maximal organic matter
degradation. Methane first appears at ∼20 m subbottom after sulfate is depleted, and its concentrations quickly climb.
Received: 27 October 1997 / Revision received: 4 March 1998 相似文献
70.
Mike Walker Sigfus Johnsen Sune Olander Rasmussen Trevor Popp Jørgen‐Peder Steffensen Phil Gibbard Wim Hoek John Lowe John Andrews Svante Björck Les C. Cwynar Konrad Hughen Peter Kershaw Bernd Kromer Thomas Litt David J. Lowe Takeshi Nakagawa Rewi Newnham Jakob Schwander 《第四纪科学杂志》2009,24(1):3-17
The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene–Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in δ18O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi‐parameter annual layer counting provides an age of 11 700 calendar yr b2 k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene–Holocene boundary have also been recognised. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献