全文获取类型
收费全文 | 659篇 |
免费 | 29篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 18篇 |
大气科学 | 70篇 |
地球物理 | 160篇 |
地质学 | 274篇 |
海洋学 | 71篇 |
天文学 | 84篇 |
自然地理 | 18篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 29篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 39篇 |
2017年 | 27篇 |
2016年 | 39篇 |
2015年 | 17篇 |
2014年 | 27篇 |
2013年 | 34篇 |
2012年 | 42篇 |
2011年 | 42篇 |
2010年 | 35篇 |
2009年 | 41篇 |
2008年 | 35篇 |
2007年 | 23篇 |
2006年 | 30篇 |
2005年 | 25篇 |
2004年 | 16篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 19篇 |
2000年 | 15篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有695条查询结果,搜索用时 15 毫秒
151.
Sandro da Silva Fernandes 《Celestial Mechanics and Dynamical Astronomy》1995,63(3-4):375-408
Expansions of the functions (r/a)cos
jv and (r/a)m
sin
jv of the elliptic motion are extended to highly eccentric orbits, 0.6627 ... <e<1. The new expansions are developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients of these expansions are expressed in terms of the derivatives of Hansen's coefficients with respect to the eccentricity. The new expansions are convergent for values of the eccentricity such that |e–e*|<(e*), where the radius of convergence (e*) is the same of the extended solution of Kepler's equation. The new expansions are intrinsically related to Lagrange's series. 相似文献
152.
Protohematite (Fe2?x/3(OH) x O3?x 1 ≤ x < 0.5) and hydrohematite (Fe2?x/3(OH) x O3?x 0.5 ≤ x < 0) are iron-defective phases containing hydroxyl groups in their structures. These species were described in prior studies mainly with the aid of X-ray diffraction and Infrared spectroscopy. The existence of these phases in soils might have influence in redox processes, and they were considered as a possible water reservoir in Martian soils. In this study, we have used for the first time the Karl Fischer titration method to determine the amount of water released after heating several synthetic samples of goethite, hematite and natural iron ores at 105, 400, 600 and 900 °C. It was found that heating at 105 °C did not remove all moisture from the samples, and higher temperatures were necessary to completely remove all the absorbed water. The water contents determined at 400, 600 and 900 °C were found to be the same within the experimental errors, suggesting the inexistence of both protohematite and hydrohematite in the investigated samples. Therefore, the above-mentioned effects of these phases in soils might have to be reevaluated. 相似文献
153.
Complex coastal change in response to autogenic basin infilling: An example from a sub‐tropical Holocene strandplain
下载免费PDF全文
![点击此处可从《Sedimentology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Christopher J. Hein Duncan M. FitzGerald Luis H. P. de Souza Ioannis Y. Georgiou Ilya V. Buynevich Antonio H. da F. Klein João Thadeu de Menezes William J. Cleary Thelma L. Scolaro 《Sedimentology》2016,63(6):1362-1395
Thick bay‐fill sequences that often culminate in strandplain development serve as important sedimentary archives of land–ocean interaction, although distinguishing between internal and external forcings is an ongoing challenge. This study employs sediment cores, ground‐penetrating radar surveys, radiocarbon dates, palaeogeographic reconstructions and hydrodynamic modelling to explore the role of autogenic processes – notably a reduction in wave energy in response to coastal embayment infilling – in coastal evolution and shoreline morphodynamics. Following a regional 2 to 4 m highstand at ca 5·8 ka, the 75 km2 Tijucas Strandplain in southern Brazil built from fluvial sediments deposited into a semi‐enclosed bay. Holocene regressive deposits are underlain by fluvial sands and a Pleistocene transgressive–regressive sequence, and backed by a highstand barrier‐island. The strandplain is immediately underlain by 5 to 16 m of seaward‐thickening, fluvially derived, Holocene‐age, basin‐fill mud. Several trends are observed from the landward (oldest) to the seaward (youngest) sections of the strandplain: (i) the upper shoreface and foreshore become finer and thinner and shift from sand‐dominated to mud‐dominated; (ii) beachface slopes decrease from >11° to ca 7°; and (iii) progradation rates increase from 0·4 to 1·8 m yr?1. Hydrodynamic modelling demonstrates a correlation between progressive shoaling of Tijucas Bay driven by sea‐level fall and sediment infilling and a decrease in onshore wave‐energy transport from 18 to 4 kW m?1. The combination of allogenic (sediment supply, falling relative sea‐level and geology) and autogenic (decrease in wave energy due to bay shoaling) processes drove the development of a regressive system with characteristics that are rare, if not unique, in the Holocene and rock records. These findings demonstrate the complexities in architecture styles of highstand and regressive systems tracts. Furthermore, this article highlights the diverse internal and external processes and feedbacks responsible for the development of these intricate marginal marine sedimentary systems. 相似文献
154.
155.
156.
157.
158.
159.
160.
Michel Michaelovitch de Mahiques Ilson Carlos Almeida da SilveiraSilvia Helena de Mello e Sousa Marcelo Rodrigues 《Marine Geology》2002,181(4):387-400
Sedimentary and isotope data as well as 14C AMS dating on 15 box cores were used to identify the main post-Last Glacial Maximum (LGM) processes in the outer shelf and upper slope of the northernmost part of the São Paulo Bight, southeastern Brazil. Results show slight but significant variations in calcium carbonate, total sulphur and nitrogen contents as well as carbon and oxygen isotope ratios. Sedimentation rates, varying from 5 to 184 mm kyr−1 are controlled by the shelf and upper slope morphology, the Brazil Current meander dynamics, and the Coastal Water offshore motion. 相似文献