全文获取类型
收费全文 | 2164篇 |
免费 | 134篇 |
国内免费 | 122篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 1篇 |
地球物理 | 1153篇 |
地质学 | 489篇 |
海洋学 | 354篇 |
天文学 | 10篇 |
综合类 | 21篇 |
自然地理 | 389篇 |
出版年
2024年 | 2篇 |
2023年 | 25篇 |
2022年 | 38篇 |
2021年 | 28篇 |
2020年 | 39篇 |
2019年 | 50篇 |
2018年 | 44篇 |
2017年 | 48篇 |
2016年 | 54篇 |
2015年 | 34篇 |
2014年 | 96篇 |
2013年 | 81篇 |
2012年 | 44篇 |
2011年 | 127篇 |
2010年 | 87篇 |
2009年 | 150篇 |
2008年 | 178篇 |
2007年 | 185篇 |
2006年 | 110篇 |
2005年 | 101篇 |
2004年 | 87篇 |
2003年 | 102篇 |
2002年 | 83篇 |
2001年 | 72篇 |
2000年 | 66篇 |
1999年 | 80篇 |
1998年 | 44篇 |
1997年 | 56篇 |
1996年 | 31篇 |
1995年 | 32篇 |
1994年 | 41篇 |
1993年 | 29篇 |
1992年 | 37篇 |
1991年 | 28篇 |
1990年 | 22篇 |
1989年 | 21篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2420条查询结果,搜索用时 31 毫秒
991.
在灵山岛东南水深大于25m海域的表层,发现大片砂砾、砾砂类沉积。根据对此类沉积物特征、成熟度、粒度分布、概率累积曲线、粒度参数、贝壳种类和沉积物展布特征的分析,发现此类沉积与现今海洋动力环境和海相沉积特征不相符合,推知此类沉积可能为残留沉积,其沉积环境为陆相洪积扇沉积。 相似文献
992.
Albert Palanques Emilio García-Ladona Dami Gomis Jacobo Martín Marta Marcos Ananda Pascual Pere Puig Josep-Maria Gili Mikhail Emelianov Sebasti Monserrat Jorge Guilln Joaquín Tintor Mariona Segura Antoni Jordi Simn Ruiz Gotzon Basterretxea Jordi Font Dolors Blasco Francesc Pags 《Progress in Oceanography》2005,66(2-4):89
Currents, particle fluxes and ecology were studied in the Palamós submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data showed that mean near surface and mid-depth currents were oriented along the mean flow direction (NE–SW), although at 400 and 1200 m depth within the canyon current reversals were significant, indicating a more closed circulation inside the canyon. Mean near-bottom currents were constrained by the local bathymetry, especially at the canyon head. The most significant frequency at all levels was the inertial frequency. A second frequency of about three days, attributed to a topographic wave, was observed at all depths, suggesting that this wave was probably not trapped near the bottom. The current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon. The associated vertical velocity ranged between 10 and 20 m/day and was constrained to the upper 300 m. This latter feature, together with other computations, suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow.In the canyon, suspended sediment concentration, downward particle fluxes, chlorophyll and particulate C and N were significantly higher up-canyon from about 1200 m depth than offshore, defining, along with the different hydrodynamics, two canyon domains: one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf-slope front. The higher near-bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows. During the deployment period, the increase in downward particle fluxes occurred by mid-November, when a severe storm took place. On the canyon walls at 1200 m depth, suspended sediment concentrations, downward particle fluxes, chlorophyll and particulate C and N were higher on the southern wall than on the northern wall inversely to the current’s energy. This could be caused by an upward water supply on the southern canyon wall and/or the mean flow interacting with the canyon bathymetry. In the swimmers collected by the sediment traps, the dominant species was an elasipod holothurian, which has not been recorded in other canyons or elsewhere in the Mediterranean, indicating particular speciation. 相似文献
993.
通过下佛罗统磁性地层学研究,获得了一些能记录岩石形成时的地磁场的样品,根据常规的古地磁方法,等温剩磁和热退磁实验,说明这些岩石的主要载磁矿物为磁铁矿.磁滞回线参数的测量表明多数载磁矿物磁铁矿为假单磁畴,少量样品则可能为假单磁畴与多磁畴的混合物.通过与北美古生代重磁化岩石的磁滞回线参数比值对比,说明重磁化与非重磁化岩五磁滞回线参数比值的分布趋势有明显差别,这一差别可能用于判定岩石的重磁化和非重磁化性质. 相似文献
994.
通过下佛罗统磁性地层学研究,获得了一些能记录岩石形成时的地磁场的样品,根据常规的古地磁方法,等温剩磁和热退磁实验,说明这些岩石的主要载磁矿物为磁铁矿.磁滞回线参数的测量表明多数载磁矿物磁铁矿为假单磁畴,少量样品则可能为假单磁畴与多磁畴的混合物.通过与北美古生代重磁化岩石的磁滞回线参数比值对比,说明重磁化与非重磁化岩五磁滞回线参数比值的分布趋势有明显差别,这一差别可能用于判定岩石的重磁化和非重磁化性质. 相似文献
995.
996.
997.
998.
近年来示踪技术作为研究水动力和泥沙冲淤规律的工具得到越来越广泛的应用。示踪技术比传统的水文观测方法方便、准确。传统研究方法往往只能进行定点或走航采样监测,而示踪技术则能准确判定某一区域泥沙或水流的具体运动过程和最终运动结果,甚至给出定量的结论,从而为数学模型参数的确定提供有效的依据。Pujol使用3H监测西班牙Ebro河的横向扩散速率[1],Albert在Ebo河用同样的方法研究水 相似文献
999.
1000.
Lawrence M. Mayer Linda L. Schick Mead A. Allison Kathleen C. Ruttenberg Samuel J. Bentley 《Marine Chemistry》2007
Recent data on the sources of organic carbon buried in the ocean have emphasized the probable importance of terrigenous organic matter in burial budgets of deltaic depocenters. The many markers used to assess relative importance of marine vs. terrestrial sources each have ambiguities. We use the ratio of bromine to organic carbon (Br:OC) as a source indicator for organic matter in the Mississippi delta. Progressive increases in bromine concentrations from the river to the slope indicate increasing content of marine-derived organic matter. Quantitative estimates of marine vs. terrigenous organic matter using Br:OC ratios in a two-endmember mixing model are consistent with recent estimates using a combination of three other source markers [Gordon, E.S., Goñi, M.A. 2003. Sources and distribution of terrigenous organic matter delivered by the Atchafalaya River to sediments in the northern Gulf of Mexico. Geochim. Cosmochim. Acta, 67:2359–2375]. The Br:OC vs. δ13C relationship indicates seaward increase in δ13C without proportionate incorporation of marine organic matter, consistent with recent arguments that isotopically depleted terrestrial detritus derived from C3 plants is separated from C4-derived terrigenous organic matter during transport. Decreasing Br:OC ratios downcore at many sites that have significant amounts of marine organic matter indicate that the marine organic matter is preferentially lost during burial diagenesis. This preferential loss constrains the contribution of organic matter burial in deltaic environments to global removal of Br. 相似文献