全文获取类型
收费全文 | 998篇 |
免费 | 47篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 64篇 |
地球物理 | 231篇 |
地质学 | 273篇 |
海洋学 | 103篇 |
天文学 | 163篇 |
综合类 | 2篇 |
自然地理 | 185篇 |
出版年
2023年 | 8篇 |
2021年 | 7篇 |
2020年 | 26篇 |
2019年 | 19篇 |
2018年 | 13篇 |
2017年 | 19篇 |
2016年 | 23篇 |
2015年 | 23篇 |
2014年 | 36篇 |
2013年 | 53篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 54篇 |
2009年 | 45篇 |
2008年 | 42篇 |
2007年 | 48篇 |
2006年 | 38篇 |
2005年 | 31篇 |
2004年 | 40篇 |
2003年 | 36篇 |
2002年 | 47篇 |
2001年 | 28篇 |
2000年 | 22篇 |
1999年 | 24篇 |
1998年 | 23篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 13篇 |
1977年 | 14篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有1045条查询结果,搜索用时 15 毫秒
871.
872.
In this study, we use seismic reflection, well and core data to investigate the role that basin physiography and sediment routing systems played on the distribution, geometry and stratigraphic architecture of Upper Cretaceous submarine fans (SF) offshore Norway. The Late Cretaceous Møre‐Trøndelag margin of western Norway was characterised by steep submarine slopes (gradient of ~0.3°–3°). Mudstones dominate the Upper Cretaceous slope succession, although a few regionally extensive, sandstone‐dominated units are developed. We focus on the most regionally extensive sandstone unit, which is of Late Turonian‐to‐Early Coniacian age. Mapping and visualisation of 2D and 3D seismic reflection data and analysis of well data indicates that the sandstone unit comprises a total of 11 SF, which were fed by sand‐rich sediment gravity flows routed through multiple upper slope canyons. Based on the internal organisation of seismic facies, four fan types have been identified: (i) Type Ia fans, which are characterised by <10 erosional channel complexes at their bases and aggradational to landward‐stepping lobes in their upper parts; (ii) Type Ib fans, which are characterised by >10 erosional channel complexes at their bases and aggradational to landward‐stepping lobe and mass‐transport deposits near the fan apex in their upper parts; (iii) Type II fans, which are dominated by aggradational lobe deposits; and (iv) Type III fans, which are dominated by a single channel complex that passes downdip into a small terminal lobe. The different fan types are interpreted to reflect variable stratigraphic responses to source proximity and basin physiography, which is principally related to the degree of local fault reactivation and differential compaction. This variability highlights the diversity of fan types that may occur over short distances along continental margins, and demonstrates the importance of local controls in understanding the internal stratigraphic variability that may be present in deep‐marine successions. 相似文献
873.
C. Halliday D. Carter T. J. Bridges Z. C. Jackson M. I. Wilkinson D. P. Quinn N. W. Evans N. G. Douglas H. R. Merrett M. R. Merrifield A. J. Romanowsky K. Kuijken M. J. Irwin 《Monthly notices of the Royal Astronomical Society》2006,369(1):97-119
We present radial velocities for a sample of 723 planetary nebulae in the disc and bulge of M31, measured using the WYFFOS fibre spectrograph on the William Herschel Telescope. Velocities are determined using the [O iii ] λ5007 emission line. Rotation and velocity dispersion are measured to a radius of 50 arcmin (11.5 kpc), the first stellar rotation curve and velocity dispersion profile for M31 to such a radius. Our kinematics are consistent with rotational support at radii well beyond the bulge effective radius of 1.4 kpc, although our data beyond a radius of 5 kpc are limited. We present tentative evidence for kinematic substructure in the bulge of M31 to be studied fully in a later work. This paper is part of an ongoing project to constrain the total mass, mass distribution and velocity anisotropy of the disc, bulge and halo of M31. 相似文献
874.
Argument rages in the media on the effects of road-building on sites of archaeological importance. Certainly there have been many cases where sites of value have been lost, but others where sites of importance have been revealed that would probably have gone undetected for a considerable time, if not for ever. One example of a lucky discovery arose from a proposal to widen the road between the towns of Tralee and Killarney in County Kerry, south-west Ireland. A preliminary archaeological survey carried out along the route in 1996 revealed an area of exceptional archaeological richness. What was particularly surprising was that one feature contained a significant collection of fossils used for funereal or ceremonial purposes. 相似文献
875.
876.
877.
878.
The advent of new observational facilities in the last two decades has allowed the rapid discovery and high-resolution optical imaging of many strong lens systems from galaxy to cluster scales, as well as their spectroscopic follow-up. Radio telescopes have played the dominant role in the systematic detection of dozens of new arcsec-scale lens systems. For the future, we expect nothing less! The next major ground- and space-based facilities, especially the Square Kilometer Array can discover tens of thousands of new lens systems in large sky surveys. For optical imaging and spectroscopic follow-up a strong synergy with planned optical facilities is needed. Here, we discuss the field where strong gravitational lensing is expected to play the dominant role and where SKA can have a major impact: The study of the internal mass structure and evolution of galaxies and clusters to z 1. In addition, studies of more exotic phenomena are contemplated. For example, milli- and micro-lensing can provide a way to measure the mass-functions of stars and CDM substructure at cosmological distances. All-sky radio monitoring will also rapidly develop the field of time-domain lensing. 相似文献
879.
880.
Nicholas Cross Simon P. Driver Warrick Couch Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Gavin Dalton Kathryn Deeley Roberto De Propris George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Stephen Moody Peder Norberg John A. Peacock Bruce A. Peterson Ian Price Mark Seaborne Will Sutherland Helen Tadros Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,324(4):825-841