全文获取类型
收费全文 | 199篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 16篇 |
地球物理 | 47篇 |
地质学 | 68篇 |
海洋学 | 17篇 |
天文学 | 29篇 |
自然地理 | 25篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 15篇 |
2012年 | 11篇 |
2011年 | 4篇 |
2010年 | 12篇 |
2009年 | 17篇 |
2008年 | 17篇 |
2007年 | 18篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有210条查询结果,搜索用时 15 毫秒
101.
102.
Alison J Williams 《Area》2010,42(1):51-59
The implementation of policies of pre-emption and securitisation by a number of states has led to an increase in the number of aerial incursions by one state's air force into another state's territory in recent years, often occurring before and, indeed, instead of ground incursions. This paper argues that it is vital that we conceptualise territory as a three-dimensional volume, rather than simply a flat area, in order to enable an analysis of how these events impact state sovereignty. The central contention of the paper is to extend recent work on territorial integrity and contingent sovereignty into this aerial dimension. A number of brief case studies are provided to illustrate how different incursion practices actively violate territorial integrity or render state sovereignty contingent. The conclusion seeks to answer the question of whether these incidents imply a crisis in aerial sovereignty or whether they confirm the chronic decline of this norm of international law. 相似文献
103.
Michael C. Cooper Jeffrey A. Newman Benjamin J. Weiner Renbin Yan Christopher N. A. Willmer Kevin Bundy Alison L. Coil † Christopher J. Conselice Marc Davis S. M. Faber Brian F. Gerke Puragra Guhathakurta David C. Koo Kai G. Noeske 《Monthly notices of the Royal Astronomical Society》2008,383(3):1058-1078
Using galaxy samples drawn from the Sloan Digital Sky Survey and the DEEP2 Galaxy Redshift Survey, we study the relationship between star formation and environment at z ∼ 0.1 and 1. We estimate the total star formation rate (SFR) and specific star formation rate (sSFR) for each galaxy according to the measured [O ii ]λ 3727 Å nebular line luminosity, corrected using empirical calibrations to match more robust SFR indicators. Echoing previous results, we find that in the local Universe star formation depends on environment such that galaxies in regions of higher overdensity, on average, have lower SFRs and longer star formation time-scales than their counterparts in lower density regions. At z ∼ 1 , we show that the relationship between sSFR and environment mirrors that found locally. However, we discover that the relationship between total SFR and overdensity at z ∼ 1 is inverted relative to the local relation. This observed evolution in the SFR–density relation is driven, in part, by a population of bright, blue galaxies in dense environments at z ∼ 1 . This population, which lacks a counterpart at z ∼ 0 , is thought to evolve into members of the red sequence from z ∼ 1 to ∼0. Finally, we conclude that environment does not play a dominant role in the cosmic star formation history at z < 1 : the dependence of the mean galaxy SFR on local galaxy density at constant redshift is small compared to the decline in the global SFR space density over the last 7 Gyr. 相似文献
104.
105.
A. Macleod 《The Photogrammetric Record》1986,12(68):155-165
With the advent of powerful computers and cheap optical devices, photogrammetric methods are now being used in several aspects of medicine. The application of close range photogrammetry to human movement analysis and body shape measurement is described. 相似文献
106.
Rb‐Sr and Sm‐Nd isotopic and REE studies of igneous components in the bulk matrix domain of Martian breccia Northwest Africa 7034 下载免费PDF全文
Laurence E. Nyquist Chi‐Yu Shih Francis M. McCubbin Alison R. Santos Charles K. Shearer Zhan X. Peng Paul V. Burger Carl B. Agee 《Meteoritics & planetary science》2016,51(3):483-498
The bulk matrix domain of the Martian breccia NWA 7034 was examined petrographically and isotopically to better understand the provenance and age of the source material that make up the breccia. Both 147Sm‐143Nd and 146Sm‐142Nd age results for mineral separates from the bulk matrix portion of breccia NWA 7034 suggest that various lithological components in the breccia probably formed contemporaneously ~4.44 Ga ago. This old age is in excellent agreement with the upper intersection ages (4.35–4.45 Ga) for U‐Pb discordia and also concordia defined by zircon and baddeleyite grains in matrix and igneous‐textured clasts. Consequently, we confirm an ancient age for the igneous components that make up the NWA 7034 breccia. Substantial disturbance in the Rb‐Sr system was detected, and no age significance could be gleaned from our Rb‐Sr data. The disturbance to the Rb‐Sr system may be due to a thermal event recorded by bulk‐rock K‐Ar ages of 1.56 Ga and U‐Pb ages of phosphates at about 1.35–1.5 Ga, which suggest partial resetting from an unknown thermal event(s), possibly accompanying breccia formation. The NWA 7034 bulk rock is LREE enriched and similar to KREEP‐rich lunar rocks, which indicates that the earliest Martian crust was geochemically enriched. This enrichment supports the idea that the crust is one of the enriched geochemical reservoirs on Mars that have been detected in studies of other Martian meteorites. 相似文献
107.
Michael J.S. Tevesz Alison L. Spongberg Jonathan A. Fuller 《Journal of Paleolimnology》1998,20(3):295-305
Stable carbon and oxygen isotope data from mollusc aragonite extracted from sediment cores provide new information on the origin and history of sedimentation in the southwestern area of the central basin of Lake Erie. Sediments infilling the Sandusky subbasin consist of three lithologic units overlying glacial deposits. The lowest of these is a soft gray mud overlain by a shell hash layer containing Sphaerium striatinum fragments. A fluid mud unit caps the shell hash layer and extends upwards to the sediment-water interface. New stable isotope data suggest that the soft gray mud unit is of postglacial, rather than proglacial, origin. These data also suggest that the shell hash layer was derived from erosional winnowing of the underlying soft gray mud layer. This winnowing event may have occurred as a result of the Nipissing flood.The Pelee-Lorain moraine, which forms the eastern boundary of the Sandusky subbasin, is an elevated area of till capped by a sand deposit that originated as a beach. The presence of both the shell hash layer and relict beach deposit strengthens the interpretation that the Nipissing flood was a critical event in the development of the southwestern area of the central basin of Lake Erie. This event, which returned drainage from the upper lakes to the Lake Erie basin, was a dominant influence on regional stratigraphy, bathymetry, and depositional setting. 相似文献
108.
Natural hazards in Australia: droughts 总被引:3,自引:0,他引:3
109.
Alison Porter 《Area》2000,32(1):41-48
Summary This paper describes how people with a range of physical impairments use the 'disabled role' to enable them to make local journeys in Swansea. It examines the processes by which interaction between people and social institutions serves to overcome transport disability and to reinforce prevailing meanings and structures of disability. 相似文献
110.
Mercury contamination of fish is dependent upon a system’s ability to transform inorganic Hg into biologically available forms; however, fish biometrics also play an important role. To assess long term trends in Hg concentrations in sand flathead (Platycephalus bassensis) a polynomial model, corrected for fish length, was used to evaluate temporal trends and spatial variability, while growth rates were estimated using the Von Bertalanffy length-at-age model. Hg concentrations showed no decrease over time, and generally remained near recommended consumption levels (0.5 mg kg−1). Previously reported spatial differences in Hg concentrations were not supported by the data once the models were corrected for fish length. Growth rate variation accounted for a large part of the previously published spatial differences. These results suggest that inclusion of fish biometrics is necessary to facilitate an accurate interpretation of spatial and temporal trends of contaminant concentrations in long term estuarine and marine monitoring programs. 相似文献