全文获取类型
收费全文 | 940篇 |
免费 | 34篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 43篇 |
大气科学 | 69篇 |
地球物理 | 220篇 |
地质学 | 249篇 |
海洋学 | 130篇 |
天文学 | 183篇 |
综合类 | 3篇 |
自然地理 | 89篇 |
出版年
2021年 | 8篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 28篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 52篇 |
2012年 | 30篇 |
2011年 | 39篇 |
2010年 | 39篇 |
2009年 | 70篇 |
2008年 | 37篇 |
2007年 | 46篇 |
2006年 | 47篇 |
2005年 | 38篇 |
2004年 | 27篇 |
2003年 | 31篇 |
2002年 | 31篇 |
2001年 | 20篇 |
2000年 | 26篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 14篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1969年 | 4篇 |
1954年 | 4篇 |
排序方式: 共有986条查询结果,搜索用时 15 毫秒
11.
The Nordic geological surveys: Geology for society in practice 总被引:1,自引:0,他引:1
Morten Smelror Andreas AhlstrФm Lena Ekelund Jens Morten Hansen Keijo Nenonen Anette K. Mortensen 《《幕》》2008,31(1):193-200
Since the mid-nineteenth century., when the first of the Nordic Geological Surveys were established, they have generated a substantial amount of information on the Earth's crust, its natural resources, its processes, and on the geological history of Nordic areas. The collective mission of the geological surveys is to carry out "Geology for Society", by doing research and providing services, and by making geological information and data easily accessible to all the varied end users in industry, government agencies, government institutes, public administrations, technical offices, academia and research institutes, as well as for private individuals. The present paper gives a brief overview of a few, selected, research areas and projects currently undertaken by the Nordic geological surveys. These serve as practical examples of how the Nordic geological surveys address important societal problems and challenges that require geological input for their solution. 相似文献
12.
13.
Phytoplankton variability on the Faroe Shelf 总被引:2,自引:2,他引:2
14.
15.
In the present study, long-term exposure to PCB resulted in marked induction of the xenobiotic biotransformation enzymes UDP glucuronosyl transferase, glutathione transferase and DT-diaphorase (measured as menadione reductase and DCPIP reductase) in rainbow trout 15 or 20 weeks post-injection during the experimental period. The increase of the phase II enzymes were paralleled by a marked increase of the glutathione reductase activity. These results indicate that prolonged exposure to PCB results in increased production of organo-radicals. 相似文献
16.
17.
Accelerated relative sea-level rise and rapid coastal erosion:: testing a causal relationship for the Louisiana barrier islands 总被引:1,自引:0,他引:1
Jeffrey H. List Asbury H. Sallenger Jr. Mark E. Hansen Bruce E. Jaffe 《Marine Geology》1997,140(3-4):347-365
The role of relative sea-level rise as a cause for the rapid erosion of Louisiana's barrier island coast is investigated through a numerical implementation of a modified Bruun rule that accounts for the low percentage of sand-sized sediment in the eroding Louisiana shoreface. Shore-normal profiles from 150 km of coastline west of the Mississippi delta are derived from bathymetric surveys conducted during the 1880s, 1930s and 1980s. An RMS difference criterion is employed to test whether an equilibrium profile form is maintained between survey years. Only about half the studied profiles meet the equilibrium criterion; this represents a significant limitation on the potential applicability of the Bruun rule. The profiles meeting the equilibrium criterion, along with measured rates of relative sea-level rise, are used to hindcast shoreline retreat rates at 37 locations within the study area. Modeled and observed shoreline retreat rates show no significant correlation. Thus, in terms of the Bruun approach, relative sea-level rise has no power for hindcasting (and presumably forecasting) rates of coastal erosion for the Louisiana barrier islands. 相似文献
18.
The stochastic properties of the drag force maxima on a circular cylinder subjected to nonlinear random waves are investigated. Unseparated laminar high Reynolds number flow is considered. A simplified approach based on second order Stokes waves is presented, including the sum-frequency effect only. It is demonstrated how a drag force formula valid for regular linear waves can be used to find the cumulative distribution function of individual drag force maxima for nonlinear irregular waves. Here the [Wang, 1968] drag force coefficient is used. 相似文献
19.
20.
Lars Chresten Lund-Hansen Morten Pejrup Jens Valeur Anders Jensen 《Estuarine, Coastal and Shelf Science》1994,38(6)
Gross sedimentation rates (GSR) have been measured using sediment traps placed at nine different levels above the bed (0·3, 0·5, 0·8, 1·0, 2·0, 4·0, 6·0, 8·0 and 10·0 m). The sediment traps were deployed for 1·25 years and recovered 28 times during the study period. Low average GSR values of 5·5 g m-2 day-1 were obtained at 10·0 m, and high average GSR values of 114·8 g m-2 day-1 were obtained at 0·3 m. An expression for the eddy diffusion coefficient of suspended particulate matter (Ks), based on the measured GSR is given. The expression has been used for modelling of Ks at the different trap levels above the bed. High values (≈42 cm2 s-1) of Ks were obtained at the upper traps, whereas low values (≈2 cm2 s-1) were obtained near the bed. Comparison between level of turbulent energy in terms of shear stress at the boundaries of the water column, i.e. from the wind and the bed flow, showed that wind energy exceeded that of the bed flow by a factor 16. At 5·0 m Ks was positively correlated (r=0·66) to the eddy diffusion coefficient of momentum (Km) derived from the wind energy transfer to the water, giving an average β of 0·5 for Ks =βKm. The density difference between surface and bottom waters has been designated a parameter of stratification, and is discussed in relation to variations of Ks and Km . 相似文献