全文获取类型
收费全文 | 8471篇 |
免费 | 1249篇 |
国内免费 | 1545篇 |
专业分类
测绘学 | 947篇 |
大气科学 | 1226篇 |
地球物理 | 1064篇 |
地质学 | 3788篇 |
海洋学 | 612篇 |
天文学 | 15篇 |
综合类 | 751篇 |
自然地理 | 2862篇 |
出版年
2024年 | 43篇 |
2023年 | 102篇 |
2022年 | 309篇 |
2021年 | 402篇 |
2020年 | 362篇 |
2019年 | 407篇 |
2018年 | 305篇 |
2017年 | 372篇 |
2016年 | 398篇 |
2015年 | 411篇 |
2014年 | 547篇 |
2013年 | 556篇 |
2012年 | 576篇 |
2011年 | 628篇 |
2010年 | 461篇 |
2009年 | 505篇 |
2008年 | 512篇 |
2007年 | 564篇 |
2006年 | 523篇 |
2005年 | 438篇 |
2004年 | 386篇 |
2003年 | 344篇 |
2002年 | 323篇 |
2001年 | 292篇 |
2000年 | 257篇 |
1999年 | 224篇 |
1998年 | 216篇 |
1997年 | 189篇 |
1996年 | 118篇 |
1995年 | 106篇 |
1994年 | 86篇 |
1993年 | 81篇 |
1992年 | 66篇 |
1991年 | 27篇 |
1990年 | 30篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 5篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
21.
Weather in the North Gulf of Alaska is characterized by a high frequency of deep synoptic-scale low-pressure systems, especially during the cold season. The strong pressure gradients of these storms interact with the extremely rugged terrain of the coastal mountains to produce a variety of channeled flows. These surface wind regimes are not well documented in the scientific community, due to the paucity of observations. Modeling of these phenomena in regions of complex terrain is of great interest to those working with hydrodynamic, wave, and pollutant transport models in coastal and shelf areas. Such models, when coupled with ocean and coastal-ecology counterparts, give a broad view of the role surface winds play in shaping local coastal marine ecosystem in this region. This paper presents a climatology of simulated low-level wind jets over the domain of Cook Inlet and Shelikof Strait along Alaska's south-central coast. Daily simulations using the RAMS model were conducted in a 36-h forecast mode for the cold-season period 10/1/03 to 3/31/04. Systematic analysis of the resulting simulated low-level wind field makes it possible to characterize these jets and gap flows in spatial and temporal detail. The comparison between the RAMS winds and the Synthetic Aperture Radar (SAR)-derived winds when available verifies the existence of these wind jets and the capability of the model to simulate these cases. Clearly, the results of a study in this region depend on the fidelity of the model at these scales (O[5 km]). The SAR comparisons attempt to help establish this. From the 6 months of simulations over Cook Inlet and Shelikof Strait, the low-level wind jets are classified into 10 different regimes by location and orientation. These regimes are categorized into four more general groups: cross-channel westerly, easterly, and up and down Inlet flows. The nature of a particular regime is largely a function of pressure gradient orientation and local topography. Jets in the same group have a similar occurrence distribution with time. Some form of jet occurred in the study region almost daily each month of the period, with December 2003 having the highest frequency of wind jets. 相似文献
22.
23.
24.
本文阐述了东亚海区海岸带综合管理实践如何从地方性的示范发展到区域性的合作管理框架,如何实现海洋和海岸带资源的可持续利用.文中着重突出了厦门市政府在维持环境保护和经济发展的平衡,启动和实施海岸带综合管理,以及与沿海国在国际合作方面的经验,总结了厦门实施海岸带综合管理的主要经验,包括多部门间综合协调机制、海岸带综合管理法律框架、科技支撑体系的建立,海洋功能区划、环境剖面和战略环境管理计划的制定,以及实现海上联合执法等等.同时阐述了东亚海域环境管理区域合作计划(PEMSEA)与澳大利亚合作伙伴之间的关系在推动沿海城市的国际合作中将起到的作用. 相似文献
25.
A. Mascle R. Vially E. Deville B. Biju-Duval J.P. Roy 《Marine and Petroleum Geology》1996,13(8):941-961
The Southeast Basin of France is the thickest onshore French sedimentary basin which contains locally as much as 10 km of Mesozoic-Cenozoic sediment. Basin development occurred in several stages between late Carboniferous and late Cretaceous times. Partial tectonic inversion took place during two compressive events, the so-called ‘Pyrenean’ and ‘Alpine’ phases of late Cretaceous-early Tertiary and late Tertiary ages respectively. They are separated by an intervening stretching event of Oligocene age, which further south resulted in the opening of the western Mediterranean oceanic basin. As a result of this complex tectonic history, structural traps were difficult to image on the seismic data shot during the first phase of exploration prior to 1980. Oil and gas natural seeps, and shows in several wells, indicate that some petroleum systems are, or have been active, at least in some places.The present erosional western margin of the basin is more or less superimposed on the initial Triassic-Jurassic margin. Margin subsidence and Tertiary inversion are discussed using regional sections on which the polyphase history of the entire basin is well shown. These sections are located on three major segments where the Mesozoic margin is either partly preserved (Ardèche), or has been partly inverted in late Tertiary times (Vercors-Chartreuse), or has been completely inverted in early Tertiary times (Corbières-eastern Pyrenees). 1-D ‘Genex’ basin modelling on the Ardèche segment, and 2-D ‘Thrustpack’ structural-maturity modelling in the Vercors-Chartreuse segment are used to further assess the remaining petroleum plays. 相似文献
26.
27.
This paper investigates the use of data assimilation in coastal area morphodynamic modelling using Morecambe Bay as a study site. A simple model of the bay has been enhanced with a data assimilation scheme to better predict large-scale changes in bathymetry observed in the bay over a 3-year period. The 2DH decoupled morphodynamic model developed for the work is described, as is the optimal interpolation scheme used to assimilate waterline observations into the model run. Each waterline was acquired from a SAR satellite image and is essentially a contour of the bathymetry at some level within the inter-tidal zone of the bay. For model parameters calibrated against validation observations, model performance is good, even without data assimilation. However the use of data assimilation successfully compensates for a particular failing of the model, and helps to keep the model bathymetry on track. It also improves the ability of the model to predict future bathymetry. Although the benefits of data assimilation are demonstrated using waterline observations, any observations of morphology could potentially be used. These results suggest that data assimilation should be considered for use in future coastal area morphodynamic models. 相似文献
28.
29.
30.
ARGO计划的最新研究进展 总被引:4,自引:0,他引:4
本文主要介绍了ARGO计划的最新研究进展,并分析了我国参加ARGO计划的必要性与紧迫性。 相似文献