全文获取类型
收费全文 | 2585篇 |
免费 | 212篇 |
国内免费 | 263篇 |
专业分类
测绘学 | 263篇 |
大气科学 | 302篇 |
地球物理 | 842篇 |
地质学 | 678篇 |
海洋学 | 334篇 |
天文学 | 91篇 |
综合类 | 67篇 |
自然地理 | 483篇 |
出版年
2024年 | 8篇 |
2023年 | 12篇 |
2022年 | 31篇 |
2021年 | 55篇 |
2020年 | 81篇 |
2019年 | 62篇 |
2018年 | 56篇 |
2017年 | 86篇 |
2016年 | 87篇 |
2015年 | 86篇 |
2014年 | 115篇 |
2013年 | 236篇 |
2012年 | 83篇 |
2011年 | 99篇 |
2010年 | 60篇 |
2009年 | 123篇 |
2008年 | 156篇 |
2007年 | 180篇 |
2006年 | 136篇 |
2005年 | 157篇 |
2004年 | 112篇 |
2003年 | 120篇 |
2002年 | 112篇 |
2001年 | 83篇 |
2000年 | 99篇 |
1999年 | 85篇 |
1998年 | 65篇 |
1997年 | 88篇 |
1996年 | 39篇 |
1995年 | 43篇 |
1994年 | 33篇 |
1993年 | 46篇 |
1992年 | 34篇 |
1991年 | 25篇 |
1990年 | 20篇 |
1989年 | 24篇 |
1988年 | 27篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有3060条查询结果,搜索用时 15 毫秒
21.
Estuary/ocean exchange and tidal mixing in a Gulf of Maine Estuary: A Lagrangian modeling study 总被引:2,自引:0,他引:2
Ata Bilgili Jeffrey A. Proehl Daniel R. Lynch Keston W. Smith M. Robinson Swift 《Estuarine, Coastal and Shelf Science》2005,65(4):607-624
A Lagrangian particle method embedded within a 2-D finite element code, is used to study the transport and ocean–estuary exchange processes in the well-mixed Great Bay Estuarine System in New Hampshire, USA. The 2-D finite element model, driven by residual, semi-diurnal and diurnal tidal constituents, includes the effects of wetting and drying of estuarine mud flats through the use of a porous medium transport module. The particle method includes tidal advection, plus a random walk model in the horizontal that simulates sub-grid scale turbulent transport processes. Our approach involves instantaneous, massive [O(500,000)] particle releases that enable the quantification of ocean–estuary and inter-bay exchanges in a Markovian framework. The effects of the release time, spring–neap cycle, riverine discharge and diffusion strength on the intra-estuary and estuary–ocean exchange are also investigated.The results show a rather dynamic interaction between the ocean and the estuary with a fraction of the exiting particles being caught up in the Gulf of Maine Coastal Current and swept away. Three somewhat different estimates of estuarine residence time are calculated to provide complementary views of estuary flushing. Maps of residence time versus release location uncover a strong spatial dependency of residence time within the estuary that has very important ramifications for local water quality. Simulations with and without the turbulent random walk show that the combined effect of advective shear and turbulent diffusion is very effective at spreading particles throughout the estuary relatively quickly, even at low (1 m2/s) diffusivity. The results presented here show that a first-order Markov Chain approach has applicability and a high potential for improving our understanding of the mixing processes in estuaries. 相似文献
22.
Temperature data from 18 measurement series obtained during logging of the Oseberg field in the northern North Sea are presented. Because the measurement series are taken at approximately the same depth, they should give identical temperatures after depth correction, and are suitable for assessing the performance of different models used to determine virgin rock temperatures from well log information.We have used this data set to test the properties of the different models given by Shen and Beck (1986). Although these models were built to simulate closely the thermal recovery of a well and are unbiased, the uncertainties in the temperature estimates when applied to real data are found to be no less than those from simpler (biased) models. This fact confirms the conclusion of Hermanrud (1989a) who showed that physical factors other than those presently accounted for significantly influence the thermal recovery of a borehole. 相似文献
23.
青岛市大气污染时间序列分析预报方法研究 总被引:5,自引:0,他引:5
根据青岛市大气污染监测资料 ,采用时间序列分析方法 ,建立多种预报模型 ,有原序列周期外延法、均生函数周期外延法、均生函数逐步回归法以及自回归预报法等 ,最后提出一种综合预报模型。连续预报试验表明 ,综合预报模型优于任何个别预报模型 ,有较好的预报能力。利用马尔可夫概型对污染状态 (轻、中、重 )进行了分级预报试验 ,也获得良好的效果。 相似文献
24.
25.
Viability theory for an ecosystem approach to fisheries 总被引:1,自引:1,他引:1
26.
The paper is intended to extend the investigations about the nature of abnormal waves that have been reported in the work of Guedes Soares et al. (Characteristics of abnormal waves in North Sea states. Applied Ocean Research 25, [337–344]). The same dataset gathered at the oil platform North Alwyn in the North Sea during the November storm in 1997 is used along with the time series from the Draupner platform, in which an abnormal wave occurred. The data are reanalyzed from the viewpoint of the applicability of second-order models to fit large waves. The observed results confirm that the second-order approximation is not adequate to describe highly asymmetric and abnormal waves. 相似文献
27.
28.
29.
30.
NPZ Models of Plankton Dynamics: Their Construction, Coupling to Physics, and Application 总被引:9,自引:0,他引:9
Peter J. S. Franks 《Journal of Oceanography》2002,58(2):379-387
Nutrient-phytoplankton-zooplankton (NPZ) models have been in use in oceanography for at least three decades, and are still
a common research tool. Given the discoveries of the last two decades, particularly concerning the role of bacteria in the
plankton, there are questions as to whether NPZ models can still be supported as a useful tool in planktonic research. Here
I review the construction of NPZ models, and some of the physical platforms they have been coupled to. I then discuss the
applications of NPZ-physical models, and conclude that they still constitute an important and viable research tool, provided
that the questions being explored are clearly stated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献