全文获取类型
收费全文 | 7532篇 |
免费 | 1185篇 |
国内免费 | 1454篇 |
专业分类
测绘学 | 305篇 |
大气科学 | 1498篇 |
地球物理 | 1230篇 |
地质学 | 3096篇 |
海洋学 | 975篇 |
天文学 | 22篇 |
综合类 | 508篇 |
自然地理 | 2537篇 |
出版年
2024年 | 19篇 |
2023年 | 84篇 |
2022年 | 245篇 |
2021年 | 310篇 |
2020年 | 307篇 |
2019年 | 338篇 |
2018年 | 279篇 |
2017年 | 289篇 |
2016年 | 324篇 |
2015年 | 338篇 |
2014年 | 451篇 |
2013年 | 535篇 |
2012年 | 407篇 |
2011年 | 510篇 |
2010年 | 357篇 |
2009年 | 415篇 |
2008年 | 448篇 |
2007年 | 499篇 |
2006年 | 549篇 |
2005年 | 433篇 |
2004年 | 410篇 |
2003年 | 356篇 |
2002年 | 335篇 |
2001年 | 252篇 |
2000年 | 244篇 |
1999年 | 246篇 |
1998年 | 227篇 |
1997年 | 205篇 |
1996年 | 143篇 |
1995年 | 112篇 |
1994年 | 98篇 |
1993年 | 85篇 |
1992年 | 73篇 |
1991年 | 45篇 |
1990年 | 47篇 |
1989年 | 26篇 |
1988年 | 28篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
You Yuming Hou Min Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing Assistant Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1992,(3)
- The data of landsat TM of multi-temporal for Lingdingyang Estuary, Pearl River in China is firstly used with suspended sediment concentration of field measurement to establish a correlative model equation. After the ratio processing of TM data and atmospheric correction, the images of suspended sediment concentration of different temporals are exported from the image processing systems AREIS II and III. These images express the characteristics of suspended sediment distribution, the mode of sediment transport and the extent of dispersion under the actions of tidal current and wind condition of different seasons. 相似文献
32.
33.
本文概述了建国以来我国海洋地质调查与研究工作取得的丰硕成果。论述区域地质调查在海洋地质基础工作和未来海洋开发中的战略意义,介绍了国内外海洋区域地质调查的现状,对开展这项调查的可行性条件,以及进行1/100万海洋区域地质调查的项目内容、技术方法和提交成果等提出了设想和建议。 相似文献
34.
35.
Data collected in three Californian estuaries indicate that hypersaline conditions exist during the dry summers typical of a Mediterranean climate. The generalised seasonal and longitudinal hydrographic structures are described and explained. It is argued that this seasonal hypersalinity is common and that it represents a major class of estuaries. The observed accumulation of salt indicates surprisingly long residence times in small basins which have free exchange with the ocean. This semi-isolation of the inner basin leads to a large build-up or severe depletion of nutrients, pollutants and plankton in these systems. Of concern are the trends to increase pollutant loading in the same systems that are experiencing an increase in residence times owing to freshwater extraction in the watershed. 相似文献
36.
南沙海域万安盆地地质构造特征 总被引:1,自引:3,他引:1
利用在南沙海域万安盆地所采集的地震、重磁资料及钻井、地质资料,对该盆地的地震反向特征,沉积特征、区域地质、构造特征及构造发展史进行了的简要的论述,本文以该区Tg深度资料为基础,并利用CCOP年刊发表的新生代基底深度资料,初步圈定了万安盆地的边界,并对盆地二级构造单元进行了划分,将盆地划分为5坳3隆、坳隆相间的构造格局。 相似文献
37.
38.
A vertical two-dimensional turbulence numerical model for the interaction of waves and currents is developed in the paper based on the nonlinear two-equation k-ε model with the VOF method.The one-dimensional equivalent advection velocity and equivalent mixing coefficient are defined and the solving process is introduced:The pollutant concentration field,generated by an instant source in waves and currents,is calculated with the model,and then the equivalent advection velocity and equivalent mixing coefficient are obtained by calculating the time derivative of the mean and variance of pollutant concentration probability distribution.The effects of wave period and wave height on the equivalent mixing coefficient for waves and wave-currents are also investigated. 相似文献
39.
北极海冰变化特征分析 总被引:3,自引:0,他引:3
本文利用NASA的海冰密集度资料(时间为1978年10月~2002年9月,分辨率为1.0×0.25),计算并分析了1978~2002年的北极海冰面积、范围的时间变化趋势以及变化的空间分布。 相似文献
40.
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