全文获取类型
收费全文 | 3004篇 |
免费 | 554篇 |
国内免费 | 924篇 |
专业分类
测绘学 | 281篇 |
大气科学 | 1133篇 |
地球物理 | 877篇 |
地质学 | 711篇 |
海洋学 | 769篇 |
天文学 | 64篇 |
综合类 | 208篇 |
自然地理 | 439篇 |
出版年
2024年 | 22篇 |
2023年 | 55篇 |
2022年 | 109篇 |
2021年 | 153篇 |
2020年 | 140篇 |
2019年 | 147篇 |
2018年 | 133篇 |
2017年 | 156篇 |
2016年 | 164篇 |
2015年 | 171篇 |
2014年 | 229篇 |
2013年 | 205篇 |
2012年 | 218篇 |
2011年 | 217篇 |
2010年 | 155篇 |
2009年 | 213篇 |
2008年 | 225篇 |
2007年 | 249篇 |
2006年 | 198篇 |
2005年 | 160篇 |
2004年 | 157篇 |
2003年 | 147篇 |
2002年 | 125篇 |
2001年 | 107篇 |
2000年 | 90篇 |
1999年 | 75篇 |
1998年 | 83篇 |
1997年 | 71篇 |
1996年 | 70篇 |
1995年 | 48篇 |
1994年 | 38篇 |
1993年 | 31篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 23篇 |
1989年 | 11篇 |
1988年 | 22篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有4482条查询结果,搜索用时 15 毫秒
21.
Evaporation (E) rate and precipitation (P) rate are two significant meteorological elements required in the ocean baroclinic
modeling as external forcings. However, there are some uncertainties in the currently used E/P rates datasets, especially
in terms of the data quality. In this study, we collected E/P rates data from ERA-40, NCEP/NCAR Reanalysis, HOAPS for the
Bohai Sea and nine routine stations around Laizhou Bay, and made comparisons among them. It was found that the differences
in E/P rates between land and sea are remarkable, which was due to the difference in underlying surfaces. Therefore, the traditional
way of using E/P rates acquired on land directly at sea is not correct. Since no final conclusion has been reached concerning
the net water transport between the Bohai Sea and the Yellow Sea, it is unfeasible to judge the adequacy of the four kinds
of data by using the water budget equation. However, the E/P rates at ERA-40 sea points were considered to be the optimal
in terms of temporal/spatial coverage and resolution for the hindcast of salinity variation in the Bohai Sea. Besides, using
the 3-D hydrodynamic model HAMSOM (HAMburg Shelf Ocean Model), we performed numerical experiments with different E/P datasets
and found that the E/P rates at sea points from ERA-40 dataset are better than those from NCEP/NCAR Reanalysis dataset. If
NCEP/NCAR Reanalysis E/P rates are to be used, they need to be adjusted and tested prior to simulation so that more close-to-reality
salinity values can be reproduced. 相似文献
22.
Cindy Lee Robert A. Armstrong J. Kirk Cochran Anja Engel Scott W. Fowler Madeleine Goutx Pere Masqu Juan Carlos Miquel Michael Peterson Christian Tamburini Stuart Wakeham 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1363-1368
The MedFlux project was devised to determine and model relationships between organic matter and mineral ballasts of sinking particulate matter in the ocean. Specifically we investigated the ballast ratio hypothesis, tested various commonly used sampling and modeling techniques, and developed new technologies that would allow better characterization of particle biogeochemistry. Here we describe the rationale for the project, the biogeochemical provenance of the DYFAMED site, the international support structure, and highlights from the papers published here. Additional MedFlux papers can be accessed at the MedFlux web site (http://msrc.sunysb.edu/MedFlux/). 相似文献
23.
24.
25.
以西北半干旱地区的内蒙古农牧交错地带锡林郭勒盟为研究区,以不同退化程度的草地为研究对象,通过叶面积指数计算各像元的动力传输粗糙度长度,以改进显热通量算法;并结合植被/土壤组分温度分别计算基于亚像元的植被/土壤的显热通量。由敏感性分析和模型验证表明,改进的显热通量算法能够提高区域尺度的能量平衡计算精度。 相似文献
26.
A. N. V. Satyanarayana U. C. Mohanty N. V. Sam Swati Basu V. N. Lykossov 《Journal of Earth System Science》2000,109(2):293-303
An attempt has been made to study the marine boundary layer characteristics over Bay of Bengal using BOBMEX (Bay of Bengal
and Monsoon Experiment) pilot experiment data sets, which was conducted between 23rd October and 12th November 1998 on board
ORV Sagar Kanya. A one-dimensional multilevel atmospheric boundary layer with TKE-ε closure scheme is employed to study the
marine boundary layer characteristics. In this study two synoptic situations are chosen: one represents an active convection
case and the other a suppressed convection. In the present article the marine boundary layer characteristics such as temporal
evolution of turbulent kinetic energy, height of the boundary layer and the airsea exchange processes such as sensible and
latent heat fluxes, drag coefficient for momentum are simulated during both active and suppressed convection. Marine boundary
layer height is estimated from the vertical profiles of potential temperature using the stability criterion. The model simulations
are compared with the available observations. 相似文献
27.
Valentin N. Mitkin 《Geostandards and Geoanalytical Research》2000,24(2):157-170
A novel method is described for the rapid dissolution of various geological, geochemical and related reference samples for the determination of Au and the platinum-group elements. The decomposition procedure is based on reaction with the fluoroxidants, liquid bromine trifluoride or molten potassium tetrafluorobromate. Results by this novel procedure are compared with data obtained by traditional methods of sample decomposition, including fire assay, autoclave techniques and an aqua regia leach. The oxidative fluorination procedure with the subsequent conversion of fluorocomplexes into the chloride form was found to be an effective and rapid method for the quantification of all the precious metals in a range of sample types. 相似文献
28.
由于地质过程的复杂性及成矿过程的多期次叠加性,原始重磁异常往往是多种地质因素的混合信息,既包含区域背景异常信息,也包含与矿床(体)、矿化蚀变带以及隐伏岩体等与找矿密切相关的地质要素所引起的局部重磁异常.如何从复杂的叠加重磁异常中分离出具有找矿意义的局部异常,是当前矿产勘查和资源潜力评价工作中面临的难题之一.采用经验模态分解(EMD)方法来分解重磁异常,为提高分解的稳健性提出了用双调和样条插值(BSI)进行包罗面插值的新方法,并以云南个旧地区重磁数据为例,对其进行非线性多尺度分解,实现对区域异常与局部重磁异常的分离,揭示了深层次找矿信息并拓宽了经验模态分解方法的应用领域. 相似文献
29.
在多种类覆盖区,由于植被、河道、阴影、第四系等干扰因素影响,难于客观有效提取与成矿有关的遥感蚀变信息。应用混合像元分解的方法技术可以区分出混合像元中各类干扰信息的反射率值及其所占丰度值,从混合像元光谱中减去各干扰因素的反射率值及其所占份额,可以获取土壤或岩石的反射率值及其所占丰度值,将土壤或岩石反射率值除以其所占的份额... 相似文献
30.
2007年9月在长江河口3条控制断面的全潮观测结果表明,长江口南支均以落潮流和落潮输沙占优,而北支大、小潮期间的水沙输运特征迥异; 其特征与长江径流、河口地形地貌特征密切相关。小潮期间,长江口北支以落潮流占优; 大潮期间,则以涨潮流占优,且悬沙输运率比小潮期间增大一个数量级。分析结果进一步表明,从1958年至今,长江口北支的分流比呈下降的趋势,已由11.8% 降至目前的1.9%; 长江口北支也由早期的悬沙输入(与径流方向相反)通道变为输出通道,目前其分沙比仍达6.4% ~7.9% 左右。总体上,分流分沙比呈显著减小趋势,这是长江口北支萎缩的重要特征之一。此外,北支分沙比显著大于分流比,将可能造成北支的进一步淤积。 相似文献