全文获取类型
收费全文 | 30778篇 |
免费 | 5209篇 |
国内免费 | 7528篇 |
专业分类
测绘学 | 6552篇 |
大气科学 | 5257篇 |
地球物理 | 7150篇 |
地质学 | 13524篇 |
海洋学 | 4114篇 |
天文学 | 597篇 |
综合类 | 2375篇 |
自然地理 | 3946篇 |
出版年
2024年 | 194篇 |
2023年 | 517篇 |
2022年 | 1133篇 |
2021年 | 1360篇 |
2020年 | 1519篇 |
2019年 | 1640篇 |
2018年 | 1368篇 |
2017年 | 1648篇 |
2016年 | 1773篇 |
2015年 | 1851篇 |
2014年 | 2042篇 |
2013年 | 2260篇 |
2012年 | 2098篇 |
2011年 | 2097篇 |
2010年 | 1716篇 |
2009年 | 1923篇 |
2008年 | 1979篇 |
2007年 | 1979篇 |
2006年 | 1897篇 |
2005年 | 1706篇 |
2004年 | 1494篇 |
2003年 | 1233篇 |
2002年 | 1213篇 |
2001年 | 961篇 |
2000年 | 890篇 |
1999年 | 792篇 |
1998年 | 729篇 |
1997年 | 628篇 |
1996年 | 523篇 |
1995年 | 491篇 |
1994年 | 450篇 |
1993年 | 383篇 |
1992年 | 244篇 |
1991年 | 205篇 |
1990年 | 145篇 |
1989年 | 98篇 |
1988年 | 109篇 |
1987年 | 65篇 |
1986年 | 32篇 |
1985年 | 31篇 |
1984年 | 18篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1954年 | 13篇 |
1900年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Tidal mixing plays an important role in the modification of dense water masses around the Antarctic continent. In addition to the vertical (diapycnal) mixing in the near-bottom layers, lateral mixing can also be of relevance in some areas. A numerical tide simulation shows that lateral tidal mixing is not uniformly distributed along the shelf break. In particular, strong mixing occurs all along the Ross Sea and Southern Weddell Sea shelf breaks, while other regions (e.g., the western Weddell Sea) are relatively quiet. The latter regions correspond surprisingly well to areas where indications for cross-shelf exchange of dense water masses have been found. The results suggest that lateral tidal mixing may account for the relatively small contribution of Ross Sea dense water masses to Antarctic Bottom Water. 相似文献
62.
63.
Most geostatistical studies consider multiple-related variables. These relationships often show complex features such as nonlinearity, heteroscedasticity, and mineralogical or other constraints. These features are not handled by the well-established Gaussian simulation techniques. Earth science variables are rarely Gaussian. Transformation or anamorphosis techniques make each variable univariate Gaussian, but do not enforce bivariate or higher order Gaussianity. The stepwise conditional transformation technique is proposed to transform multiple variables to be univariate Gaussian and multivariate Gaussian with no cross correlation. This makes it remarkably easy to simulate multiple variables with arbitrarily complex relationships: (1) transform the multiple variables, (2) perform independent Gaussian simulation on the transformed variables, and (3) back transform to the original variables. The back transformation enforces reproduction of the original complex features. The methodology and underlying assumptions are explained. Several petroleum and mining examples are used to show features of the transformation and implementation details. 相似文献
64.
Xavier Emery 《Mathematical Geology》2003,35(6):699-718
This paper presents a methodology for assessing local probability distributions by disjunctive kriging when the available data set contains some imprecise measurements, like noisy or soft information or interval constraints. The basic idea consists in replacing the set of imprecise data by a set of pseudohard data simulated from their posterior distribution; an iterative algorithm based on the Gibbs sampler is proposed to achieve such a simulation step. The whole procedure is repeated many times and the final result is the average of the disjunctive kriging estimates computed from each simulated data set. Being data-independent, the kriging weights need to be calculated only once, which enables fast computing. The simulation procedure requires encoding each datum as a pre-posterior distribution and assuming a Markov property to allow the updating of pre-posterior distributions into posterior ones. Although it suffers some imperfections, disjunctive kriging turns out to be a much more flexible approach than conditional expectation, because of the vast class of models that allows its computation, namely isofactorial models. 相似文献
65.
66.
JiangWenping XiDaping 《中国地质大学学报(英文版)》2003,14(4):374-380
With the development of computer graphics, the three-dimensional (3D) visualization brings new technological revolution to the traditional cartography. Therefore, the topographic 3D-map emerges to adapt to this technological revolution, and the applications of topographic 3D-map are spread rapidly to other relevant fields due to its incomparable advantage. The researches on digital map and the construction of map database offer strong technical support and abundant data source for this new technology, so the research and development of topographic 3D-map will receive greater concern. The basic data of the topographic 3D-map are rooted mainly in digital map and its basic model is derived from digital elevation model (DEM) and 3D-models of other DEM-based geographic features. In view of the potential enormous data and the complexity of geographic features, the dynamic representation of geographic information becomes the focus of the research of topographic 3D-map and also the prerequisite condition of 3D query and analysis. In addition to the equipment of hardware that are restraining, to a certain extent, the 3D representation, the data organization structure of geographic information will be the core problem of research on 3D-map. Level of detail (LOD). space partitioning, dynamic object loading (DOL) and object culling are core technologies of the dynamic 3D representation. The objectselection, attribute-query and model-editing are important functions and interaction tools for users with 3D-maps provided by topographic 3D-map system, all of which are based on the data structure of the 3D-model. This paper discusses the basic theories, concepts and cardinal principles of topographic 3I)-map,expounds the basic way to organize the scene hierarchy of topographic 3D-map based on the node mechanism and studies the dynamic representation technologies of topographic 3D-map based on LOD, space partitioning, DOL and object culling. Moreover. such interactive operation functions are explored, in this paper, as spatial query, scene editing and management of topographic 3D-map. Finally, this paper describes briefly the applications of topographic 3D-map in its related fields. 相似文献
67.
68.
We compare flux and concentration footprint estimates of athree-dimensional Lagrangian stochastic dispersion modelapplying backward trajectories with the results of ananalytical footprint model by Kormann and Meixner.The comparison is performed for varying stability regimesof the surface layer as well as for different measurementheights. In general, excellent correspondence is found. 相似文献
69.
介绍试用1:33000比例尺航测资料,在JX-3解析测图仪上高倍放大航测1:1000比例尺地形图的成图方案和应采取的技术措施,运用 解析法模型绝对定向的原理,在全野布点时采用两种方案对照比较,进行理论和试验精度的分析,并给出试验结果。 相似文献
70.
科学计算可视化技术的研究与应用 总被引:7,自引:3,他引:7
本文介绍了科学计算可视化技术的发展和应用情况,论述了这一新技术的特点及其在油气藏描述,工程设计CAD等学科的应用和发展趋势。阐述了目前国际国内计算机图形学领域具体的研究方向和方法及图形软件、图形硬件的发展概况。 相似文献