全文获取类型
收费全文 | 59631篇 |
免费 | 10317篇 |
国内免费 | 14999篇 |
专业分类
测绘学 | 5165篇 |
大气科学 | 7500篇 |
地球物理 | 11692篇 |
地质学 | 37550篇 |
海洋学 | 6792篇 |
天文学 | 2730篇 |
综合类 | 4175篇 |
自然地理 | 9343篇 |
出版年
2024年 | 338篇 |
2023年 | 967篇 |
2022年 | 1872篇 |
2021年 | 2139篇 |
2020年 | 2252篇 |
2019年 | 2597篇 |
2018年 | 2091篇 |
2017年 | 2407篇 |
2016年 | 2629篇 |
2015年 | 2749篇 |
2014年 | 3384篇 |
2013年 | 3304篇 |
2012年 | 3697篇 |
2011年 | 3842篇 |
2010年 | 3308篇 |
2009年 | 3836篇 |
2008年 | 3823篇 |
2007年 | 4169篇 |
2006年 | 4091篇 |
2005年 | 3525篇 |
2004年 | 3291篇 |
2003年 | 3107篇 |
2002年 | 2787篇 |
2001年 | 2478篇 |
2000年 | 2243篇 |
1999年 | 2027篇 |
1998年 | 1809篇 |
1997年 | 1629篇 |
1996年 | 1490篇 |
1995年 | 1258篇 |
1994年 | 1271篇 |
1993年 | 1050篇 |
1992年 | 873篇 |
1991年 | 617篇 |
1990年 | 510篇 |
1989年 | 422篇 |
1988年 | 324篇 |
1987年 | 219篇 |
1986年 | 130篇 |
1985年 | 95篇 |
1984年 | 42篇 |
1983年 | 34篇 |
1982年 | 34篇 |
1981年 | 25篇 |
1980年 | 26篇 |
1979年 | 33篇 |
1978年 | 36篇 |
1977年 | 31篇 |
1975年 | 4篇 |
1954年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Quantifying Storm Tide Risk in Cairns 总被引:6,自引:5,他引:6
Ken Granger 《Natural Hazards》2003,30(2):165-185
The United Nations International Decade for Natural Disaster Reduction (IDNDR)gave rise to an increasing level of attention to the risks posed by a range of naturalhazards and the development of strategies by which to reduce those risks. It waswidely recognised that in order to evaluate risk treatment strategies it was necessaryto `measure' the level of risk that already existed and the level of risk that would beencountered with the treatment strategy(s) in place.This paper outlines the methodology developed under the AGSO (now GeoscienceAustralia) Cities Project to quantify the risk associated with storm tide inundation. It includes the methodology for `measuring' the level of community exposure to storm tide hazards and the methodology for `measuring' community vulnerability. The Far North Queensland city of Cairns is used as the case study to demonstrate the application of these methods. 相似文献
92.
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
93.
The anisotropy of magnetic susceptibility (AMS) of single crystals of biotite, muscovite and chlorite has been measured in order to provide accurate values of the magnetic anisotropy properties for these common rock-forming minerals. The low-field AMS and the high-field paramagnetic susceptibility are defined. For the high-field values, it is necessary to combine the paramagnetic deviatoric tensor obtained from the high-field torque magnetometer with the paramagnetic bulk susceptibility measured from magnetization curves of the crystals. This leads to the full paramagnetic susceptibility ellipsoid due to the anisotropic distribution of iron cations in the silicate lattice. The ellipsoid of paramagnetic susceptibility, which was obtained for the three phyllosilicates, is highly oblate in shape and the minimum susceptibility direction is subparallel to the crystallographic c-axes. The anisotropy of the susceptibility within the basal plane of the biotite has been evaluated and found to be isotropic within the accuracy of the instrumental measurements. The degree of anisotropy of biotite and chlorite is compatible with previously reported values while for muscovite the smaller than previously published values. The shape of the chlorite AMS ellipsoid for all the samples is near-perfect oblate in contrast with a wide distribution of oblate and prolate values reported in earlier studies. Reliable values are important for deriving models of the magnetic anisotropy where it reflects mineral fabrics and deformation of rocks. 相似文献
94.
95.
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
96.
97.
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
98.
高斯平面坐标换算到测区平均高程面上的方法 总被引:5,自引:2,他引:5
依据高斯投影原理,提出了一种在高斯平面与任决高程平面间进行坐标转换的方法,并设计了相应的计算软件。 相似文献
99.
变形体的稳定性及其定量分析方法初探 总被引:3,自引:0,他引:3
变形体的稳定性是变形体性质的重要内容,它是工程实际中极为关注的问题,但从变形监测的角度上来分析变形的稳定性目前在国内外还未见任何实质性的报导。本文讨论了从变形监测角度上分析变形体稳定性的一般方法,进行变形稳定性的分类,初步研究了变形体稳定性的定量分析方法,定义了一系列量化指标,如稳定度、因素的影响域与因素的稳定域等。这些有利于把稳定性分析推向应用和深入,从而提高变形监测在变形体定性分析中的地位,增 相似文献
100.