全文获取类型
收费全文 | 2941篇 |
免费 | 195篇 |
国内免费 | 219篇 |
专业分类
测绘学 | 1569篇 |
大气科学 | 41篇 |
地球物理 | 198篇 |
地质学 | 791篇 |
海洋学 | 177篇 |
天文学 | 38篇 |
综合类 | 216篇 |
自然地理 | 325篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 82篇 |
2021年 | 83篇 |
2020年 | 129篇 |
2019年 | 92篇 |
2018年 | 62篇 |
2017年 | 211篇 |
2016年 | 174篇 |
2015年 | 142篇 |
2014年 | 163篇 |
2013年 | 275篇 |
2012年 | 202篇 |
2011年 | 184篇 |
2010年 | 126篇 |
2009年 | 101篇 |
2008年 | 182篇 |
2007年 | 164篇 |
2006年 | 141篇 |
2005年 | 122篇 |
2004年 | 94篇 |
2003年 | 89篇 |
2002年 | 76篇 |
2001年 | 68篇 |
2000年 | 48篇 |
1999年 | 41篇 |
1998年 | 54篇 |
1997年 | 37篇 |
1996年 | 26篇 |
1995年 | 25篇 |
1994年 | 16篇 |
1993年 | 18篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 18篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 3篇 |
排序方式: 共有3355条查询结果,搜索用时 31 毫秒
961.
MAPGIS和AutoCAD 2004是地质勘查行业使用较为广泛的数字制图软件,二者各有优劣。本文介绍了一种在MAPGIS制作完成的地形地质图上,利用AutoCAD 2004制图程序完成图切剖面图编制的方法。 相似文献
962.
区域化探数据包含丰富的地质信息,可用于浅覆盖区区域地质填图。笔者系统研究了浅覆盖区水系沉积物化学成分与基岩化学成分的关系,利用水系沉积物氧化物成分,以区域岩石化学成分为约束,提出了基岩化学成分推断方法;根据水系沉积物与其矿物化学成分间质量平衡关系,提出了基岩矿物组成推断方法。在此基础上提出了地球化学推断地质图的编制方法,并在典型森林-沼泽浅覆盖区进行了试验,地质调查和钻探工程验证了该方法的有效性。充分利用区域化探资料,提取地质填图信息,是提高浅覆盖区地质填图质量的有效途径。 相似文献
963.
We present here a methodology implemented within a geographical information system (GIS) for hazard mapping of small volume
pyroclastic density currents (PDCs). This technique is implemented as a set of macros written in Visual Basic for Applications
(VBA) that run within GIS-software (i.e. ArcGIS). Based on the energy line concept, we calibrated an equation that relates
the volume (V) and the mobility (ΔH/L) of single PDCs using data from Soufrière Hills volcano (Montserrat) and Arenal volcano (Costa Rica). Maximum potential run-outs
can be predicted with an associated uncertainty of about 30%. Also based on the energy line concept and with data from Soufrière
Hills volcano and Mt. St. Helens (USA), we were able to calibrate an equation that predicts the flow velocity as a function
of the vertical distance between the energy line and the ground surface (Δh). Velocities derived in this way have an associated uncertainty of 3 m s−1. We wrote code to implement these equations and allow the automatic mapping of run-out and velocity with the inputs being
(i) the height and location of the vent (ii) the flow volume and (iii) a digital elevation model (DEM) of the volcano. Dynamic
pressure can also be estimated and mapped by incorporating the density of the pyroclastic density current (PDC). This computer
application allows the incorporation of uncertainties in the location of the vent and of statistical uncertainties expressed
by the 95% confidence limits of the regression model. We were able to verify predictions by the proposed methodology with
data from Unzen volcano (Japan) and Mayon volcano (The Philippines). The consistencies observed highlight the applicability
of this approach for hazard mitigation and real-time emergency management. 相似文献
964.
地理信息科学的迅速发展为矿集区预测提供了新的理论依据,使地理信息理论、相应的技术方法组合及应用的整体研究成为可能。在大量理论和实验研究的基础上提出了基于地理信息元组的分类预测理论体系,该理论体系由六个概念、一个空间信息本质、两个空间信息特性以及六个空间信息相关方法和约定的构成。并在该理论体系基础上结合空间数据分析方法和探索式空间数据分析方法,建立了基于地理信息元组的分类预测模型。应用该模型在中亚区域实现了Au矿集区预测目标。为中亚成矿域中其它区域(如新疆)的矿集区预测研究奠定了理论与方法论基础。 相似文献
965.
Pinnaduwa H. S. W. Kulatilake Jinyong Park Pirahas Balasingam Sean A. Mckenna 《Geotechnical and Geological Engineering》2007,25(1):79-102
A 1 km square regular grid system created on the Universal Transverse Mercator zone 54 projected coordinate system is used
to work with volcanism related data for Sengan region. The following geologic variables were determined as the most important
for identifying volcanism: geothermal gradient, groundwater temperature, heat discharge, groundwater pH value, presence of
volcanic rocks and presence of hydrothermal alteration. Data available for each of these important geologic variables were
used to perform directional variogram modeling and kriging to estimate geologic variable vectors at each of the 23949 centers
of the chosen 1 km cell grid system. Cluster analysis was performed on the 23949 complete variable vectors to classify each
center of 1 km cell into one of five different statistically homogeneous groups with respect to potential volcanism spanning
from lowest possible volcanism to highest possible volcanism with increasing group number. A discriminant analysis incorporating
Bayes’ theorem was performed to construct maps showing the probability of group membership for each of the volcanism groups.
The said maps showed good comparisons with the recorded locations of volcanism within the Sengan region. No volcanic data
were found to exist in the group 1 region. The high probability areas within group 1 have the chance of being the no volcanism
region. Entropy of classification is calculated to assess the uncertainty of the allocation process of each 1 km cell center
location based on the calculated probabilities. The recorded volcanism data are also plotted on the entropy map to examine
the uncertainty level of the estimations at the locations where volcanism exists. The volcanic data cell locations that are
in the high volcanism regions (groups 4 and 5) showed relatively low mapping estimation uncertainty. On the other hand, the
volcanic data cell locations that are in the low volcanism region (group 2) showed relatively high mapping estimation uncertainty.
The volcanic data cell locations that are in the medium volcanism region (group 3) showed relatively moderate mapping estimation
uncertainty. Areas of high uncertainty provide locations where additional site characterization resources can be spent most
effectively. The new data collected can be added to the existing database to perform future regionalized mapping and reduce
the uncertainty level of the existing estimations. 相似文献
966.
Landslide susceptibility mapping using GIS and digital photogrammetric techniques: a case study from Ardesen (NE-Turkey) 总被引:3,自引:3,他引:3
Ardesen is a settlement area which has been significantly damaged by frequent landslides which are caused by severe rainfalls
and result in many casualties. In this study a landslide susceptibility map of Ardesen was prepared using the Analytical Hierarchy
Process (AHP) with the help of Geographical Information Systems (GIS) and Digital Photogrametry Techniques (DPT). A landslide
inventory, lithology–weathering, slope, aspect, land cover, shear strength, distance to the river, stream density and distance
to the road thematics data layers were used to create the map. These layer maps are produced using field, laboratory and office
studies, and by the use of GIS and DPT. The landslide inventory map is also required to determine the relationship between
these maps and landslides using DPT. In the study field in the Hemsindere Formation there are units that have different weathering
classes, and this significantly affects the shear strength of the soil. In this study, shear strength values are calculated
in great detail with field and laboratory studies and an additional layer is evaluated with the help of the stability studies
used to produce the landslide susceptibility map. Finally, an overlay analysis is carried out by evaluating the layers obtained
according to their weight, and the landslide susceptibility map is produced. The study area was classified into five classes
of relative landslide susceptibility, namely, very low, low, moderate, high, and very high. Based on this analysis, the area
and percentage distribution of landslide susceptibility degrees were calculated and it was found that 28% of the region is
under the threat of landslides. Furthermore, the landslide susceptibility map and the landslide inventory map were compared
to determine whether the models produced are compatible with the real situation resulting in compatibility rate of 84%. The
total numbers of dwellings in the study area were determined one by one using aerial photos and it was found that 30% of the
houses, with a total occupancy of approximately 2,300 people, have a high or very high risk of being affected by landslides. 相似文献
967.
A. Verruijt 《Engineering Geology》2007,91(1):78-83
This paper presents an analytical solution of a groundwater flow problem involving a local drainage system embedded in a regional system. As an extension of the usual complex variable methods it combines the planes of the hodograph and the Zhukovsky function. This combination of basic parameters appears to be useful for problems involving a free water table and horizontal potential lines. The solution may elucidate the relation between local and regional water divides. 相似文献
968.
969.
970.
信息技术的飞速发展,为信息资源的建设和服务工作提供了新的模式和新的手段。本文简要介绍了测绘科技信息服务系统的框架结构、数据流程、主要技术创新点等研究成果,试图为测绘科技信息共享平台的建设,提供一种网上信息作业和服务支持系统。 相似文献