全文获取类型
收费全文 | 11540篇 |
免费 | 1472篇 |
国内免费 | 1332篇 |
专业分类
测绘学 | 2703篇 |
大气科学 | 1197篇 |
地球物理 | 3064篇 |
地质学 | 2519篇 |
海洋学 | 1142篇 |
天文学 | 597篇 |
综合类 | 1093篇 |
自然地理 | 2029篇 |
出版年
2024年 | 31篇 |
2023年 | 130篇 |
2022年 | 418篇 |
2021年 | 497篇 |
2020年 | 492篇 |
2019年 | 591篇 |
2018年 | 330篇 |
2017年 | 452篇 |
2016年 | 451篇 |
2015年 | 463篇 |
2014年 | 556篇 |
2013年 | 665篇 |
2012年 | 673篇 |
2011年 | 676篇 |
2010年 | 523篇 |
2009年 | 658篇 |
2008年 | 643篇 |
2007年 | 794篇 |
2006年 | 713篇 |
2005年 | 572篇 |
2004年 | 554篇 |
2003年 | 512篇 |
2002年 | 408篇 |
2001年 | 402篇 |
2000年 | 307篇 |
1999年 | 286篇 |
1998年 | 325篇 |
1997年 | 194篇 |
1996年 | 171篇 |
1995年 | 177篇 |
1994年 | 165篇 |
1993年 | 129篇 |
1992年 | 82篇 |
1991年 | 57篇 |
1990年 | 51篇 |
1989年 | 63篇 |
1988年 | 42篇 |
1987年 | 27篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
131.
132.
133.
通过分析虚拟参考站技术和主辅站技术的不足,提出了一种新的网络RTK技术——增强参考站技术(ARS).分析了这种技术的原理并阐述了该技术中改正数的生成方法,同时,提出了一种基于RTCM编码的适合于该技术的改正数编码格式.在此基础上,分析了该技术的RTK定位精度、数据传输效率和系统可靠性,从理论上说明了增强参考站的技术优势.最后,以四川综合GPS服务网(SIGN)的子网数据对该技术进行了验证,结果表明,该技术具有高定位精度、高数据传输效率的特点,是一种理想的网络RTK技术. 相似文献
134.
135.
张亮 《测绘与空间地理信息》2008,31(2):145-148
抗差估计具有较好的抗拒异常观测值及粗差的能力,而最小二乘配置又能较好地处理系统误差,本文结合两者的优点,利用抗差最小二乘配置对数字化地图进行几何纠正,其中对协方差函数采用抗差拟合,得到了较好的结果。实验证明在GIS数据处理的扫描数字化地图几何纠正中,抗差最小二乘配置在抗拒异常值和处理系统误差方面优于单纯的最小二乘估计和单纯的最小二乘配置方法。 相似文献
136.
137.
Dynamic data integration for structural modeling: model screening approach using a distance-based model parameterization 总被引:2,自引:0,他引:2
This paper proposes a novel history-matching method where reservoir structure is inverted from dynamic fluid flow response.
The proposed workflow consists of searching for models that match production history from a large set of prior structural
model realizations. This prior set represents the reservoir structural uncertainty because of interpretation uncertainty on
seismic sections. To make such a search effective, we introduce a parameter space defined with a “similarity distance” for
accommodating this large set of realizations. The inverse solutions are found using a stochastic search method. Realistic
reservoir examples are presented to prove the applicability of the proposed method. 相似文献
138.
Artificial neural network and liquefaction susceptibility assessment: a case study using the 2001 Bhuj earthquake data,Gujarat, India 总被引:2,自引:0,他引:2
D. Ramakrishnan T. N. Singh N. Purwar K. S. Barde Akshay. Gulati S. Gupta 《Computational Geosciences》2008,12(4):491-501
This study pertains to prediction of liquefaction susceptibility of unconsolidated sediments using artificial neural network
(ANN) as a prediction model. The backpropagation neural network was trained, tested, and validated with 23 datasets comprising
parameters such as cyclic resistance ratio (CRR), cyclic stress ratio (CSR), liquefaction severity index (LSI), and liquefaction
sensitivity index (LSeI). The network was also trained to predict the CRR values from LSI, LSeI, and CSR values. The predicted
results were comparable with the field data on CRR and liquefaction severity. Thus, this study indicates the potentiality
of the ANN technique in mapping the liquefaction susceptibility of the area. 相似文献
139.
Heinz Schneider Marco Schwab Fritz Schlunegger 《International Journal of Earth Sciences》2008,97(1):179-192
This paper uses the results of landscape evolution models and morphometric data from the Andes of northern Peru and the eastern
Swiss Alps to illustrate how the ratio between sediment transport on hillslopes and in channels influences landscape and channel
network morphologies and dynamics. The headwaters of fluvial- and debris-flow-dominated systems (channelized processes) are
characterized by rough, high-relief, highly incised surfaces which contain a dense and hence a closely spaced channel network.
Also, these systems tend to respond rapidly to modifications in external forcing (e.g., rock uplift and/or precipitation).
This is the case because the high channel density results in a high bulk diffusivity. In contrast, headwaters where landsliding
is an important sediment source are characterized by a low channel density and by rather straight and unstable channels. In
addition, the topographies are generally smooth. The low channel density then results in a relatively low bulk diffusivity.
As a consequence, response times are greater in headwaters of landslide-dominated systems than in highly dissected drainages.
The Peruvian and Swiss case studies show how regional differences in climate and the litho-tectonic architecture potentially
exert contrasting controls on the relative importance of channelized versus hillslope processes and thus on the overall geomorphometry.
Specifically, the Peruvian example illustrates to what extent the storminess of climate has influenced production and transport
of sediment on hillslopes and in channels, and how these differences are seen in the morphometry of the landscape. The Swiss
example shows how the bedding orientation of the bedrock drives channelized and hillslope processes to contrasting extents,
and how these differences are mirrored in the landscape.
An erratum to this article can be found at 相似文献
140.