全文获取类型
收费全文 | 4687篇 |
免费 | 884篇 |
国内免费 | 1207篇 |
专业分类
测绘学 | 708篇 |
大气科学 | 805篇 |
地球物理 | 1013篇 |
地质学 | 2321篇 |
海洋学 | 847篇 |
天文学 | 255篇 |
综合类 | 354篇 |
自然地理 | 475篇 |
出版年
2024年 | 23篇 |
2023年 | 76篇 |
2022年 | 181篇 |
2021年 | 204篇 |
2020年 | 211篇 |
2019年 | 264篇 |
2018年 | 198篇 |
2017年 | 206篇 |
2016年 | 233篇 |
2015年 | 249篇 |
2014年 | 322篇 |
2013年 | 349篇 |
2012年 | 292篇 |
2011年 | 317篇 |
2010年 | 232篇 |
2009年 | 319篇 |
2008年 | 362篇 |
2007年 | 331篇 |
2006年 | 354篇 |
2005年 | 292篇 |
2004年 | 260篇 |
2003年 | 198篇 |
2002年 | 174篇 |
2001年 | 142篇 |
2000年 | 150篇 |
1999年 | 123篇 |
1998年 | 114篇 |
1997年 | 97篇 |
1996年 | 82篇 |
1995年 | 78篇 |
1994年 | 77篇 |
1993年 | 55篇 |
1992年 | 58篇 |
1991年 | 31篇 |
1990年 | 34篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有6778条查询结果,搜索用时 609 毫秒
101.
102.
103.
基于Kiwi数据格式的地图显示研究 总被引:7,自引:1,他引:7
在分析Kiwi显示数据存储组织方法的基础上,研究了Kiwi显示数据在内存中的动态组织,改进了地图显示的二级缓存方法,提出了地图显示的双缓冲池策略。试验结果表明,本文研究的数据动态组织方法和地图显示策略提高了地图显示速度。 相似文献
104.
105.
Passive energy dissipation devices (EDDs), such as viscous dampers, viscoelastic dampers, etc., have been used to effectively reduce the dynamic response of civil infrastructures, such as buildings and bridges, subject to earthquakes and strong winds. The design of these passive energy dissipation devices (EDDs) involves the determination of the optimal locations and the corresponding capacities. In this paper, we present two optimal design methodologies for passive EDDs based on active control theories, including H∞ and H2 performances, respectively. The optimal design methodologies presented are capable of determining the optimal locations and the corresponding capacities of EDDs. Emphasis is placed on the application of linear matrix inequality (LMI) for the effective design of passive EDDs using the popular MATLAB toolboxes. One important advantage of the proposed approaches is that the computation of the structural response is not needed in the design process. The proposed optimal design methodologies have been applied to: (i) a 10‐storey building and a 24‐storey building both subject to earthquake excitations, and (ii) a 76‐storey wind‐excited benchmark building, to demonstrate the advantages of the proposed design methodologies over the conventional equal capacity design. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
106.
Authigenic albites in carbonate rocks typically grow in a high-grade diagenetic to low-grade metamorphic environment and often show Roc-Tourné-twinning sensu Füchtbauer. Based on an investigation of four Middle to South European occurrences, they show Mn2+- and Fe3+-activated cathodoluminescence (CL), as revealed by combined high resolution spectroscopy of cathodoluminescence emission (HRS-CL), electron paramagnetic resonance (EPR), and proton-induced X-ray emission (μPIXE). 相似文献
107.
通过月整点值数据文件和滑动值数据文件这两种数据处理形式。对九江台地倾斜资料进行调和分析计算。分析了M2潮汐因子与瑞昌ML4.9级地震的关系。认为存在震前短临异常或震后异常,并与趋势异常得到相互印证。 相似文献
108.
IntroductionTrial-and-error forward modeling of wide-angle seismic reflection/refraction traveltimes for 2-D velocity structure is extremely time-consuming, even for experienced data interpreters. For wide-angle seismic reflection/refraction experiments that consist of numerous shots along a single line, it is quite difficult through repeated trial-and-error forward modeling to construct a 2-D model that fits the data within acceptable limits (Cerveny, et al, 1977; ZHANG, et al, 200 . In ad… 相似文献
109.
Pierre Hudon In-Ho Jung Don R. Baker 《Physics of the Earth and Planetary Interiors》2002,130(3-4):159-174
Melting relations of β-quartz were experimentally determined at 1.0 GPa (1900±20 °C), 1.5 GPa (2033±20 °C), and 2.0 GPa (2145±20 °C) using a new high-pressure assembly in a piston–cylinder apparatus and substantial differences were found with data previously reported. The new melting data of β-quartz were combined and optimized with all available thermodynamic, volumetric, and phase equilibria data for β-cristobalite, β-quartz and coesite to produce a P–T liquidus diagram for silica valid up to 6.0 GPa. Using the new optimized thermodynamic parameters, the invariant point β-cristobalite+β-quartz+liquid and β-quartz+coesite+liquid were determined to lie at 1687±17 °C and 0.457 GPa, and 2425±25 °C and 5.00 GPa, respectively. 相似文献
110.