全文获取类型
收费全文 | 2983篇 |
免费 | 629篇 |
国内免费 | 579篇 |
专业分类
测绘学 | 262篇 |
大气科学 | 619篇 |
地球物理 | 1323篇 |
地质学 | 874篇 |
海洋学 | 497篇 |
天文学 | 159篇 |
综合类 | 224篇 |
自然地理 | 233篇 |
出版年
2024年 | 14篇 |
2023年 | 36篇 |
2022年 | 101篇 |
2021年 | 96篇 |
2020年 | 136篇 |
2019年 | 148篇 |
2018年 | 123篇 |
2017年 | 145篇 |
2016年 | 133篇 |
2015年 | 163篇 |
2014年 | 172篇 |
2013年 | 224篇 |
2012年 | 189篇 |
2011年 | 223篇 |
2010年 | 156篇 |
2009年 | 187篇 |
2008年 | 179篇 |
2007年 | 187篇 |
2006年 | 177篇 |
2005年 | 157篇 |
2004年 | 132篇 |
2003年 | 125篇 |
2002年 | 118篇 |
2001年 | 103篇 |
2000年 | 93篇 |
1999年 | 91篇 |
1998年 | 85篇 |
1997年 | 81篇 |
1996年 | 83篇 |
1995年 | 67篇 |
1994年 | 63篇 |
1993年 | 70篇 |
1992年 | 37篇 |
1991年 | 20篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1972年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有4191条查询结果,搜索用时 15 毫秒
81.
82.
Cyclic tests on two large‐scale models of existing bridge piers with rectangular hollow cross‐section were performed in the ELSA laboratory. The prototype structure is an existing reinforced concrete highway bridge constructed in Austria in 1975. The piers presented several seismic deficiencies and consequently they showed poor hysteretic behaviour and limited deformation capacity as well as undesirable failure modes that do not comply with the requirements of modern codes for seismic‐resistant structures. Experimental data are compared to numerical and empirical predictions. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
83.
Ottavia Corbi 《地震工程与结构动力学》2003,32(2):173-185
In this paper, a control strategy for structural systems is proposed and developed in the frequency domain. The algorithm is substantially based on a linear derivative feedback and a convolution of the control parameter, whose distribution in the frequency field is chosen in such a manner as to comply with the requirements of an ad hoc formulated constrained optimum problem, with the response data monitored until the instant of control action application. Some numerical testing is carried out by referring to given recorded accelerograms, showing a good performance of the proposed approach. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
84.
85.
从118.75 GHz附近六通道亮温反演大气温度廓线的数值模拟研究 总被引:5,自引:0,他引:5
为了能在静止气象卫星上实现微波被动遥感探测大气温度廓线,并保持一定的地面空间分辨率(如视场小于60 km),就需要使用高频微波及大天线.欧洲和美国下一代静止气象卫星上都已考虑采用118.75 GHz附近通道.为了充分了解118.75 GHz附近通道遥感反演温度廓线的能力,为仪器研制及今后资料的解释反演提供必要的基础数据,作者开展了采用118.75 GHz附近六个通道遥感反演大气温度廓线的数值模拟研究.统计反演的数值试验表明,118.75 GHz附近六通道对温度垂直分布有一定的遥感反演能力;温度反演较好的层次对应于权重函数峰值所在的位置. 相似文献
86.
VLBI观测的电离层延迟改正模型研究 总被引:2,自引:1,他引:2
电离层是大气层中的一个电离区域,高度范围大约在60-1000km。电磁波信号穿越电离层时其传播速度会发生变化,传播路径也会略微发生弯曲,从而使信号的传播时间乘以在真空中的光速不等于信号源至测站的几何距离。对VLBI观测来讲,电离层引起的差异可达近百米百米。文中从电磁波的传播原理出发,讨论了信号传播速度和传播路径变化引起的VLBI观测延迟;对目前采用的各种电离层延迟模型进行了分析总结;并指出单频率VLBI观测应顾及高阶项和路径弯曲的影响或使用区域性电离层延迟改正模型。 相似文献
87.
The Northward Shift of Climatic Belts in China During the Last 50 Years and the Corresponding Seasonal Responses 总被引:29,自引:0,他引:29
Along the meridian of 105°E, the Chinese region are divided into two parts, east and west. The results show that in the east part of China the temperate extratropical belt, the warm extratropical belt,and the northern subtropical belt shift northward significantly, whereas the middle subtropical belt and the southern subtropical belt have less or no change. As for the northern subtropical belt, the maximal northward shift can reach 3.7 degrees of latitude. As for the warm extratropical belt, along the meridian of 120°-125°E, the maximal northward shift can reach 3-4 degrees. In the west part of China, each climatic belt changes little. Only in the Xinjiang area are the significant northward shifts. Correspondingly, it is found that in the last 50 years the traditional seasons have changed. For Beijing, Hailar, and Lanzhou, in general, summer becomes longer and winter shorter over the last 50 years. Summer begins early and ends late with respect to early 1950s. Contrary to the summer, winter begins la 相似文献
88.
89.
90.
THE ANALYSIS ON THE STATISTICAL CHARACTER OF QUIKSCAT SCATTEROMETER WINDS AND STRONG WIND FREQUENCY USING REMOTE SENSOR DATA FROM QUIKSCAT 总被引:1,自引:1,他引:1
1 INTRODUCTION Most of the conventional sea surface wind data are measurements from ships, buoys and islands, with coverage and spatial resolution far below the requirements of research and application. At present, due to limited understanding of physical processes and efficient exploitation of data, numerical prediction models have not been used as they should be, although routine procedures are able to give sea surface wind fields at the intervals of 6 hours. With the development of sp… 相似文献