全文获取类型
收费全文 | 4362篇 |
免费 | 672篇 |
国内免费 | 755篇 |
专业分类
测绘学 | 409篇 |
大气科学 | 866篇 |
地球物理 | 1193篇 |
地质学 | 1468篇 |
海洋学 | 500篇 |
天文学 | 17篇 |
综合类 | 378篇 |
自然地理 | 958篇 |
出版年
2024年 | 20篇 |
2023年 | 70篇 |
2022年 | 152篇 |
2021年 | 173篇 |
2020年 | 176篇 |
2019年 | 200篇 |
2018年 | 159篇 |
2017年 | 196篇 |
2016年 | 218篇 |
2015年 | 196篇 |
2014年 | 253篇 |
2013年 | 315篇 |
2012年 | 295篇 |
2011年 | 284篇 |
2010年 | 246篇 |
2009年 | 255篇 |
2008年 | 253篇 |
2007年 | 283篇 |
2006年 | 241篇 |
2005年 | 221篇 |
2004年 | 203篇 |
2003年 | 196篇 |
2002年 | 142篇 |
2001年 | 98篇 |
2000年 | 127篇 |
1999年 | 112篇 |
1998年 | 102篇 |
1997年 | 107篇 |
1996年 | 102篇 |
1995年 | 64篇 |
1994年 | 69篇 |
1993年 | 62篇 |
1992年 | 43篇 |
1991年 | 47篇 |
1990年 | 28篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1984年 | 6篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1972年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有5789条查询结果,搜索用时 0 毫秒
1.
2.
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
3.
b值在地震预测中的三类应用及其物理基础与须注意的问题 总被引:1,自引:0,他引:1
将b值在地震预测中的直接应用归为三类:1)根据b值的动态变化预测地震。2)根据G-R律求出各级地震平均复发周期或年均发生率,推测未来一定时段如50年或100年内发生各级地震的危险性。3)根据G-R直线在横轴的截距,预测强余震的震级。讨论了这三种用法的物理基础及现有工作中容易出现的问题。 相似文献
4.
5.
This study presents the evolution of agreements between the governments of Canadaand Québec on flood damage reduction. In Québec, the implementation of a regulation about building in floodplains came about in 1983–1984. Today, this regulation takes the form of a policy called ``Policy of shores, littoral and floodplain protection'. Municipalities must adopt rules that concur with the principles of this policy.The Chaudiére River basin was selected for analysis of urban developmentduring the period following the application of building rules in flood-risk areas.Despite the ban on building in the strong current zone (0–20 year return periodflood zone), many buildings, essentially residential, have been erected in thiszone. These new constructions generally account for a low percentage of thetotal property value in the 0–100 year flooding area, but are legal since theyare connected to a water and sewage network that existed prior to the officialfloodplain regulation.Flood damage along the Chaudiére River will tend to increase for two reasons.Firstly, while respecting the policy mentioned above, sites are still available infloodplains for future development. Secondly, no structural flood protection workshave been erected in view of the fact they are only marginally profitable from anbenefit-cost point of view. 相似文献
6.
地震前兆观测仪器标定问题的探讨 总被引:2,自引:1,他引:2
标定工作,在地震前兆观测仪器的研究,使用及所得数据的处理中均已成为一个不可少的环节,但缺少有关标定问题的基石性研究和讨论。本文就标定的定义、种类、目的、要求、存在的问题等做一粗线的讨论,以期今后加强这一工作的深入研究。 相似文献
7.
城市化对北京平均气温的影响 总被引:40,自引:2,他引:40
本文利用北京(观象台)及周围几个气象台站月平均气温资料,滑动平均后,采用主成分分析方法,再进行倾向性分析,探讨了北京城市化对气平均气温的影响,估算对北京(观象台)气温记录的影响约为0.21℃/33a推断市中心二环路以内强烈地影响。 相似文献
8.
9.
By means of barotropic model, the characteristic and initial value problems are investigated to reveal the local two-dimensional
barotropic instability of the nonuniform current to the dynamic mechanism of the formation of the Yangtze-Huaihe River severe
storm in July 1991. Analytical theory and numerical experiment show that (i) the unstable developing modes are chiefly the
two periods of about 44 d and 10 d, which are fundamentally consistent with that of the precipitation change of the Yangtze-Huaihe
River. (ii) The growth rate of the local perturbation is dominated by the meridional wave numbern = 1–5 and zonal wave numberk = 1–12, i.e. the severe storm over the Yangtze-Huaihe River results from the interaction of the systems at different latitudes
and waves of different scales, (iii) The perturbation over the Yangtze-Huaihe River possesses the property of local intensification,
which slowly migrates westward over the lower and middle reaches of the Yangtze-Huaihe River. (iv) The growth rate of the
instability, especially the propagation velocity of the perturbation, is sensitive to the external parameters ū and α.
Project supported by the National Natural Science Foundation of China. 相似文献
10.
The temporal and spatial characteristics of the surface air temperature variations over the Antarctic and its surrounding area 总被引:1,自引:0,他引:1
The characteristics of the spatial distribution, temporal variations trend and oscillation for the surface air temperature
variations during 1957—1993 in the Antarctic and its surrounding area were analyzed. The results show that the short-time
climate change in the Antarctic is complex both temporally and spatially. The Antarctic is by no means the strongest responding
region to the global greenhouse effect. There is a distinguished difference in the trends of the temperature changes for the
Antarctic and global mean, which could not be explained simply by the global greenhouse effect.
Project supported by the National Antarctic Key Project of China (85-905). 相似文献