全文获取类型
收费全文 | 1715篇 |
免费 | 264篇 |
国内免费 | 45篇 |
专业分类
测绘学 | 52篇 |
大气科学 | 35篇 |
地球物理 | 1426篇 |
地质学 | 119篇 |
海洋学 | 46篇 |
天文学 | 26篇 |
综合类 | 151篇 |
自然地理 | 169篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 14篇 |
2021年 | 35篇 |
2020年 | 34篇 |
2019年 | 35篇 |
2018年 | 35篇 |
2017年 | 43篇 |
2016年 | 33篇 |
2015年 | 43篇 |
2014年 | 49篇 |
2013年 | 61篇 |
2012年 | 61篇 |
2011年 | 64篇 |
2010年 | 59篇 |
2009年 | 100篇 |
2008年 | 67篇 |
2007年 | 98篇 |
2006年 | 89篇 |
2005年 | 56篇 |
2004年 | 87篇 |
2003年 | 68篇 |
2002年 | 79篇 |
2001年 | 54篇 |
2000年 | 83篇 |
1999年 | 88篇 |
1998年 | 87篇 |
1997年 | 84篇 |
1996年 | 105篇 |
1995年 | 82篇 |
1994年 | 61篇 |
1993年 | 45篇 |
1992年 | 37篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有2024条查询结果,搜索用时 296 毫秒
161.
The solar eclipse on August 11, 1999, observed in the region covered by many geomagnetic observatories, has offered a unique opportunity to look for an effect of the eclipse on geomagnetic pulsations. The pulsation activity digital data have been taken from Budkov Observatory in the Czech Republic (in the X component only), from observatories in Germany (Niemegk, Fürstenfeldbruck, Bad Bergzabern), in Hungary (Nagycenk), and for comparison in South Africa (Hermanus, conjugate-point station), and in Finland (Sodankylä, far from the eclipse zone). At all these stations the field in all three component has been recorded. The pulsation amplitudes in the X component exhibit a long-term minimum near the time of the eclipse. Spectral analysis of selected short intervals confirmed this decrease and also revealed a decrease of the average pulsation period during the eclipse. Such a change in the amplitude or in the period was not observed outside of the eclipse interval or in other days. Investigation in some narrower frequency bands showed that the maximal decrease occurred in the 15–20 s band. All these changes can be found in records from all the stations near the eclipse totality belt, also in records at the conjugate-point station, where no eclipse occurred. No signature has been found in records at the station situated far from the eclipse zone. 相似文献
162.
163.
GPS揭示的现今地壳运动与地震前兆特征 总被引:10,自引:8,他引:2
利用“中国地壳运动观测网络”产出的GPS观测资料,采用球坐标系下非连续变形算法对资源进行计算,以此为基础,对我国大陆地块及其边界带运动与形变进行了分析。对GPS基准站的连续观测序列采用小波变换进行分解变换,分析了部分震例,探讨了从GPS连续观测序列提取地震前兆的方法。初步取得两点认识:(1)7级以上的大地震主要发生在走滑运动量大的活动边界,且与高应变率地块有关,这可以作为地震中长期预测判据;(2)GPS基准站连续观测序列中的低频段,地震前6个月或稍长时段有一定的前兆异常出现,这可以作为地震中短期预测判据。 相似文献
164.
165.
1997年伽师强震群活动的近场定点形变异常特征 总被引:3,自引:0,他引:3
对1997年伽师强震群前后的近场宁点形变资料和卡尔曼滤波结果的前兆异常进行了分析,结果表明,震前短临异常较为明显。通过密切跟踪,在后续强震的预报中发挥了重要作用。文中还对异常与孕震构造和应力场的关系进行了讨论。 相似文献
166.
Guangzhou spring rainfall mainly exhibits interannual variation of Quasi-biannual and
interdecadal variation of 30 yrs, and is in the period of weak rainfall at interdecadal time scale.
SST anomalies (SSTA) of Nino3 are the strongest precursor of Guangzhou spring rainfall. They
have significant positive correlation from previous November and persist stably to April. Nino3
SSTA in the previous winter affects Guangzhou spring rainfall through North Pacific subtropical
high and low wind in spring. When Nino3 SSTA is positive in the previous winter, spring
subtropical high is intense and westward, South China is located in the area of ascending airflow at
the edge of the subtropical high, and water vapor transporting to South China is intensified by
anticyclone circulation to the east of the Philippines. So Guangzhou spring rainfall is heavy. When
Nino3 SSTA is negative, the subtropical high is weak and eastward, South China is far away from
the subtropical high and is located in the area of descending airflow, and water vapor transporting
to South China is weak because low-level cyclonic circulation controls areas to the east of the
Philippines and north wind prevails in South China. So Guangzhou spring rainfall is weak and
spring drought is resulted. 相似文献
167.
168.
169.
170.