全文获取类型
收费全文 | 1271篇 |
免费 | 203篇 |
国内免费 | 192篇 |
专业分类
测绘学 | 507篇 |
大气科学 | 201篇 |
地球物理 | 336篇 |
地质学 | 266篇 |
海洋学 | 159篇 |
天文学 | 30篇 |
综合类 | 134篇 |
自然地理 | 33篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 27篇 |
2021年 | 27篇 |
2020年 | 46篇 |
2019年 | 67篇 |
2018年 | 51篇 |
2017年 | 74篇 |
2016年 | 51篇 |
2015年 | 70篇 |
2014年 | 78篇 |
2013年 | 96篇 |
2012年 | 93篇 |
2011年 | 114篇 |
2010年 | 98篇 |
2009年 | 84篇 |
2008年 | 84篇 |
2007年 | 83篇 |
2006年 | 79篇 |
2005年 | 73篇 |
2004年 | 60篇 |
2003年 | 31篇 |
2002年 | 38篇 |
2001年 | 34篇 |
2000年 | 29篇 |
1999年 | 24篇 |
1998年 | 31篇 |
1997年 | 22篇 |
1996年 | 19篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1954年 | 1篇 |
排序方式: 共有1666条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
75.
76.
本文提出一种利用LAU效应测定干涉滤光片中心透过率波长值的理论和实验方法,这一方法不但具有精度高、装置简单、方法简便等优点,而且由该方法所获得的实验结果,可以作为当前有关平面周期物体LAU 效应新理论的一种实践检验。 相似文献
77.
78.
A. Ian McLeod K. W. Hipel 《Stochastic Environmental Research and Risk Assessment (SERRA)》1995,9(3):171-205
Current methods of estimation of the univariate spectral density are reviewed and some improvements are made. It is suggested that spectral analysis may perhaps be best thought of as another exploratory data analysis (EDA) tool which complements, rather than competes with, the popular ARMA model building approach. A new diagnostic check for ARMA model adequacy based on the nonparametric spectral density is introduced. Additionally, two new algorithms for fast computation of the autoregressive spectral density function are presented. For improving interpretation of results, a new style of plotting the spectral density function is suggested. Exploratory spectral analyses of a number of hydrological time series are performed and some interesting periodicities are suggested for further investigation. The application of spectral analysis to determine the possible existence of long memory in natural time series is discussed with respect to long riverflow, treering and mud varve series. Moreover, a comparison of the estimated spectral densities suggests the ARMA models fitted previously to these datasets adequately describe the low frequency component. Finally, the software and data used in this paper are available by anonymous ftp from fisher.stats.uwo.ca. 相似文献
79.
80.
On 30 January 1997 an intrusion on Kīlauea volcano opened a new fissure within the East Rift Zone (ERZ) at Nāpau Crater, 3 km
uprift from the ongoing eruptions at Pu’u ’Ō’ō. The fissure eruption lasted 22 h and opened a 5.1 km long, nearly vertical
dike 1.9 m, extending from the surface to a depth of 2.4 km (Owen et al. 2000b). During the eruption, the lava pond at Pu’u ’Ō’ō drained, and eruptions ceased there. Pu’u ’Ō’ō eventually refilled in late
February and eruptions resumed there on 28 March 1997. Continuous GPS data show a large transient following the 30 January
1997 dike intrusion. After lengthening 40 cm during the initial eruption, the baseline between two stations spanning the ERZ
lengthened an additional 10 cm over the following 6 months. A coastal station KAEP also exhibited transient deformation, as
it continued to move southward (5 cm) over the same 6-month period. The baseline between two stations spanning Kīlauea’s summit
caldera contracted sharply during the eruption, but gradually recovered to slightly longer than its previous length 2 months
after the intrusion. We use the extended network inversion filter (McGuire and Segall 2003) to invert continuous GPS data for volume change of a spherical pressure source under Kīlauea’s summit, opening distribution
on a nearly vertical dike in the ERZ and potential slip on a decollement 9 km beneath the south flank. Following the 30 January
intrusion, rift extension continued below the initial dike intrusion for the duration of the transient. Decollement slip,
regardless of its assumed depth, is not required to fit the data. The modeled transient summit reinflation and rift opening
patterns under Nāpau crater coincide with changes in observed behavior of Pu’u ’Ō’ō’s lava pond. Rift opening accelerated
while Pu’u ’Ō’ō eruptions paused and began to decelerate after the lava pond reappeared nearly a month after the Nāpau eruption.
The transient deformation is interpreted as resulting from shallow accommodation of the new dike volume. 相似文献