全文获取类型
收费全文 | 11395篇 |
免费 | 3000篇 |
国内免费 | 2471篇 |
专业分类
测绘学 | 216篇 |
大气科学 | 292篇 |
地球物理 | 4692篇 |
地质学 | 8629篇 |
海洋学 | 1062篇 |
天文学 | 18篇 |
综合类 | 922篇 |
自然地理 | 1035篇 |
出版年
2024年 | 33篇 |
2023年 | 121篇 |
2022年 | 306篇 |
2021年 | 438篇 |
2020年 | 399篇 |
2019年 | 519篇 |
2018年 | 463篇 |
2017年 | 488篇 |
2016年 | 556篇 |
2015年 | 535篇 |
2014年 | 668篇 |
2013年 | 714篇 |
2012年 | 674篇 |
2011年 | 670篇 |
2010年 | 610篇 |
2009年 | 780篇 |
2008年 | 803篇 |
2007年 | 780篇 |
2006年 | 771篇 |
2005年 | 655篇 |
2004年 | 701篇 |
2003年 | 578篇 |
2002年 | 543篇 |
2001年 | 486篇 |
2000年 | 490篇 |
1999年 | 395篇 |
1998年 | 389篇 |
1997年 | 338篇 |
1996年 | 326篇 |
1995年 | 328篇 |
1994年 | 290篇 |
1993年 | 246篇 |
1992年 | 193篇 |
1991年 | 127篇 |
1990年 | 103篇 |
1989年 | 111篇 |
1988年 | 78篇 |
1987年 | 56篇 |
1986年 | 26篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1980年 | 4篇 |
1979年 | 22篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1954年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
941.
旅游资源非优区主要是在资源质量及其开发条件等方面表现出"非优性"的特征.在区域发展中如果仍然沿用传统的旅游资源开发思路和方法,必然使区域旅游业处于市场竞争中的劣势.因此,对于该类型区域有必要探索出新的经济发展思路.从区域比较优势角度,旅游资源非优区的发展应以资源禀赋特征为基础,以旅游经济园区发展为主体,走产业多样化的道路.以吕梁山苍儿会生态旅游经济区为例,提出加快园区化建设的步伐,促进旅游经济与区域产业经济的良性互动,是避免片面强调旅游经济而抑制其它产业发展,以及促进区域可持续发展的根本战略选择. 相似文献
942.
黄淮海平原气候变化及其对耕地生产潜力的影响 总被引:8,自引:0,他引:8
利用1991年和2000年黄淮海平原气象台站的历史观测资料,分析该地区气温、降水的变化趋势,并利用农业生态地带(AEZ)模型估算黄淮海平原各农业生态区的耕地生产潜力。通过分析气温、降水与耕地生产潜力的关系,评价气候变化对耕地生产潜力的影响。研究发现,黄淮海平原耕地生产潜力与降水量、气温呈显著正相关。对各农业生态区的回归分析表明,如果气温或降水量提高10%,耕地生产潜力将分别提高3.2%与0.3%。该研究对制订应对气候变化、保护耕地与提高耕地生产潜力方面的决策具有参考价值。 相似文献
943.
944.
Naoyuki Kato 《Geophysical Journal International》2007,168(2):797-808
945.
946.
G. Wilson D. Damaske H.-D. Möller K. Tinto T. Jordan 《Geophysical Journal International》2007,170(1):93-100
Magnetic anomaly data are presented from a new helicopter-borne high-resolution aeromagnetic survey in southern McMurdo Sound. Anomaly data have been acquired at a common 305 m elevation above the McMurdo and southern McMurdo ice shelves and draped over the volcanic islands that pin them. The resulting anomaly patterns provide a significant advance in the understanding of the rift related geology beneath the floating ice shelves. More extensive Erebus Volcanic Province (McMurdo Volcanic Group) rocks are indicated along with a significant blanket of glaci-volcaniclastic sediment on the seafloor between the volcanic islands in southern McMurdo Sound. These glaci-volcaniclastic sediments are inferred to originate from former grounding of the southern McMurdo Ice Shelf as a marine ice sheet. A strong N–S fabric is also observed in the anomaly data suggesting that the rift structure observed in the Victoria Land basin persists to the south beneath the McMurdo and southern McMurdo ice shelves. W–N–W transfer faults identified within the Transantarctic Mountain rift flank to the west are not obvious in the aeromagnetic data set, implying that the 'Discovery Accommodation Zone' may be restricted to the region between a southward extension of the range bounding fault that marks the limit of the Victoria Land Basin and the right lateral offset in the Transantarctic Mountain front in southern Victoria Land. 相似文献
947.
We present observations of ground accelerations recorded at a small array close to the fault during the Düzce earthquake and its early aftershocks. The records show the strong spatial variability of ground acceleration over distances of only a few hundred metres. During the main shock, the peak horizontal acceleration values ranged from 0.3 to about 1.0 g at stations distant of 1.5 km only. We attribute this spatial variability to a fault zone site effect as peak ground acceleration steadily increases as the distance to the fault trace decreases. The spectral ratio between the ground motion recorded near the fault and the one outside the fault zone shows a shift of the spectral peak to lower frequencies with increasing peak accelerations. Such an observation suggests a non-linear behaviour of the fault zone due to the strong ground shaking. As much as a 45 per cent reduction in the shear wave velocity is necessary for the observed shifts. The opening of pre-existing cracks throughout the fault zone is the proposed mechanism to account for the observed shear wave reductions. The observation that elastic fault zone properties are soon recovered following episodes of large strains shows that cracks and fissures close rapidly after the strong shaking is over. 相似文献
948.
949.
950.
G. Hillers P. M. Mai Y. Ben-Zion J.-P. Ampuero 《Geophysical Journal International》2007,169(2):515-533
We perform a systematic parameter space study of the seismic response of a large fault with different levels of heterogeneity, using a 3-D elastic framework within the continuum limit. The fault is governed by rate-and-state friction and simulations are performed for model realizations with frictional and large scale properties characterized by different ranges of size scales. We use a number of seismicity and stress functions to characterize different types of seismic responses and test the correlation between hypocenter locations and the employed distributions of model parameters. The simulated hypocenters are found to correlate significantly with small L values of the rate-and-state friction. The final sizes of earthquakes are correlated with physical properties at their nucleation sites. The obtained stacked scaling relations are overall self-similar and have good correspondence with properties of natural earthquakes. 相似文献