全文获取类型
收费全文 | 15889篇 |
免费 | 3447篇 |
国内免费 | 4177篇 |
专业分类
测绘学 | 1112篇 |
大气科学 | 2312篇 |
地球物理 | 4690篇 |
地质学 | 9536篇 |
海洋学 | 2497篇 |
天文学 | 383篇 |
综合类 | 1030篇 |
自然地理 | 1953篇 |
出版年
2024年 | 64篇 |
2023年 | 185篇 |
2022年 | 448篇 |
2021年 | 623篇 |
2020年 | 667篇 |
2019年 | 817篇 |
2018年 | 709篇 |
2017年 | 741篇 |
2016年 | 808篇 |
2015年 | 791篇 |
2014年 | 1012篇 |
2013年 | 1116篇 |
2012年 | 955篇 |
2011年 | 1009篇 |
2010年 | 858篇 |
2009年 | 1112篇 |
2008年 | 1108篇 |
2007年 | 1165篇 |
2006年 | 1066篇 |
2005年 | 935篇 |
2004年 | 907篇 |
2003年 | 760篇 |
2002年 | 735篇 |
2001年 | 598篇 |
2000年 | 587篇 |
1999年 | 527篇 |
1998年 | 486篇 |
1997年 | 426篇 |
1996年 | 415篇 |
1995年 | 350篇 |
1994年 | 306篇 |
1993年 | 283篇 |
1992年 | 222篇 |
1991年 | 160篇 |
1990年 | 146篇 |
1989年 | 123篇 |
1988年 | 87篇 |
1987年 | 60篇 |
1986年 | 39篇 |
1985年 | 30篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1954年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Dynamic faulting under rate-dependent friction 总被引:2,自引:0,他引:2
We discuss the effects of rate-dependent friction on the propagation of seismic rupture on active faults. Several physicists using Burridge and Knopoff's box and spring model of faulting have proposed that fault complexity may arise from the spontaneous development of a self-similar stress distribution on the fault plane. If this model proves to be correct, it has important consequences for the origin of the complexity of seismic sources. In order to test these ideas on a more realistic earthquake model, we developed a new boundary integral equation method for studying rupture propagation along an antiplane fault in the presence of nonlinear rate-dependent friction. We study rupture dynamics of models with single and twin asperities. In our models, asperities are places on the fault with a higher value of prestress. Othewise all fault parameters are homogeneous. We show that for models with such asperities, a slip velocity weakening friction leads to the propagation of supersonic healing phases and to the spontaneous arrest of fracture if the prestress outside the asperities is low enough. For models with asperities, we can also observe narrow slip velocity pulses, qualitatively similar to the so-called Heaton pulses observed in some earthquake accelerograms. We also observe a complex distribution of stress after the rupture that depends on details of the initial distribution of asperities and on the details of the friction law. 相似文献
992.
L. N. Germanovich R. L. Salganik A. V. Dyskin K. K. Lee 《Pure and Applied Geophysics》1994,143(1-3):117-149
993.
Kalyani Chatterjea 《地球表面变化过程与地形》1994,19(7):585-607
The nature and rates of fluvial and slope processes change over time and space as urbanized areas replace forested land in Singapore. Storm-based and time-based data, from undisturbed rainforests, heavily disturbed construction sites, urban grass-covered slopes and an experimental plot, are collected to observe the impact of rainwater on the soil moisture conditions, surface microtopography, runoff generation, sediment movement, and ground lowering in the three different categories of land use. The undisturbed forested environment is characterized by high throughfall (58% of total rainfall) and frequent negative soil moisture suctions. The slow and unconcentrated overland flow during heavy storms is restricted by the forest floor microtopography. No rills develop. Ground lowering is recorded as 3·2–3·4 mm a?1. But sediment movement is episodic and suspended sediment concentrations in overland flow are 172–222 mg l?1. During urban construction, gully development is rapid on the bare slopes, runoff generation, voluminous, and sediment-laden discharges (5200–75498 mg l?1) lead to sediment plumes at channel mouths. Ground lowering rates are measured at 132·4 mm a?1. Once grass-covered, runoff carries less suspended sediment (800 mg l?1) and ground lowering rates are reduced, but depend on the condition of the cover, ranging from 0·2 to 8·2 mm a?1. As urban development continues, environments are altered both in time as well as spatially. 相似文献
994.
Long-period surface waves and mantle boundary undulations 总被引:2,自引:0,他引:2
995.
Y.Y. Kagan 《Geophysical Journal International》1994,117(2):345-364
996.
997.
998.
本文在系统的有限应变测量的基础上,对闽东南长乐—南澳断裂带东山段剪切变形特征进行了分析:利用变形石英显微亚结构。(动态重结晶颗粒)估算了剪切带内古应力并(σ—σ_3):通过对剪切变形能密度分布W(x)格离散化计算,采用有限差分数值近方法,获得了剪切热数值解:最后总结了研究地区剪切变形,剪切加热与动热成岩成矿作用的相对时空关系以及长乐—南澳断裂域构造意义 相似文献
999.
三山岛金矿F3断裂带的水文地质工程地质特征及灾害防治 总被引:2,自引:0,他引:2
本文对三山岛金矿F3断裂带的构造、岩性和水动力学特征进行了研究,对矿坑开挖中的突水和坑道碎屑流的成因做了探讨,并在水文地质结构、水化学、水同位素及水文地热学的综合研究基础上,对未来的二期井下工程开挖中可能出现的工程地质问题进行了预测,提出了防治方案。 相似文献
1000.