全文获取类型
收费全文 | 49394篇 |
免费 | 640篇 |
国内免费 | 324篇 |
专业分类
测绘学 | 1334篇 |
大气科学 | 3830篇 |
地球物理 | 9285篇 |
地质学 | 16261篇 |
海洋学 | 4172篇 |
天文学 | 12164篇 |
综合类 | 108篇 |
自然地理 | 3204篇 |
出版年
2020年 | 339篇 |
2019年 | 337篇 |
2018年 | 828篇 |
2017年 | 810篇 |
2016年 | 1052篇 |
2015年 | 696篇 |
2014年 | 1170篇 |
2013年 | 2441篇 |
2012年 | 1110篇 |
2011年 | 1543篇 |
2010年 | 1436篇 |
2009年 | 1930篇 |
2008年 | 1774篇 |
2007年 | 1776篇 |
2006年 | 1678篇 |
2005年 | 1544篇 |
2004年 | 1508篇 |
2003年 | 1413篇 |
2002年 | 1357篇 |
2001年 | 1230篇 |
2000年 | 1155篇 |
1999年 | 1121篇 |
1998年 | 1056篇 |
1997年 | 1062篇 |
1996年 | 844篇 |
1995年 | 836篇 |
1994年 | 794篇 |
1993年 | 738篇 |
1992年 | 709篇 |
1991年 | 680篇 |
1990年 | 776篇 |
1989年 | 674篇 |
1988年 | 648篇 |
1987年 | 741篇 |
1986年 | 620篇 |
1985年 | 824篇 |
1984年 | 947篇 |
1983年 | 912篇 |
1982年 | 861篇 |
1981年 | 819篇 |
1980年 | 722篇 |
1979年 | 698篇 |
1978年 | 692篇 |
1977年 | 627篇 |
1976年 | 596篇 |
1975年 | 517篇 |
1974年 | 597篇 |
1973年 | 586篇 |
1972年 | 362篇 |
1971年 | 334篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
291.
Vegard Gundersen Bjørn Petter Kaltenborn Daniel R. Williams 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(4):216-229
Local communities in the Gudbrandsdalen region in Norway are increasingly exposed to climate-induced hazards such as floods and landslides. A core question is how community members respond to climate change and what factors contribute to more resilient communities. The authors used a contextual approach to analyze data from semi-structured interviews along five dimensions. In Gaustad Muncipality they found that individuals’ motivation to adapt to climate change depended largely on subjective values such as identity, place attachment, cultural values, and social networks among individuals, which means it is crucial that strategic plans for adaptation to climate change at different policy levels are experienced as relevant by community members. While the studied community has experienced heavy floods in river systems and streams, little evidence of adaptation was observed. Instead, they appeared to adopt coping strategies. Landowners may have limited incentives to adapt to climate change due to contraproductive policy measures such as economic compensation for direct losses without requiring improved practices. Effective adaptation to climate change on the local level is likely to require making compensation mechanisms contingent upon landowners showing willingness to change from coping to adaptive practices, as well as a contextualized approach integrating local and scientific forms of knowledge. 相似文献
292.
Potential of river bank filtration (RBF) in Egypt 总被引:1,自引:0,他引:1
293.
294.
Tension-Only Concentrically Braced Frames (TOCBF) exhibit deteriorating pinched hysteretic behaviour during strong earthquakes. Slender braces transit between an elastic buckling state, a restraightening state, in which they carry almost no load, an elastic tensile loading state as they are suddenly taut and, finally, a tensile yielding state. It has long been suspected that the sudden increase in tensile forces in the braces of TOCBSF creates detrimental impact loading on the connections and other structural elements. No experimental evidence, however, has been provided so far to confirm, or to quantify, this impact phenomenon. This paper addresses this issue through shake table tests of half scale, two-storey, TOCBF models. By normalizing the hysteresis loops of braces obtained from shake table tests to the yield strength of steel obtained from quasi-static tests, the increase in tensile forces in the braces was obtained. Results of dynamic tensile tests on steel coupons under similar strain rates as observed during the shake table tests showed that this increase in tensile forces is not the result of impact, but is rather caused by a yield strength increase of the steel under high strain rate. A procedure is proposed to estimate and account for this increase in tensile forces in the braces at the design stage. 相似文献
295.
296.
Ivanova J. N. Vyhristenko R. I. Vikentyev I. V. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1537-1545
Izvestiya, Atmospheric and Oceanic Physics - The central part of the Malouralsky volcanic–plutonic belt, which includes the Manyukuyu–Vorchatinsky ore cluster, is analyzed using... 相似文献
297.
298.
Kenneth R. Young 《Geographical review》2019,109(2):258-264
299.
J. Sprinks R. Houghton S. Bamford J. G. Morley 《Meteoritics & planetary science》2019,54(6):1325-1346
Virtual citizen science platforms allow nonscientists to take part in scientific research across a range of disciplines, including planetary science. What is required of the volunteer can vary considerably in terms of task type, variety, judgment required, and autonomy—even when the overall goal is unchanged. Through analysis of our live Zooniverse Planet Four: Craters citizen science platform, the effects of task workflow design factors including volunteer autonomy, task variety, task type, and judgment required on volunteer engagement and crater marking performance were investigated. Website analytics showed volunteers using the Full interface (most autonomy and variety) were more likely to return to the platform, although the amount of time spent per visit was unaffected by the interface used. However, analysis of performance suggested that how this time was used did differ. The interface involving the least complex task resulted in the greatest amount of data and rate of collection, although this also coincided with a greater number of false positives when compared with the expert. Performance in terms of agreement, both between participants and with the expert judgment, was significantly improved when using the Stepped interface for crater position and the Ramped (Mark) when measuring diameter—interfaces that both directly measured the metric with a specific, delineated task. The implications for planetary scientists considering the citizen science route is that there is a balancing act to perform, weighing the importance of volunteer engagement with scientists' data needs and the resources that can be committed to data validation. 相似文献
300.