首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   51601篇
  免费   679篇
  国内免费   371篇
测绘学   1390篇
大气科学   4093篇
地球物理   9763篇
地质学   17046篇
海洋学   4297篇
天文学   12629篇
综合类   123篇
自然地理   3310篇
  2020年   350篇
  2019年   350篇
  2018年   871篇
  2017年   844篇
  2016年   1098篇
  2015年   718篇
  2014年   1227篇
  2013年   2528篇
  2012年   1178篇
  2011年   1642篇
  2010年   1497篇
  2009年   2020篇
  2008年   1877篇
  2007年   1867篇
  2006年   1747篇
  2005年   1634篇
  2004年   1581篇
  2003年   1465篇
  2002年   1416篇
  2001年   1284篇
  2000年   1218篇
  1999年   1182篇
  1998年   1127篇
  1997年   1107篇
  1996年   892篇
  1995年   893篇
  1994年   833篇
  1993年   780篇
  1992年   742篇
  1991年   719篇
  1990年   813篇
  1989年   711篇
  1988年   663篇
  1987年   766篇
  1986年   650篇
  1985年   851篇
  1984年   988篇
  1983年   938篇
  1982年   891篇
  1981年   855篇
  1980年   754篇
  1979年   720篇
  1978年   717篇
  1977年   642篇
  1976年   615篇
  1975年   529篇
  1974年   625篇
  1973年   602篇
  1972年   372篇
  1971年   343篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
311.
312.
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   
313.
314.
315.
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   
316.
317.
On the southwest-facing slopes of a bedrock ridge lying between Cardigan Bay to the north and the Afon Teifi to the south stands a group of hills in which 30-35 m of cross-laminated and parallel-laminated sands with lenticular upward-fining gravel sequences are overlain by 10-12 m of gravel in a single foreset bed. The sediments mantle a surface of till sloping gently toward the southwest, were transported toward the southwest (across one margin of the Afon Teifi valley), and were cut by a system of densely arranged conjugate normal faults striking northwest-southeast. The lenticular gravels and fault system suggest that the deposits accumulated as a glaciofluvial outwash spread, and on top of an ice-lobe that became isolated in the Teifi valley during the downwasting of a glacier which had occupied Cardigan Bay and much of the country to the south. The large gravel foresets capping the succession are the only indication at Banc-y-Warren of the former existence of a lake, but neither a large nor deep body of water need be envisaged.  相似文献   
318.
The influence of potassium bromide on the bands near 10 μm, 18 μm and 33 μm was calculated for any silicate. The wavelength shift, the deepening, and the broadening of the bands were calculated for different band's depths of each band. The results were applied on the investigation of an extensive catalogue of silicate spectra, which were got on the basis of the KBr pressing technique too. So it was possible to picle out those silicates from the variety of silicates, which are probable candidates for the interstellar silicate component.  相似文献   
319.
320.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号