全文获取类型
收费全文 | 665篇 |
免费 | 27篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 38篇 |
大气科学 | 86篇 |
地球物理 | 160篇 |
地质学 | 284篇 |
海洋学 | 64篇 |
天文学 | 34篇 |
综合类 | 5篇 |
自然地理 | 32篇 |
出版年
2022年 | 6篇 |
2021年 | 26篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 33篇 |
2017年 | 25篇 |
2016年 | 37篇 |
2015年 | 30篇 |
2014年 | 38篇 |
2013年 | 45篇 |
2012年 | 36篇 |
2011年 | 54篇 |
2010年 | 45篇 |
2009年 | 35篇 |
2008年 | 37篇 |
2007年 | 34篇 |
2006年 | 40篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1955年 | 1篇 |
1953年 | 1篇 |
1940年 | 1篇 |
1939年 | 3篇 |
排序方式: 共有703条查询结果,搜索用时 0 毫秒
701.
Jose I. Castillo-Manzano Lourdes López-Valpuesta Fernando Gonzalez Laxe 《Ocean & Coastal Management》2010,53(9):577-580
Spain’s port system was subjected to significant legislative reforms during the 1990s. Spanish Law 62/97 allowed regional governments to manage commercial ports, whereas the central government continued to control the main organisation in charge of the Spanish port system – the Spanish National Ports and Harbours Authority (SNPHA). This paper analyses the evolution of maritime traffic to measure the possible costs of political coordination between the SNPHA and the port authorities controlled by various political parties that rule regional governments. The findings point to coordination costs having a limited effect on the evolution of maritime traffic. 相似文献
702.
Fernando González Taboada Ricardo González Gil Juan Höfer Sonia González Ricardo Anadón 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):65-77
Trichodesmium spp. population structure was studied based on a transect in the eastern subtropical North Atlantic in October 2006, covering a gradient from near-temperate conditions up to fully subtropical, oligotrophic waters. Trichodesmium spp. trichomes were counted and measured, distinguishing free trichomes from those forming macroscopic colonies (“puffs” or “tufts”). Moreover, for both free and colonial individuals, abundance and size structure variation were quantified from single trichome-level data. Nitrogen fixation rates were estimated using an empirical approach based on abundance observations and a heuristic approach to incorporate variation in trichome size and environmental temperature. A gradual change towards greater sizes and increased abundances was observed as physical conditions became subtropical. An extreme response was detected at one station (29.8°W, 26.3°N), in which both in situ and remote sensing data revealed the presence of a Trichodesmium bloom. Despite the presence of a mesoscale anticyclonic eddy, a close examination of prior surface conditions using altimeter data indicated that the bloom was related to the advection of southern waters. In general, our results highlighted the importance of free trichomes in Trichodesmium spp. populations in this part of the North Atlantic. Furthermore, they suggested a possible role of both size and population structure on the wide range of N2 fixation estimates currently available in the literature. 相似文献
703.
Jorge Fernndez Vera Markgraf Hctor O. Panarello Miguel Albero Fernando E. Angiolini Susana Valencio Mirta Arriaga 《Geoarchaeology》1991,6(3):251-272
The Barro Negro site (23°S lat., 65°37′W long.) in the Altiplano (Puna) of northwestern Argentina contains a well stratified sequence of remains of Hippidion, the American extinct horse, camelids, and archaeological materials, which is the focus of this study. In addition to establishing a reliable chronology, paleoenvironmental information was obtained based on analyses of pollen and stable isotopes (oxygen and carbon) from bone and marl. The data indicate that Hippidion was present at the site between 12,000 and 10,000 yr B. P., at a time when Altoandean grasslands had expanded to lower elevations. By 10,000 yr B.P., when modern semi-arid sub-puna scrub had replaced the Altoandean grasslands, only camelids (Lama or Vicugna) were present, simultaneous with the first evidence of local human occupation. This suggests that a climatic shift from cool and moist (winter rain regime) to warm and dry (summer rain regime) conditions took place simultaneously with the disappearance of the American horse and the appearance of camelids and man. 相似文献