全文获取类型
收费全文 | 5722篇 |
免费 | 23篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 1027篇 |
地球物理 | 1324篇 |
地质学 | 3148篇 |
海洋学 | 53篇 |
天文学 | 72篇 |
综合类 | 4篇 |
自然地理 | 97篇 |
出版年
2013年 | 68篇 |
2009年 | 42篇 |
2006年 | 39篇 |
1997年 | 38篇 |
1996年 | 74篇 |
1995年 | 44篇 |
1994年 | 42篇 |
1993年 | 62篇 |
1992年 | 149篇 |
1991年 | 153篇 |
1990年 | 141篇 |
1989年 | 135篇 |
1988年 | 136篇 |
1987年 | 176篇 |
1986年 | 130篇 |
1985年 | 117篇 |
1984年 | 152篇 |
1983年 | 171篇 |
1982年 | 183篇 |
1981年 | 184篇 |
1980年 | 151篇 |
1979年 | 187篇 |
1978年 | 159篇 |
1977年 | 149篇 |
1976年 | 118篇 |
1975年 | 139篇 |
1974年 | 125篇 |
1973年 | 142篇 |
1972年 | 131篇 |
1971年 | 137篇 |
1970年 | 144篇 |
1969年 | 103篇 |
1968年 | 132篇 |
1967年 | 123篇 |
1966年 | 85篇 |
1965年 | 96篇 |
1964年 | 100篇 |
1963年 | 44篇 |
1962年 | 91篇 |
1960年 | 104篇 |
1959年 | 35篇 |
1957年 | 41篇 |
1956年 | 37篇 |
1955年 | 40篇 |
1954年 | 67篇 |
1953年 | 38篇 |
1952年 | 49篇 |
1951年 | 38篇 |
1950年 | 61篇 |
1949年 | 44篇 |
排序方式: 共有5748条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
Jennifer M. Galloway Christine T. Doherty R. Timothy Patterson Helen M. Roe 《第四纪科学杂志》2009,24(4):322-335
A pollen‐based study from Tiny Lake in the Seymour‐Belize Inlet Complex of central coastal British Columbia, Canada, permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change. Open Pinus parklands grew at the site during the early Lateglacial when the climate was cool and dry, but more humid conditions in the later phases of the Lateglacial permitted mesophytic conifers to colonise the region. Early Holocene conditions were warmer than present and a successional mosaic of Tsuga heterophylla and Alnus occurred at Tiny Lake. Climate cooling and moistening at 8740 ± 70 14C a BP initiated the development of closed, late successional T. heterophylla–Cupressaceae forests, which achieved modern character after 6860 ± 50 14C a BP, when a temperate and very wet climate became established. The onset of early Holocene climate cooling and moistening at Tiny Lake may have preceded change at more southern locations, including within the Seymour‐Belize Inlet Complex, on a meso‐ to synoptic scale. This would suggest that an early Holocene intensification of the Aleutian Low pressure system was an important influence on forest dynamics in the Seymour‐Belize Inlet Complex and that the study region was located near the southern extent of immediate influence of this semi‐permanent air mass. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
9.
Dr M. J. Wooller D. L. Swain K. J. Ficken A. D. Q. Agnew F. A. Street-Perrott G. Eglinton 《第四纪科学杂志》2003,18(1):3-15
Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755‐cm‐long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon‐isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C4 photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C4 grass taxa were present at the LGM and that the majority followed the cold‐tolerant NADP‐MEC4 subpathway. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
10.