全文获取类型
收费全文 | 186篇 |
免费 | 7篇 |
国内免费 | 1篇 |
出版年
2019年 | 2篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 3篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 2篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1972年 | 5篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1963年 | 1篇 |
1961年 | 2篇 |
1959年 | 8篇 |
1958年 | 5篇 |
1957年 | 6篇 |
1956年 | 6篇 |
1955年 | 5篇 |
1954年 | 6篇 |
1953年 | 5篇 |
1952年 | 7篇 |
1951年 | 4篇 |
1950年 | 3篇 |
1949年 | 2篇 |
1948年 | 5篇 |
1947年 | 1篇 |
1946年 | 2篇 |
1945年 | 2篇 |
1930年 | 1篇 |
1927年 | 2篇 |
排序方式: 共有194条查询结果,搜索用时 78 毫秒
101.
102.
103.
104.
105.
106.
107.
RICHARDS V 《California medicine》1952,77(5):293-298
Recent advances in pediatric surgery have been made in several fields. Hydrocephalus is again being treated by draining the cerebrospinal fluid into either the ureter, the mastoid antrum or the peritoneal cavity. Funnel chest should be corrected surgically. Congenital atresia of the esophagus is best treated by a one-stage operative repair. Patent ductus should be closed. Operations are available for cyanotic children. Intussusception is again being treated by barium enema in selected cases. Megacolon can be benefited by surgical procedures, which now are directed at the distal spastic segment rather than the proximal dilated segment. 相似文献
108.
109.
Both resource and disturbance controls have been invoked to explain tree persistence among grasses in savannas. Here we determine the extent to which competition for available resources restricts the rooting depth of both grasses and trees, and how this may influence nutrient cycling under an infrequently burned savanna near Darwin, Australia. We sampled fine roots <2 mm in diameter from 24 soil pits under perennial as well as annual grasses and three levels of canopy cover. The relative proportion of C3 (trees) and C4 (grasses) derived carbon in a sample was determined using mass balance calculations. Our results show that regardless of the type of grass both tree and grass roots are concentrated in the top 20 cm of the soil. While trees have greater root production and contribute more fine root biomass grass roots contribute a disproportional amount of nitrogen and carbon to the soil relative to total root biomass. We postulate that grasses maintain soil nutrient pools and provide biomass for regular fires that prevent forest trees from establishing while savanna trees, are important for increasing soil N content, cycling and mineralization rates. We put forward our ideas as a hypothesis of resource‐regulated tree–grass coexistence in tropical savannas. 相似文献
110.
Wytske A Altenburg Marieke L Duiverman Nick HT ten Hacken Huib AM Kerstjens Mathieu HG de Greef Peter J Wijkstra Johan B Wempe 《Respiratory research》2015,16(1)