全文获取类型
收费全文 | 193篇 |
免费 | 11篇 |
专业分类
204篇 |
出版年
2018年 | 2篇 |
2017年 | 3篇 |
2015年 | 6篇 |
2013年 | 11篇 |
2012年 | 8篇 |
2011年 | 12篇 |
2010年 | 16篇 |
2009年 | 15篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1967年 | 1篇 |
1959年 | 1篇 |
1958年 | 10篇 |
1957年 | 7篇 |
1954年 | 1篇 |
1951年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有204条查询结果,搜索用时 0 毫秒
201.
ADAM S. BURSA 《The Journal of eukaryotic microbiology》1969,16(3):411-418
SYNOPSIS. The family Actiniscaceae Kützing, 1845, (generally placed in the dinoflagellates) includes species derived from Actiniscus pentasterias Schütt, some of which became lacustrine relicts. A. pentasterias v. arcticus. living in Arctic and Altantic waters, differs from the Mediterranean species in having a greater number of siliceous skeletons (pentasters). Advanced atrophy of pentasters in lacustrine A. canadensis , and absence of such structures in Pseudoactiniscus apentasterias , probably results from decreased salinity and an undetermined ecologic factor. Morphogenesis and physiologic transformation of past euryhaline Actiniscaceae into contemporary limnobionts began, presumably, during the prelimnic phase of Great Bear Lake and Keyhole Lake. Arctic Actiniscus which exist under subzero temperatures and endure 10-month-long winters, appear to satisfy their energy requirements by heterotrophy and frequent phagocytosis. Survival of lacustrine Actiniscus species in both Arctic lakes seems possible because of lack of competition from co-existing phytoplankton organisms which can endure extreme dystrophic conditions. 相似文献
202.
LOUISE A. SHILTON PETER J. LATCH ADAM MCKEOWN PETINA PERT DAVID A. WESTCOTT 《Austral ecology》2008,33(4):549-561
Abstract Severe category 4 Tropical Cyclone Larry, which crossed north‐east Queensland on 20 March 2006, provided a unique opportunity to examine the short‐term impacts of a major disturbance event on the population of a highly mobile threatened species, Pteropus conspicillatus. As we had recorded, the species’ population distribution in colonial roosts (camps) across the region each month for almost 2 years prior to Cyclone Larry, we continued monthly surveying of P. conspicillatus camp‐sites for a year post‐cyclone. Here we report on how P. conspicillatus responded and redistributed immediately after the cyclone, and over the subsequent year. Post‐cyclone, P. conspicillatus typically roosted in smaller camps than pre‐cyclone, suggesting that these animals had largely dispersed to locate available blossoms and fruit. For 6 months after Cyclone Larry, up to 90% of the pre‐cyclone P. conspicillatus population (ca. 250 000) was unaccounted for across the region. Information provided by the general public assisted us in locating six small camps of P. conspicillatus at ‘new’ locations, but contributed little to increase our overall population estimate for the species at this time. After November 2006, the number of P. conspicillatus built up at located camp‐sites until a post‐cyclone peak of 209 000 at the end of the study in March 2007, comparable with the population estimates in March 2005 and 2006. There is no evidence that the cyclone caused significant direct mortality among P. conspicillatus, although there may yet be longer‐term and indirect effects on population size. We suggest that redistribution by P. conspicillatus makes sense ecologically in the face of major habitat disturbance and short‐ to long‐term food resource limitation, and is not unlike the response of other Australian mainland Pteropus species to seasonal changes in food availability. 相似文献
203.
Oxytricha granulifera sp.n. differs from other members of the genus by its subpellicular granules and the strongly shortened dorsal kinety 4. The overall pattern of the morphogenetic events is similar to that known from other Oxytrichidae. However, the oral primordium evolves de novo between the left marginal cirral row and the postoral cirri. The six anlagen of the frontoventral cirri are of different origin. Two anlagen of the proter evolve from parental frontal cirri, two from the opisthe, and one includes basal bodies of the proter and opisthe. Two anlagen of the opisthe evolve from the oral primordium, and three primordia originate from the postoral cirri. Frontal cirrus 1 evolves from the paroral membrane in the proter, and from the oral primordium and the anlagen of the frontoventral cirri in the opisthe. The genus Oxytricha can be subdivided into several groups with regard to the origin of its oral primordium and the development of the frontoventral cirri. The morphogenesis of the dorsal kineties in the Hypotrichida is reviewed. Seven different modes of origin are distinguished. We conclude that morphogenetic features cannot be used in the classification of the Hypotrichida at the generic level, because we have too little information to decide whether special morphogenetic features are important at the generic or species level. 相似文献
204.