全文获取类型
收费全文 | 321篇 |
免费 | 9篇 |
国内免费 | 3篇 |
出版年
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 5篇 |
2011年 | 15篇 |
2010年 | 15篇 |
2009年 | 13篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 4篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1989年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1972年 | 7篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1960年 | 2篇 |
1959年 | 6篇 |
1958年 | 16篇 |
1957年 | 14篇 |
1956年 | 10篇 |
1955年 | 16篇 |
1954年 | 12篇 |
1953年 | 8篇 |
1952年 | 15篇 |
1951年 | 8篇 |
1950年 | 5篇 |
1949年 | 6篇 |
1948年 | 8篇 |
1946年 | 3篇 |
排序方式: 共有333条查询结果,搜索用时 421 毫秒
11.
12.
13.
GIOVANNA MASSEI JULIA COATS ROGER QUY KATE STORER DAVE P. COWAN 《The Journal of wildlife management》2010,74(2):333-336
ABSTRACT Bait-delivered pharmaceuticals, increasingly used to manage populations of wild boar (Sus scrofa) and feral pigs, may be ingested by nontarget species. Species-specificity could be achieved through a delivery system. We designed the BOSTM (Boar-Operated-System) as a device to deliver baits to wild pigs. The BOSTM consists of a metal pole onto which a round perforated base is attached. A metal cone with a wide rim slides up and down the pole and fully encloses the base onto which the baits are placed. We conducted a pilot, captive trial and found that captive wild boar fed from the BOSTM either directly, by lifting the cone, or indirectly, by feeding once another animal had lifted the cone. Thus, we tested whether free-living wild boar fed from the BOSTM and whether the BOSTM could prevent bait uptake by nontarget species. We observed that free-living wild boar fed regularly from the BOSTM and that the device successfully prevented bait uptake by nontarget species. The BOSTM should be trialed more extensively to confirm its effectiveness and species-specificity to distribute pharmaceuticals to wild suids. If successful, the BOSTM could be used to deliver vaccines in disease control programs as well as contraceptives to manage overabundant populations of wild suids. 相似文献
14.
Phylogeny of the parasitic wasp subfamily Euphorinae (Braconidae) and evolution of its host preferences 下载免费PDF全文
The braconid subfamily Euphorinae is a large, cosmopolitan group of endoparasitoid wasps. The majority of species attack adult hosts, a strategy that is rare among parasitic wasps, but there are also many species that attack nymphs and larval stages. Euphorine hosts may belong to a variety of insect orders (Coleoptera, Hemiptera, Hymenoptera, Neuroptera, Psocoptera, Orthoptera and Lepidoptera) although most euphorine tribes are confined to Coleoptera. Here we investigate the phylogenetic relationships of the Euphorinae based on molecular data (3 kb of nucleotide data from four markers: 18S, 28S, CAD and COI) and propose a higher‐level classification based upon the resulting phylogeny. We also infer the evolution of host associations and discuss the diversification of the Euphorinae. Results from both Bayesian inference and maximum‐likelihood analysis show that the subfamily, as previously circumscribed, is paraphyletic. We propose that the subfamily be expanded to include the tribes Meteorini and Planitorini (Mannokeraia + Planitorus), so that it corresponds to a clade that is strongly supported as monophyletic in our analyses. Based on our results, a revised higher classification of the Euphorinae is proposed, in which 52 extant genera and 14 tribes are recognized. We reinstate the genus Microctonus belonging to the tribe Perilitini, and synonymize Ussuraridelus with Holdawayella, Sinuatophorus with Eucosmophorus. Furthermore, we propose the following tribal rearrangements: Spathicopis and Stenothremma are transferred to Perilitini; Tuberidelus, Eucosmophorus and Plynops to Cosmophorini; Ecclitura to Dinocampini; Chrysopophthorus, Holdawayella and Wesmaelia to Helorimorphini; Proclithroporus and Heia to Townesilitini. The monotypic tribe Cryptoxilonini is synonymized with Cosmophorini. The genera Pygostolus and Litostolus are placed in a separate tribe, Pygostolini, previously recognized as a subtribe among the Centistini. Parsimony‐based ancestral state reconstructions suggest that the ancestor of Euphorinae was a parasitoid of lepidopteran larvae, and that a host shift to larval Coleoptera occurred only in one clade of the Meteorini, some members of which secondarily shifted back to larval lepidopteran hosts. In the remainder of the subfamily, there was an initial shift from larval to adult coleopterans, followed by subsequent shifts to adults or larvae of Hemiptera, Hymenoptera, Neuroptera, Orthoptera and Psocoptera. 相似文献
15.
Phosphorus recycling in photorespiration maintains high photosynthetic capacity in woody species 下载免费PDF全文
DAVID S. ELLSWORTH KRISTINE Y. CROUS HANS LAMBERS JULIA COOKE 《Plant, cell & environment》2015,38(6):1142-1156
Leaf photosynthetic CO2 responses can provide insight into how major nutrients, such as phosphorus (P), constrain leaf CO2 assimilation rates (Anet). However, triose‐phosphate limitations are rarely employed in the classic photosynthesis model and it is uncertain as to what extent these limitations occur in field situations. In contrast to predictions from biochemical theory of photosynthesis, we found consistent evidence in the field of lower Anet in high [CO2] and low [O2] than at ambient [O2]. For 10 species of trees and shrubs across a range of soil P availability in Australia, none of them showed a positive response of Anet at saturating [CO2] (i.e. Amax) to 2 kPa O2. Three species showed >20% reductions in Amax in low [O2], a phenomenon potentially explained by orthophosphate (Pi) savings during photorespiration. These species, with largest photosynthetic capacity and Pi > 2 mmol P m?2, rely the most on additional Pi made available from photorespiration rather than species growing in P‐impoverished soils. The results suggest that rarely used adjustments to a biochemical photosynthesis model are useful for predicting Amax and give insight into the biochemical limitations of photosynthesis rates at a range of leaf P concentrations. Phosphate limitations to photosynthetic capacity are likely more common in the field than previously considered. 相似文献
16.
17.
18.
19.
20.