全文获取类型
收费全文 | 1287篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
1313篇 |
出版年
2013年 | 21篇 |
2012年 | 32篇 |
2011年 | 49篇 |
2010年 | 67篇 |
2009年 | 52篇 |
2008年 | 62篇 |
2007年 | 68篇 |
2006年 | 46篇 |
2005年 | 47篇 |
2004年 | 25篇 |
2003年 | 22篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 23篇 |
1997年 | 35篇 |
1996年 | 27篇 |
1995年 | 31篇 |
1994年 | 22篇 |
1993年 | 20篇 |
1992年 | 32篇 |
1991年 | 30篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 13篇 |
1985年 | 23篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 8篇 |
1980年 | 26篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1974年 | 16篇 |
1973年 | 20篇 |
1972年 | 28篇 |
1971年 | 32篇 |
1958年 | 12篇 |
1957年 | 12篇 |
1956年 | 11篇 |
1955年 | 11篇 |
1954年 | 14篇 |
1953年 | 11篇 |
1952年 | 19篇 |
排序方式: 共有1313条查询结果,搜索用时 0 毫秒
1.
EMMA DESPLAND MARIA GUNDERSEN SIMON P. DAOUST BRIAN J. MADER NATHALIE DELVAS PAUL J. ALBERT ERIC BAUCE 《Physiological Entomology》2011,36(1):39-46
The pattern of feeding of Eastern spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera, Tortricidae) is compared on foliage from white spruce Picea glauca (Moench) Voss. (Pinaceae) trees previously determined to be susceptible and resistant to defoliation by budworm. No differences are observed in electrophysiological responses from taste sensilla to aqueous extracts of the two foliage types, nor is there a preference for either extract type in a choice test. Acetone extracts from the two foliage types are both preferred to a control sucrose solution, although neither elicits a preference relative to the other. These results suggest that there is no difference in phagostimulatory power of internal leaf contents of the two foliage types. Longer‐term observation of feeding behaviour in a no‐choice situation shows no difference in meal duration, confirming the lack of difference in phagostimulatory power. However, on average, intermeal intervals are twice as long on the resistant foliage, leading to an overall lower food consumption during the assay. This result suggests an anti‐digestive or toxic effect of the resistant foliage that slows behaviour and limits food intake. Previous research has shown that waxes of the resistant foliage deter initiation of feeding by the spruce budworm and that this foliage contains higher levels of tannins and monoterpenes. The data suggest that the resistant foliage contains a post‐ingestive second line of defence against the spruce budworm. 相似文献
2.
3.
Neopomacentrus filamentosus, a common damselfish on the Indo–Australian archipelago, undergoes significant shifts in size and mitochondrial genetic structure upon larval settlement and metamorphosis to juvenile stages. We characterized five polymorphic microsatellite loci in order to study temporal genetic shifts within a single generation of N. filamentosus sampled first as larval settlers then again as demersal juvenile recruits. All loci were extremely polymorphic and exhibited high levels of heterozygosity. While all loci from the larval samples conformed to Hardy – Weinberg expectations, significant heterozygote deficiencies were seen in two loci in the juvenile samples, likely due to extreme size‐selective mortality imposed post‐settlement. 相似文献
4.
5.
Novel strategies for assessing and managing the risks posed by invasive alien species to global crop production and biodiversity 总被引:3,自引:0,他引:3
RICHARD BAKER RAY CANNON PAUL BARTLETT IAN BARKER 《The Annals of applied biology》2005,146(2):177-191
International actions to combat the threat posed by invasive alien species (IAS) to crops and biodiversity have intensified in recent years. The formulation of 15 guiding principles on IAS by the Convention on Biological Diversity (CBD) stimulated the International Plant Protection Convention (IPPC) to review its role in protecting biodiversity. IPPC standards now demonstrate clearly that the risks posed by any organism that is directly or indirectly injurious to cultivated or uncultivated plants can be assessed and managed under the IPPC. Since the IPPC, unlike the CBD, constitutes an international legal instrument recognised by the World Trade Organization, greater protection from the introduction of IAS is now available. However, phytosanitary measures can only be enacted if they can be justified by risk analysis and we outline some novel strategies to improve the assessment and management of the risks posed by IAS, highlighting some of the key challenges which remain. 相似文献
6.
Prorocentrum micans Ehrenberg, a free-living marine dinoflagellate, was used to test the intracellular toxic action of cadmium. The cells were cultivated in Erdschreiber medium, with Cd concentrations of 10–100 ppb. Thin sections of treated cells, examined ultramicroscopically, exhibited vacuolations, increased numbers of lysosomes, and severe mitochondrial damage. The first two alterations are a general response to toxicity; the third is Cd specific. Although some chloroplasts were affected by Cd, they were not very sensitive to its action. The nuclear apparatus was not morphologically affected. 相似文献
7.
8.
DAVID WEETMAN LORENZ HAUSER PAUL W. SHAW MICHELLE K. BAYES 《Molecular ecology resources》2005,5(2):361-362
Five microsatellite loci are described for the commercially exploited marine gastropod, Buccinum undatum. Levels of polymorphism were variable with three to 19 alleles per locus and expected heterozygosities of 0.26–0.94 in 60 individuals of the population from which the loci were isolated. Homozygote excess at two of the loci might be attributable to null alleles, and these loci should not be used in, for example, parentage analysis. Nevertheless, because null allele frequencies can be estimated and their effects partitioned, all are useful markers for studies of population differentiation. 相似文献
9.
10.