Keywords: Social wasps; Hornet nest; Thermal homeostasis; Thermoregulation 相似文献
全文获取类型
收费全文 | 6383篇 |
免费 | 554篇 |
国内免费 | 1篇 |
出版年
2021年 | 57篇 |
2019年 | 52篇 |
2018年 | 76篇 |
2017年 | 71篇 |
2016年 | 126篇 |
2015年 | 199篇 |
2014年 | 222篇 |
2013年 | 330篇 |
2012年 | 341篇 |
2011年 | 325篇 |
2010年 | 240篇 |
2009年 | 207篇 |
2008年 | 314篇 |
2007年 | 349篇 |
2006年 | 290篇 |
2005年 | 299篇 |
2004年 | 302篇 |
2003年 | 293篇 |
2002年 | 332篇 |
2001年 | 123篇 |
2000年 | 115篇 |
1999年 | 105篇 |
1998年 | 109篇 |
1997年 | 78篇 |
1996年 | 71篇 |
1995年 | 99篇 |
1994年 | 71篇 |
1993年 | 63篇 |
1992年 | 90篇 |
1991年 | 102篇 |
1990年 | 89篇 |
1989年 | 99篇 |
1988年 | 78篇 |
1987年 | 59篇 |
1986年 | 55篇 |
1985年 | 73篇 |
1984年 | 71篇 |
1983年 | 53篇 |
1982年 | 70篇 |
1981年 | 63篇 |
1979年 | 47篇 |
1978年 | 51篇 |
1977年 | 37篇 |
1976年 | 48篇 |
1975年 | 43篇 |
1974年 | 42篇 |
1973年 | 43篇 |
1971年 | 38篇 |
1970年 | 38篇 |
1968年 | 37篇 |
排序方式: 共有6938条查询结果,搜索用时 15 毫秒
1.
Patterns generated from ecological surveys are rarely tested in similar habitats to assess the accuracy of predictions. Testing empirically derived predictions provides a strong tool for establishing the consistency of general patterns in ecology. We test the consistency of beetle community associations with habitat complexity in open canopy forests and make both community and morphospecies-level comparisons with results from a previous study. We use Normalized Difference Vegetation Indices (NDVIs) from remote sensing as a surrogate for habitat complexity. The positive relationships between NDVIs and site-based beetle species richness and abundance were consistent in open canopy forests both south and north of Sydney, Australia. NDVIs were also useful for predicting differences in beetle composition in open canopy forests. Taxon-specific responses to NDVI differences in 'southern forests' were very similar to responses in 'northern forests', most likely reflecting beetle trophic roles. This study shows that NDVIs can be used as rapid biodiversity indicators, when integrated with identified faunal responses to vegetation structure, provided that the lower vegetation strata may be measured by remote sensing. 相似文献
2.
The Biology of CRISPR-Cas: Backward and Forward 总被引:1,自引:0,他引:1
Frank Hille Hagen Richter Shi Pey Wong Majda Bratovič Sarah Ressel Emmanuelle Charpentier 《Cell》2018,172(6):1239-1259
3.
4.
Hairless (H) is the major antagonist within the Notch signalling pathway of Drosophila melanogaster. By binding to Suppressor of Hairless [Su(H)] and two co-repressors, H induces silencing of Notch target genes in the absence of Notch signals. We have applied genomic engineering to create several new H alleles. To this end the endogenous H locus was replaced with an attP site by homologous recombination, serving as a landing platform for subsequent site directed integration of different H constructs. This way we generated a complete H knock out allele H
attP, reintroduced a wild type H genomic and a cDNA-construct (H
gwt, H
cwt) as well as two constructs encoding H proteins defective of Su(H) binding (H
LD, H
iD). Phenotypes regarding viability, bristle and wing development were recorded, and the expression of Notch target genes wingless and cut was analysed in mutant wing discs or in mutant cell clones. Moreover, genetic interactions with Notch (N
5419) and Delta (Dl
B2) mutants were addressed. Overall, phenotypes were largely as expected: both H
LD and H
iD were similar to the H
attP null allele, indicating that most of H activity requires the binding of Su(H). Both rescue constructs H
gwt and H
cwt were homozygous viable without phenotype. Unexpectedly, the hemizygous condition uncovered that they were not identical to the wild type allele: notably H
cwt showed a markedly reduced activity, suggesting the presence of as yet unidentified regulatory or stabilizing elements in untranslated regions of the H gene. Interestingly, H
gwt homozygous cells expressed higher levels of H protein, perhaps unravelling gene-by-environment interactions. 相似文献
5.
6.
- 1. With the derived free-run temperature of light paper nests the influence of the thermal capacity of the nest or the nest site, respectively, on thermal homeostasis is quantified.
2. Gravimetric information from the continuous investigation of the nest weight coupled with temperature and humidity measurement allows the correlation of the colonies’ foraging behavior with their heat production inside the nest.
3. Wasps (Vespa crabro) do not regulate their nest environment towards a specific and constant temperature but rather build nests adapted to their foraging behavior and general energy budget.
7.
Sunscreens protect the skin against erythemal radiation (Eer). But at the same time they reduce the effective radiation dose (EVD) responsible for the formation of previtamin D in the skin. The paper describes a calculation method for optimizing the ratio EVD/Eer behind sunscreens e.g. with SPF 5, 15 and 30 respectively. Taking into account that a majority of people in industrialized countries suffer from a shortage in vitamin D even in summer time, the ratio Evd/Eer is a new and important criterion for the quality of sunscreens. Furthermore the exposure time tvd needed per day for forming the equivalent of the recommended amount of 2000 IU of vitamin D per day for skin type 2 is estimated when sunscreens with different filter compositions are used. In vitro experiments show a significant increase of the conversion of 7-dehydrocholesterol (7-DHC) to previtamin D when exposed to artificial solar radiation behind an experimental sunscreen optimized for previtamin D production compared to a commercial sunscreen having the same SPF. 相似文献
8.
A lightweight finger printing stand is described which can be adjusted to the proper printing height. Based upon experience printing over 1,100 subjects, 12 advantages of using the stand are suggested. 相似文献
9.
In order to measure the flow-dynamical effect of arteriosclerotic changes of the vessel wall we determined volume elasticity E' and modulus of elasticity of 53 human aortae in a static p-V-test as other authors did, too. The p-V-curves are normalized to the aortic basic volume Vo, so that we could determine the haemodynamic effect of arteriosclerosis immediately from E' and. Diameter, length, and, accordingly, the basic volume of the aorta without prestressing increase significantly in aortae with severe arteriosclerosis in comparison to those without sclerosis. The volume elasticity E' as a function of the static aortic pressure has a minimum within physiological pressure range and changes into a linear function when arteriosclerosis increases. The modulus of elasticity of a normal aorta remains constant within a pressure range of 20 to 100 mm Hg and it shows a linear increase at higher pressure. The differences between Vo, E' and of aortae with and without severe arteriosclerosis, however, are highly significant. 相似文献
10.