全文获取类型
收费全文 | 227篇 |
免费 | 9篇 |
专业分类
236篇 |
出版年
2016年 | 2篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 8篇 |
2011年 | 9篇 |
2010年 | 13篇 |
2009年 | 11篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1982年 | 2篇 |
1979年 | 4篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1958年 | 4篇 |
1957年 | 6篇 |
1956年 | 4篇 |
1955年 | 5篇 |
1954年 | 4篇 |
1953年 | 4篇 |
1952年 | 2篇 |
1951年 | 2篇 |
1950年 | 8篇 |
1948年 | 2篇 |
排序方式: 共有236条查询结果,搜索用时 15 毫秒
231.
232.
233.
ALEXANDRE GURBA VINCENT HARRACA JEAN‐LUC PERRET STEVE CASERA STÉPHANE DONNET PATRICK M. GUERIN 《Physiological Entomology》2012,37(3):250-257
Tsetse flies Glossina spp. (Diptera; Glossinidae) are blood‐feeding vectors of disease that are attracted to vertebrate hosts by odours and visual cues. Studies on how tsetse flies approach visual devices are of fundamental interest because they can help in the development of more efficient control tools. The responses of a forest tsetse fly species Glossina brevipalpis (Newstead) to human breath are tested in a wind tunnel in the presence or absence of a blue sphere as a visual target. The flight responses are video recorded with two motion‐sensitive cameras and characterized in three dimensions. Although flies make meandering upwind flights predominantly in the horizontal plane in the plume of breath alone, upwind flights are highly directed at the visual target presented in the plume of breath. Flies responding to the visual target fly from take‐off within stricter flight limits at lower ground speeds and with a significantly lower variance in flight trajectories in the horizontal plane. Once at the target, flies fly in loops principally in the horizontal plane within 40 cm of the blue sphere before descending in spirals beneath it. Successful field traps designed for G. brevipalpis take into account the strong horizontal component in local search behaviour by this species at objects. The results suggest that trapping devices should also take into account the propensity of G. brevipalpis to descend to the lower parts of visual targets. 相似文献
234.
ISABELLE AMAT SEBASTIEN BESNARD VINCENT FORAY PERRINE PELOSSE CARLOS BERNSTEIN EMMANUEL DESOUHANT 《Ecological Entomology》2012,37(6):480-489
1. Flight is an energy‐demanding behaviour in insects. In parasitic wasps, strategies of nutrient acquisition and allocation, resulting life‐history trade‐offs and relationships with foraging strategies and resource availability have received much attention. However, despite the ecological importance of dispersal between host and food patches, and the great impact energy diverted to flight should have on lifetime reproductive success, the eco‐physiology of flight in parasitoids is poorly understood. 2. The objective of this study is to (i) identify the energetic resources used to fuel flight, and (ii) relate nutrient type and rate of utilisation to selective pressures in terms of resource availability posed by the environment. 3. Using a flight mill and biochemical assays, we compared flight performance and nutrient dynamics during flight between two reproductive modes of the parasitoid Venturia canescens Gravenhorst, which is known to thrive preferentially in contrasted environments (i.e. natural vs. anthropogenic habitat), differing notably in host and food distribution. 4. Biochemical analyses of different nutrient types showed that glycogen is the flight fuel used by this species, yet no significant differences in its dynamics in flight were found between the two reproductive modes. 5. Results suggest that both glycogen quantity and flight performance are related to the diverging ecological conditions experienced by thelytokous and arrhenotokous strains. 相似文献
235.
PAOLO FASCE LAURA FASCE ALEXANDRE VILLERS FRANCO BERGESE VINCENT BRETAGNOLLE 《Ibis》2011,153(3):581-591
Few studies have quantified the dynamics of recovering populations of large raptors using long‐term, spatially explicit studies. Using data collected over 37 years in the western Italian Alps, we assessed the trends in distribution, abundance, fecundity and breeding population structure of Golden Eagles Aquila chrysaetos. Using the spatial distribution of territory centroids in 2007, we found that the spatial distribution of eagle territories was over‐dispersed up to 3 km. Although population size and total productivity increased from 1972 to 2008, the proportion of pairs that laid eggs showed a strong decline, falling to no more than 50% after 2003. On average, 15% of successful nests produced two fledglings, and productivity also declined over time. No significant relationship between population growth rate and total population size was detected, but the percentage of pairs that bred and breeding success showed evidence of density dependence, as they declined significantly with increasing density. Our results suggest that density dependence, operating across heterogeneous habitats, is currently regulating this population, while the carrying capacity may still be increasing. This may explain the apparent paradox of reduced breeding effort despite increasing total productivity. 相似文献
236.
WILLIAM A. GAHL BRIAN POTTERF DONNA DURHAM-PIERRE MURRAY H. BRILLIANT VINCENT J. HEARING 《Pigment cell & melanoma research》1995,8(5):229-233
Tyrosine is the endogenous substrate for melanin production within melanosomes, but the method of tyrosine transport into the melanosome has not been investigated. In the mouse, melanogenesis is disrupted by mutations in the p gene resulting in the pink-eyed dilution phenotype; it has been suggested that the p gene codes for a tyrosine transport protein. We determined that normal (melan-a) melanosome-rich granular fractions take up 10 μm [3H]tyrosine at 21.1 ± 6.1 (SEM, standard error of the mean) pmol/min/mg protein (N=7) compared with 21.3 ± 5.8 SEM pmol/min/mg protein (N=5) for pink-eyed dilution, whose plasma membrane tyrosine transport was also normal (Km 89 μM; Vmax 302 pmol/min/mg cell protein). We also demonstrated that pink-eyed dilution melanosomes are immature by virtue of their low density, high hexosaminidase activity, and lack of pigment. These data indicate that a tyrosine transport system exists in the melanosomal membrane and that the p gene does not encode a tyrosine transporter of critical importance. 相似文献