全文获取类型
收费全文 | 92篇 |
免费 | 10篇 |
出版年
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2008年 | 9篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 2篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1959年 | 1篇 |
1958年 | 6篇 |
1957年 | 2篇 |
1956年 | 1篇 |
1955年 | 3篇 |
1954年 | 2篇 |
1953年 | 5篇 |
1952年 | 5篇 |
1950年 | 3篇 |
1949年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有102条查询结果,搜索用时 31 毫秒
11.
12.
Leaf phenology mediates provenance differences in herbivore populations on valley oaks in a common garden 下载免费PDF全文
IAN S. PEARSE JILL H. BATY DUSTIN HERRMANN RICHARD SAGE WALTER D. KOENIG 《Ecological Entomology》2015,40(5):525-531
1. Plants from different populations often display a variation in herbivore resistance. However, it is rarely understood what plant traits mediate such differences. 2. It was tested how leaf phenology affects herbivore populations in a 15‐year‐old common garden of valley oaks (Quercus lobata Née) with different populations and maternal parents from throughout the Q. lobata range. 3. The abundance of leaf miners (Stigmella sp. Shrank) and leaf phenology of oaks in the common garden was measured. 4. Leaf miner abundance varied among provenance locations (population), but not among maternal parents within populations. Leaf phenology varied by provenance location and maternal parent, and trees that leafed out earlier accrued higher leaf‐miner abundance. Path analysis indicated that leaf phenology was the likely driver of provenance and parental differences in resistance to leaf miners. 5. Understanding population differences is particularly important when considering transport of genotypes for ornamental or restoration purposes. The present study suggests that similarity in leaf phenology may be one factor that could be used to find genotypes with a similar herbivore resistance to local genotypes. 相似文献
13.
1. Plant–plant communication has been found to affect interactions between herbivores and plants in several model systems. In these systems, herbivore‐induced volatile chemical cues are emitted and perceived by other plants (receivers), which subsequently change their defensive phenotypes. Most studies have focused on how the effects of volatile cues affect plant damage, whereas herbivore performance has rarely been examined. 2. In this study, it is shown that plant–plant communication between willows reduced the growth rate, feeding rate, and conversion efficiency of some individuals but not others of a generalist caterpillar, Orgyia vetusta. 3. Using a paired, no‐choice trial design, there was substantial variation between caterpillar individuals in their response to willows that had been induced with a volatile plant–plant cue. This variation was explained by feeding parameters of the individual herbivores. Individuals behaved similarly when fed induced and non‐induced willow leaves. Specifically, growth rates of caterpillars that grew rapidly on non‐induced willow leaves were negatively affected by plant–plant cues, but growth rates of caterpillars that grew slowly on non‐induced willow leaves were not affected by the responses to volatiles from neighbouring willows. 4. Induction by volatile plant–plant cues reduced the growth rates of those individual herbivores that caused the greatest damage to willow, but had little effect on weak growers. 相似文献
14.
JENNIFER KROSS RICHARD M. KAMINSKI KENNETH J. REINECKE EDWARD J. PENNY AARON T. PEARSE 《The Journal of wildlife management》2008,72(3):707-714
Abstract: Managed moist-soil units support early succession herbaceous vegetation that produces seeds, tubers, and other plant parts used by waterfowl in the Mississippi Alluvial Valley (MAV), USA. We conducted a stratified multi-stage sample survey on state and federal lands in the MAV of Arkansas, Louisiana, Mississippi, and Missouri during autumns 2002–2004 to generate a contemporary estimate of combined dry mass of seeds and tubers (herein seed abundance) in managed moist-soil units for use by the Lower Mississippi Valley Joint Venture (LMVJV) of the North American Waterfowl Management Plan. We also examined variation in mean seed abundance among moist-soil units in 2003 and 2004 in relation to management intensity (active or passive), soil pH and nutrient levels, proportional occurrence of plant life-forms (e.g., grass, flatsedge, and forb; vine; woody plants), and unit area. Estimates of mean seed abundance were similar in 2002 (x̄ = 537.1 kg/ha, SE = 100.1) and 2004 (x̄ = 555.2 kg/ha, SE = 105.2) but 35–40% less in 2003 (x̄ = 396.8 kg/ha, SE = 116.1). Averaged over years, seed abundance was 496.3 kg/ha (SE = 62.0; CV = 12.5%). Multiple regression analysis indicated seed abundance varied among moist-soil units inversely with proportional occurrence of woody vegetation and unit area and was greater in actively than passively managed units (R2adj = 0.37). Species of early succession grasses occurred more frequently in actively than passively managed units (P ≤ 0.09), whereas mid- and late-succession plants occurred more often in passively managed units (P ≤ 0.02). We recommend the LMVJV consider 556 kg/ha as a measure of seed abundance for use in estimating carrying capacity in managed moist-soil units on public lands in the MAV. We recommend active management of moist-soil units to achieve maximum potential seed production and further research to determine recovery rates of seeds of various sizes from core samples and the relationship between seed abundance and unit area. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):707–714; 2008) 相似文献
15.
Thomas GH; Newbern EC; Korte CC; Bales MA; Muse SV; Clark AG; Kiehart DP 《Molecular biology and evolution》1997,14(12):1285-1295
Many structural, signaling, and adhesion molecules contain tandemly
repeated amino acid motifs. The alpha-actinin/spectrin/dystrophin
superfamily of F-actin-crosslinking proteins contains an array of triple
alpha-helical motifs (spectrin repeats). We present here the complete
sequence of the novel beta-spectrin isoform beta(Heavy)- spectrin (beta H).
The sequence of beta H supports the origin of alpha- and beta-spectrins
from a common ancestor, and we present a novel model for the origin of the
spectrins from a homodimeric actin-crosslinking precursor. The pattern of
similarity between the spectrin repeat units indicates that they have
evolved by a series of nested, nonuniform duplications. Furthermore, the
spectrins and dystrophins clearly have common ancestry, yet the repeat unit
is of a different length in each family. Together, these observations
suggest a dynamic period of increase in repeat number accompanied by
homogenization within each array by concerted evolution. However, today,
there is greater similarity of homologous repeats between species than
there is across repeats within species, suggesting that concerted evolution
ceased some time before the arthropod/vertebrate split. We propose a
two-phase model for the evolution of the spectrin repeat arrays in which an
initial phase of concerted evolution is subsequently retarded as each new
protein becomes constrained to a specific length and the repeats diverge at
the DNA level. This evolutionary model has general applicability to the
origins of the many other proteins that have tandemly repeated motifs.
相似文献
16.
Higher‐order assemblies of oligomeric cargo receptor complexes form the membrane scaffold of the Cvt vesicle 下载免费PDF全文
Arjen J Jakobi Abul K Tarafder Yury S Bykov Andrea Picco Wanda Kukulski Jan Kosinski Wim JH Hagen Arvind C Ravichandran Matthias Wilmanns Marko Kaksonen John AG Briggs Carsten Sachse 《EMBO reports》2016,17(7):1044-1060
Selective autophagy is the mechanism by which large cargos are specifically sequestered for degradation. The structural details of cargo and receptor assembly giving rise to autophagic vesicles remain to be elucidated. We utilize the yeast cytoplasm‐to‐vacuole targeting (Cvt) pathway, a prototype of selective autophagy, together with a multi‐scale analysis approach to study the molecular structure of Cvt vesicles. We report the oligomeric nature of the major Cvt cargo Ape1 with a combined 2.8 Å X‐ray and negative stain EM structure, as well as the secondary cargo Ams1 with a 6.3 Å cryo‐EM structure. We show that the major dodecameric cargo prApe1 exhibits a tendency to form higher‐order chain structures that are broken upon interaction with the receptor Atg19 in vitro. The stoichiometry of these cargo–receptor complexes is key to maintaining the size of the Cvt aggregate in vivo. Using correlative light and electron microscopy, we further visualize key stages of Cvt vesicle biogenesis. Our findings suggest that Atg19 interaction limits Ape1 aggregate size while serving as a vehicle for vacuolar delivery of tetrameric Ams1. 相似文献
17.
In the course of a freeze-cleave study on intercellular junctions in the regenerating rat liver, we observed an unusual array of intramembranous particles located in regions of contact between endothelial cells lining the hepatic sinusoids. These arrays were characterized by an accumulation of particles which resembled a zonula occludens in their linear deployment but differed in that the contact regions were composed of individual particles which remained separated from each other by regular particle-free intervals. 相似文献
18.
Experimental Studies of the Factors Controlling Transpiration: II. THE RELATION BETWEEN TRANSPIRATION RATE AND LEAF WATER CONTENT 总被引:1,自引:0,他引:1
GREGORY F. G.; MILTHORPE F. L.; PEARSE H. L.; SPENCER H. J. 《Journal of experimental botany》1950,1(1):15-28
Data are presented which show, when stomatal control is eliminated,that wheat leaves may lose 56 per cent. and Pelargoniumleaves 1012 per cent. of their water without any reductionin the transpiration rate. Experiments in which Pelargonium and wheat leaves, with stomatalcontrol present, were submitted to cycles of changing watercontent also failed to establish any direct relation betweentranspiration rate and leaf water content. It is concluded that leaf water content over the range of 70100per cent. of that present in the turgid state has no significanteffect in determining the rate of water loss from leaves. A repetition of Knight's experiment showed that stomata openedin still air and closed in moving air. This was not recordedby Knight, who used a porometer cup permanently attached tothe leaf. It is concluded that the higher transpiration raterecorded by Knight after a period of still air was due to widerstomatal aperture and not to the higher leaf water content assuggested by him. 相似文献
19.
20.
A homologous family of UDP- N -acetylgalactosamine: polypeptide N -
acetylgalactosaminyltransferases (GalNAc-transferases) initiate O-
glycosylation. These transferases share overall amino acid sequence
similarities of approximately 45-50%, but segments with higher similarities
of approximately 80% are found in the putative catalytic domain. Here we
have characterized the genomic organization of the coding regions of three
GalNAc-transferase genes and determined their chromosomal localization. The
coding regions of GALNT1 , -T2 , and -T3 were found to span 11, 16, and 10
exons, respectively. Several intron/exon boundaries were conserved within
the three genes. One conserved boundary was shared in a homologous C.
elegans GalNAc- transferase gene. Fluorescence in situ hybridization showed
that GALNT1 , -T2 , and -T3 are localized at chromosomes 18q12-q21,
1q41-q42, and 2q24-q31, respectively. These results suggest that the
members of the polypeptide GalNAc-transferase family diverged early in
evolution from a common ancestral gene through gene duplication.
相似文献