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1.
2.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
3.
T. Jermy 《Entomologia Experimentalis et Applicata》1993,66(1):3-12
Most hypotheses concerning the evolution of insect-plant relationships are based on the assumptions that, (1) phytophagous
insects reduce plant fitness, and that (2) insect-plant relationships are the result of unconstrained selection. It can be
shown, however, that there is little evidence to support these assumptions. As an alternative, it is proposed that the evolution
of insect-plant relationships results primarily from autonomous evolutionary events; namely from heritable functional changes
within the insects' nervous system that determine plant recognition and ultimately host plant specificity. These changes cannot
be evoked by selective ecological agents. They originate from intrinsic changes (mutationssensu lato) within the insect genome. Ecological factors play a secondary role: by either supporting or preventing the establishment
of the new genotype with the novel food preference.
This paper has been dedicated in warm friendship to Professor Louis M. Schoonhoven, the leading scientist in sensory physiology
of phytophagous insects, on the occasion of his 60th birthday. 相似文献
4.
5.
T. Jermy 《Entomologia Experimentalis et Applicata》1958,1(3):197-208
Zusammenfassung Zwecks Ausarbeitung biozönoseschonender, selektiver Bekämpfungsmethoden wurden die reflektorischen Bedingungen der Nahrungswahl des Kartoffelkäfers untersucht. Die überwinterten Käfer können im Freiland die Anwesenheit der Wirtspflanze höchstens aus einer Entfernung von einigen Dezimetern wahrnehmen. Jungkäfer sprechen nur nach erfolgter Dressur (= Nahrungsaufnahme) auf die von der Wirtspflanze stammenden olfaktorischen Reize an. Beim Auffinden der Pflanzen spielen die visuellen Reize bei den Alt- und Jungkäfern, allerdings nur aus kleinen Entfernungen, eine wichtige Rolle. Die Jungkäfer halten bei der Nahrungssuche eine konstante Laufrichtung ein. Die Frass-Stoffe sind nur begrenzt spezifisch, die Oligophagie des Kartoffelkäfers ist demnach auf eine negative Anpassung an vergällend wirkender Stimuli zurückzuführen. Die vergällende Wirkung der Stoffe ist von der chemischen Struktur weitgehend unabhängig. Eine Reduktion der Vermehrungsrate des Schädlings kann durch Veränderung des Reizstoffgehaltes der Wirtspflanze bzw. durch Anwendung von Vergällungsstoffen erreicht werden.
Summary In order to find selective control methods, which would not disturb the biocoenoses, the reflex mechanism of food finding and host selection by the Colorado potato beetle was investigated. The greater part of the overwintered beetles do not begin to feed just after emergence, but first migrate. Seeking the food they perceive the host plant in the field by olfaction from a distance of not more than a few decimetres. The newly hatched young beetles react upon the olfactostimuli coming from the host plant only after some training (= feeding). During the food-seeking of old and young beetles sight only plays an important role, however, within a very limited distance. If searching for food, young beetles keep a constant direction in creeping. In the Colorado beetle host selection depends mainly on taste. Feeding stimuli are not markedly specific; the oligophagy of the beetles is based largely upon the negative reactions to repellent stimuli. Repellency is to a great extent independent of chemical structure and is therefore to be found in the many different groups of compounds. For example the repellency of the Bordeaux mixture is very high and is thereupon able to reduce the rate of reproduction very considerably. The selective reduction of the biotic potential of the pest could be achieved (1) by changing the quantity of acceptants and rejectants in the host plant (by selection or by cultural methods) or (2) by applying repellents.相似文献
6.
大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育 总被引:1,自引:0,他引:1
本实验用免疫组织化学ABC法研究了大鼠胼胝体内神经肽Y免疫反应阳性(NPY-IR)纤维的生后发育。结果发现,许多NPY-IR纤维在大鼠出生时便存在于胼胝体内。NPY-IR胼胝体纤维的密度在生后1周内继续逐渐增高,在第2周内达到最高峰。之后,NPY-IR胼胝体纤维的密度逐渐下降,至第3周末时接近成年时的水平,即仅有少量NPY-IR纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多NPY-IR胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。 相似文献
7.
8.
Für eine effiziente Resistenzzüchtung stellt eine Resistenzprüfmethode, die eine schnelle und zuverlässige Evaluierung einer möglichst großen Zahl von Genotypen erlaubt, eine wichtige Voraussetzung dar. Für das Freiland wurde eine Preßluftinjektionsmethode entwickelt, die eine nahezu 100 %ige Infektion von Maispflanzen mit dem Zuckerrohrmosaik‐Virus (sugarcane mosaic virus, SCMV) und dem Maisver‐zwergungsmosaik‐Virus (maize dwarf mosaic virus, MDMV) garantiert. Bei den empfindlicheren Pflanzen im Gewächshaus hatte eine mechanische Inokulation von Hand Vorteile. 相似文献
9.
10.
Black AP Bhayani H Ryder CA Pugh MT Gardner-Medwin JM Southwood TR 《Arthritis research & therapy》2003,5(5):R277-R284
The aim of this research was to determine whether all memory T cells have the same propensity to migrate to the joint in patients
with juvenile idiopathic arthritis. Paired synovial fluid and peripheral blood mononuclear cell proliferative responses to
a panel of antigens were measured and the results correlated with a detailed set of laboratory and clinical data from 39 patients
with juvenile idiopathic arthritis. Two distinct patterns of proliferative response were found in the majority of patients:
a diverse pattern, in which synovial fluid responses were greater than peripheral blood responses for all antigens tested;
and a restricted pattern, in which peripheral blood responses to some antigens were more vigorous than those in the synovial
fluid compartment. The diverse pattern was generally found in patients with a high acute phase response, whereas patients
without elevated acute phase proteins were more likely to demonstrate a restricted pattern. We propose that an association
between the synovial fluid T cell repertoire and the acute phase response suggests that proinflammatory cytokines may influence
recruitment of memory T cells to an inflammatory site, independent of their antigen specificity. Additionally, increased responses
to enteric bacteria and the presence of αEβ7 T cells in synovial fluid may reflect accumulation of gut associated T cells
in the synovial compartment, even in the absence of an elevated acute phase response. This is the first report of an association
between the acute phase response and the T cell population recruited to an inflammatory site. 相似文献