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991.
Anna C. Lewis Katrina J. Rankin Andrew J. Pask Devi Stuart‐Fox 《Ecology and evolution》2017,7(20):8262-8272
Stress is an important potential factor mediating a broad range of cellular pathways, including those involved in condition‐dependent (i.e., honest) color signal expression. However, the cellular mechanisms underlying the relationship between stress and color expression are largely unknown. We artificially elevated circulating corticosterone levels in male tawny dragon lizards, Ctenophorus decresii, to assess the effect of stress on the throat color signal. Corticosterone treatment increased luminance (paler throat coloration) and decreased the proportion of gray, thereby influencing the gray reticulations that produce unique patterning. The magnitude of change in luminance for corticosterone‐treated individuals in our study was around 6 “just noticeable differences” to the tawny dragon visual system, suggesting that lizards are likely to be able to perceive the measured variation. Transmission electron microscopy (TEM) of iridophore cells indicated that luminance increased with increasing density of iridophore cells and increased spacing (and/or reduced size) of crystalline guanine platelets within them. Crystal spacing within iridophores also differed between skin colors, being greater in cream than either gray or yellow skin and greater in orange than yellow skin. Our results demonstrate that stress detectably impacts signal expression (luminance and patterning), which may provide information on individual condition. This effect is likely to be mediated, at least in part, by structural coloration produced by iridophore cells. 相似文献
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993.
Conventional autophagy is a lysosome-dependent degradation process that has crucial homeostatic and regulatory functions in eukaryotic organisms. As malaria parasites must dispose a number of self and host cellular contents, we investigated if autophagy in malaria parasites is similar to the conventional autophagy. Genome wide analysis revealed a partial autophagy repertoire in Plasmodium, as homologs for only 15 of the 33 yeast autophagy proteins could be identified, including the autophagy marker Atg8. To gain insights into autophagy in malaria parasites, we investigated Plasmodium falciparum Atg8 (PfAtg8) employing techniques and conditions that are routinely used to study autophagy. Atg8 was similarly expressed and showed punctate localization throughout the parasite in both asexual and sexual stages; it was exclusively found in the pellet fraction as an integral membrane protein, which is in contrast to the yeast or mammalian Atg8 that is distributed among cytosolic and membrane fractions, and suggests for a constitutive autophagy. Starvation, the best known autophagy inducer, decreased PfAtg8 level by almost 3-fold compared to the normally growing parasites. Neither the Atg8-associated puncta nor the Atg8 expression level was significantly altered by treatment of parasites with routinely used autophagy inhibitors (cysteine (E64) and aspartic (pepstatin) protease inhibitors, the kinase inhibitor 3-methyladenine, and the lysosomotropic agent chloroquine), indicating an atypical feature of autophagy. Furthermore, prolonged inhibition of the major food vacuole protease activity by E64 and pepstatin did not cause accumulation of the Atg8-associated puncta in the food vacuole, suggesting that autophagy is primarily not meant for degradative function in malaria parasites. Atg8 showed partial colocalization with the apicoplast; doxycycline treatment, which disrupts apicoplast, did not affect Atg8 localization, suggesting a role, but not exclusive, in apicoplast biogenesis. Collectively, our results reveal several atypical features of autophagy in malaria parasites, which may be largely associated with non-degradative processes. 相似文献
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995.
Sarvamangala J.N. Devi Arthur B. Karpas Carl E. Frasch 《FEMS immunology and medical microbiology》1996,14(4):211-220
Abstract Murine monoclonal antibodies (mAbs) were generated using group B Neisseria meningitidis and Escherichia coli K1 polysaccharides (PSs) conjugated to outer membrane vesicle (OMV) via adipic acid dihydrazide, and were used to identify the immunodeterminants expressed on these capsular PSs. Ten mAbs representative of IgM and all subclasses of IgG were obtained which recognized diverse immunodeterminants on α(2 → 8) polysialic acid (PSA). The specificity of mAbs to different antigenic determinants was assessed by their differential binding to PSA attached to a solid phase by different methods and confirmed by absorption studies. Two mAbs from the E. coli K1 fusion were directed to the O -acetyl epitope and the rest reacted with both the PSs only when attached to a solid phase by certain means. The methods by which PSA was coated on the solid phase had an impact on the epitope expression and binding pattern. At the concentrations used, the O -acetyl-specific mAbs, IgG1 and IgG3 mAbs were not bactericidal against group B N. meningitidis , whereas other mAbs were. The conjugates B and K1 PSs present to the murine immune system different antigenic determinants, some of which elicit bactericidal antibodies. 相似文献
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997.
Tim S. Jessop Rita Chan Devi Stuart-Fox 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(7):619-630
In some species, females develop bright colouration to signal reproductive status and exhibit behavioural repertoires to incite
male courtship and/or reduce male harassment and forced copulation. Sex steroids, including progesterone and testosterone,
potentially mediate female reproductive colouration and reproductive behaviour. We measured associations among plasma profiles
of testosterone and progesterone with variation in colour expression and reproductive behaviour, including unique courtship
rejection behaviours, in female Lake Eyre dragon lizards, (Ctenophorus maculosus). At onset of breeding, progesterone and testosterone increased with vitellogenesis, coincident with colour intensification
and sexual receptivity, indicated by acceptance of copulations. As steroid levels peaked around the inferred ovulation time,
maximal colour development occurred and sexual receptivity declined. When females were gravid and exhibited maximal mate rejection
behaviours, progesterone levels remained consistently high, while testosterone exhibited a discrete second peak. At oviposition,
significant declines in plasma steroid levels, fading of colouration and a dramatic decrease in male rejection behaviours
co-occurred. Our results indicate a generally concordant association among steroid levels, colouration, behaviour and reproductive
events. However, the prolonged elevation in progesterone and a second peak of testosterone was unrelated to reproductive state
or further colour change, possibly suggesting selection on females to retain high steroid levels for inducing rejection behaviours. 相似文献
998.
999.
1000.
Haimanti Biswas Subhadra Devi Gadi V. Venkata Ramana M. Durga Bharathi R. Kesava Priyan D. Taruni Manjari M. Dileep Kumar 《Biodiversity and Conservation》2012,21(5):1309-1326
The role of microzooplankton (MZP) in the pelagic trophodynamics is highly significant, but the responses of marine MZP to
increasing CO2 levels are rather poorly understood. Hence the present study was undertaken to understand the responses of marine plankton
to increasing CO2 concentrations. Natural water samples from the coastal Bay of Bengal were incubated under the ambient condition and high
CO2 levels (703–711 μatm) for 5 days in May and June 2010. A significant negative correlation was obtained between phytoplankton
and MZP abundance which indicated that phytoplankton community structure can considerably be controlled by MZP in this region.
The average relative abundances of tintinnids under elevated CO2 levels were found to be significantly higher (68.65 ± 5.63% in May; 85.46 ± 9.56% in June) than observed in the ambient condition
(35.68 ± 6.83% in May; 79 ± 5.36% in June). The observed dominance of small chain forming diatom species probably played a
crucial role as they can be potentially grazed by tintinnids. This fact was strengthened by the observed high negative correlations
between the relative abundance of major phytoplankton and tintinnids. Moreover, particulate organic carbon and total bacterial
counts were also enhanced under elevated CO2 level and can serve as additional food source for ciliates. The observed responses of tintinnids to increasing CO2 might have multiple impacts on the energy transfer, nutrient and carbon cycling in the coastal water. The duration of the
present study was relatively short and therefore further investigation on longer time scale needs to be done and might give
us a better insight about phytoplankton and MZP species succession under elevated CO2 level. 相似文献