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排序方式: 共有98条查询结果,搜索用时 15 毫秒
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KA Hyndman DH Evans 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2009,152(1):58-65
We recently determined that rapid changes in environmental salinity alter endothelin-1 (EDN1) mRNA levels in the euryhaline killifish, Fundulus heteroclitus, so we hypothesized that EDN1 may be a local regulator of gill ion transport in teleost fishes. The purpose of the present study was to examine the effects of changes in environmental salinity on the gill endothelin receptors: EDNRA, EDNRB, and EDNRC. Using quantitative real-time PCR, we determined that after a fresh water (FW) to seawater (SW) transfer, there is a two to threefold increase in gill EDNRA and EDNRB mRNA levels. Likewise, we found a two to three fold increase in gill EDNRA and EDNRB protein concentration. In addition, killifish that have acclimated to FW for 30 days had significantly lower EDNRA mRNA and protein levels than SW killifish. ENDRA were immunolocalized to the mitochondrion-rich cells of the killifish gill, suggesting that EDN1 signaling cascades may affect MRC function. EDNRB were found throughout the gill vasculature and on lamellar pillar cells. We previously immunolocalized EDN1 to the pillar cell suggesting that EDN1 acts as an autocrine signaling molecule and potentially regulates pillar cell tone and lamellar perfusion. We conclude that EDN1 is physiologically active in the teleost gill, and regulated by environmental salinity. Future functional studies examining the physiological role of this system are necessary to completely understand EDN1 in the fish gill. 相似文献
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Aeromonas hydrophila and A. salmonicida grown in pure cultures were found to secrete extracellular membrane nanovesicles into the environment. Outer membrane nanovesicle
preparations were isolated by differential centrifugation and ultrafiltration and visualized by transmission electron microscopy
applying the negative staining technique. Membrane nanovesicle size (10–300 nm) and ultrastructure were determined. The vesicles
were especially numerous around bacteria at the edge of small colonies. The process of the vesicle budding off the bacterial
cell was observed. On ultrathin sections of rat intestine, outer membrane nanovesicles were revealed among bacterial aggregates
of various species of parietal microorganisms. Short chains of such vesicles were also detected inside the glycocalyx between
the microvilli of the apical surface of the intestine epitheliocytes. On the basis of the results, together with the literature
data, the secretion of the outer membrane nanovesicles by pathogenic gram-negative bacteria, such as A. hydrophila and A. salmonicida, is proposed as a possible mechanism of pathogenesis leading to the host disease, as well as a means for cellular interactions
both within the prokaryote population and between the bacteria and the host organism. 相似文献
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Lennart KA Lundblad Lisa M Rinaldi Matthew E Poynter Erik P Riesenfeld Min Wu Steven Aimi Leesa M Barone Jason HT Bates Charles G Irvin 《Respiratory research》2011,12(1):27
Background
Inhaled short acting β2-agonists (SABA), e.g. albuterol, are used for quick reversal of bronchoconstriction in asthmatics. While SABA are not recommended for maintenance therapy, it is not uncommon to find patients who frequently use SABA over a long period of time and there is a suspicion that long term exposure to SABA could be detrimental to lung function. To test this hypothesis we studied the effect of long-term inhaled albuterol stereoisomers on immediate allergic response (IAR) and airway hyperresponsiveness (AHR) in mouse models of asthma.Methods
Balb/C mice were sensitized and challenged with ovalbumin (OVA) and then we studied the IAR to inhaled allergen and the AHR to inhaled methacholine. The mice were pretreated with nebulizations of either racemic (RS)-albuterol or the single isomers (S)- and (R)-albuterol twice daily over 7 days prior to harvest.Results
We found that all forms of albuterol produced a significant increase of IAR measured as respiratory elastance. Similarly, we found that AHR was elevated by albuterol. At the same time a mouse strain that is intrinsically hyperresponsive (A/J mouse) was not affected by the albuterol isomers nor was AHR induced by epithelial disruption with Poly-L-lysine affected by albuterol.Conclusions
We conclude that long term inhalation treatment with either isomer of albuterol is capable of precipitating IAR and AHR in allergically inflamed airways but not in intrinsically hyperresponsive mice or immunologically naïve mice. Because (S)-albuterol, which lacks affinity for the β2-receptor, did not differ from (R)-albuterol, we speculate that isomer-independent properties of the albuterol molecule, other than β2-agonism, are responsible for the effect on AHR. 相似文献68.
Abstract The palatability to common carp, Cyprinus carpio L. of three newly developed differently flavoured floating pellets made from a high proportion (40%) of brewer's spent grain (BSG) was tested using a multiple-offer feeding experiment. The addition of ‘bold’ flavours, such as vanilla or strawberry essence, may help mask the unpleasant taste of some piscicides; however, their inclusion must not compromise uptake by carp. There were no significant differences between the consumption rates of the three varieties, and all flavours were readily consumed. Therefore, it is suggested that highly flavoured pellets made with BSG have a strong potential to mask the flavour of an unpalatable toxin, and further research is now needed to test this hypothesis. 相似文献
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Multiple interspecies transmissions of human and simian T-cell leukemia/lymphoma virus type I sequences 总被引:8,自引:0,他引:8
Using two sets of nucleotide sequences of the human and simian T-cell
leukemia/lymphoma virus type I (HTLV-I/STLV-I), one consisting of 522 bp of
the env gene from 70 viral strains and the other a 140-bp segment from the
pol gene of 52 viral strains, I estimated cladograms based on a statistical
parsimony procedure that was developed specifically to estimate
within-species gene trees. An extension of a nesting procedure is offered
for sequence data that forms nested clades used in hypothesis testing. The
nested clades were used to test three hypotheses relating to transmission
of HTLV/STLV sequences: (1) Have cross-species transmissions occurred and,
if so, how many? (2) In what direction have they occurred? (3) What are the
geographic relationships of these transmission events? The analyses support
a range of 11-16 cross-species transmissions throughout the history of
these sequences. Additionally, outgroup weights were assigned to haplotypes
using arguments from coalescence theory to infer directionality of
transmission events. Conclusions on geographic origins of transmission
events and particular viral strains are inconclusive due to small samples
and inadequate sampling design. Finally, this approach is compared directly
to results obtained from a traditional maximum parsimony approach and found
to be superior at establishing relationships and identifying instances of
transmission.
相似文献