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排序方式: 共有135条查询结果,搜索用时 15 毫秒
1.
Gaute W. Seljestad María Quintela Ellika Faust Kim T. Halvorsen Franois Besnier Eeva Jansson Geir Dahle Halvor Knutsen Carl Andr Arild Folkvord Kevin A. Glover 《Ecology and evolution》2020,10(12):6120-6135
Capture and long‐distance translocation of cleaner fish to control lice infestations on marine salmonid farms has the potential to influence wild populations via overexploitation in source regions, and introgression in recipient regions. Knowledge of population genetic structure is therefore required. We studied the genetic structure of ballan wrasse, a phenotypically diverse and extensively used cleaner fish, from 18 locations in Norway and Sweden, and from Galicia, Spain, using 82 SNP markers. We detected two very distinct genetic groups in Scandinavia, northwestern and southeastern. These groups were split by a stretch of sandy beaches in southwest Norway, representing a habitat discontinuity for this rocky shore associated benthic egg‐laying species. Wrasse from Galicia were highly differentiated from all Scandinavian locations, but more similar to northwestern than southeastern locations. Distinct genetic differences were observed between sympatric spotty and plain phenotypes in Galicia, but not in Scandinavia. The mechanisms underlying the geographic patterns between phenotypes are discussed, but not identified. We conclude that extensive aquaculture‐mediated translocation of ballan wrasse from Sweden and southern Norway to western and middle Norway has the potential to mix genetically distinct populations. These results question the sustainability of the current cleaner fish practice. 相似文献
2.
Halvor Aarnes 《Planta》1978,140(2):185-192
Homoserine kinase was purified 700-fold by fractional ammonium sulfate precipitation, heat treatment, CM-Sephadex C-50 and DEAE-Sephadex A-50 ion exchange chromatography, and Sephadex G-100 gel filtration. The reaction products O-phosphohomoserine and ADP were the only compounds which caused considerable inhibition of homoserine kinase activity. Product inhibition studies showed non-competitive inhibition between ATP and O-phosphohomoserine and between homoserine and O-phosphohomoserine, and competitive inhibition between ATP and ADP. ADP showed non-competitive inhibition versus homoserine at suboptimal concentrations of ATP. At saturating concentrations of ATP no effect of ADP was observed. The homoserine kinase activity was negligible in the absence of K+ and the Km value for K+ was observed to be 4.3 mmol l–1. A non-competitive pattern was observed with respect to the substrates homoserine and ATP. Threonine synthase in the first green leaf of 6-day-old barley seedlings was partially purified 15-fold by ammonium sulfate fractionation and Sephadex G-100 gel chromatography. Threonine synthase was shown to require pyridoxal 5-phosphate as coenzyme for optimum activity and the enzyme was strongly activated by S-adenosyl-L-methionine. The optimum pH for threonine synthase activity was 7 to 8.Abbreviations PLP
Pyridoxal 5-phosphate
- SAM
S-adenosyl-L-methionine
- HSP
O-phosphohomoserine 相似文献
3.
Multiplex real-time PCR for monitoring Heterobasidion annosum colonization in Norway spruce clones that differ in disease resistance 总被引:1,自引:0,他引:1
Hietala AM Eikenes M Kvaalen H Solheim H Fossdal CG 《Applied and environmental microbiology》2003,69(8):4413-4420
A multiplex real-time PCR assay was developed to monitor the dynamics of the Picea abies-Heterobasidion annosum pathosystem. Tissue cultures and 32-year-old trees with low or high resistance to this pathogen were used as the host material. Probes and primers were based on a laccase gene for the pathogen and a polyubiquitin gene for the host. The real-time PCR procedure was compared to an ergosterol-based quantification method in a tissue culture experiment, and there was a strong correlation (product moment correlation coefficient, 0.908) between the data sets. The multiplex real-time PCR procedure had higher resolution and sensitivity during the early stages of colonization and also could be used to monitor the host. In the tissue culture experiment, host DNA was degraded more rapidly in the clone with low resistance than in the clone with high resistance. In the field experiment, the lesions elicited were not strictly proportional to the area colonized by the pathogen. Fungal colonization was more restricted and localized in the lesion in the clone with high resistance, whereas in the clone with low resistance, the fungus could be detected until the visible end of the lesion. Thus, the real-time PCR assay gives better resolution than does the traditionally used lesion length measurement when screening host clones for resistance. 相似文献
4.
5.
A fragment of the amyloid beta protein, βA(25-35), was investigated for its effect on production of reactive oxygen species (ROS) in human neutrophil granulocytes. The formation and identification of ROS were examined by using a 2',7'-dichlorofluorescin (DCF) fluorescence assay, a luminol chemiluminescence assay, electron paramagnetic resonance (EPR) spectroscopy with DEPMPO as a spin trap, and hydroxylation of 4-hydroxybenzoate (4-HBA). The DCF assay showed that βA(25-35) stimulated formation of ROS in a concentration and time dependent manner. The inverted peptide, βA(35-25), gave no response. Also, luminol-amplified chemiluminescence was stimulated by βA(25-35). Incubation with diethyldithiocarbamate (a superoxide dimustase inhibitor) and salicylhydroxamate (SHA; a myeloperoxidase inhibitor) reduced the chemiluminescence. This indicates that hypochlorous acid (HOCl) is formed after exposure to βA(25-35). The EPR spectra indicated a concentration dependent formation of superoxide ( O 2 • - ) - and hydroxyl ( •OH)- radicals. Hydroxylation of 4-HBA to 3,4,-dihydroxybenzoate confirmed production of •OH. This response was attenuated by SHA, indicating involvement of HOCl in formation of •OH. The DCF fluorescence was inhibited with U0126 (an extracellular signal regulated protein kinase (ERK) inhibitor). Further analysis with western blot confirmed phosphorylation of ERK1/2 after exposure to βA(25-35). The phospholipase A 2 (PLA 2 ) inhibitor 7,7-dimethyl-(5Z,8Z)-eicosadienoic acid, and diphenyleneiodonium, which inhibits the NADPH oxidase, also led to a reduction of the DCF fluorescence. The present findings indicate that βA(25-35) stimulates the NADPH oxidase by activating the ERK pathway and PLA 2 . Production of O 2 • - can lead to HOCl and further formation of •OH, which both have a cytotoxic potential. 相似文献
6.
Nina Elisabeth Nagy Vincent R Franceschi Harald Kvaalen Halvor Solheim 《Trees - Structure and Function》2005,19(6):695-703
In field experiments, clones of Norway spruce [Picea abies (L.) Karst.] showed different degrees of resistance against pathogenic fungi inoculated into the bark that correlate with
differences in polyphenolic parenchyma (PP) cells of the bark. Cells of spruce callus cultures, particularly towards the callus
surface, resemble PP cells and this study looks at changes in callus cells during infection and the relative resistance of
cultures from clones of low (weak) or high (strong) resistance to fungal infection. Callus cultures, initiated from trees
with different resistance, were co-inoculated with Ceratocystis polonica (Siem.) C. Moreau and Heterobasidion annosum (Fr.) Bref. Callus cells from strong clones resemble PP cells of bark tissue from strong clones, having more polyphenolic
bodies, while callus cells from weak clones are more similar to PP cells from those clones, which have less extensive phenolic
bodies. Callus cultures from trees with weak resistance were more quickly overgrown by both species of pathogenic fungi than
cultures from trees with strong resistance. Callus cells of infected cultures showed changes similar to activated PP cells
of bark, including enhanced accumulation of polyphenolics. Phenolic bodies were more numerous and more extensive (larger and
denser) in callus cells of strong versus weak clones under all conditions. Thus, callus cells may perform similar functions
in defense as PP cells in the bark. Callus from trees of varying resistance seem to reflect the relative resistance of the
trees from which they are derived, and this study indicates that some mechanisms of resistance can be studied using callus
from trees of different resistance. 相似文献
7.
Halvor Rollag Thor Ueland Anders ?sberg Anders Hartmann Alan G. Jardine Atul Humar Mark D. Pescovitz Angelo A. Bignamini P?l Aukrust 《PloS one》2013,8(4)
Background
While several studies have examined the general inflammatory responses in relation to cytomegalovirus infection, the identification of the various inflammatory mediators as well as their relative importance is far from clear.Patients and Methods
Solid organ recipients enrolled in an international multicenter trial of cytomegalovirus disease treatment (the VICTOR study) were analyzed (n = 289) (ClinicalTrials.gov ). Plasma markers of inflammation and endothelial cell activation were assessed at baseline by enzyme immunoassays. NCT00431353Results
The major findings were: (i) Plasma levels of the CXC-chemokine interferon-inducible protein-10 (P<0.001) and C-reactive protein (P = 0.046) were independently associated with the presence of cytomegalovirus DNAemia above lower level of quantification. (ii) High levels of CC-chemokine ligand 21 (P = 0.027) and pentraxin 3 (P = 0.033) were independently associated with tissue invasive cytomegalovirus disease as opposed to cytomegalovirus syndrome.Conclusion
Our findings illustrate the complex interaction between cytomegalovirus and the immune system, involving a wide range of inflammatory mediators that could be associated to disease manifestations in cytomegalovirus related disease. 相似文献8.
Lumbwe Chola Lars T. Fadnes Ingunn M. S. Engebretsen Lungiswa Nkonki Victoria Nankabirwa Halvor Sommerfelt James K. Tumwine Thorkild Tylleskar Bjarne Robberstad PROMISE-EBF Study Group 《PloS one》2015,10(11)
Background
Community based breastfeeding promotion programmes have been shown to be effective in increasing breastfeeding prevalence. However, there is limited data on the cost-effectiveness of these programmes in sub-Saharan Africa. This paper evaluates the cost-effectiveness of a breastfeeding promotion intervention targeting mothers and their 0 to 6 month old children.Methods
Data were obtained from a community randomized trial conducted in Uganda between 2006–2008, and supplemented with evidence from several studies in sub-Saharan Africa. In the trial, peer counselling was offered to women in intervention clusters. In the control and intervention clusters, women could access standard health facility breastfeeding promotion services (HFP). Thus, two methods of breastfeeding promotion were compared: community based peer counselling (in addition to HFP) and standard HFP alone. A Markov model was used to calculate incremental cost-effectiveness ratios between the two strategies. The model estimated changes in breastfeeding prevalence and disability adjusted life years. Costs were estimated from a provider perspective. Uncertainty around the results was characterized using one-way sensitivity analyses and a probabilistic sensitivity analysis.Findings
Peer counselling more than doubled the breastfeeding prevalence as reported by mothers, but there was no observable impact on diarrhoea prevalence. Estimated incremental cost-effectiveness ratios were US$68 per month of exclusive or predominant breastfeeding and U$11,353 per disability adjusted life year (DALY) averted. The findings were robust to parameter variations in the sensitivity analysesConclusions
Our strategy to promote community based peer counselling is unlikely to be cost-effective in reducing diarrhoea prevalence and mortality in Uganda, because its cost per DALY averted far exceeds the commonly assumed willingness-to-pay threshold of three times Uganda’s GDP per capita (US$1653). However, since the intervention significantly increases prevalence of exclusive or predominant breastfeeding, it could be adopted in Uganda if benefits other than reducing the occurrence of diarrhoea are believed to be important. 相似文献9.
10.
In winter 2000–2001, there was a serious outbreak of Gremmeniella abietina Morelet in southeastern Norway. During the outbreak, we noted that injured Scots pine trees (Pinus sylvestris L.) developed secondary buds in response to the fungus attack, and we decided to study the relationship between injury, appearance
of secondary buds and recovery of the trees thereafter. For this purpose, 143 trees from 10 to 50 years of age were chosen
and grouped into crown density classes. Injury was assessed in detail, and buds were counted before bud burst in the spring
of 2002. In addition, a subset of 15 trees was followed through the summer of 2002 to assess recovery. All injured trees developed
secondary buds, with a clear overweight of dormant winter buds in proportion to interfoliar buds. Healthy control trees did
not develop secondary buds at all. The secondary buds appeared predominantly on the injured parts of the tree; interfoliar
buds in particular developed just beneath the damaged tissue. Most of the secondary buds died during the winter of 2001–2002,
mainly because the fungus continued to spread after the first outbreak. Many of the remaining buds developed shoots with abnormal
growth during the summer. Secondary buds may help trees to recover from Gremmeniella attacks, but this strategy may fail when the fungus continues to grow and injure the newly formed buds and shoots. 相似文献