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51.
Ultraviolet inactivation and excision-repair in Bacillus subtilis. II. Differential inactivation and differential repair of transforming markers 总被引:6,自引:0,他引:6
Ultraviolet inactivation of transforming Bacillus subtilis markers was studied with the aid of an eightfold auxotrophic recipient and its excision-repair-deficient derivative. The results allow the following conclusions. (i) Wild-type B. subtilis cells are able to repair approx. 80% of the UV-induced lesions causing inactivation of transforming activity in UV-sensitive recipients; (ii) Saturating amounts of donor DNA increase the apparent marker sensitivities. This phenomenon is most pronounced in transformation of UV-sensitive recipients; (iii) various markers are inactivated to different degrees, both when assayed on the wild-type as well as on the UV-sensitive strain; (iv) Various markers are repaired to different degrees in the wild-type recipient. 相似文献
52.
The purpose of this work was to evaluate the effects of ethylene action blockade and cold storage on the ripening of ‘Golden’
papaya fruit. Papayas harvested at maturity stage 1 (up to 15% yellow skin) were evaluated. Half of the fruits, whether treated
or not treated with 100 nL L−1 of 1-methylcyclopropene (1-MCP), were stored at 23°C, while the other half were stored at 11°C for 20 days prior to being
stored at 23°C. Non-refrigerated fruits receiving 1-MCP application presented a reduction in respiratory activity, ethylene
production, skin color development and pectinmethylesterase activity. Even with a gradual increase in ethylene production
at 23°C, fruits treated with 1-MCP maintained a high firmness, but presented a loss of green skin color. Cold storage caused
a decrease in ethylene production when fruits were transferred to 23°C. The results suggest that pulp softening is more dependent
on ethylene than skin color development, and that some processes responsible for loss of firmness do not depend on ethylene. 相似文献
53.
Fourgeux C Bron A Acar N Creuzot-Garcher C Bretillon L 《Chemistry and physics of lipids》2011,164(6):496-499
Free cholesterol is the predominant form of cholesterol in the neural retina. The vertebrate neural retina exhibits its own capacity to synthesize cholesterol and meets its demand also by taking it from the circulation. Defects in cholesterol synthesis and trafficking in the neural retina has detrimental consequences on its structure and function, highlighting the crucial importance of maintaining cholesterol homeostasis in the retina. Our purpose was to give a review on the functioning of the retina, the role of cholesterol and cholesterol metabolism therein, with special emphasis on cholesterol-24S-hydroxylase (CYP46A1). Similar to the brain, the retina expresses cholesterol-24S-hydroxylase (CYP46A1) and is enriched in its metabolic product, 24S-hydroxycholesterol. We recently published that one single nucleotide polymorphism in CYP46A1 gene, designated as rs754203, was a risk factor for glaucoma. Glaucoma is the second leading cause of blindness worldwide, affecting more than 60 million people. Glaucoma is characterized by the loss of retinal ganglion cells, which show high CYP46A1 expression. These data suggest the potential involvement of CYP46A1 and 24S-hydroxycholesterol in the pathophysiology of glaucoma. 相似文献
54.
Ghrelin, a peptide hormone from the stomach, has been recently discovered to reduce sodium excretion from the kidney. Although
the effects on the kidney suggest actions in the distal nephron, the sites of expression of ghrelin receptors have not been
localised. In the present work we have used a mouse that expresses green fluorescent protein under the control of the ghrelin
receptor promoter to locate sites of receptor expression in the kidney. Receptor expression was confined to the straight parts
of the distal tubules and the thin limbs of the loops of Henle. No expression was detected in other structures, including
the glomeruli, proximal tubules and collecting ducts. Ghrelin receptors were not found in extra-renal or intra-renal arteries,
despite observations that ghrelin is a vasodilator. The distribution revealed by in situ hybridisation histochemistry was the same as that revealed by the reporter. In conclusion, ghrelin receptors have a restricted
distribution in the kidney. The location in the straight parts of the distal tubules accords with observations that ghrelin
promotes sodium retention. 相似文献
55.
Ontogenetic changes in the location, size, density and morphology of chloride cells in the Nile tilapia Oreochromis niloticus adapted to fresh and brackish water are described using Na(+) /K(+) -ATPase immunohistochemistry, light microscopy (LM), scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM). The pattern of chloride cell distribution changed during development under both treatments, with chloride cell density decreasing significantly from hatch to 7 days post-hatch, but appearing on the inner opercular area at 3 days post-hatch and increasing significantly thereafter (P < 0·05). Chloride cells were always denser in fresh- than in brackish-water larvae. In both treatments, chloride cells located on the outer operculum and tail showed a marked increase in size with age, but cells located on the abdominal epithelium of the yolk sac and the inner operculum showed a significant decrease in size (P < 0·05). Chloride cells from brackish-water adapted larvae from 1 day post-hatch onwards were always significantly larger (P < 0·05) than those from freshwater-adapted larvae. SEM revealed structural differences in chloride cell apical morphology according to environmental conditions. There appears to be clearly defined temporal staging of the appearance of adaptive mechanisms that confer an ability to cope with varying environmental conditions during early development. 相似文献
56.
Diego I. Cattoni Shreyasi Thakur Cedric Godefroy Antoine Le Gall Josephine Lai-Kee-Him Pierre-Emmanuel Milhiet Patrick Bron Marcelo N?llmann 《Nucleic acids research》2014,42(4):2624-2636
SpoIIIE/FtsK are a family of ring-shaped, membrane-anchored, ATP-fuelled motors required to segregate DNA across bacterial membranes. This process is directional and requires that SpoIIIE/FtsK recognize highly skewed octameric sequences (SRS/KOPS for SpoIIIE/FtsK) distributed along the chromosome. Two models have been proposed to explain the mechanism by which SpoIIIE/FtsK interact with DNA. The loading model proposes that SpoIIIE/FtsK oligomerize exclusively on SpoIIIE recognition sequence/orienting polar sequences (SRS/KOPS) to accomplish directional DNA translocation, whereas the target search and activation mechanism proposes that pre-assembled SpoIIIE/FtsK hexamers bind to non-specific DNA, reach SRS/KOPS by diffusion/3d hopping and activate at SRS/KOPS. Here, we employ single-molecule total internal reflection imaging, atomic force and electron microscopies and ensemble biochemical methods to test these predictions and obtain further insight into the SpoIIIE–DNA mechanism of interaction. First, we find that SpoIIIE binds DNA as a homo-hexamer with neither ATP binding nor hydrolysis affecting the binding mechanism or affinity. Second, we show that hexameric SpoIIIE directly binds to double-stranded DNA without requiring the presence of SRS or free DNA ends. Finally, we find that SpoIIIE hexamers can show open and closed conformations in solution, with open-ring conformations most likely resembling a state poised to load to non-specific, double-stranded DNA. These results suggest how SpoIIIE and related ring-shaped motors may be split open to bind topologically closed DNA. 相似文献
57.
58.
Philippe Koehrer Sarah Saab Olivier Berdeaux Rodica Isa?co Stéphane Grégoire Stéphanie Cabaret Alain M. Bron Catherine P. Creuzot-Garcher Lionel Bretillon Niyazi Acar 《PloS one》2014,9(9)
Background
Long chain polyunsaturated fatty acids (LCPUFAs) including docosahexaenoic acid and arachidonic acid are suspected to play a key role in the pathogenesis of diabetes. LCPUFAs are known to be preferentially concentrated in specific phospholipids termed as plasmalogens. This study was aimed to highlight potential changes in the metabolism of phospholipids, and particularly plasmalogens, and LCPUFAs at various stages of diabetic retinopathy in humans.Methodology and Principal Findings
We performed lipidomic analyses on red blood cell membranes from controls and mainly type 2 diabetes mellitus patients with or without retinopathy. The fatty acid composition of erythrocytes was determined by gas chromatography and the phospholipid structure was determined by liquid chromatography equipped with an electrospray ionisation source and coupled with a tandem mass spectrometer (LC-ESI-MS/MS). A significant decrease in levels of docosahexaenoic acid and arachidonic acid in erythrocytes of diabetic patients with or without retinopathy was observed. The origin of this decrease was a loss of phosphatidyl-ethanolamine phospholipids esterified with these LCPUFAs. In diabetic patients without retinopathy, this change was balanced by an increase in the levels of several phosphatidyl-choline species. No influence of diabetes nor of diabetic retinopathy was observed on the concentrations of plasmalogen-type phospholipids.Conclusions and Significance
Diabetes and diabetic retinopathy were associated with a reduction of erythrocyte LCPUFAs in phosphatidyl-ethanolamines. The increase of the amounts of phosphatidyl-choline species in erythrocytes of diabetic patients without diabetic retinopathy might be a compensatory mechanism for the loss of LC-PUFA-rich phosphatidyl-ethanolamines. 相似文献59.
Stephanie J. Salyer Esther M. Ellis Corvil Salomon Christophe Bron Stanley Juin Ryan R. Hemme Elizabeth Hunsperger Emily S. Jentes Roc Magloire Kay M. Tomashek Anne Marie Desormeaux Jorge L. Mu?oz-Jordán Lesly Etienne Manuela Beltran Tyler M. Sharp Daphne Moffett Jordan Tappero Harold S. Margolis Mark A. Katz 《PLoS neglected tropical diseases》2014,8(10)
In October 2012, the Haitian Ministry of Health and the US CDC were notified of 25 recent dengue cases, confirmed by rapid diagnostic tests (RDTs), among non-governmental organization (NGO) workers. We conducted a serosurvey among NGO workers in Léogane and Port-au-Prince to determine the extent of and risk factors for dengue virus infection. Of the total 776 staff from targeted NGOs in Léogane and Port-au-Prince, 173 (22%; 52 expatriates and 121 Haitians) participated. Anti-dengue virus (DENV) IgM antibody was detected in 8 (15%) expatriates and 9 (7%) Haitians, and DENV non-structural protein 1 in one expatriate. Anti-DENV IgG antibody was detected in 162 (94%) participants (79% of expatriates; 100% of Haitians), and confirmed by microneutralization testing as DENV-specific in 17/34 (50%) expatriates and 42/42 (100%) Haitians. Of 254 pupae collected from 68 containers, 65% were Aedes aegypti; 27% were Ae. albopictus. Few NGO workers reported undertaking mosquito-avoidance action. Our findings underscore the risk of dengue in expatriate workers in Haiti and Haitians themselves. 相似文献
60.