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排序方式: 共有312条查询结果,搜索用时 31 毫秒
1.
Summary Factors affecting the polyethylene glycol (PEG)-induced membrane fusion were examined. Human erythrocyte membrane ghosts, cytoskeleton-free vesicles budded from erythrocytes, mechanically disrupted erythrocyte vesicles, and recombinant vesicles from glycophorin and egg phosphatidylcholine were used as models. Fusion was monitored by darkfield light microscopy and by freeze-fracture electron microscopy. Osmotic swelling was found necessary for fusion between membrane ghosts following PEG treatment. The sample with the highest fusion percentage was sealed ghosts incubated in hypotonic media after at least 5 min of treatment in <25% PEG. At similar osmolarity, glycerol, dextran and PEG produced progressively more pronounced intramembranous particle (IMP) patching, correlating with their increasing fusion percentages. The patching of IMP preceded cell-cell contact, and occurred without direct PEG-protein interaction. The presence of cytoskeletal elements in small vesicles had no significant effect on fusion, nor on the aggregation of intramembranous particle (IMP) upon PEG treatment. Disrupting the membrane by lysolecithin, dimethylsulfoxide, retinol or mild sonication resulted in the fragmentation of ghosts without an increase in fusion percentage. The purity of the commercial PEG used had no apparent effect on fusion. We concluded that the key steps in PEG-induced fusion of cell membrane are the creation of IMP-free zones, and the osmotic swelling of cells after the formation of bilayer contacts during the PEG treatment. Cell cytoskeleton affects PEG-induced fusion only to the extent of affecting IMP patching. 相似文献
2.
G. Yelenosky 《Plant Growth Regulation》1985,3(1):47-53
Rate of extension growth, as measured by height, of 2-month-old Valencia orange trees (Citrus sinensis (L.) Osbeck) on rough lemon rootstock (C. limon Burm. f.) was reduced to 0.5 mm from 5.0 mm day–1 with 0.1% (w/v) sprays of the growth retardant AMO-1618 (4 hydroxy-5-isopropyl-2-methyl phenyl trimethyl-ammonium chloride, 1 piperdine carboxylate) every 2 weeks during 11 weeks under natural daylight in a glasshouse. Trees sprayed with AMO-1618 were 10-fold shorter, more compact in appearance, and leaves were greener and more oval shaped than those on untreated trees. There was no chemical burn. AMO-1618-sprayed trees were more cold hardy than untreated trees during controlled-temperature, cold-hardening regimes. Alone, AMO-1618 had no effect on freeze tolerance at -5.5° C. AMO-1618 also was associated with greater tree tolerance to freeze injury determined by O2 uptake in Valencia leaves to as low as -6.7° C.This paper reports the results of research only. Mention of a trademark of a proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be suitable. 相似文献
3.
D. R. Joanisse K. B. Storey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(3):247-255
The activity of some enzymes of intermediary metabolism, including enzymes of glycolysis, the hexose monophosphate shunt, and polyol cryoprotectant synthesis, were measured in freeze-tolerant Eurosta solidaginis larvae over a winter season and upon entry into pupation. Flexible metabolic rearrangement was observed concurrently with acclimatization and development. Profiles of enzyme activities related to the metabolism of the cryoprotectant glycerol indicated that fall biosynthesis may occur from two possible pathways: 1. glyceraldehyde-phosphate glyceraldehyde glycerol, using glyceraldehyde phosphatase and NADPH-linked polyol dehydrogenase, or 2. dihydroxyacetonephosphate glycerol-3-phosphate glycerol, using glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase. Clearance of glycerol in the spring appeared to occur by a novel route through the action of polyol dehydrogenase and glyceraldehyde kinase. Profiles of enzyme activities associated with sorbitol metabolism suggested that this polyol cryoprotectant was synthesized from glucose-6-phosphate through the action of glucose-6-phosphatase and NADPH-linked polyol dehydrogenase. Removal of sorbitol in the spring appeared to occur through the action of sorbitol dehydrogenase and hexokinase. Glycogen phosphorylase activation ensured the required flow of carbon into the synthesis of both glycerol and sorbitol. Little change was seen in the activity of glycolytic or hexose monophosphate shunt enzymes over the winter. Increased activity of the -glycerophosphate shuttle in the spring, indicated by greatly increased glycerol-3-phosphate dehydrogenase activity, may be key to removal and oxidation of reducing equivalents generated from polyol cryoprotectan catabolism.Abbreviations 6PGDH
6-Phosphogluconate dehydrogenase
- DHAP
dihydroxy acetone phosphate
- F6P
fructose-6-phosphate
- F6Pase
fructose-6-phospha-tase
- FBPase
fructose-bisphosphatase
- G3P
glycerol-3-phosphate
- G3Pase
glycerol-3-phosphate phophatase
- G3PDH
glycerol-3-phosphate dehydrogenase
- G6P
glucose-6-phosphate
- G6Pase
glucose-6-phosphatase
- G6PDH
glucose-6-phosphate dehydrogenase
- GAK
glyceraldehyde kinase
- GAP
glyceraldehyde-3-phosphate
- GAPase
glyceraldehyde-3-phosphatase
- GAPDH
glyceraldehyde-3-phosphate dehydrogenase
- GDH
glycerol dehydrogenase
- GPase
glycogen phosphorylase
- HMS
hexose monophosphate shunt
- LDH
lactate dehydrogenase
- NADP-IDH
NADP+-dependent isocitrate dehydrogenase
- PDHald
polyol dehydrogenase, glyceraldehyde activity
- PDHgluc
polyol dehydrogenase, glucose activity
- PFK
phosphofructokinase
- PGI
phosphoglucoisomerase
- PGK
phosphoglycerate kinase
- PGM
phosphoglucomutase
- PK
pyruvate kinase
- PMSF
phenylmethylsulfonylfluoride
- SoDH
sorbitol dehydrogenase
-
V
max
maximal enzyme activity
- ww
wet weight 相似文献
4.
We have previously reported that when garter snakesThamnophis sirtalis parietalis, a freeze tolerant species, were exposed to 5 h freezing at –2.5° C organs showed increases in the activities of anti-oxidant enzymes, especially catalase in skeletal muscle. This was interpreted to be an adaptation to deal with the potentially injurious postischemic situation of thawing. The present work analyzesin vitro oxidative inactivation of a possible target of postischemic-induced free radical damage, the secondary anti-oxidant defense glutathione-S transferase, and the protective role of endogenous catalase. Approximately 50% of GST activity from snake muscle homogenates was lost within 2 min after addition of H2O2 plus Fe(II) (0.4–2 mM) in media containing azide whereas addition of iron alone resulted in no damaging effects. The opposing effects of dimethyl sulfoxide and EDTA in modifying this process strongly suggested the involvement of ·OH radicals in the GST inactivation. A partial recovery of the activity was promoted by mercaptoethanol, indicating that sulphydryl groups oxidation participate in the mechanism of GST inactivation. Pre-incubation of the reaction media containing H2O2 caused protection of the GST activity only in the absence of azide, indicating that endogenous catalase modulates the extent of oxyradical damage. The protective pre-incubation effect was more efficacious when employing homogenates from lung and liver, organs that have higher catalase activities, as well as homogenates from freezing-exposed muscle (that show an 80% increase in catalase activity, compared with control). The protection against GST inactivation observed in muscle from frozen snakes demonstrates that increased anti-oxidant defenses during freezing exposure can be a key factor in controllingin vitro oxyradical damage. The implications for natural freeze tolerance are discussed. 相似文献
5.
真空负压和常规ABC法显示HPV—1抗原的应用比较 总被引:3,自引:1,他引:2
应用真空负压 ABC 法显示 HPV-1抗原比常规 ABC 法效果好,敏感性高,时间短,整个过程只需一个多小时,阳性物明显突出,颗粒均匀,色泽鲜艳,呈黄棕色,背景清晰等优点。还可提高抗体的稀释度,降低成本。与微波技术相比,具有设备简单,易于操作,安全可靠,不受条件限制,经对26例尖锐湿疣的病例进行多层次稀释度的研究,取得了满意的结果,认为该法值得推广应用。 相似文献
6.
Fusarium oxysporum f. sp. vasinfectum penetration hyphae infect living cells in the meristematic zone of cotton (Gossypium barbadense L.) roots. We characterized wall modifications induced by the fungus during infection of the protodermis using antibodies against callose, arabinogalactan-proteins, xyloglucan, pectin, polygalacturonic acid and rhamnogalacturonan I in high-pressure frozen, freeze-substituted root tissue. Using quantitative immunogold labelling we compared the cell walls before and after hyphal contact, cell plates with plasmodesmata during cytokinesis, and wall appositions induced by fungal contact. In the already-existing wall, fungal contact induced only minor modifications such as an increase of xyloglucan epitopes. Wall appositions mostly exhibited epitopes similar to the cell plate except that wall appositions had a much higher callose content. This study shows that wall appositions induced by Fusarium oxysporum hyphae are the result of normal cell wall synthesis and the addition of large amounts of callose. The appositions do not stop fungal growth. 相似文献
7.
Calcium-induced interaction of liposomes composed of pure phosphatidylserine (PS) has been studied using a rapid-mixing, rapid-freeze device. Freeze-fracture electron microscopy of this material revealed that liposomes react very rapidly after addition of calcium ions. After only 10 ms (the resolution of the technique) vesicle fusion was apparent. At the same time, however, vesicles also collapsed, and appeared as aggregates of flattened membranes. This may explain controversies which have arisen over vesicle fusion studied with more indirect methods. 相似文献
8.
L. T. Boni T. P. Stewart J. L. Alderfer S. W. Hui 《The Journal of membrane biology》1981,62(1-2):65-70
Summary Fusion between unilamellar vesicles of both egg phosphatidylcholine and bovine phosphatidylserine was induced by polyethylene glycol. Aggregation and fusion events were monitored by electron microscopy and turbidity measurements. The threshold concentration of polyethylene glycol for aggregation and fusion is found to be independent of lipid concentration. Typically, aggregation of phosphatidylcholine vesicles starts at 2.5% (wt/wt) polyethylene glycol, but fusion is not significant until the polyethylene glycol concentration reaches 35%. Multilamellar vesicles were formed as a result of fusion.Abbreviations PEG
Polyethylene glycol
- IMP
Intramembranous particle
- PC
Phosphatidylcholine
- PS
Phosphatidylserine
- SUV
Small unilamellar vesicles
- MLV
Multilamellar vesicles
- DPPC
Dipalmitoyl phosphatidylcholine
- DSC
Differential scanning calorimetry 相似文献
9.
L. T. Boni T. P. Stewart J. L. Alderfer S. W. Hui 《The Journal of membrane biology》1981,62(1-2):71-77
Summary Polyethylene glycol, a known cell fusogen, is found to induce the formation of structural defects in egg phosphatidylcholine multilamellar vesicles, as shown by freeze-fracture microscopy.31P NMR spectra of these vesicles reveal the existence of a nonbilayer (isotropic) phase. The observed disruption in the bilayers is believed to be associated with an intermediate stage of membrane fusion.Abbreviations PEG
Polyethylene glycol
- IMP
Intramembranous particle
- PC
Phosphatidylcholine
- PS
Phosphatidylserine
- SUV
Small unilamellar vesicles
- MLV
Multilamellar vesicles
- DPPC
Dipalmitoyl phosphatidylcholine
- DSC
Differential scanning calorimetry
- DMPC
Dimyristoylphosphatidylcholine
-
T
c
Phase transition temperature 相似文献
10.
Cell junctions and intercellular communication 总被引:1,自引:0,他引:1
J. -P. Revel S. B. Yancey D. J. Meyer B. Nicholson 《In vitro cellular & developmental biology. Plant》1980,16(12):1010-1017
Summary We have compared intercellular communication in normal and regenerating rat liver. Gap junctions are greatly reduced in size
and numbers 29 to 35 hr after hepatectomy, but we still find some 90% of hepatocytes coupled by electrophysiological criteria.
The spread of dyes such as carboxyfluorescein however is very limited in the regenerating organs as compared to the situation
in the controls. We show how the apparent discrepancies between morphological and physiological data can be reconciled. We
also present a summary of preliminary findings on the biosynthesis of gap junction protein and some of the conclusions one
can draw from the sequence of 58 amino acids at the amino terminal of the protein.
Presented in the symposium on Molecular and Morphological Aspects of Cell-Cell Communication at the 31st Annual Meeting of
the Tissue Culture Association, St. Louis, Missouri, June 1–5, 1980.
The original research described was supported by Grants GM 06965 and RR 07003 from the National Institute of Health, and funds
from the North-west Area Foundation. David Meyer and Barbara Yancey were the recipients of NIH postdoctoral fellowships (NS
06240 and AM05700). This symposium was supported in part by Contract 263-MD-025754 from the National Cancer Institute and
the Fogarty International Center. 相似文献