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61.
62.
Scirpentriol and its seven acetylated derivatives comprise a family of type-A trichothecene toxins produced by several species
of Fusarium fungi. Out of this group 4,15-diacetoxyscirpenol has attracted most attention. It elicits toxic responses in several species
and was detected in a variety of substrates. Out of the three possible monoacetylated derivatives 15-monoacetoxyscirpenol
and the parent alcohol scirpentriol received some attention, whereas the remaining members of the family were mentioned in
few reports. The present review deals with the structure, biosynthesis, analysis and toxicity of scirpentriol toxins. Formation
by Fusarium species as well as culture conditions used for toxigenicity studies are reviewed; data about the natural occurrence of scirpentriol
toxins in different cereal types, cereal associated products as well as in non-grain matrices including potato and soya bean
are reported. Basing on literature reports about the toxicity of scirpentriol toxins an attempt is made to summarise the state
of knowledge for risk evaluation for human and animal health. 相似文献
63.
Ivanova V Kolarova M Aleksieva K Dornberger KJ Haertl A Moellmann U Dahse HM Chipev N 《Preparative biochemistry & biotechnology》2007,37(4):343-352
Sanionins A (1) and B (2) were isolated from the moss Sanionia georgico-uncinata, collected on the Antarctic Livingston Island. The compounds 1 and 2 were purified by solvent extraction, silica gel column chromatography, and preparative HPLC, consecutively. The structures of the both compounds were elucidated by 1D and 2D NMR experiments and mass spectrometric investigations. These compounds showed activity against important Gram-positive pathogens, such as mycobacteria, multiresistant staphylococci, and vancomycin resistant enterococci. This activity is combined with antiinflammatoric activity and low cytotoxicity. 相似文献
64.
Molecular genetics of pituitary development in zebrafish 总被引:1,自引:0,他引:1
65.
The reaction of ethyl vinyl ether and 2,3,4,6-tetra-O-acetyl-β-d-glucopyranose (1) in the presence of Hg-(OAc)2 and toluene-p-sulphonic acid as catalysts yielded the acetylated vinyl, l-ethoxyethyl, and l-ethoxybut-3-enyl glycosides in varying proportions. Crystalline l-ethoxybut-3-enyl 2,3,4,6-tetra-O-acetyl-β-d-glucopyranoside (2), vinyl 2,3,4,6-tetra-O-acetyl-α-d-glucopyranoside (3), and l-ethoxyethyl 2,3,4,6-tetra-O-acetyl-β-d-glucopyranoside (4) were isolated by chromatography. Compound 4 was also prepared by the reaction of 1 with cold acetaldehyde diethyl acetal containing a trace of acetic acid, and its α anomer (5) by the reaction of 1 with boiling acetaldehyde diethyl acetal containing a trace of acetic acid. Each deacetylated d-glucoside was cleaved by the corresponding d-glucosidase, to yield d-glucose and either acetaldehyde (from deacetylated 3-5) or but-3-enal (from deacetylated 2). 相似文献
66.
Hans-Martin Müller 《Archives of microbiology》1960,36(4):350-359
Zusammenfassung Ein Stamm von Aspergillus niger häuft in einer physiologisch alkalischen Nährlösung bei 43° mehr Oxalsäure an als bei 30°. Dieser Unterschied beruht auf der verstärkten Anhäufung vor dem Zeitpunkt des völligen Glucoseverbrauches.Die autolytische Herkunft des größten Teils der nach diesem Zeitpunkt bei 30° und 43° noch hinzukommenden Oxalsäure wird nachgewiesen, ebenso die Intensivierung der Autolyse bei der hohen Temperatur. Dagegen, daß die Oxalsäure auch vor dem völligen Glucoseverbrauch autolytischen Ursprungs ist und bei 43° aus diesem Grunde in verstärktem Maße angehäuft wird, spricht der Befund, daß die Fraktion des NH4
+- und Amid-N vor diesem Zeitpunkt nur in sehr geringer Menge nachzuweisen ist. Es wird jedoch darauf hingewiesen, daß sie im Gegensatz zur Oxalsäure vielleicht wieder in das der Autolyse parallel laufende Wachstum mit einbezogen wird, solange noch Glucose vorhanden ist.Die Geschwindigkeit der Oxalsäurezersetzung ist bei 43° geringer als bei 30°. Eine Beteiligung dieses Temperatureffektes an der verstärkten Anhäufung bei 43° wird diskutiert, ebenso die Möglichkeit eines temperaturbedingten Shunt-Effektes. 相似文献
67.
68.
- Hydrogen peroxide excretion by photosynthesizing intact spinachchloroplasts was determined. The rates were dependent on theoxygen concentration and on the ATP/NADPH requirement of thefinal electron acceptor. Upon CO2 assimilation a maximum rateof 0.9 µmol H2O2/mg chlorophyll/hr and half saturationat 7.5 x 105 M O2 were found. Excretion of H2O2 was considerablyreduced upon photosynthetic reduction of glycerate 3-phosphateor oxaloacetate.
- Light- and HCO3-saturated CO2 assimilationwas inhibited bymore than 50% by anaerobic conditions, whereuponquantum efficiencywas also drastically decreased. However,no anoxic influencewas detected with glycerate 3-phosphateas the terminal electronacceptor and the quantum requirementwith this acceptor wasnot increased by anaerobiosis. Thus theenhancing effect ofoxygen on CO2 assimilation was ascribedto an improvement ofphotosynthetic ATP supply.
- Since thestimulation of anaerobic photosynthetic CO2 assimilationbyoxygen was markedly greater than the concomitant increaseinH2O2 evolution, photosynthetic oxygen reduction alone isnotsufficient to produce the required additional ATP for theobservedenhanced CO2 assimilation. But it provides a meansto avoidthe over-reduction of photosynthetic electron carriersand thusenables aerobic cyclic photophosphorylation. This supportsthehypothesis that cyclic photophosphorylation is not an alternativeto ATP formation by "pseudocyclic" electron transport, but ratherthat it depends on the latter.
69.
2,6-Anhydro-3-deoxy-aldehydo-d-lyxo-hept-2-enose (7) 2,6-anhydro-3-deoxy-d-lyxo-hept-2-enitol (8) were synthesized as half-chair analogs of d-galactal (1). As 1 is a strong inhibitor of, as well as a substrate for, β-d-galactosidase from Escherichia coli, the same properties were expected for 7 and 8; however, both were ineffective. This result, together with those of other authors, allows speculative conclusions on the tight binding of 1 to the enzyme only, when water or an alcohol is bound as a co-substrate. 相似文献
70.
erbb3 and erbb2 are essential for schwann cell migration and myelination in zebrafish 总被引:7,自引:0,他引:7
Lyons DA Pogoda HM Voas MG Woods IG Diamond B Nix R Arana N Jacobs J Talbot WS 《Current biology : CB》2005,15(6):513-524
BACKGROUND: Myelin is critical for efficient axonal conduction in the vertebrate nervous system. Neuregulin (Nrg) ligands and their ErbB receptors are required for the development of Schwann cells, the glial cells that form myelin in the peripheral nervous system. Previous studies have not determined whether Nrg-ErbB signaling is essential in vivo for Schwann cell fate specification, proliferation, survival, migration, or the onset of myelination. RESULTS: In genetic screens for mutants with disruptions in myelinated nerves, we identified mutations in erbb3 and erbb2, which together encode a heteromeric tyrosine kinase receptor for Neuregulin ligands. Phenotypic analysis shows that both genes are essential for development of Schwann cells. BrdU-incorporation studies and time-lapse analysis reveal that Schwann cell proliferation and migration, but not survival, are disrupted in erbb3 mutants. We show that Schwann cells can migrate in the absence of DNA replication. This uncoupling of proliferation and migration indicates that erbb gene function is required independently for these two processes. Pharmacological inhibition of ErbB signaling at different stages reveals a continuing requirement for ErbB function during migration and also provides evidence that ErbB signaling is required after migration for proliferation and the terminal differentiation of myelinating Schwann cells. CONCLUSIONS: These results provide in vivo evidence that Neuregulin-ErbB signaling is essential for directed Schwann cell migration and demonstrate that this pathway is also required for the onset of myelination in postmigratory Schwann cells. 相似文献