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181.
In a series of experiments, it is demonstrated that the trace element vanadium (4·10-7 g-at/l as NH4VO3) has a considerable positive influence on the synthesis of -aminolevulinic acid (-ALA) in the autotrophically growing green algaChlorella pyrenoidosa, the effect being visible by an enhanced output of the amino acid into the culture medium in presence of levulinic acid (LA). The level of intracellularly accumulated -ALA, however, is not changed in presence of the metal. The V-effect on exogenous found -ALA is suppressed, when LA is added to the nutrient medium at low pH (pH 5), although V-uptake into the algal cells is not disturbed by LA. As demonstrated in culture media with various nitrogen sources (urea, partially hydrolized urea, ammonium salts), the development of the pH during the cultivation time is important for the presentation of the V-effect on -ALA. It is suggested that vanadium acts as a catalyst in the conversion of 4,5-dioxovaleric acid to -ALA by transamination.Abbreviations -ALA
-aminolevulinic acid
- LA
levulinic acid
- DOVA
4,5-dioxovaleric acid 相似文献
182.
SS Neukamm R Toth N Morrice DG Campbell C Mackintosh R Lehmann HU Haering ED Schleicher C Weigert 《PloS one》2012,7(8):e43296
Phosphorylation of insulin receptor substrate (IRS)-2 on tyrosine residues is a key event in IGF-1/insulin signaling and leads to activation of the PI 3-kinase and the Ras/MAPK pathway. Furthermore, phosphorylated serine/threonine residues on IRS-2 can induce 14-3-3 binding. In this study we searched IRS-2 for novel phosphorylation sites and investigated the interaction between IRS-2 and 14-3-3. Mass spectrometry identified a total of 24 serine/threonine residues on IRS-2 with 12 sites unique for IRS-2 while the other residues are conserved in IRS-1 and IRS-2. IGF-1 stimulation led to increased binding of 14-3-3 to IRS-2 in transfected HEK293 cells and this binding was prevented by inhibition of the PI 3-kinase pathway and an Akt/PKB inhibitor. Insulin-stimulated interaction between endogenous IRS-2 and 14-3-3 was observed in rat hepatoma cells and in mice liver after an acute insulin stimulus and refeeding. Using different IRS-2 fragments enabled localization of the IGF-1-dependent 14-3-3 binding region spanning amino acids 300-600. The 24 identified residues on IRS-2 included several 14-3-3 binding candidates in the region 300-600. Single alanine mutants of these candidates led to the identification of serine 573 as 14-3-3 binding site. A phospho-site specific antibody was generated to further characterize serine 573. IGF-1-dependent phosphorylation of serine 573 was reduced by inhibition of PI 3-kinase and Akt/PKB. A negative role of this phosphorylation site was implicated by the alanine mutant of serine 573 which led to enhanced phosphorylation of Akt/PKB in an IGF-1 time course experiment. To conclude, our data suggest a physiologically relevant role for IGF-1/insulin-dependent 14-3-3 binding to IRS-2 involving serine 573. 相似文献
183.
The soil bacterium Stenotrophomonas maltophilia was found to transform various long-chain fatty acids selectively into 3-hydroxy fatty acids of shorter chain length. Their chiral evaluation was performed by multidimensional gas chromatography (MDGC) on modified cyclodextrin phase comparing the enantiodistribution of 1,3-diol formed without loss of stereochemical information from a representative microbial product with those of synthetic (3RS)- and (3S)-1,3-diols. Enantiomeric excesses of 84-98% (R) were determined for the microbially produced 3-hydroxy acids. In addition, the CD exciton chirality method was applied to determine their absolute configuration. Derivatization with 9-anthryldiazomethane and 2-naphthoylimidazole led to the required bichromophoric structures. Their CD spectra displayed a positive first Cotton effect around 254 nm and a negative second Cotton effect around 237 nm, which confirmed the (R)-configuration of the bacterial products. 相似文献
184.
185.
Isolation and growth of a bacterium able to degrade nitrilotriacetic acid under denitrifying conditions 总被引:2,自引:0,他引:2
Ursula Wanner Judith Kemmler Hans-Ulrich Weilenmann Thomas Egli Tarek El-Banna Georg Auling 《Biodegradation》1990,1(1):31-41
A Gram-negative bacterium was isolated from river sediment which was able to grow with nitrilotriacetic acid as a combined carbon, nitrogen and energy source in the absence of molecular oxygen using nitrate as the terminal electron acceptor. Batch growth parameters and mass balances are reported for growth under both aerobic and denitrifying conditions.The strain was characterized with respect to its substrate spectrum and other physiological properties. This denitrifying isolate is serologically unrelated to the comprehensively described Gram-negative obligately aerobic NTA-degrading bacteria all of which belong to the -subclass of Proteobacteria. Chemotaxonomic characterization, which revealed the presence of spermidine as the main polyamine and ubiquinone Q-8, excludes the new isolate from the phylogenetically redefined genus Pseudomonas and indicates a possible location within the -subclass of Proteobacteria close to, but separate from the genus Xanthomonas. 相似文献
186.
Martin Heni Caroline Ketterer Robert Wagner Katarzyna Linder Anja B?hm Silke A. Herzberg-Sch?fer Fausto Machicao Klaus-Peter Knoch Andreas Fritsche Harald Staiger Hans-Ulrich H?ring Michele Solimena 《PloS one》2012,7(10)
Objective
Polypyrimidine tract-binding protein 1 (PTBP1) promotes stability and translation of mRNAs coding for insulin secretion granule proteins and thereby plays a role in β-cells function. We studied whether common genetic variations within the PTBP1 locus influence insulin secretion, and/or proinsulin conversion.Methods
We genotyped 1,502 healthy German subjects for four tagging single nucleotide polymorphisms (SNPs) within the PTBP1 locus (rs351974, rs11085226, rs736926, and rs123698) covering 100% of genetic variation with an r2≥0.8. The subjects were metabolically characterized by an oral glucose tolerance test with insulin, proinsulin, and C-peptide measurements. A subgroup of 320 subjects also underwent an IVGTT.Results
PTBP1 SNP rs11085226 was nominally associated with lower insulinogenic index and lower cleared insulin response in the OGTT (p≤0.04). The other tested SNPs did not show any association with the analyzed OGTT-derived secretion parameters. In the IVGTT subgroup, SNP rs11085226 was accordingly associated with lower insulin levels within the first ten minutes following glucose injection (p = 0.0103). Furthermore, SNP rs351974 was associated with insulin levels in the IVGTT (p = 0.0108). Upon interrogation of MAGIC HOMA-B data, our rs11085226 result was replicated (MAGIC p = 0.018), but the rs351974 was not.Conclusions
We conclude that common genetic variation in PTBP1 influences glucose-stimulated insulin secretion. This underlines the importance of PTBP1 for beta cell function in vivo. 相似文献187.
The type A trichothecenes T-2 and HT-2 toxins are toxic secondary metabolites produced by fungi of the Fusarium genus. Their occurrence in cereals, especially in oats, implies health risks for the consumer. Therefore, it is an important
task to develop selective and sensitive methods for the analysis of T-2 and HT-2 toxins, and to undertake further studies
on their stability and toxicity. Although most toxins are commercially available, their high prices are the limiting factor
on the realization of these experiments. Thus, we developed a method for large-scale production of T-2 and HT-2 toxin as well
as T-2 triol and T-2 tetraol. T-2 toxin was obtained in gram quantities by biosynthetic production with cultures of F. sporotrichioides. As HT-2 toxin was only formed as a by-product, and T-2 triol and T-2 tetraol were not generated, these compounds were produced
by alkaline hydrolysis of T-2 toxin. Separation and isolation of crude toxins was achieved by fast centrifugal partition chromatography
(FCPC), which is an efficient tool for the large-scale purification of natural products. Using this fast and yield effective
technique, several hundred milligrams of HT-2 toxin, T-2 triol, and T-2 tetraol were obtained. Subsequent, HT-2 toxin and
T-2 triol were used for the large-scale synthesis of isotope-labeled T-2 and HT-2 toxin, respectively. Using these standards,
an isotope dilution-(ID)-HPLC-MS/MS method for the quantification of T-2 and HT-2 toxin in different matrices was developed. 相似文献
188.
Ying Zhang Felicia Ranta Cai Tang Ekaterina Shumilina Hasan Mahmud Michael Föller Susanne Ullrich Hans-Ulrich Häring Florian Lang 《Apoptosis : an international journal on programmed cell death》2009,14(7):878-889
Amyloid peptides interfere with survival of pancreatic beta-cells. In some cells apoptosis is paralleled by ceramide-dependent alterations of ion channel activity. The purpose of the present study was to elucidate the dependence of amyloid peptides Aß1-42 and islet amyloid polypeptide (IAPP)-induced cell death on ceramide formation and ion channel activity in murine pancreatic islet cells. As disclosed by TUNEL (terminal dUTP nick-end labelling) and cleaved caspase 3 staining, apoptotic cell death was induced by Aß1-42, IAPP and exogenously added C2-ceramide in islet cells from wild type mice. In islet cells from acid sphingomyelinase-deficient mice (ASMKO) Aß1-42 and IAPP but not exogenously added N-acetyl-d-sphingosine (C2-ceramide, 20 μM) failed to stimulate apoptosis. Immunofluorescent staining revealed a stimulatory effect of Aß1-42 on ceramide formation. According to patch clamp experiments, administration of Aß1-42 and IAPP significantly decreased outwardly rectifying whole cell currents in wild type but not in ASMKO islet cells. C2-ceramide but not inactive di-ceramide (20 μM) mimicked the inhibitory effect on Kv channel current. In conclusion, amyloid peptides induce apoptosis of pancreatic islet cells at least in part through activation of acid sphingomyelinase resulting in production of ceramide and subsequent inhibition of ion channel activity. 相似文献
189.
Anja Gladbach Christina Braun Anja Nordt Hans-Ulrich Peter Petra Quillfeldt 《Polar Biology》2009,32(9):1315-1321
Seabirds show a range of patterns of sexual size dimorphism and sex-specific parental investment, but the underlying causes
remain poorly understood. The aim of the present study was to test two longstanding hypotheses of parental investment in a
sexually monomorphic species, Wilson’s storm petrel Oceanites oceanicus, namely that males attend chicks more frequently and females deliver larger meals (Beck and Brown in Br Antarct Surv Sci
Rep 69:1–54, 1972). We recorded in eight seasons, both during incubation and chick rearing, which adult was caught first in a nest and found
no difference in the probability of catching a male or a female first in any year. Additionally, in five seasons we employed
a miniature video camera to record nest attendance during chick rearing and found no significant difference except for 2006,
a year with very low krill availability, where females visited the nest less often than males. We then combined video observations
with periodic weighing of chicks to estimate mean daily feeding mass (g/day) of males and females and found no difference
in the amount of food delivered per day between the sexes. However, in years with low krill availability, males and females
tended to use different strategies to achieve the same feeding rates, with females undertaking longer foraging trips and delivering
heavier meals. Thus, our results do not support the hypothesis of a general sex-specific parental investment in Wilson’s storm
petrels, but a tendency for a context-dependent sex-specific investment in the years of food shortage. 相似文献
190.
Mühlbauer SK Lössl A Tzekova L Zou Z Koop HU 《The Plant journal : for cell and molecular biology》2002,32(2):175-184
Sequences described as chloroplast DNA replication origins were analysed in vivo by creating deletion and insertion mutants via plastid transformation in tobacco. Deletion of the described oriA sequence, which is located within the intron of the trnI gene, resulted in heteroplastomic transformants, when the selection marker was inserted within the intron. Removal of the complete intron sequence together with the oriA sequence, however, yielded homoplastomic transformants of normal phenotype, in which wild-type signals were no longer detectable through Southern analysis, thus bringing the role of the described oriA sequence for plastome replication into question. Similarly, deletion of sequence elements upstream of trnI, which have a possible ori function in Oenothera, did not show any effect in tobacco. The two copies of oriB, which are located at the very end of the plastome Inverted Repeats, were targeted with two different transformation vectors in a cotransformation approach. While in initial transformants integration of the selection marker could be detected at both sites, the transgene was found exclusively at one site or the other after additional rounds of regeneration. Whereas the copy of oriB in Inverted Repeat B could be completely deleted, targeting of the copy in Inverted Repeat A resulted in heteroplastomic lines, as the essential ycf1 gene was also affected. Due to the strong selection against cotransformants we conclude that at least one copy of the oriB sequence is essential for plastome replication, whereas replication appears possible without oriA elements. 相似文献