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71.
Kristof Haneca Ilse Boeren Joris Van Acker Hans Beeckman 《Vegetation History and Archaeobotany》2006,15(2):137-144
Throughout the Middle Ages forests in Flanders (northern Belgium) experienced a dramatic human influence. Forests were logged
for wood supply and converted to arable land. The structure of the remaining forests was altered. This, combined with the
tempering influence of the Atlantic climate, results in conditions that are suboptimal for dendrochronological research. Tree-ring
series of Quercus robur and Q. petraea of timber from medieval archaeological sites are often short, show abrupt growth-rate variations and are complacent. The
question arises whether tree-ring series of this type are potential records of past management and whether they could constitute
the basis of a reference chronology for archaeological dating. During six archaeological excavations in and around the medieval
town of Ypres, cross-sections were collected. The tree-ring series could be dated back to the 12th–14th centuries, using reference
chronologies from surrounding regions. The growth pattern of the short sequences displays a high similarity to tree-ring series
from modern coppice. For the first time, it has been confirmed that dendrochronological analysis in Flanders is possible and
can provide valuable information on medieval forest use and structure. 相似文献
72.
Vandebroek T Terwel D Vanhelmont T Gysemans M Van Haesendonck C Engelborghs Y Winderickx J Van Leuven F 《The Journal of biological chemistry》2006,281(35):25388-25397
Phosphorylation of Tau protein and binding to microtubules is complex in neurons and was therefore studied in the less complicated model of humanized yeast. Human Tau was readily phosphorylated at pathological epitopes, but in opposite directions regulated by kinases Mds1 and Pho85, orthologues of glycogen synthase kinase-3beta and cdk5, respectively (1). We isolated recombinant Tau-4R and mutant Tau-P301L from wild type, Delta mds1 and Delta pho85 yeast strains and measured binding to Taxol-stabilized mammalian microtubules in relation to their phosphorylation patterns. Tau-4R isolated from yeast lacking mds1 was less phosphorylated and bound more to microtubules than Tau-4R isolated from wild type yeast. Paradoxically, phosphorylation of Tau-4R isolated from kinase Pho85-deficient yeast was dramatically increased resulting in very poor binding to microtubules. Dephosphorylation promoted binding to microtubules to uniform high levels, excluding other modifications. Isolated hyperphosphorylated, conformationally altered Tau-4R completely failed to bind microtubules. In parallel to Tau-4R, we expressed, isolated, and analyzed mutant Tau-P301L. Total dephosphorylated Tau-4R and Tau-P301L bound to microtubules very similarly. Surprisingly, Tau-P301L isolated from all yeast strains bound to microtubules more extensively than Tau-4R. Atomic force microscopy demonstrated, however, that the high apparent binding of Tau-P301L was due to aggregation on the microtubules, causing their deformation and bundling. Our data explain the pathological presence of granular Tau aggregates in neuronal processes in tauopathies. 相似文献
73.
Renckens R Roelofs JJ Florquin S de Vos AF Lijnen HR van't Veer C van der Poll T 《Journal of immunology (Baltimore, Md. : 1950)》2006,176(6):3735-3741
Matrix metalloproteinase (MMP)-9 is involved in extracellular matrix degradation and leukocyte migration. To determine the role of MMP-9 in the innate immune response to peritonitis, MMP-9 gene-deficient (MMP-9(-/-)) and normal wild-type mice were i.p. infected with Escherichia coli. MMP-9 mRNA and pro-MMP-9 protein levels increased rapidly upon induction of peritonitis. Although MMP-9(-/-) neutrophils showed a normal phagocytosis of E. coli in vitro, MMP-9(-/-) mice displayed a reduced resistance against E. coli peritonitis, as indicated by an enhanced bacterial outgrowth in the peritoneal cavity and increased dissemination of the infection. Furthermore, the cytokine response to LPS was not influenced by MMP-9 deficiency. However, during E. coli peritonitis, MMP-9(-/-) mice showed much higher peritoneal chemokine and cytokine levels compared with wild-type mice. Despite the increased local chemokine concentrations, MMP-9(-/-) mice displayed a diminished recruitment of leukocytes to the site of infection, indicating that cellular migration was impaired. Moreover, MMP-9(-/-) mice developed more severe distant organ damage during infection. These data suggest that MMP-9 is an essential component of an effective host response to E. coli peritonitis. 相似文献
74.
Renckens R Roelofs JJ Florquin S de Vos AF Pater JM Lijnen HR Carmeliet P van 't Veer C van der Poll T 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(2):1189-1196
Sepsis is associated with enhanced production of tissue-type plasminogen activator (tPA). We investigated the function of endogenous tPA in the immune responses to Escherichia coli-induced abdominal sepsis using tPA gene-deficient (tPA(-/-)) and normal wild-type (WT) mice. tPA(-/-) mice demonstrated an impaired defense against E. coli peritonitis as indicated by higher bacterial loads at the primary site of the infection, enhanced dissemination, and reduced survival. The protective function of tPA was independent of plasmin since plasminogen gene-deficient (Plg(-/-)) mice were indistinguishable from WT mice. Relative to WT mice, tPA(-/-) mice demonstrated similar neutrophil counts in the peritoneal cavity despite much higher bacterial loads and higher local concentrations of neutrophil attracting chemokines, suggesting a reduced migratory response. In line, tPA(-/-) mice demonstrated a reduced thioglycolate-induced neutrophil influx into the peritoneal cavity and i.p. injection of WT mice with a replication-defective adenoviral vector expressing tPA caused an enhanced cell migration to the peritoneal cavity during E. coli peritonitis. These findings identify a novel protective function of tPA in abdominal sepsis caused by E. coli that seems independent of its role in the generation of plasmin. 相似文献
75.
76.
Martens-Uzunova ES Zandleven JS Benen JA Awad H Kools HJ Beldman G Voragen AG Van den Berg JA Schaap PJ 《The Biochemical journal》2006,400(1):43-52
The fungus Aspergillus niger is an industrial producer of pectin-degrading enzymes. The recent solving of the genomic sequence of A. niger allowed an inventory of the entire genome of the fungus for potential carbohydrate-degrading enzymes. By applying bioinformatics tools, 12 new genes, putatively encoding family 28 glycoside hydrolases, were identified. Seven of the newly discovered genes form a new gene group, which we show to encode exoacting pectinolytic glycoside hydrolases. This group includes four exo-polygalacturonan hydrolases (PGAX, PGXA, PGXB and PGXC) and three putative exo-rhamnogalacturonan hydrolases (RGXA, RGXB and RGXC). Biochemical identification using polygalacturonic acid and xylogalacturonan as substrates demonstrated that indeed PGXB and PGXC act as exo-polygalacturonases, whereas PGXA acts as an exo-xylogalacturonan hydrolase. The expression levels of all 21 genes were assessed by microarray analysis. The results from the present study demonstrate that exo-acting glycoside hydrolases play a prominent role in pectin degradation. 相似文献
77.
Griffioen G Duhamel H Van Damme N Pellens K Zabrocki P Pannecouque C van Leuven F Winderickx J Wera S 《Biochimica et biophysica acta》2006,1762(3):312-318
We have developed a yeast-based model recapitulating neurotoxicity of alpha-synuclein fibrilization. This model recognized metal ions, known risk factors of alpha-synucleinopathy, as stimulators of alpha-synuclein aggregation and cytotoxicity. Elimination of Yca1 caspase activity augmented both cytotoxicity and inclusion body formation, suggesting the involvement of apoptotic pathway components in toxic alpha-synuclein amyloidogenesis. Deletion of hydrophobic amino acids at positions 66-74 in alpha-synuclein reduced its cytotoxicity but, remarkably, did not lower the levels of insoluble alpha-synuclein, indicating that noxious alpha-synuclein species are different from insoluble aggregates. A compound screen aimed at finding molecules with therapeutic potential identified flavonoids with strong activity to restrain alpha-synuclein toxicity. Subsequent structure-activity analysis elucidated that these acted by virtue of anti-oxidant and metal-chelating activities. In conclusion, this yeast-cell model as presented allows not only fundamental studies related to mechanisms of alpha-synuclein-instigated cellular degeneration, but is also a valid high-throughput identification tool for novel neuroprotective agents. 相似文献
78.
Abstract. Osmotic stress associated with the freshwater environment and desiccation stress associated with the terrestrial environment may have a shortening effect on the length of the innervation of crustacean aesthetascs. Physical stress of the littoral environment may have a similar effect on the length of the cuticular portion of aesthetascs. The aesthetascs of crustaceans that inhabit these environments share a similar ultrastructural feature, which may help animals cope with these environmental stresses. This ultrastructural feature, the position of the basal bodies proximal to the lumen of the aesthetasc, is absent from the aesthetascs of crustaceans that occur in the typical marine environment. Interestingly, the ultrastructural feature associated with these stressful habitats is present in the peduncular aesthetascs of the remipede Speleonectes tanumekes , even though the environmental stresses that may invoke the reduction of aesthetascs are absent in the marine-cave environment where this animal occurs. The importance of the sensitivity of aesthetascs for survival in this lightless environment may result in a selective pressure that favors basal bodies to be positioned proximal to the lumen of the aesthetasc. 相似文献
79.
Villadangos AF Fu HL Gil JA Messens J Rosen BP Mateos LM 《The Journal of biological chemistry》2012,287(1):723-735
Resistance to arsenite (As(III)) by cells is generally accomplished by arsenite efflux permeases from Acr3 or ArsB unrelated families. We analyzed the function of three Acr3 proteins from Corynebacterium glutamicum, CgAcr3-1, CgAcr3-2, and CgAcr3-3. CgAcr3-1 conferred the highest level of As(III) resistance and accumulation in vivo. CgAcr3-1 was also the most active when everted membranes vesicles from Escherichia coli or C. glutamicum mutants were assayed for efflux with different energy sources. As(III) and antimonite (Sb(III)) resistance and accumulation studies using E. coli or C. glutamicum arsenite permease mutants clearly show that CgAcr3-1 is specific for As(III). In everted membrane vesicles expressing CgAcr3-1, dissipation of either the membrane potential or the pH gradient of the proton motive force did not prevent As(III) uptake, whereas dissipation of both components eliminated uptake. Further, a mutagenesis study of CgAcr3-1 suggested that a conserved cysteine and glutamate are involved in active transport. Therefore, we propose that CgAcr3-1 is an antiporter that catalyzes arsenite-proton exchange with residues Cys129 and Glu305 involved in efflux. 相似文献
80.