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91.
White JA Heasman J 《Journal of experimental zoology. Part B. Molecular and developmental evolution》2008,310(1):73-84
We review the essential role of maternal factors in pattern formation for Xenopus laevis, focusing on VegT, Vg1, and Wnt11. Results from loss of function experiments demonstrate a clear requirement for these genes in germ layer specification, dorsal-ventral axis formation, and convergence extension. We also discuss these genes in the broader context of metazoan development, exploring whether and how their functions in the X. laevis model organism may or may not be conserved in other species. Wnt11 signaling in particular provides a classic example where understanding context in development is crucial to understanding function. Genomic sequencing, gene expression, and functional screening data that are becoming available in more species are providing invaluable aid to decoding and modeling signaling pathways. More work is needed to develop a comprehensive catalog of the Wnt signaling, T-box, and TGF-beta genes in metazoans both near and far in evolutionary distance. We finally discuss some specific experimental and modeling efforts that will be needed to understand the behavior of these signaling networks in vivo so that we can interpret these critical pathways in an evolutionary framework. 相似文献
92.
Rosenblatt J 《Current biology : CB》2008,18(7):R292-R293
Ezrin/radixin/moesin proteins link the actin cytoskeleton to the plasma membrane. Two new reports have found that moesin phosphorylation is essential for mitotic cell rounding and identify a new role for cell rounding in spindle assembly. 相似文献
93.
Ataxia-telangiectasia (A-T) is an autosomal recessive disorder characterized by cerebellar ataxia and oculocutaneous telangiectasias. Patients with A-T also have high incidences of type 2 diabetes mellitus. The gene mutated in this disease, ATM (A-T, mutated), encodes a protein kinase. Previous studies have demonstrated that cytoplasmic ATM is an insulin-responsive protein and a major upstream activator of Akt following insulin treatment. To further investigate the function of ATM in insulin signal transduction, insulin resistance was induced in rats by feeding them a high-fat diet. Muscle tissue of rats with insulin resistance had both dramatically reduced ATM levels and substantially decreased Akt phosphorylation at Ser473 in comparison to that of regular chow-fed controls. The decreased ATM expression suggests that ATM is involved in the development of insulin resistance through down-regulation of Akt activity. The role of ATM in activation of Akt was further confirmed in mouse embryonic fibroblast (MEF) A29 (ATM+/+) and A38 (ATM-/-) cells. In addition, insulin-mediated Akt phosphorylation in mouse L6 muscle cells was greatly reduced by KU-55933, a specific inhibitor of ATM. A 2-deoxyglucose incorporation assay showed that this inhibitor also caused a significant reduction in insulin-mediated glucose uptake in L6 cells. An immunofluorescence experiment demonstrated that in L6 cells transfected with wild-type (WT) ATM, insulin caused a dramatic increase of the cell surface glucose transporter 4 (GLUT4), while in cells transfected with kinase-dead (KD) ATM, translocation of GLUT4 to the cell surface in response to insulin was markedly inhibited. 相似文献
94.
Mhp493 (P216) is a proteolytically processed, cilium and heparin binding protein of Mycoplasma hyopneumoniae 总被引:1,自引:0,他引:1
Jody Wilton Cheryl Jenkins Stuart J. Cordwell Linda Falconer F. Chris Minion David C. Oneal Michael A. Djordjevic Angela Connolly Idris Barchia Mark J. Walker Steven P. Djordjevic 《Molecular microbiology》2009,71(3):566-582
Mycoplasma hyopneumoniae induces respiratory disease in swine by colonizing cilia causing ciliostasis, cilial loss and epithelial cell death. Heparin binds to M. hyopneumoniae cells in a dose-dependent manner and blocks its ability to adhere to porcine cilia. We show here that Mhp493 (P216), a paralogue of the cilium adhesin P97 (Mhp183), is cleaved between amino acids 1040 and 1089 generating surface-accessible, heparin-binding proteins P120 and P85. Antiphosphoserine antibodies recognized P85 in 2-D immunoblotting studies and TiO2 chromatography of trypsin digests of P85 isolated a single peptide with an m/z of 917.3. A phosphoserine residue in the tryptic peptide 90 VSELpSFR96 (position 94 in P85) was identified by MALDI-MS/MS. Polyhistidine fusion proteins (F1P216 , F2P216 , F3P216 ) spanning Mhp493 bound heparin with biologically significant Kd values, and heparin, fucoidan and mucin inhibited this interaction. Latex beads coated with F1P216 , F2P216 and F3P216 adhered to and entered porcine kidney epithelial-like (PK15) cell monolayers. Microtitre plate-based assays showed that sequences within P120 and P85 bind to porcine cilia and are recognized by serum antibodies elicited during infection by M. hyopneumoniae . Mhp493 contributes significantly to the surface architecture of M. hyopneumoniae and is the first cilium adhesin to be described that lacks an R1 cilium-binding domain. 相似文献
95.
Xinfeng Xie Barry Goodell Dajie Zhang Dennis C. Nagle Yuhui Qian Michael L. Peterson Jody Jellison 《Bioresource technology》2009,100(5):1797-1802
In this study the oxidative behavior of carbons derived from cellulose and lignin were compared using thermogravimetric analysis (TGA). Specific surface area and chemical composition of the two types of carbon were analyzed using nitrogen adsorption at 77 K and infrared spectroscopy respectively. The results demonstrate that cellulose carbon has a higher reaction order and lower activation energy than lignin carbon under identical experimental conditions when they were prepared at temperatures lower than 500 °C. However, such differences were considerably reduced for the carbon samples prepared at temperatures greater than 700 °C. It was verified that lignin carbon is more stable than cellulose carbon due to its higher content of aromatic structures when they are prepared at lower temperature. The specific surface area and porosity have a more limited contribution to the differential oxidative behaviors of the two types of carbon. This research has significance related to the formation of carbon nanotubes from plant materials during low temperature carbonization. 相似文献
96.
Caitlin Howell Anne Christine Steenkjær Hastrup Barry Goodell Jody Jellison 《International biodeterioration & biodegradation》2009,63(4):414-419
The degradation of wood by brown rot fungi has been studied intensely for many years in order to facilitate the preservation of in-service wood. In this work we used X-ray diffraction to examine changes in wood cellulose crystallinity caused by the brown rot fungi Gloeophyllum trabeum, Coniophora puteana, and two isolates of Serpula lacrymans. All fungi increased apparent percent crystallinity early in the decay process while decreasing total amounts of both crystalline and amorphous material. Data also showed an apparent decrease of approximately 0.05 Å in the average spacing of the crystal planes in all degraded samples after roughly 20% weight loss, as well as a decrease in the average observed relative peak width at 2θ = 22.2°. These results may indicate a disruption of the outer most semi-crystalline cellulose chains comprising the wood microfibril. X-ray diffraction analysis of wood subjected to biological attack by fungi may provide insight into degradative processes and wood cellulose structure. 相似文献
97.
Jody A Winter Panayiotis Christofi Shaun Morroll Karen A Bunting 《BMC structural biology》2009,9(1):55
Background
The high intracellular salt concentration required to maintain a halophilic lifestyle poses challenges to haloarchaeal proteins that must stay soluble, stable and functional in this extreme environment. Proliferating cell nuclear antigen (PCNA) is a fundamental protein involved in maintaining genome integrity, with roles in both DNA replication and repair. To investigate the halophilic adaptation of such a key protein we have crystallised and solved the structure of Haloferax volcanii PCNA (HvPCNA) to a resolution of 2.0 ?. 相似文献98.
Edith Y. Cheng Patricia A. Hunt Theresa A. Naluai-Cecchini Corrine L. Fligner Victor Y. Fujimoto Tanya L. Pasternack Jackie M. Schwartz Jody E. Steinauer Tracey J. Woodruff Sheila M. Cherry Terah A. Hansen Rhea U. Vallente Karl W. Broman Terry J. Hassold 《PLoS genetics》2009,5(9)
Studies of human trisomies indicate a remarkable relationship between abnormal meiotic recombination and subsequent nondisjunction at maternal meiosis I or II. Specifically, failure to recombine or recombination events located either too near to or too far from the centromere have been linked to the origin of human trisomies. It should be possible to identify these abnormal crossover configurations by using immunofluorescence methodology to directly examine the meiotic recombination process in the human female. Accordingly, we initiated studies of crossover-associated proteins (e.g., MLH1) in human fetal oocytes to analyze their number and distribution on nondisjunction-prone human chromosomes and, more generally, to characterize genome-wide levels of recombination in the human female. Our analyses indicate that the number of MLH1 foci is lower than predicted from genetic linkage analysis, but its localization pattern conforms to that expected for a crossover-associated protein. In studies of individual chromosomes, our observations provide evidence for the presence of “vulnerable” crossover configurations in the fetal oocyte, consistent with the idea that these are subsequently translated into nondisjunctional events in the adult oocyte. 相似文献
99.
Martin D. Burkhalter Steven A. Roberts Jody M. Havener Dale A. Ramsden 《DNA Repair》2009,8(11):1258-1263
Mammalian cells can choose either nonhomologous end joining (NHEJ) or homologous recombination (HR) for repair of chromosome breaks. Of these two pathways, HR alone requires extensive DNA synthesis and thus abundant synthesis precursors (dNTPs). We address here if this differing requirement for dNTPs helps determine how cells choose a repair pathway. Cellular dNTP pools are regulated primarily by changes in ribonucleotide reductase activity. We show that an inhibitor of ribonucleotide reductase (hydroxyurea) hypersensitizes NHEJ-deficient cells, but not wild type or HR-deficient cells, to chromosome breaks introduced by ionizing radiation. Hydroxyurea additionally reduces the frequency of irradiated cells with a marker for an early step in HR, Rad51 foci, consistent with reduced initiation of HR under these conditions. Conversely, promotion of ribonucleotide reductase activity protects NHEJ-deficient cells from ionizing radiation. Importantly, promotion of ribonucleotide reductase activity also increases usage of HR in cells proficient in both NHEJ and HR at a targeted chromosome break. Activity of ribonucleotide reductase is thus an important factor in determining how mammalian cells repair broken chromosomes. This may explain in part why G1/G0 cells, which have reduced ribonucleotide reductase activity, rely more on NHEJ for DSB repair. 相似文献
100.
Experiments using functional neuroimaging and transcranial magnetic stimulation in humans have revealed regions of the parietal lobes that are specialized for particular visuomotor actions, such as reaching, grasping and eye movements. In addition, the human parietal cortex is recruited by processing and perception of action-related information, even when no overt action occurs. Such information can include object shape and orientation, knowledge about how tools are employed and the understanding of actions made by other individuals. We review the known subregions of the human posterior parietal cortex and the principles behind their organization. 相似文献