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991.
Oleosin genes in maize kernels having diverse oil contents are constitutively expressed independent of oil contents 总被引:2,自引:0,他引:2
Julie T. L. Ting Keunmyoung Lee Chandra Ratnayake Kathryn A. Platt Ronald A. Balsamo Anthony H. C. Huang 《Planta》1996,199(1):158-165
In seeds, the subcellular storage oil bodies have a matrix of oils (triacylglycerols) surrounded by a layer of phospholipids embedded with abundant structural proteins called oleosins. We used two maize (Zea mays L.) strains having diverse kernel (seed) oil contents to study the effects of varying the oil and oleosin contents on the structure of the oil bodies. Illinois High Oils (IHO, 15% w/w oils) and Illinois Low Oils (ILO, 0.5%) maize kernels were the products of breeding for diverse oil contents for about 100 generations. In both maize strains, although the genes for oil synthesis had apparently been modified drastically, the genes encoding oleosins appeared to be unaltered, as revealed by Southern blot analyses of the three oleosin genes and sodium dodecyl sulfate-polyacrylamide gel electrophoresis with immunoblotting of the oleosins. In addition, both strains contained the same three oleosin isoforms of a defined proportion, and both accumulated oils and oleosins coordinately. Oleosins in both strains were restricted to the oil bodies, as shown by analyses of the various subcellular fractions separated by sucrosedensity-gradient centrifugation. Electron microscopy of the embryos and the isolated organelles revealed that the oil bodies in IHO were larger and had a spherical shape, whereas those in ILO were smaller and had irregular shapes. We conclude that in seeds, oleosin genes are expressed independent of the oil contents, and the size and shape of the oil bodies are dictated by the ratio of oils to oleosins synthesized during seed maturation. The extensive breeding for diverse oil contents has not altered the apparent mechanism of oil-body synthesis and the occurrence of hetero-dimer or -multimer of oleosin isoforms on the oil bodies.Abbreviations IHO
Illinois High Oils
- ILO
Illinois Low Oils
This work was supported by a USDA NRICGP grant. We thank Dr. J.W. Dudley of the University of Illinois for the IHO and ILO maize kernels, and Dr. W. Thomson for discussion on the stereological method. 相似文献
992.
Kathryn A. Hanley Robert N. Fisher Ted J. Case 《Evolution; international journal of organic evolution》1995,49(3):418-426
What advantage do sexually reproducing organisms gain from their mode of reproduction that compensates for their twofold loss in reproductive rate relative to their asexual counterparts? One version of the Red Queen hypothesis suggests that selective pressure from parasites is strongest on the most common genotype in a population, and thus genetically identical clonal lineages are more vulnerable to parasitism over time than genetically diverse sexual lineages. Our surveys of the ectoparasites of an asexual gecko and its two sexual ancestral species show that the sexuals have a higher prevalence, abundance, and mean intensity of mites than asexuals sharing the same habitat. Our experimental data indicate that in one sexual/asexual pair this pattern is at least partly attributable to higher attachment rates of mites to sexuals. Such a difference may occur as a result of exceptionally high susceptibility of the sexuals to mites because of their low genetic diversity (relative to other more-outbred sexual species) and their potentially high stress levels, or as a result of exceptionally low susceptibility of the asexuals to mites because of their high levels of heterozygosity. 相似文献
993.
Kathryn L. Evans John Brown Yoshiro Shibasaki Rebecca S. Devon Lin He Benoit Arveiler Sheila Christie John C. Maule David Baillie Euan M. Slorach Susan M. Anderson John R. Gosden Joelle Petit Andreas Weith Christine M. Gosden Douglas H. R. Blackwood David M. St. Clair Walter J. Muir Anthony J. Brookes David J. Porteous 《Genomics》1995,28(3)
Forty-nine clones derived by microdissection of a schizophrenia-associated t(1;11)(q42.1;q14.3) breakpoint region have been assigned by somatic cell hybrid mapping to seven discrete intervals on the long arm of human chromosome 11. Eleven of the clones were shown to map to a small region immediately distal to the translocation breakpoint on 11q.A 3-Mb contiguous clone map of this region was established by isolation of corresponding YAC recombinants. The contig was oriented and shown to traverse the translocation breakpoint by FISH and microsatellite marker analysis. This contig will facilitate the isolation of candidate sequences whose expression may be affected by the translocation. 相似文献
994.
Tracheal cytotoxin structural requirements for respiratory epithelial damage in pertussis 总被引:1,自引:0,他引:1
Kathryn E. Luker rew N. Tyler Garland R. Marshall William E. Goldman 《Molecular microbiology》1995,16(4):733-743
The respiratory epithelial pathology of pertussis (whooping cough) can be reproduced by tracheal cyto-toxin (TCT), a disaccharide-tetrapeptide released by Bordetella pertussis. TCT is a muramyl peptide, a class of peptidoglycan-derived compounds which have many biological activities including adjuvanticity, somnogenicity, pyrogenicity, and cytotoxicity. The structural requirements for muramyl peptides to produce some of these biological effects have been partially characterized. Using in vitro assays with respiratory epithelial cells and tissue, we have previously determined that the disaccharide moiety of TCT is not involved in toxicity and that the side-chain functional groups of diaminopimelic acid (A2pm) are crucial for toxicity. In this study, we determine the importance of every amino acid, functional group and chiral centre in the peptide portion of TCT. Although lactyl tetrapeptides are the most toxic of the TCT fragments, producing dose-response curves identical to TCT, the smallest analogues of TCT which are active in our assay are of the form X-γ-(d )-Glu-meso-A2pm, where X may be an amino acid or a blocking group. Within this active substructure, main-chain chirality and all functional groups are essential for toxicity. This definition of the core region of TCT indicates that the TCT interaction site is unlike almost all other muramyl peptide interaction sites for which structure-activity data are available. 相似文献
995.
Phosphatidylinositol 3–Kinase Is Required for the Formation of Constitutive Transport Vesicles from the TGN 下载免费PDF全文
An 85-kD cytosolic complex (p62cplx), consisting of a 62-kD phosphoprotein (p62) and a 25-kD GTPase, has been shown to be essential for the cell-free reconstitution of polymeric IgA receptor (pIgA-R)-containing exocytic transport vesicle formation from the TGN (Jones, S.M., J.R. Crosby, J. Salamero, and K.E. Howell. 1993. J. Cell Biol. 122:775–788). Here the p62cplx is identified as a regulatory subunit of a novel phosphatidylinositol 3–kinase (PI3-kinase). This p62cplx-associated PI3-kinase activity is stimulated by activation of the p62cplx-associated GTPase, and is specific for phosphatidylinositol (PI) as substrate, and is sensitive to wortmannin at micromolar concentrations. The direct role of this p62cplx-associated PI3-kinase activity in TGN-derived vesicle formation is indicated by the finding that both lipid kinase activity and the formation of pIgA-R–containing exocytic vesicles from the TGN are inhibited by wortmannin with similar dose-response curves and 50% inhibitory concentrations (3.5 μM). These findings indicate that phosphatidylinositol-3-phosphate (PI[3]P) is required for the formation of TGN-derived exocytic transport vesicles, and that the p62cplx-associated PI3-kinase and an activated GTPase are the essential molecules that drive production of this PI(3)P. 相似文献
996.
A Nuclear Export Signal in Kap95p Is Required for Both Recycling the Import Factor and Interaction with the Nucleoporin GLFG Repeat Regions of Nup116p and Nup100p 总被引:11,自引:4,他引:7 下载免费PDF全文
During nuclear import, cytosolic transport factors move through the nuclear pore complex (NPC) to the nuclear compartment. Kap95p is required during import for docking the nuclear localization signal-receptor and ligand to the NPC. Recycling of this factor back to the cytoplasm is necessary for continued rounds of import; however, the mechanism for Kap95p recycling is unknown. We have determined that recycling of Kap95p requires a nuclear export signal (NES). A region containing the NES in Kap95p was sufficient to mediate active nuclear export in a microinjection assay. Moreover, the NES was necessary for function. Mutation of the NES in Kap95p resulted in a temperaturesensitive import mutant, and immunofluorescence microscopy experiments showed that the mutated Kap95p was not recycled but instead localized in the nucleus and at the nuclear envelope. Srp1p, the yeast nuclear localization signal-receptor, also accumulated in the nuclei of the arrested kap95 mutant cells. Wild-type and NES-mutated Kap95p both bound Gsp1p (the yeast Ran/TC4 homologue), Srp1p, and the FXFG repeat region of the nucleoporin Nup1p. In contrast, the NES mutation abolished Kap95p interaction with the GLFG repeat regions from the nucleoporins Nup116p and Nup100p. In vivo interaction was demonstrated by isolation of Kap95p from yeast nuclear lysates in either protein A–tagged Nup116p or protein A–tagged Nup100p complexes. The protein A–tagged Nup116p complex also specifically contained Gle2p. These results support a model in which a step in the recycling of Kap95p is mediated by interaction of an NES with GLFG regions. Analysis of genetic interactions suggests Nup116p has a primary role in Kap95p recycling, with Nup100p compensating in the absence of Nup116p. This finding highlights an important role for a subfamily of GLFG nucleoporins in nuclear export processes. 相似文献
997.
Impact of different levels of cinnamyl alcohol dehydrogenase down-regulation on lignins of transgenic tobacco plants 总被引:1,自引:0,他引:1
Nabila Yahiaoui Christiane Marque Kathryn E. Myton Jonathan Negrel Alain Michel Boudet 《Planta》1997,204(1):8-15
The effects of cinnamyl alcohol dehydrogenase (CAD, EC.1.1.1.195) down-regulation on lignin profiles of plants were analysed
in four selected transgenic lines of tobacco (Nicotiana tabacum L. cv. Samsun) exhibiting different levels of CAD activity (8–56% of the control). A significant decrease in thioacidolysis
yields (i.e. yield of β-O-4 linked monomers) and in the ratio of syringyl to guaiacyl monomers (S/G) was observed for three transgenic lines and the
most drastic reduction (up to 50%) was correlated with the lowest level of CAD activity. Higher lignin extractability by mild
alkali treatment was confirmed, and, in addition to a tenfold increase in C6-C1 aldehydes, coniferyl aldehyde was detected by high-performance liquid chromatography in the alkali extracts from the xylem
of transgenic plants. In-situ polymerisation of cinnamyl aldehydes in stem sections of untransformed tobacco gave a xylem
cell wall coloration strikingly similar to the reddish-brown coloration of the xylem of antisense CAD-down-regulated plants.
Overall, these data provide new arguments for the involvement of polymerised cinnamyl aldehydes in the formation of the red-coloured
xylem of CAD-down-regulated plants.
Received: 24 January 1997 / Accepted: 14 May 1997 相似文献
998.
Characterization of the Golgi Complex Cleared of Proteins in Transit and Examination of Calcium Uptake Activities 总被引:5,自引:1,他引:4 下载免费PDF全文
Randall S. Taylor Steven M. Jones Rolf H. Dahl Mark H. Nordeen Kathryn E. Howell 《Molecular biology of the cell》1997,8(10):1911-1931
To characterize endogenous molecules and activities of the Golgi complex, proteins in transit were >99% cleared from rat hepatocytes by using cycloheximide (CHX) treatment. The loss of proteins in transit resulted in condensation of the Golgi cisternae and stacks. Isolation of a stacked Golgi fraction is equally efficient with or without proteins in transit [control (CTL SGF1) and cycloheximide (CHX SGF1)]. Electron microscopy and morphometric analysis showed that >90% of the elements could be positively identified as Golgi stacks or cisternae. Biochemical analysis showed that the cis-, medial-, trans-, and TGN Golgi markers were enriched over the postnuclear supernatant 200- to 400-fold with and 400- to 700-fold without proteins in transit. To provide information on a mechanism for import of calcium required at the later stages of the secretory pathway, calcium uptake into CTL SGF1 and CHX SGF1 was examined. All calcium uptake into CTL SGF1 was dependent on a thapsigargin-resistant pump not resident to the Golgi complex and a thapsigargin-sensitive pump resident to the Golgi. Experiments using CHX SGF1 showed that the thapsigargin-resistant activity was a plasma membrane calcium ATPase isoform in transit to the plasma membrane and the thapsigargin-sensitive pump was a sarcoplasmic/endoplasmic reticulum calcium ATPase isoform. In vivo both of these calcium ATPases function to maintain millimolar levels of calcium within the Golgi lumen. 相似文献
999.
1000.
Robert C. Tuckey Julie Lawrence Kathryn J. Cameron 《The Journal of steroid biochemistry and molecular biology》1996,58(5-6):605-610
In order to define the substrate binding site of human cytochrome P-450scc in the vicinity of the 3β-hydroxyl group of cholesterol, we have tested the ability of the cytochrome to cleave the side chain of a range of cholesterol esters and cholesterol methyl ether. Using a Tween-20 detergent reconstituted system we found that cholesterol sulphate could undergo side-chain cleavage with the same turnover number (kcat) as that for cholesterol, but with a higher Km. Cholesterol methyl ether underwent side-chain cleavage to pregnenolone methyl ether with kcat and Km values 30% of those for cholesterol. Cholesterol fatty acid esters with acyl chain lengths of up to four carbons were able to undergo side-chain cleavage with Km values similar to those for cholesterol, but kcat values only 12–23% of those for cholesterol. Turnover numbers decreased as the acyl group length increased beyond four carbons, although some activity was still detected with cholesterol palmitate as substrate. Analysis of bovine cytochrome P-450scc revealed that it could also cleave the side chain of acyl and sulphate esters of cholesterol. This study indicates that the substrate binding site of cytochrome P-450scc in the vicinity of the 3β-hydroxyl group is larger than previously believed. 相似文献