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951.
952.
In this work we used molecular simulations to investigate the elastic properties of collagen single chain and triple helix with the aim of understanding its features starting from first principles. We analysed ideal collagen peptides, homotrimeric and heterotrimeric collagen type I and pathological models of collagen. Triple helices were found much more rigid than single chains, thus enlightening the important role of interchain stabilizing forces, like hydrophobic interaction and hydrogen bonds. We obtained Young's moduli close to 4.5GPa for the ideal model of collagen and for the physiological heterotrimer, while the physiological homotrimer presented a Young's modulus of 2.51GPa, that can be related to a mild form of Osteogenesis Imperfecta in which only the homotrimeric form of collagen type I is produced. Otherwise, the pathological model (presenting a glycine to alanine substitution) showed an elastic modulus of 4.32GPa, thus only slightly lower than the ideal model. This suggests that this mutation only slightly affects the mechanical properties of the collagen molecule, but possibly acts on an higher scale, such as the packing of collagen fibrils. 相似文献
953.
Involvement of non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase in response to oxidative stress 总被引:1,自引:0,他引:1
Glyceraldehyde-3-phosphate dehydrogenases catalyze key steps in energy and reducing power partitioning in cells of higher plants. Because non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (NP-Ga3PDHase) is involved in the production of reductive power (NADPH) in the cytosol, its behavior under oxidative stress conditions was analyzed. The specific activity of the enzyme was found to increase up to 2-fold after oxidative conditions imposed by methylviologen in wheat and maize seedlings. Under moderate oxidant concentration, lack of mRNA induction was observed. The increase in specific activity would thus be a consequence of a significant stability of NP-Ga3PDHase. Our results suggest that the enzyme could be modified by oxidation of cysteine residues, but formation of disulfide bridges is dependent on levels of divalent cations and 14-3-3 proteins. The latter differential effect could be critical to relatively maintain energy and reductant levels in the cytoplasm of plant cells under oxidative stress. 相似文献
954.
Brian A Stacy Mario Santoro Juan Alberto Morales Louis M Huzella Victor F Kalasinsky Allen Foley Nancy Mettee Elliott R Jacobson 《Diseases of aquatic organisms》2008,80(1):45-49
Eighteen green turtles Chelonia mydas recovered from the Atlantic and Gulf coasts of Florida and Tortuguero National Park, Costa Rica, were diagnosed with renal oxalosis by histopathological examination. Affected sea turtles included 14 adults and 4 immature animals, which comprised 26% (18/69) of green turtle necropsy cases available for review. Calcium oxalate deposition ranged from small to moderate amounts and was associated with granuloma formation and destruction of renal tubules. All affected turtles died from traumatic events or health problems unrelated to renal oxalosis; however, 1 immature turtle had notable associated renal injury. Crystal composition was confirmed by infrared and scanning electron microscopy and energy dispersive X-ray analysis. The source of calcium oxalate is unknown and is presumed to be of dietary origin. 相似文献
955.
956.
957.
Puerma E Acosta MJ Barragán MJ Martínez S Marchal JA Bullejos M Sánchez A 《Genetica》2008,134(3):287-295
The karyotype of individuals of the species Rhinolophus hipposideros from Spain present a chromosome number of 2n = 54 (NFa = 62). The described karyotype for these specimens is very similar to another previously described in individual
from Bulgaria. However, the presence of one additional pair of autosomal acrocentric chromosomes in the Bulgarian karyotype
and the differences in X chromosome morphology indicated that we have described a new karyotype variant in this species. In
addition, we have analyzed several clones of 1.4 and 1 kb of a PstI repeated DNA sequence from the genome of R. hipposideros. The repeated sequence included a region with high identity with the 5S rDNA genes and flanking regions, with no homology
with GenBank sequences. Search for polymerase III regulatory elements demonstrated the presence of type I promoter elements
(A-box, Intermediate Element and C-box) in the 5S rDNA region. In addition, upstream regulatory elements, as a D-box and Sp1
binding sequences, were present in flanking regions. All data indicated that the cloned repeated sequences are the functional
rDNA genes from this species. Finally, FISH demonstrated the presence of rDNA in nine chromosome pairs, which is surprising
as most mammals have only one carrier chromosome pair. 相似文献
958.
Paola Rebuzzini Tui Neri Maurizio Zuccotti Carlo Alberto Redi Silvia Garagna 《Cytotechnology》2008,58(1):17-23
Although mouse embryonic stem cell lines (mESCs) have been established since 1981, systematic studies about chromosomal changes
during culture are lacking. In this study, we report the results of a cytogenetic analysis performed on three mESC lines (named
UPV02, UPV06 and UPV08) cultured for a period of 3 months. At time intervals, the variation of the chromosome number together
with the expression of markers of the undifferentiated status, i.e., OCT-4, SSEA-1, FOM-1 and alkaline phosphatase activity,
were determined. The three mESC lines showed a progressive loss of euploid metaphases during the 3 months period of culture.
Chromosome abnormalities were accumulated at the latest passages analysed. Metacentric chromosomes were the most frequent
chromosome abnormality observed throughout the period of culture. Interestingly, in coincidence with, or few passages after,
the drop of euploidy, the alkaline phosphatase activity was partially or totally lost, whereas the OCT-4, SSEA-1 and FOM-1
stem markers were always positive throughout the period of culture. Our results remark the necessity to perform the karyotype
analysis during culture in order to develop new culture conditions to maintain the correct chromosome complement in long-term
culture of mESC lines. 相似文献
959.
Murciano C Yáñez A O'Connor JE Gozalbo D Gil ML 《FEMS immunology and medical microbiology》2008,53(2):214-221
Previous work by our group showed that aged C57BL/6 mice develop an altered innate and adaptive immune response to Candida albicans and are more susceptible to systemic primary candidiasis. In this work, we used young (2-3 months old) and aged (18-20 months old) C57BL/6 mice to study in vitro the influence of aging on (1) the fungicidal activity of neutrophils and macrophages, (2) the production of cytokines by resident peritoneal macrophages in response to C. albicans, and (3) cell surface Toll-like receptor (TLR) 2 expression on resident peritoneal macrophages. Our results indicate that murine phagocytes have a fungicidal activity well preserved with aging. In vitro production of proinflammatory cytokines (IL-6, IL-1beta, and tumor necrosis factor-alpha and chemokines (MIP-2) by purified (CD11b(+)) peritoneal macrophages in response to yeasts and hyphae of C. albicans was significantly lower in aged mice as compared with young mice. However, the production of IL-10 by macrophages, in response to C. albicans, was similar in both young and aged animals. Moreover, baseline TLR2 surface expression level was lower on aged macrophages than on control macrophages. Taken together, these data indicate that the increased susceptibility to C. albicans disseminated infections in aged mice is correlated with defects in TLR2 expression and in cytokine production, but not with an impaired fungicidal activity. 相似文献
960.
The trans-Golgi network (TGN) is one of the main, if not the main, sorting stations in the process of intracellular protein trafficking.
It is therefore of central importance to understand how the key players in the TGN-based sorting and delivery process, the
post-Golgi carriers (PGCs), form and function. Over the last few years, modern morphological approaches have generated new
insights into the questions of PGC biogenesis, structure and dynamics. Here, we present a view by which the “lifecycle” of
a PGC consists of several distinct stages: the formation of TGN tubular export domains (where different cargoes are segregated
from each other and from the Golgi enzymes); the docking of these tubular domains onto molecular motors and their extrusion
towards the cell periphery along microtubules; the fission of the forming PGC from the donor membrane; and the delivery of
the newly formed PGC to its specific acceptor organelle. It is now important to add the many molecular machineries that have
been described as operating at the TGN to this “morphofunctional map” of the TGN export process. 相似文献