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991.
João CR Cardoso Florbela A Vieira Ana S Gomes Deborah M Power 《BMC evolutionary biology》2010,10(1):135
Background
The secretin family is a pleotropic group of brain-gut peptides with affinity for class 2 G-protein coupled receptors (secretin family GPCRs) proposed to have emerged early in the metazoan radiation via gene or genome duplications. In human, 10 members exist and sequence and functional homologues and ligand-receptor pairs have been characterised in representatives of most vertebrate classes. Secretin-like family GPCR homologues have also been isolated in non-vertebrate genomes however their corresponding ligands have not been convincingly identified and their evolution remains enigmatic. 相似文献992.
The ZIP (ZRT-, IRT-like Protein) protein ZupT from Escherichia coli is a transporter with a broad substrate range. Phenotypic and transport analysis showed that ZupT, in addition to Zn(II),
Fe(II) and Co(II) uptake, is also involved in transport of Mn(II) and Cd(II). Competition experiments with other substrate
cations suggested that ZupT has a slight preference for Zn(II) and kinetic parameters for Zn(II) in comparison to Co(II) and
Mn(II) transport support this observation. Metal uptake into cells by ZupT was optimum at near neutral pH and inhibited by
ionophores. Bicarbonate or other ions did not influence metal-uptake via ZupT. Amino acid residues of ZupT contributing to
substrate specificity were identified by site directed mutagenesis. ZupT with a H89A exchange lost Co(II) and Fe(II) transport
activity, while the S117V mutant no longer transported Mn(II). ZupT with E152D was impaired in overall metal uptake but completely
lost its ability to transport the substrates Zn(II) and Mn(II). These experimental findings expand our knowledge on the substrate
specificity of ZupT and provide further insight into the function of ZupT as a bacterial member of the vastly distributed
and important ZIP family. 相似文献
993.
Sediment organic matter (OM) and its stable carbon and nitrogen isotopes were studied in 12 Slovenian mountain lakes in the
Julian Alps. The lakes have different catchment areas and display a range of trophic states. Surface sediment atomic C/N ratios
ranged from 8.4 to 13.2. Based on these C/N ratios, we concluded that autochthonous OM dominates in these lakes and constitutes
approximately 65–92% of the total OM. Higher contributions of autochthonous OM sources were observed in lakes above the tree
line. Relatively constant C/N ratios in the deeper sediments suggest that degradation processes are most intense in the upper
few centimetres of the sediments and/or that remaining OM is relatively resistant to further degradation. Surface sediment
δ13C and δ15N values ranged from −36.1 to −14.1‰ and from −5.2 to +1.1‰, respectively. In sediment cores from seven lakes, higher δ13C and lower δ15N values characterize oligotrophic lakes situated above the tree line, whereas the reverse is true for eutrophic lakes below
the tree line that are also exposed to more anthropogenic impact. Carbon and nitrogen biogeochemical cycling differs considerably
among the lakes. Stratigraphic shifts in carbon, total nitrogen, C/N ratios and stable C and N isotopes in cores record changes
in inputs, and hence water column processes, as well as alterations in loading to the lakes. The stratigraphic variations
are also the result of post-depositional diagenetic changes in the upper few centimetres of sediment. All the lakes show impacts
from recent increases in atmospheric deposition of dissolved inorganic nitrogen. Application of sediment OM analysis thus
proved to be useful to reconstruct paleoecological changes in sensitive mountain lake ecosystems that are either natural and/or
anthropogenically derived. 相似文献
994.
995.
Gregor Ilc Gabriele Giachin Mariusz Jaremko ?ukasz Jaremko Federico Benetti Janez Plavec Igor Zhukov Giuseppe Legname 《PloS one》2010,5(7)
Prion diseases are fatal neurodegenerative disorders caused by an aberrant accumulation of the misfolded cellular prion protein (PrPC) conformer, denoted as infectious scrapie isoform or PrPSc. In inherited human prion diseases, mutations in the open reading frame of the PrP gene (PRNP) are hypothesized to favor spontaneous generation of PrPSc in specific brain regions leading to neuronal cell degeneration and death. Here, we describe the NMR solution structure of the truncated recombinant human PrP from residue 90 to 231 carrying the Q212P mutation, which is believed to cause Gerstmann-Sträussler-Scheinker (GSS) syndrome, a familial prion disease. The secondary structure of the Q212P mutant consists of a flexible disordered tail (residues 90–124) and a globular domain (residues 125–231). The substitution of a glutamine by a proline at the position 212 introduces novel structural differences in comparison to the known wild-type PrP structures. The most remarkable differences involve the C-terminal end of the protein and the β2–α2 loop region. This structure might provide new insights into the early events of conformational transition of PrPC into PrPSc. Indeed, the spontaneous formation of prions in familial cases might be due to the disruptions of the hydrophobic core consisting of β2–α2 loop and α3 helix. 相似文献
996.
The Donaciinae consist of approximately 165 species predominantly occurring in the northern hemisphere. We analysed mitochondrial and nuclear DNA (COI, EF-1alpha) of 46 species to investigate their phylogeny and to discuss general topics in the context of insect herbivory (generalists versus specialists, ecological speciation). Phylogenetic reconstructions from various methodical approaches yielded very similar results. Clades corresponding to the traditional tribes/genera were recovered. Within the genus Donacia, species groups with characteristic host plant preference were identified. Estimated divergence times are discussed on the background of geological events. The origin of the Donaciinae is dated to 75-100 million years before present, after which they quickly diversified into the main groups. An initial split of those groups occurred in the Palaeocene. In the Eocene and Oligocene, major lineages specialized on certain host plants, where they radiated in the Miocene. This radiation was enforced by geographic isolation brought about by the final separation of America and Europe, after which there arose continental lineages within three larger species groups. In their evolution based on ecological specialization with a recently superimposed geographic isolation, the Donaciinae follow a pattern of specialists arising from generalists. Host plant shifts show that such a specialization is not necessarily an 'evolutionary dead-end'. 相似文献
997.
Rabzelj S Viero G Gutiérrez-Aguirre I Turk V Dalla Serra M Anderluh G Zerovnik E 《The FEBS journal》2008,275(10):2455-2466
Human stefin B, from the family of cystatins, is used as a model amyloidogenic protein in studies of the mechanism of amyloid fibril formation and related cytotoxicity. Interaction of the protein's prefibrillar oligomers/aggregates with predominantly acidic phospholipid membranes is known to correlate with cellular toxicity. In the present study, we measured membrane interaction of the prefibrillar and native states for three variants: the Y31 isoform studied previously, the wild-type protein and the G4R mutant; the latter is observed in progressive myoclonus epilepsy of type 1. In addition to using critical pressure and surface plasmon resonance, we assessed membrane permeabilization by calcein release and electrophysiological measurements. It was demonstrated for the first time that wild-type stefin B and the Y31 isoform are able to form pores in planar lipid bilayers, whereas G4R destroys the bilayer by a non pore-forming process. Similarities to other amyloidogenic proteins and the possible physiological implications of our findings are discussed. 相似文献
998.
999.
Larsson J Ohishi M Garrison B Aspling M Janzen V Adams GB Curto M McClatchey AI Schipani E Scadden DT 《Cell Stem Cell》2008,3(2):221-227
Stem cell population size is highly regulated across species and tissue types, and alterations are associated with premature tissue failure or cancer. We assessed whether the tumor suppressor and mediator of cell contact inhibition Nf2/merlin plays a role in governing the hematopoietic stem cell pool by stem cell-autonomous or niche-determined processes. Hematopoietic stem cells in Nf2-deficient mice were increased in number and demonstrated a marked shift in location to the circulation. These changes were entirely dependent on changes in the microenvironment, with a marked increase in trabecular bone and marrow vascularity associated with increased VEGF, but without cell-autonomous alterations in stem cell characteristics. Nf2/merlin is critical for maintaining normal structure and function of the hematopoietic stem cell niche. It limits both bone and vascular components, and our model suggests that it thereby constrains stem cell number and position. 相似文献
1000.
Lutz Brutigam Gregor Vetter Irmgard Tegeder Georg Heinkele Gerd Geisslinger 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2001,761(2)
Methods for the determination of celecoxib in human plasma and rat microdialysis samples using liquid chromatography tandem mass spectrometry are described. Celecoxib and an internal standard were extracted from plasma by solid-phase extraction with C18 cartridges. Thereafter compounds were separated on a short narrow bore RP C18 column (30×2 mm). Microdialysis samples did not require extraction and were injected directly using a narrow bore RP C18 column (70×2 mm). The detection was by a PE Sciex API 3000 mass spectrometer equipped with a turbo ion spray interface. The compounds were detected in the negative ion mode using the mass transitions m/z 380→316 and m/z 366→302 for celecoxib and internal standard, respectively. The assay was validated for human plasma over a concentration range of 0.25–250 ng/ml using 0.2 ml of sample. The assay for microdialysis samples (50 μl) was validated over a concentration range of 0.5–20 ng/ml. The method was utilised to determine pharmacokinetics of celecoxib in human plasma and in rat spinal cord perfusate. 相似文献