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61.
Importance of topography and soil texture in the spatial distribution of two sympatric dipterocarp trees in a Bornean rainforest 总被引:1,自引:0,他引:1
Akira?ItohEmail author Takuo?Yamakura Tatsuhiro?Ohkubo Mamoru?Kanzaki Peter A.?Palmiotto James V.?LaFrankie Peter S.?Ashton Hua Seng?Lee 《Ecological Research》2003,18(3):307-320
Relationships between spatial distributions and site conditions, namely topography and soil texture, were analyzed for two congeneric emergent trees, Dryobalanops aromatica and Dryobalanops lanceolata (Dipterocarpaceae), in a tropical rainforest in Sarawak, East Malaysia. A 52-ha permanent plot was divided into 1300 quadrats measuring 20m×20m; for each Dryobalanops species, the number and total basal area of trees 1cm in d.b.h. were compared among groups of quadrats with different site conditions. Because spatial distributions of both Dryobalanops and site-condition variables were aggregated, Monte-Carlo permutation tests were applied to analyze the relationships. Both single and multifactor statistical tests showed that the density and basal area distributions of the two species were significantly non-random in relation to soil texture and topographic variables. D.aromatica was significantly more abundant at higher elevations, in sandy soils, and on convex and steep slopes. In contrast, D.lanceolata preferred lower elevations and less sandy soils. In the study plot, there were very few sites (3 of 1150 quadrats tested) where the models of Hayashis method predicted the co-occurrence of the two species. These results suggest that between-species differences in habitat preferences are so large that they alone explain the spatially segregated distributions of these two species within the 52-ha study plot. 相似文献
62.
63.
Ashton JR 《BMJ (Clinical research ed.)》2000,321(7274):1473
64.
Fibrinogen Lille, a congenital dysfibrinogenemia, has been reported to arise from a mutation from Asp to Asn at position 7 of the A alpha chain of human fibrinogen, thereby reducing the thrombin-catalyzed rate of hydrolysis of the Arg(16)-Gly(17) peptide bond of this chain. Synthetic peptides of relevant portions of the wild-type and mutant A alpha chains were prepared, and the thrombin-catalyzed rates of hydrolysis of their Arg(16)-Gly(17) peptide bonds were determined. In addition, transferred NOE measurements were made to deduce their conformations, when complexed to bovine thrombin. The kinetics data showed little difference in the hydrolysis rates between the wild-type and mutant peptides, and the NMR data indicate no difference in the bound conformation of these two peptides. Therefore, electrostatic (or salt-bridge) interactions between Asp(7) and thrombin do not influence the bound conformations of these peptides. Asp(7) may interact with a remote residue of fibrinogen, not present in these synthetic peptides, or there may be additional mutations beyond A alpha (1-20) which have not been detected in fibrinogen Lille. Alternatively, when thrombin binds to fibrinogen at its secondary binding site, its primary (active) site may display different reactivities toward wild-type fibrinogen and fibrinogen Lille. 相似文献
65.
Facchiano Francesco Deloye Florence Doussau Frédéric Innamorati Giulio Ashton Anthony C. Dolly J. Oliver Beninati Simone Facchiano Angelo Luini Alberto Poulain Bernard Benfenati Fabio 《Amino acids》2010,38(1):257-262
The aim of this study was to collect evidences on the role of transglutaminase (TG, E.C.2.3.2.13) in the antineoplastic properties
exerted by nimesulide (NMS), a non-steroidal anti-inflammatory drug, on murine B16-F10 melanoma cells. Treatment of melanoma
cells with nimesulide produces a considerable reduction of cell proliferation, paralleled by a remarkable decrease of the
intracellular concentration of polyamines spermidine and spermine. NMS treatment induces cancer cell differentiation, likely
through the observed enhancement of TG and tyrosinase activities and increase of melanin production, well known markers of
melanocyte differentiation. The overall results highlight the possibility that nimesulide acts as antineoplastic agent likely
through the induction of intracellular TG activity. 相似文献
66.
Siegel DH Ashton GH Penagos HG Lee JV Feiler HS Wilhelmsen KC South AP Smith FJ Prescott AR Wessagowit V Oyama N Akiyama M Al Aboud D Al Aboud K Al Githami A Al Hawsawi K Al Ismaily A Al-Suwaid R Atherton DJ Caputo R Fine JD Frieden IJ Fuchs E Haber RM Harada T Kitajima Y Mallory SB Ogawa H Sahin S Shimizu H Suga Y Tadini G Tsuchiya K Wiebe CB Wojnarowska F Zaghloul AB Hamada T Mallipeddi R Eady RA McLean WH McGrath JA Epstein EH 《American journal of human genetics》2003,73(1):174-187
Kindler syndrome is an autosomal recessive disorder characterized by neonatal blistering, sun sensitivity, atrophy, abnormal pigmentation, and fragility of the skin. Linkage and homozygosity analysis in an isolated Panamanian cohort and in additional inbred families mapped the gene to 20p12.3. Loss-of-function mutations were identified in the FLJ20116 gene (renamed “KIND1” [encoding kindlin-1]). Kindlin-1 is a human homolog of the Caenorhabditis elegans protein UNC-112, a membrane-associated structural/signaling protein that has been implicated in linking the actin cytoskeleton to the extracellular matrix (ECM). Thus, Kindler syndrome is, to our knowledge, the first skin fragility disorder caused by a defect in actin-ECM linkage, rather than keratin-ECM linkage. 相似文献
67.
An 11-week crossover study was carried out in which 12 subjects smoked high-nicotine (1·84 mg standard yield) and low-nicotine (0·6 mg) cigarettes after an initial period of smoking their usual brands with a medium-nicotine yield (mean 1·4 mg). Plasma and urine nicotine concentrations, carboxyhaemoglobin (COHb) concentration, puffing behaviour, 24-hour cigarette consumption, and butt nicotine content were measured. The changes in plasma nicotine and blood COHb concentrations showed that the smokers compensated for about two-thirds of the difference in standard yields when switched to either high- or low-nicotine cigarettes. Thus, compared with the medium-nicotine brand, the intake of nicotine and carbon monoxide was only about 10% higher when subjects smoked the high-nicotine cigarettes, which had a standard yield 30-40% higher than the medium brands; and only about 15% lower when they smoked the low-nicotine cigarettes, which had a standard yield about 50% lower than the medium brands. But nicotine content and urine nicotine concentrations followed a similar pattern. Changes in puffing behaviour and in 24-hour cigarette consumption were only slight.The results show clear evidence of both upward and downward self-titration of nicotine and carbon monoxide (and tar) intakes when smokers change to cigarettes with standard yields that differ over the range studied. 相似文献
68.
Palmer DA Thompson JK Li L Prat A Wang P 《The Journal of biological chemistry》2006,281(43):32596-32605
Canonical G proteins are heterotrimeric, consisting of alpha, beta, and gamma subunits. Despite multiple Galpha subunits functioning in fungi, only a single Gbeta subunit per species has been identified, suggesting that non-conventional G protein signaling exists in this diverse group of eukaryotic organisms. Using the Galpha subunit Gpa1 that functions in cAMP signaling as bait in a two-hybrid screen, we have identified a novel Gbeta-like/RACK1 protein homolog, Gib2, from the human pathogenic fungus Cryptococcus neoformans. Gib2 contains a seven WD-40 repeat motif and is predicted to form a seven-bladed beta propeller structure characteristic of beta transducins. Gib2 is also shown to interact, respectively, with two Ggamma subunit homologs, Gpg1 and Gpg2, similar to the conventional Gbeta subunit Gpb1. In contrast to Gpb1 whose overexpression promotes mating response, overproduction of Gib2 suppresses defects of gpa1 mutation in both melanization and capsule formation, the phenotypes regulated by cAMP signaling and associated with virulence. Furthermore, depletion of Gib2 by antisense suppression results in a severe growth defect, suggesting that Gib2 is essential. Finally, Gib2 is shown to also physically interact with a downstream target of Gpa1-cAMP signaling, Smg1, and the protein kinase C homolog Pkc1, indicating that Gib2 is also a multifunctional RACK1-like protein. 相似文献
69.
Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints 下载免费PDF全文
Robert K. Colwell Nicholas J. Gotelli Louise A. Ashton Jan Beck Gunnar Brehm Tom M. Fayle Konrad Fiedler Matthew L. Forister Michael Kessler Roger L. Kitching Petr Klimes Jürgen Kluge John T. Longino Sarah C. Maunsell Christy M. McCain Jimmy Moses Sarah Noben Katerina Sam Legi Sam Arthur M. Shapiro Xiangping Wang Vojtech Novotny 《Ecology letters》2016,19(9):1009-1022
We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the diverse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor – a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon‐specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data sampled along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness. 相似文献
70.
Cyclic adenosine monophosphate (cAMP) drives genetic polycystic kidney disease (PKD) cystogenesis. Yet within certain PKD families, striking differences in disease severity exist between affected individuals, and genomic and/or environmental modifying factors have been evoked to explain these observations. We hypothesized that PKD cystogenesis is accentuated by an aberrant fetal milieu, specifically by glucocorticoids. The extent and nature of cystogenesis was assessed in explanted wild-type mouse embryonic metanephroi, using 8-Br-cAMP as a chemical to mimic genetic PKD and the glucocorticoid dexamethasone as the environmental modulator. Cysts and glomeruli were quantified by an observer blinded to culture conditions, and tubules were phenotyped using specific markers. Dexamethasone or 8-Br-cAMP applied on their own produced cysts predominantly arising in proximal tubules and descending limbs of loops of Henle. When applied together, however, dexamethasone over a wide concentration range synergized with 8-Br-cAMP to generate a more severe, glomerulocystic, phenotype; we note that prominent glomerular cysts have been reported in autosomal dominant PKD fetal kidneys. Our data support the idea that an adverse antenatal environment exacerbates renal cystogenesis. 相似文献