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231.
Evolution of Mycobacterium ulcerans and other mycolactone-producing mycobacteria from a common Mycobacterium marinum progenitor 下载免费PDF全文
Yip MJ Porter JL Fyfe JA Lavender CJ Portaels F Rhodes M Kator H Colorni A Jenkin GA Stinear T 《Journal of bacteriology》2007,189(5):2021-2029
It had been assumed that production of the cytotoxic polyketide mycolactone was strictly associated with Mycobacterium ulcerans, the causative agent of Buruli ulcer. However, a recent study has uncovered a broader distribution of mycolactone-producing mycobacteria (MPM) that includes mycobacteria cultured from diseased fish and frogs in the United States and from diseased fish in the Red and Mediterranean Seas. All of these mycobacteria contain versions of the M. ulcerans pMUM plasmid, produce mycolactones, and show a high degree of genetic relatedness to both M. ulcerans and Mycobacterium marinum. Here, we show by multiple genetic methods, including multilocus sequence analysis and DNA-DNA hybridization, that all MPM have evolved from a common M. marinum progenitor to form a genetically cohesive group among a more diverse assemblage of M. marinum strains. Like M. ulcerans, the fish and frog MPM show multiple copies of the insertion sequence IS2404. Comparisons of pMUM and chromosomal gene sequences demonstrate that plasmid acquisition and the subsequent ability to produce mycolactone were probably the key drivers of speciation. Ongoing evolution among MPM has since produced at least two genetically distinct ecotypes that can be broadly divided into those typically causing disease in ectotherms (but also having a high zoonotic potential) and those causing disease in endotherms, such as humans. 相似文献
232.
Purification, identification and activity of phomodione, a furandione from an endophytic Phoma species 总被引:1,自引:0,他引:1
Hoffman AM Mayer SG Strobel GA Hess WM Sovocool GW Grange AH Harper JK Arif AM Grant DM Kelley-Swift EG 《Phytochemistry》2008,69(4):1049-1056
Phomodione, [(4aS(*),9bR(*))-2,6-diacetyl-7-hydroxy-4a,9-dimethoxy-8,9b-dimethyl-4a.9b-dihydrodibenzo[b,d]furan-1,3(2H,4H)-dione], an usnic acid derivative, was isolated from culture broth of a Phoma species, discovered as an endophyte on a Guinea plant (Saurauia scaberrinae). It was identified using NMR, X-ray crystallography, high resolution mass spectrometry, as well as infrared and Raman spectroscopy. In addition to phomodione, usnic acid and cercosporamide, known compounds with antibiotic activity, were also found in the culture medium. Phomodione exhibited a minimum inhibitory concentration of 1.6 microg/mL against Staphylococcus aureus using the disk diffusion assay, and was active against a representative oomycete, ascomycete and basidiomycete at between three and eight micro-grams per mL. 相似文献
233.
Otto GP Wu MY Clarke M Lu H Anderson OR Hilbi H Shuman HA Kessin RH 《Molecular microbiology》2004,51(1):63-72
The Gram-negative bacterium Legionella pneumophila is a facultative intracellular pathogen of free-living amoebae and mammalian phagocytes. L. pneumophila is engulfed in phagosomes that initially avoid fusion with lysosomes. The phagosome associates with endoplasmic reticulum (ER) and mitochondria and eventually resembles ER. The morphological similarity of the replication vacuole to autophagosomes, and enhanced bacterial replication in response to macroautophagy-inducing starvation, led to the hypothesis that L. pneumophila infection requires macroautophagy. As L. pneumophila replicates in Dictyostelium discoideum, and macroautophagy genes have been identified and mutated in D. discoideum, we have taken a genetic and cell biological approach to evaluate the relationship between host macroautophagy and intracellular replication of L. pneumophila. Mutation of the apg1, apg5, apg6, apg7 and apg8 genes produced typical macroautophagy defects, including reduced bulk protein degradation and cell viability during starvation. We show that L. pneumophila replicates normally in D. discoideum macroautophagy mutants and produces replication vacuoles that are morphologically indistinguishable from those in wild-type D. discoideum. Furthermore, a green fluorescent protein (GFP)-tagged marker of autophagosomes, Apg8, does not systematically co-localize with DsRed-labelled L. pneumophila. We conclude that macroautophagy is dispensable for L. pneumophila intracellular replication in D. discoideum. 相似文献
234.
Mark L. Mallory Anthony J. Gaston Mark R. Forbes H. Grant Gilchrist 《Polar Biology》2009,32(4):529-538
The northern fulmar (Fulmarus glacialis) is a common seabird of the North Atlantic Ocean, with breeding colonies broadly dispersed between 45°N and 80°N. At higher
latitudes, breeding fulmars experience extensive sea-ice and presumably snow and low temperatures which do not affect fulmars
in the southern part of the breeding range. We studied the relationship between weather and reproductive success of northern
fulmars breeding at two colonies in the Canadian high Arctic. Collectively, hatching success, fledging success, and productivity
(chicks fledged per egg laid) were similar between our study and results from colonies located south of the Arctic. However,
a larger proportion of fulmars at apparently occupied sites (AOS) in high Arctic colonies appeared to forego egg-laying, resulting
in lower proportions of chicks fledged per AOS. Extreme inclement weather was the major factor influencing nesting success,
resulting in pulses of egg or chick loss during or immediately following major storms, although the mechanism of effects appeared
to differ between the two colonies. For Arctic fulmars, the risks of nest failure due to stochastic, deleterious weather events
may be offset by the predictable abundance of food supplies during chick-rearing in Arctic waters. 相似文献
235.
236.
Multilocus genotypes from Charles Darwin's finches: biodiversity lost since the voyage of the Beagle
Kenneth Petren Peter R. Grant B. Rosemary Grant Andrew A. Clack Ninnia V. Lescano 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1543):1009-1018
Genetic analysis of museum specimens offers a direct window into a past that can predate the loss of extinct forms. We genotyped 18 Galápagos finches collected by Charles Darwin and companions during the voyage of the Beagle in 1835, and 22 specimens collected in 1901. Our goals were to determine if significant genetic diversity has been lost since the Beagle voyage and to determine the genetic source of specimens for which the collection locale was not recorded. Using ‘ancient’ DNA techniques, we quantified variation at 14 autosomal microsatellite loci. Assignment tests showed several museum specimens genetically matched recently field-sampled birds from their island of origin. Some were misclassified or were difficult to classify. Darwin''s exceptionally large ground finches (Geospiza magnirostris) from Floreana and San Cristóbal were genetically distinct from several other currently existing populations. Sharp-beaked ground finches (Geospiza difficilis) from Floreana and Isabela were also genetically distinct. These four populations are currently extinct, yet they were more genetically distinct from congeners than many other species of Darwin''s finches are from each other. We conclude that a significant amount of the finch biodiversity observed and collected by Darwin has been lost since the voyage of the Beagle. 相似文献
237.
238.
Plasminogen activator inhibitor-type I is a major biosynthetic product of retinal microvascular endothelial cells and pericytes in culture. 总被引:2,自引:1,他引:2 下载免费PDF全文
A E Canfield A M Schor D J Loskutoff S L Schor M E Grant 《The Biochemical journal》1989,259(2):529-535
Previous studies have shown that a glycoprotein of Mr 47,000 (designated Gp47) is a major biosynthetic product of retinal endothelial cells in vitro (Canfield, Schor, West, Schor & Grant (1987) Biochem. J. 246, 121-129). We now present data indicating that (a) an identical protein is secreted by bovine retinal pericytes, (b) this protein is plasminogen activator inhibitor-type I (PAI-1), as revealed by immunoprecipitation with specific antibodies and reverse fibrin zymography, and (c) retinal endothelial cells and pericytes synthesize different species of matrix macromolecules, that is: type IV collagen is the major collagen secreted by endothelial cells, whereas pericytes produce predominantly type I collagen; fibronectin and thrombospondin are synthesized by both cell types. Our studies also indicate that PAI-1 is produced, albeit at considerably lower levels, by large vessel vascular cells (aortic endothelial and smooth muscle cells) and human skin fibroblasts. PAI-1 produced by human skin fibroblasts appears to be a distinct molecular species compared to its bovine counterpart as assessed by its slower mobility on SDS/polyacrylamide-gel electrophoresis. The potential significance of elevated PAI-1 production by retinal endothelial cells and pericytes, as well as their distinctive patterns of matrix biosynthesis, is discussed in terms of the involvement of these cells in the maintenance and remodelling of microvessel basement membrane. 相似文献
239.
Isolation,culture and regeneration of protoplasts from birdsfoot trefoil (Lotus corniculatus) 总被引:1,自引:0,他引:1
A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus L. cv. Leo). Green cotyledons from in vitro grown seedlings were preplasmolyzed in CPW salts containing 13% mannitol (CPW 13 M) for 1 h prior to the enzyme treatment. The enzyme formula consisted of 2% (w/v) Onozuka Cellulase R-10, 1% (w/v) Macerase and 0.1% (w/v) Pectolyase Y-23 in CPW 13 M. This method produced high yields of viable protoplasts after purification. The procedure is reproducible and takes approximately 2.5 months from protoplast isolation to plantlet establishment in a greenhouse. More than 100 plantlets were grown in soil. Two somaclonal variants, a chimeric plant for chlorophyll production and an albino cell line, have been obtained by this procedure. 相似文献
240.