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1.
Air transport can move patients safely and rapidly over long distances. However, changes in altitude can have disastrous effects because diminished ambient air pressure may allow gases in closed spaces and tissues to expand rapidly. Even pressurized commercial aircraft do not maintain sea-level pressure: cabin pressures equal to those at yp to 8000 ft may be experienced, diminishing oxygen tension in proportion. Air transport is absolutely contraindicated for patients with untreated pneumothorax, gas gangrene, or air trapped in the cranium and those who have recently undergone abdominal surgery. Special considerations including a planned low-altitude flight are warrented for patients who are anemic, in respiratory or cardiac distress, or immobilized in casts, or who have been engaged in underwater diving immediately before the flight. 相似文献
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Novel inhibition of proteoglycan synthesis and exocytosis by diethylcarbamazine in the Swarm rat chondrocyte 总被引:2,自引:0,他引:2
R L Stevens W G Parsons K F Austen A Hein J P Caulfield 《The Journal of biological chemistry》1985,260(9):5777-5786
Pretreatment of cultured chondrosarcoma chondrocytes at 37 degrees C for 15 min with 15 mM diethylcarbamazine (DEC) followed by a 60-min pulse with [35S] sulfate in the presence of DEC resulted in an approximate 40% inhibition of synthesis and a 75% inhibition of secretion of 35S-proteoglycan. The inhibition was dose-related and was not due to a decrease in protein synthesis. Chondrocytes exposed for 75 min to 15 mM DEC, washed, incubated for 17 h in DEC-free medium, and then pulsed with [35S]sulfate showed no inhibition in the rate of synthesis of proteoglycan or in the per cent of radiolabeled proteoglycans exocytosed into the culture medium, indicating full reversibility of the inhibitory effect. When chondrocytes were incubated for 75 min with both 1 mM beta-D-xyloside and 15 mM DEC, secretion of beta-D-xyloside-bound 35S-glycosaminoglycan was inhibited by more than 70% despite an approximate 3-fold increase in intracellular 35S-macromolecules, as compared to cells exposed to beta-D-xyloside alone. Upon removal of DEC, the block in the secretion of beta-D-xyloside-bound 35S-glycosaminoglycans was reversed, although there was a 15-30-min lag in the initiation of exocytosis. Light and electron microscopic examination of chondrocytes after 75 min of incubation with 15 mM DEC revealed large vacuoles, a distended Golgi apparatus, and a distended endoplasmic reticulum which contained electron dense material. Upon removal of DEC, the vacuoles disappeared and distended organelles returned to their normal appearance between 15 and 30 min, coincident with the start of exocytosis of 35S-proteoglycan and beta-D-xyloside-bound 35S-glycosaminoglycan. These biochemical and morphological studies indicate that DEC treatment of chondrosarcoma chondrocytes alters the transport of molecules from the endoplasmic reticulum to the Golgi and the transport of molecules from the Golgi to the cell surface. 相似文献
3.
This study evaluated the genetic consequences of a reintroduction of the endangered annual plant Cordylanthus maritimus ssp. maritimus to Sweetwater Marsh (San Diego County, California). A survey of 21 enzyme loci in natural populations revealed that genetic diversity is very low and is primarily found as rare alleles at a few loci, making this species especially susceptible to the loss of alleles and heterozygosity through genetic drift. The reintroduction was performed in 1991 and 1992 by sowing seeds (collected from Tijuana Estuary) in numerous small patches of suitable habitat. For this study, leaf tissue was collected from all plants in all patches during flowering in 1995 and surveyed for genotype at the three enzyme loci that are polymorphic at Tijuana Estuary. Rare alleles were absent in 27 out of 30 patches for Pgm-1, in 17 out of 30 patches for Pgm-2, and in 10 out of 11 patches for Mdh-1. In all, half of the patches lacked any rare allele. Rare alleles tended to occur in patches with few individuals. Overall rare allele frequency was lower than in the colonies from which seeds were collected at two of the three loci, and heterozygosity was reduced. The Sweetwater Marsh population is at risk of losing most of its genetic variation at enzyme loci through the extinction of patches with few individuals. Future reintroduction attempts should attempt to create contiguous sets of patches or to periodically reseed existing patches to reduce the loss of genetic variation. 相似文献
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Resistance to human serum of gonococci in urethral exudates is reduced by neuraminidase 总被引:3,自引:0,他引:3
N J Parsons J A Cole H Smith 《Proceedings. Biological sciences / The Royal Society》1990,241(1300):3-5
Gonococci examined directly from urethral exudates are resistant to killing by human serum, but most strains become susceptible on subculture. Previous work with gonococci grown in vitro indicates that resistance in vivo is due to sialylation of gonococcal lipopolysaccharide (LPS) by a host factor, cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA) or a related compound present in urogenital secretions and blood cells including phagocytes, which exude during inflammation. This sialylation inhibits the reaction between bactericidal IgM in serum and its target LPS sites. Here, we confirm the indication by using gonococci grown in vivo. Crucial to the above conclusions was the marked reduction of CMP-NANA-conferred serum resistance when gonococci were treated with neuraminidase to remove sialyl groups from their LPS. We now show that the serum resistance of gonococci in urethral exudates was reduced by treatment with neuraminidase from more than 95% (calculated in relation to controls incubated with heated serum) to 2-11% according to sample and incubation time. Subculture of the gonococci also reduced resistance to 9-11% but resistance was restored to more than 95% by incubation with CMP-NANA. This work is the culmination of an investigation that underlines the need to identify specific host factors and the virulence determinants they induce in vivo in future studies of pathogenicity. 相似文献
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C J Duncan C L Osborne J J Parsons K E McCall M J Jackson 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1988,90(2):459-460
1. Isolated amphibian hearts and pectoris cutaneous muscles were exposed either to DNP or to caffeine, thereby producing severe myofilament damage. 2. No accompanying change in sarcolemma permeability was detected by monitoring either CK or LDH release or Procion yellow entry in the heart, or by Procion entry in amphibian skeletal muscle. 3. The findings are in contrast with mammalian cardiac and skeletal muscles, and confirm that the pathways leading to myofilament degradation and to the breakdown in sarcolemma organization are separate. 相似文献