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961.
Globally, the eutrophication of coastal marine environments is a worsening problem that is accelerating the loss of biodiversity and ecosystem services. Coral reefs are among the most sensitive to this change, as chronic inputs of agricultural and wastewater effluents and atmospheric deposition disrupt their naturally oligotrophic state. Often, anthropogenic alteration of the coastal nitrogen pool can proceed undetected as rapid mixing with ocean waters can mask chronic and ephemeral nitrogen inputs. Monitoring nitrogen stable isotope values (δ 15N) of benthic organisms provides a useful solution to this problem. Through a 7-yr monitoring effort in Quintana Roo, Mexico, we show that δ 15N values of the common sea fan Gorgonia ventalina were more variable near a developed (Akumal) site than at an undeveloped (Mahahual) site. Beginning in 2007, the global recession decreased tourist visitations to Akumal, which corresponded with a pronounced 1.6 ‰ decline in sea fan δ 15N through 2009, at which time δ 15N values were similar to those from Mahahual. With the recovery of tourism, δ 15N values increased to previous levels. Overall, 84 % of the observed variation in δ 15N was explained by tourist visitations in the preceding year alone, indicating that variable nitrogen source contributions are correlated with sea fan δ 15N values. We also found that annual precipitation accounted for some variation in δ 15N, likely due to its role in groundwater flushing into the sea. Together, these factors accounted for 96 % of the variation in δ 15N. Using a mixing model, we estimate that sewage can account for up to 42 % of nitrogen in sea fan biomass. These findings illustrate the high connectivity between land-based activities and coral reef productivity and the measurable impact of the tourism industry on the ecosystem it relies on. 相似文献
962.
Mixtures of toluene, ethylbenzene, and the xylenes spiked with 14C-labeled toluene or m-xylene were added to bench-scale bioventing simulation columns filled with hydrocarbon-contaminated subsurface soils. After 2 to 4 weeks of incubation during which air was pumped through the column at rates of at least 2?ml·min?1·kg?1 between 54 and 84% of the radiolabel was recovered in traps as outgassed parent compound from four columns sterilized with gamma-irradiation. In contrast, seven nonsterilized but otherwise identically treated (except for inorganic nitrogen addition) columns lost less than 0.4% (and one column lost 0.7%) of the radiolabel through outgassing of the parent compound. Nonsterilized columns lost 40 to 61% of the radiolabel as 14CO2, whereas gamma-irradiated columns usually lost only trace amounts of 14C in this form. Biologically active columns also retained much larger fractions than sterilized columns of the radiolabel in the subsoil in forms, possibly microbial biomass, from which it could be recovered by wet oxidation. Addition of 10 or 40?mg/kg of mineral nitrogen had no consistent effect on bioventing performance. 相似文献
963.
Ds excision from extrachromosomal geminivirus vector DNA is coupled to vector DNA replication in maize 总被引:3,自引:3,他引:0
Uwe Wirtz Brian Osborne Barbara Baker 《The Plant journal : for cell and molecular biology》1997,11(1):125-135
Analysis of transposition products generated after Activator (Ac) excision from the P locus in maize suggest that Ac excises either during or after replication of the P locus. The frequency of excision of the non-autonomous Ac derivative, Dissociation ( Ds ), from extrachromosomal replicating and nonreplicating vector DNAs in transfected black mexican sweet maize protoplasts was compared to assess directly a role of extrachromosomal vector DNA replication in Ds excision. Replicating (rep+ ) and non-replicating (rep− ) vector DNAs comprised a Ds element that harbored a geminivirus, wheat dwarf virus (WDV), origin of replication and WDV genes required for viral DNA replication (rep+ ) or mutant, inactive derivatives of these genes (rep− ). Excision of Ds was detected only in those cell nuclei co-transfected with the replicating Ds -vector DNA and a transposase expression vector. Quantitative reconstruction experiments showed that Ds excised at least 3 × 105 -fold more frequently from replicating vector DNA as compared with nonreplicating vector DNA. Therefore, these results provide direct evidence for a coupling of Ds excision from extrachromosomal vector DNA to vector DNA replication in maize. 相似文献
964.
The presence of a substantial proportion of branched, in addition to normal compounds, was confirmed in the alkyl ester and primary alcohol components 相似文献
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969.
Activated lymphocytes increase expression of 5-lipoxygenase and its activating protein in THP-1 cells 总被引:1,自引:0,他引:1
Ring William L.; Riddick Carl A.; Baker Joseph R.; Glass Christopher K.; Bigby Timothy D. 《American journal of physiology. Cell physiology》1997,273(6):C2057
The aim of this study was to investigate the regulation of the5-lipoxygenase pathway of arachidonic acid metabolism by lymphocytes using the monocyte-like cell line, THP-1. When THP-1 cells were incubated over 4-7 days in 10% supernatant from lectin-activated human lymphocytes, their capacity to synthesize 5-lipoxygenase productswas significantly increased. In contrast, the supernatant fromnonactivated lymphocytes had no effect. The increase in capacity tosynthesize 5-lipoxygenase products was mimicked by the addition ofeither granulocyte macrophage colony-stimulating factor (GM-CSF) orinterleukin-3. These increases in synthetic capacity reflected increased enzymatic activity. Increased immunoreactive protein and mRNAfor the enzymes 5-lipoxygenase and 5-lipoxygenase-activating protein were also found in cells conditioned with activated lymphocyte supernatants. Furthermore, the increase in mRNA for both enzymes wasnot blocked by cycloheximide, suggesting that the effect on steady-state mRNA levels does not require the synthesis of new protein.The increase in mRNA could be reproduced by GM-CSF. We conclude thatlymphocytes can regulate the expression of 5-lipoxygenase in THP-1cells over a period of days via the release of soluble factors. 相似文献
970.
Katie Lidster Samuel J. Jackson Zubair Ahmed Peter Munro Pete Coffey Gavin Giovannoni Mark D. Baker David Baker 《PloS one》2013,8(11)
Multiple sclerosis is an immune-mediated, demyelinating and neurodegenerative disease that currently lacks any neuroprotective treatments. Innovative neuroprotective trial designs are required to hasten the translational process of drug development. An ideal target to monitor the efficacy of strategies aimed at treating multiple sclerosis is the visual system, which is the most accessible part of the human central nervous system. A novel C57BL/6 mouse line was generated that expressed transgenes for a myelin oligodendrocyte glycoprotein-specific T cell receptor and a retinal ganglion cell restricted-Thy1 promoter-controlled cyan fluorescent protein. This model develops spontaneous or induced optic neuritis, in the absence of paralytic disease normally associated with most rodent autoimmune models of multiple sclerosis. Demyelination and neurodegeneration could be monitored longitudinally in the living animal using electrophysiology, visual sensitivity, confocal scanning laser ophthalmoscopy and optical coherence tomography all of which are relevant to human trials. This model offers many advantages, from a 3Rs, economic and scientific perspective, over classical experimental autoimmune encephalomyelitis models that are associated with substantial suffering of animals. Optic neuritis in this model led to inflammatory damage of axons in the optic nerve and subsequent loss of retinal ganglion cells in the retina. This was inhibited by the systemic administration of a sodium channel blocker (oxcarbazepine) or intraocular treatment with siRNA targeting caspase-2. These novel approaches have relevance to the future treatment of neurodegeneration of MS, which has so far evaded treatment. 相似文献