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31.
JANET E. BERTRAM TIM J. CLOUGH ROBERT R. SHERLOCK LEO M. CONDRON MAUREEN O'CALLAGHAN† NAOMI S. WELLS JESSICA L. RAY 《Global Change Biology》2009,15(8):2067-2077
Atmospheric concentrations of the greenhouse gas nitrous oxide (N2 O) have continued to rise since the advent of the industrial era, largely because of the increase in agricultural land use. The urine deposited by grazing ruminant animals is a major global source of agricultural N2 O. With the first commitment period for reducing greenhouse gas emissions under the Kyoto Protocol now underway, mitigation options for ruminant urine N2 O emissions are urgently needed. Recent studies showed that increasing the urinary concentration of the minor urine constituent hippuric acid resulted in reduced emissions of N2 O from a sandy soil treated with synthetic bovine urine, due to a reduction in denitrification. A similar effect was seen when benzoic acid, a product of hippuric acid hydrolysis, was used. This current laboratory experiment aimed to investigate these effects using real cow urine for the first time. Increased concentrations of hippuric acid or benzoic acid in the urine led to reduction of N2 O emissions by 65% (from 17% to <6% N applied), with no difference between the two acid treatments. Ammonia volatilization did not increase significantly with increased hippuric acid or benzoic acid concentrations in the urine applied. Therefore, there was a net reduction in gaseous N loss from the soil with higher urinary concentrations of both hippuric acid and benzoic acid. The results show that elevating hippuric acid in the urine had a marked negative effect on both nitrification and denitrification rates and on subsequent N2 O fluxes. This study indicates the potential for developing a novel mitigation strategy based on manipulation of urine composition through ruminant diet. 相似文献
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Soil organic matter biochemistry and potential susceptibility to climatic change across the forest-tundra ecotone in the Fennoscandian mountains 总被引:5,自引:0,他引:5
SOFIE SJÖGERSTEN BENJAMIN L. TURNER† NATHALIE MAHIEU‡ LEO M. CONDRON§ PHILIP A. WOOKEY 《Global Change Biology》2003,9(5):759-772
We studied soil organic carbon (C) chemistry at the mountain birch forest‐tundra ecotone in three regions of the Fennoscandian mountain range with comparable vegetation cover but contrasting degrees of continentality and latitude. The aim of the study was to identify functional compound classes and their relationships to decomposition and spatial variation across the ecotone and latitudinal gradient. Solid‐state 13C nuclear magnetic resonance (CPMAS 13C NMR) was used to identify seven functional groups of soil organic C: alkyls, N‐alkyls, O‐alkyls, acetals, aromatics, phenolics and carboxyls. N‐alkyls, O‐alkyls and acetals are generally considered labile substrates for a large number of saprotrophic fungi and bacteria, whilst phenolics and aromatics are mainly decomposed by lignolytic organisms and contribute to the formation of soil organic matter together with aliphatic alkyls and carboxyls. All soils contained a similar proportional distribution of functional groups, although relatively high amounts of N‐alkyls, O‐alkyls and acetals were present in comparison to earlier published studies, suggesting that large amounts of soil C were potentially vulnerable to microbial degradation. Soil organic matter composition was different at the most southerly site (Dovrefjell, Norway), compared with the two more northerly sites (Abisko, Sweden, and Joatka, Norway), with higher concentrations of aromatics and phenolics, as well as pronounced differences in alkyl concentrations between forest and tundra soils. Clear differences between mountain birch forest and tundra heath soil was noted, with generally higher concentrations of labile carbon present in tundra soils. We conclude that, although mesic soils around the forest‐tundra ecotone in Fennoscandia are a potential source of C to the atmosphere in a changing environment, the response is likely to vary between comparable ecosystems in relation to latitude and continentality as well as soil properties especially soil nitrogen content and pH. 相似文献
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CULLEN CU 《Public Health Reports》1954,69(7):699-700
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Patterns of Mitochondrial Variation within and between African Malaria Vectors, Anopheles Gambiae and An. Arabiensis, Suggest Extensive Gene Flow 总被引:3,自引:0,他引:3
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N. J. Besansky T. Lehmann G. T. Fahey D. Fontenille LEO. Braack W. A. Hawley F. H. Collins 《Genetics》1997,147(4):1817-1828
Anopheles gambiae and An. arabiensis are mosquito species responsible for most malaria transmission in sub-Saharan Africa. They are also closely related sibling species that share chromosomal and molecular polymorphisms as a consequence of incomplete lineage sorting or introgressive hybridization. To help resolve these processes, this study examined the partitioning of mtDNA sequence variation within and between species across Africa, from both population genetic and phylogeographic perspectives. Based on partial gene sequences from the cytochrome b, ND1 and ND5 genes, haplotype diversity was high but sequences were very closely related. Within species, little or no population subdivision was detected, and there was no evidence for isolation by distance. Between species, there were no fixed nucleotide differences, a high proportion of shared polymorphisms, and eight haplotypes in common over distances as great as 6000 km. Only one of 16 shared polymorphisms led to an amino acid difference, and there was no compelling evidence for nonneutral variation. Parsimony networks constructed of haplotypes from both species revealed no correspondence of haplotype with either geography or taxonomy. This trend of low intraspecific genetic divergence is consistent with evidence from allozyme and microsatellite data and is interpreted in terms of both extensive gene flow and recent range expansion from relatively large, stable populations. We argue that retention of ancestral polymorphisms is a plausible but insufficient explanation for low interspecific genetic divergence, and that extensive hybridization is a contributing factor. 相似文献
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Tx基因与Igk基因的同源性研究及其在不同细胞株的表达 总被引:10,自引:1,他引:9
本文对以前报道的Tx基因2.8kb片段的核苷酸序列与人免疫球蛋白kappa链C区基因的核苷酸序列及其编码产物的氨基酸序列进行了同源性比较。结果表明,Tx基因与kappa链C区基因的同源性高达99.5%以上,编码区的同源性高达100%。从而提示Tx基因与kappa链C区基因可能是同一种基因。限制性内切酶图谱及Southern印迹杂交分析,也进一步支持这一观点。本文还报道了kappa链C区基因在不同细 相似文献
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Membrane Changes associated with Malignancy 总被引:8,自引:0,他引:8
The specific structural and metabolic changes on the surface membrane which result in agglutinability of transformed cells by concanavalin A are associated with cell malignancy in vivo. 相似文献