全文获取类型
收费全文 | 127篇 |
免费 | 8篇 |
国内免费 | 1篇 |
出版年
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 11篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有136条查询结果,搜索用时 15 毫秒
51.
The molecular weight of the vasoactive intestinal peptide (VIP) receptor was assessed in bovine aorta, and rat liver, lung, and brain by covalent cross-linking and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The receptor in all four tissues was found to be a single polypeptide of approximate M(r) 54,000, contradicting previous claims for substantial heterogeneity in the molecular weight of this receptor. Guanine nucleotides inhibit cross-linking of 125I-VIP to its receptor, and cross-linking with ethylene glycolbis(succinimidylsuccinate) provides further evidence for complex formation between VIP, its receptor and a guanine nucleotide-binding regulatory protein (G-protein). The precise mechanism of receptor-G-protein coupling may differ between the aorta and other tissues. 相似文献
52.
The Olifants River, a tributary of the Limpopo River system, is one of the most polluted rivers in South Africa. In May 2011 the concentrations of metals in fish muscle tissue from two impoundments, Loskop and Flag Boshielo dams, on the Olifants River were measured and a human health risk assessment conducted to investigate whether it was safe to consume Labeo rosae from these impoundments. Labeo rosae is one of the most common pan fish in these impoundments and is readily available to rural communities. Metals are accumulating in the muscle tissue of L. rosae even although the fish populations appear to be healthy. At Loskop Dam all L. rosae analysed exceeded the recommended hazard quotient (HQ) of 1 for antimony, and less than 50% exceeded that for lead. At Flag Boshielo Dam, the recommended HQ was exceeded for lead in less than 50% of L. rosae analysed, and more than 50% exceeded that for antimony. The weekly consumption of 150?g of L. rosae muscle tissue from these impoundments may pose an unacceptable health risk to rural communities. 相似文献
53.
We classify British butterflies using 136 non-biotope associated binary state ecological attributes describing all stages of butterfly life-cycles. Using cluster analysis we identify two groups of woodland species, a group occurring in tall open grassland, another group associated with short sward herb-rich grassland, and a ruderal group. Principal Component and Factor analyses (4 factor solution) are used to identify ecological attributes that determine species groupings. No single attribute or attribute type is responsible for the groupings, which are also insensitive to hostplant type. We use presence/absence data from Butterfly Monitoring Scheme transects in southern Britain to test our classification. On the basis of adult occurrences, similarities within two of the four groups identified from PCA are greater than between groups. Exclusivity between species pairs is also more frequent between groups than within groups. Species' ranges, distributions, biotope range, dispersal ability and recent decline in abundances differ between groups identified by their factor loadings. Ruderal species have large ranges, abundances, extensive mobilities and show little recent decline. The group associated with short sward grassland have the lowest mobilities, and the smallest distributions within their geographic ranges. True woodland species have the smallest biotope range, and the species associated with open areas have the second smallest decline in their distributions. Our ecological classification identifies characteristics of species that determine their habitat requirements and could serve to predict the response of species groups to environmental change on the basis of their ecological attributes. Our method may be of use in identifying the relative importance of ecological attributes of less-well studied taxa and be applicable in less well known geographic regions. 相似文献
54.
55.
We examine spatial differences in patterns of species nchness among butterfly families in Europe and North Africa When compared to global proportions for the whole region there is a surplus of Nymphalidae in northern Europe, of Piendae in North Africa and the Mediterranean islands, of Lycaenidae in Iberia and Greece, of Hesperudae in the Algarve, and a deficit of Satyridae outside the mountain areas For the Lycaenidae and Satyridae the spatial bias in numbers of species corresponds with a bias for endemism in southem Europe, regions of refuge and persistence during Pleistocene polyglaciation We argue that regional surpluses of species in at least these two families are governed more by net species production than by species maintenance Differences in species richness between families are related to ecological amplitude and dispersal capacity which determine balances between migration, clade isolation, speciation and extinction Taxa capable of migrating long distances (e g many Nymphalidae) are able to colonize distant locations but are less amenable to clade isolation, speciation or extinction, whereas, specialized taxa with limned capacity for migration (e g most Satyridae) cannot colonize distant habitats but more readily undergo clade furcation, speciation or extinction Yet, only taxa initially able to disperse and extend their ranges can undergo clade furcation Dispersal capacity divides into extnnsic and intrinsic parameters Both are influenced by environmental changes, particularly resource geography, associated with Pleistocene glacial cycles Changes in resource geography, by influencing extrinsic components of dispersal and in turn reinforcing lntrinsic components of dispersal, result in a polanzation in evolutionary dynamics, one extreme is extensive migration, gene flow and gene pool homogeneity, the other is isolation, speciation or extinction At the isolation end of this scale, the balance between clade evolution and extinction depends on the nature of environmental change and landscape structure 相似文献
56.
Priya Chatterji Patrick A Williams Kelly A Whelan Fernando C Samper Sarah F Andres Lauren A Simon Louis R Parham Rei Mizuno Emma T Lundsmith David SM Lee Shun Liang HR
Sagara Wijeratne Stefanie Marti Lillian Chau Veronique Giroux Benjamin J Wilkins Gary D Wu Premal Shah Gian G Tartaglia Kathryn E Hamilton 《EMBO reports》2021,22(8)
Correction to: EMBO Reports (2019) 20: e47074. DOI 10.15252/embr.201847074 | Published online 6 May 2019The authors noticed that the control and disease labels had been inverted in their data analysis resulting in publication of incorrect data in Figure 1C. The corrected figure is displayed below. This change affects the conclusions as detailed below. The authors apologize for this error and any confusion it may have caused.In the legend of 1C, change from, “Differential gene expression analysis of pediatric ileal CD patient samples (n = 180) shows increased (> 4‐fold) IMP1 expression as compared to non‐inflammatory bowel disease (IBD) pediatric samples (n = 43)”.Open in a separate windowFigure 1CCorrected Open in a separate windowFigure 1COriginal To, "Differential gene expression analysis of pediatric ileal CD patient samples (n = 180) shows decreased (> 4‐fold) IMP1 expression as compared to non‐inflammatory bowel disease (IBD) pediatric samples (n = 43)”.In abstract, change from, “Here, we report increased IMP1 expression in patients with Crohn''s disease and ulcerative colitis”.To, “Here, we report increased IMP1 expression in adult patients with Crohn''s disease and ulcerative colitis”.In results, change from, “Consistent with these findings, analysis of published the Pediatric RISK Stratification Study (RISK) cohort of RNA‐sequencing data 38 from pediatric patients with Crohn''s disease (CD) patients revealed that IMP1 is upregulated significantly compared to control patients and that this effect is specific to IMP1 (i.e., other distinct isoforms, IMP2 and IMP3, are not changed; Fig 1C)”.To, “Contrary to our findings in colon tissue from adults, analysis of published RNA‐sequencing data from the Pediatric RISK Stratification Study (RISK) cohort of ileal tissue from children with Crohn’s disease (CD) 38 revealed that IMP1 is downregulated significantly compared to control patients in the RISK cohort and that this effect is specific to IMP1 (i.e., other distinct isoforms, IMP2 and IMP3, are not changed; Fig 1C)”.In discussion, change from, “Indeed, we report that IMP1 is upregulated in patients with Crohn''s disease and ulcerative colitis and that mice with Imp1 loss exhibit enhanced repair following DSS‐mediated damage”.To “Indeed, we report that IMP1 is upregulated in adult patients with Crohn''s disease and ulcerative colitis and that mice with Imp1 loss exhibit enhanced repair following DSS‐mediated damage”. 相似文献
57.
Roger L. H. Dennis Leonardo Dapporto John W. Dover Tim G. Shreeve 《Biodiversity and Conservation》2013,22(12):2709-2734
Habitat loss and fragmentation, exacerbated by projected climate change, present the greatest threats to preservation of global biodiversity. As increasing habitat fragmentation and isolation of residual fragments exceeds the dispersal capacity of species, there is the growing need to address connectivity to maintain diversity. Traditionally, habitat corridors have been proposed as a solution. But, the concept of corridors (barriers) is poorly understood; typically they are defined as linear habitats linking up habitat patchwork, and are advocated without a detailed understanding of the elements making up species’ habitats and the cost-effectiveness of alternative solutions. Yet, landscapes comprise an enormous range of ‘linear’ structures that can function in different ways to promote species’ persistence and diversity. In this review, a functional definition of corridor (barrier) is developed to give prominence to connectivity as opposed to ad hoc structures purported to advance connectivity. In developing the concept, urgency to accommodate environmental changes compels a growing emphasis on organism diversity rather than a preoccupation with single species conservation. The review, in focusing on butterflies to address the issue of corridors for patchwork connectivity, draws attention to fundamental divisions among organisms in any taxon: generalists and specialists. Both groups benefit from large patches as these necessarily house species with specialist resources as well as generalists with very different resource types. But, generalists and specialists require very different solutions for connectivity, from short-range habitat corridors and gateways for specialists to habitat and resource stepping stones (nodes, surfaces) for generalists. Connectivity over extensive areas is most critical for moderate generalists and their conservation requires emphasis being placed on space–time resource heterogeneity; landscape features, of whatever dimensionality and structure, provide a vital framework for developing the variety of suitable conditions and resources for enhancing their diversity. 相似文献
58.
Diabetes mellitus is a heterogeneous metabolic disorder characterized by hyperglycaemia resulting in defective insulin secretion,
resistance to insulin action or both. The use of biguanides, sulphonylurea and other drugs are valuable in the treatment of
diabetes mellitus; their use, however, is restricted by their limited action, pharmaco-kinetic properties, secondary failure
rates and side effects. Trigonella foenum-graecum, commonly known as fenugreek, is a plant that has been extensively used as a source of antidiabetic compounds from its seeds
and leaf extracts. Preliminary human trials and animal experiments suggest possible hypoglycaemic and anti-hyperlipedemic
properties of fenugreek seed powder taken orally. Our results show that the action of fenugreek in lowering blood glucose
levels is almost comparable to the effect of insulin. Combination with trace metal showed that vanadium had additive effects
and manganese had additive effects with insulin on in vitro system in control and diabetic animals of young and old ages using adipose tissue. The Trigonella and vanadium effects were studied in a number of tissues including liver, kidney, brain peripheral nerve, heart, red blood
cells and skeletal muscle. Addition of Trigonella to vanadium significantly removed the toxicity of vanadium when used to reduce blood glucose levels. Administration of the
various combinations of the antidiabetic compounds to diabetic animals was found to reverse most of the diabetic effects studied
at physiological, biochemical, histochemical and molecular levels. Results of the key enzymes of metabolic pathways have been
summarized together with glucose transporter, Glut-4 and insulin levels. Our findings illustrate and elucidate the antidiabetic/insulin
mimetic effects of Trigonella, manganese and vanadium. 相似文献
59.
ALTERNATE GLYCOLYTIC PATHWAYS IN BRAIN 总被引:3,自引:3,他引:0
60.