全文获取类型
收费全文 | 271篇 |
免费 | 27篇 |
专业分类
298篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 13篇 |
2015年 | 20篇 |
2014年 | 30篇 |
2013年 | 27篇 |
2012年 | 38篇 |
2011年 | 28篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 17篇 |
2007年 | 11篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有298条查询结果,搜索用时 15 毫秒
21.
Filamentous Alphaproteobacteria associated with bulking in industrial wastewater treatment plants 总被引:1,自引:0,他引:1
Levantesi C Beimfohr C Geurkink B Rossetti S Thelen K Krooneman J Snaidr J van der Waarde J Tandoi V 《Systematic and applied microbiology》2004,27(6):716-727
The phylogeny and distribution of filamentous Alphaproteobacteria, morphologically similar to “Nostocoida limicola” and Eikelboom Type 021N that cause the solids separation problem of bulking in industrial activated sludge plants is described here. A combination of culture-dependent and culture-independent molecular methods has characterized 5 novel species. 16S rRNA targeted oligonucleotide probes were designed for their in situ identification by fluorescence in situ hybridisation (FISH) and used to monitor their presence in 86 WWTPs treating different industrial effluents in four European countries. The involvement of these bacteria in bulking in these plants was confirmed. Filaments hybridising with the ALF-968 probe for the Alphaproteobacteria were present in 65% of the WWTPs examined. They were dominant and therefore probably responsible for bulking in 25.5% of them. The heterogeneous filamentous alphaproteobacterial populations in these communities could be completely identified after application of the oligonucleotide probes used in this study in 91% of the plants containing them. The only filamentous Alphaproteobacteria retrieved in pure culture was isolated from three different industrial WWTPs plants. None of these isolates could grow anaerobically on glucose or denitrify, but all grew aerobically and heterotrophically on a range of carbon sources. Although morphologically similar to the Eikelboom Type 021N morphotype, they were not involved in sulphur metabolism. These bacteria accumulated lipidic storage granules that were associated with their presence under the unbalanced growth conditions existing in these plants. 相似文献
22.
Janneke G. E. Wijman Patrick P. L. A. de Leeuw Roy Moezelaar Marcel H. Zwietering Tjakko Abee 《Applied microbiology》2007,73(5):1481-1488
Biofilm formation by Bacillus cereus was assessed using 56 strains of B. cereus, including the two sequenced strains, ATCC 14579 and ATCC 10987. Biofilm production in microtiter plates was found to be strongly dependent on incubation time, temperature, and medium, as well as the strain used, with some strains showing biofilm formation within 24 h and subsequent dispersion within the next 24 h. A selection of strains was used for quantitative analysis of biofilm formation on stainless steel coupons. Thick biofilms of B. cereus developed at the air-liquid interface, while the amount of biofilm formed was much lower in submerged systems. This suggests that B. cereus biofilms may develop particularly in industrial storage and piping systems that are partly filled during operation or where residual liquid has remained after a production cycle. Moreover, depending on the strain and culture conditions, spores constituted up to 90% of the total biofilm counts. This indicates that B. cereus biofilms can act as a nidus for spore formation and subsequently can release their spores into food production environments. 相似文献
23.
Karemaker JM Gisolf J Stok WJ van Montfrans GA 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》2007,14(1):P49-P50
In 2 ESA-cosmonauts we compared the 24-hr profiles in blood pressure (BP) and heart rate (HR) to those that we had observed in an earlier head-down tilted (HDT) bed rest study. In view of the lack of gravitational stress, an attenuated profile was expected, as in HDT. To obtain a full profile we measured automatic upper-arm cuff measurements in 2 cosmonauts, combined with PortapresTM recordings in one. Unlike HDT, actual microgravity did not result in attenuated circadian profiles. The levels of systolic and diastolic pressures tended to be slightly lower in flight. Only nighttime heart rate was significantly lower in Space. 相似文献
24.
A niche for neutrality 总被引:2,自引:0,他引:2
Ecologists now recognize that controversy over the relative importance of niches and neutrality cannot be resolved by analyzing species abundance patterns. Here, we use classical coexistence theory to reframe the debate in terms of stabilizing mechanisms (niches) and fitness equivalence (neutrality). The neutral model is a special case where stabilizing mechanisms are absent and species have equivalent fitness. Instead of asking whether niches or neutral processes structure communities, we advocate determining the degree to which observed diversity reflects strong stabilizing mechanisms overcoming large fitness differences or weak stabilization operating on species of similar fitness. To answer this question, we propose combining data on per capita growth rates with models to: (i) quantify the strength of stabilizing processes; (ii) quantify fitness inequality and compare it with stabilization; and (iii) manipulate frequency dependence in growth to test the consequences of stabilization and fitness equivalence for coexistence. 相似文献
25.
van Goor SA Dijck-Brouwer DA Erwich JJ Schaafsma A Hadders-Algra M 《Prostaglandins, leukotrienes, and essential fatty acids》2011,84(5-6):139-146
Docosahexaenoic acid (DHA) and arachidonic acid (AA) are important for neurodevelopment. The effects of DHA (220 mg/day, n=41), DHA+AA (220 mg/day, n=39) or placebo (n=34) during pregnancy and lactation on neurodevelopment at 18 months, and the relations between umbilical cord DHA, AA and Mead acid and neurodevelopment were studied. An age-specific, standardized neurological assessment for the evaluation of minor neurological dysfunction (MND), and the Bayley Scales of Infant Development (BSID) were used. The intervention did not influence any of the outcomes. Umbilical venous (UV) Mead acid was negatively and n-6 fatty acids were weakly positively associated to the BSID mental developmental index. Children with simple MND had lower UV DHA compared to normally classified children. We conclude that relatively short-term maternal DHA or DHA+AA supplementation does not influence neurodevelopment at toddler age, although some parameters of brain development are related to perinatal DHA and AA status. 相似文献
26.
Lefeber DJ de Brouwer AP Morava E Riemersma M Schuurs-Hoeijmakers JH Absmanner B Verrijp K van den Akker WM Huijben K Steenbergen G van Reeuwijk J Jozwiak A Zucker N Lorber A Lammens M Knopf C van Bokhoven H Grünewald S Lehle L Kapusta L Mandel H Wevers RA 《PLoS genetics》2011,7(12):e1002427
Genetic causes for autosomal recessive forms of dilated cardiomyopathy (DCM) are only rarely identified, although they are thought to contribute considerably to sudden cardiac death and heart failure, especially in young children. Here, we describe 11 young patients (5-13 years) with a predominant presentation of dilated cardiomyopathy (DCM). Metabolic investigations showed deficient protein N-glycosylation, leading to a diagnosis of Congenital Disorders of Glycosylation (CDG). Homozygosity mapping in the consanguineous families showed a locus with two known genes in the N-glycosylation pathway. In all individuals, pathogenic mutations were identified in DOLK, encoding the dolichol kinase responsible for formation of dolichol-phosphate. Enzyme analysis in patients' fibroblasts confirmed a dolichol kinase deficiency in all families. In comparison with the generally multisystem presentation in CDG, the nonsyndromic DCM in several individuals was remarkable. Investigation of other dolichol-phosphate dependent glycosylation pathways in biopsied heart tissue indicated reduced O-mannosylation of alpha-dystroglycan with concomitant functional loss of its laminin-binding capacity, which has been linked to DCM. We thus identified a combined deficiency of protein N-glycosylation and alpha-dystroglycan O-mannosylation in patients with nonsyndromic DCM due to autosomal recessive DOLK mutations. 相似文献
27.
Chin CD Laksanasopin T Cheung YK Steinmiller D Linder V Parsa H Wang J Moore H Rouse R Umviligihozo G Karita E Mwambarangwe L Braunstein SL van de Wijgert J Sahabo R Justman JE El-Sadr W Sia SK 《Nature medicine》2011,17(8):1015-1019
One of the great challenges in science and engineering today is to develop technologies to improve the health of people in the poorest regions of the world. Here we integrated new procedures for manufacturing, fluid handling and signal detection in microfluidics into a single, easy-to-use point-of-care (POC) assay that faithfully replicates all steps of ELISA, at a lower total material cost. We performed this 'mChip' assay in Rwanda on hundreds of locally collected human samples. The chip had excellent performance in the diagnosis of HIV using only 1 μl of unprocessed whole blood and an ability to simultaneously diagnose HIV and syphilis with sensitivities and specificities that rival those of reference benchtop assays. Unlike most current rapid tests, the mChip test does not require user interpretation of the signal. Overall, we demonstrate an integrated strategy for miniaturizing complex laboratory assays using microfluidics and nanoparticles to enable POC diagnostics and early detection of infectious diseases in remote settings. 相似文献
28.
29.
Background
Type 2 diabetes mellitus and muscle insulin resistance have been associated with reduced capacity of skeletal muscle mitochondria, possibly as a result of increased intake of dietary fat. Here, we examined the hypothesis that a prolonged high-fat diet consumption (HFD) increases the saturation of muscle mitochondrial membrane phospholipids causing impaired mitochondrial oxidative capacity and possibly insulin resistance.Methodology
C57BL/6J mice were fed an 8-week or 20-week low fat diet (10 kcal%; LFD) or HFD (45 kcal%). Skeletal muscle mitochondria were isolated and fatty acid (FA) composition of skeletal muscle mitochondrial phospholipids was analyzed by thin-layer chromatography followed by GC. High-resolution respirometry was used to assess oxidation of pyruvate and fatty acids by mitochondria. Insulin sensitivity was estimated by HOMA-IR.Principal Findings
At 8 weeks, mono-unsaturated FA (16∶1n7, 18∶1n7 and 18∶1n9) were decreased (−4.0%, p<0.001), whereas saturated FA (16∶0) were increased (+3.2%, p<0.001) in phospholipids of HFD vs. LFD mitochondria. Interestingly, 20 weeks of HFD descreased mono-unsaturated FA while n-6 poly-unsaturated FA (18∶2n6, 20∶4n6, 22∶5n6) showed a pronounced increase (+4.0%, p<0.001). Despite increased saturation of muscle mitochondrial phospholipids after the 8-week HFD, mitochondrial oxidation of both pyruvate and fatty acids were similar between LFD and HFD mice. After 20 weeks of HFD, the increase in n-6 poly-unsaturated FA was accompanied by enhanced maximal capacity of the electron transport chain (+49%, p = 0.002) and a tendency for increased ADP-stimulated respiration, but only when fuelled by a lipid-derived substrate. Insulin sensitivity in HFD mice was reduced at both 8 and 20 weeks.Conclusions/Interpretation
Our findings do not support the concept that prolonged HF feeding leads to increased saturation of skeletal muscle mitochondrial phospholipids resulting in a decrease in mitochondrial fat oxidative capacity and (muscle) insulin resistance. 相似文献30.
Tanja Strecker Annette Jesch Drte Bachmann Melissa Jüds Kevin Karbstein Janneke Ravenek Christiane Roscher Alexandra Weigelt Nico Eisenhauer Stefan Scheu 《Ecology and evolution》2021,11(9):4295
Although nitrogen (N) deposition is increasing globally, N availability still limits many organisms, such as microorganisms and mesofauna. However, little is known to which extent soil organisms rely on mineral‐derived N and whether plant community composition modifies its incorporation into soil food webs. More diverse plant communities more effectively compete with microorganisms for mineral N likely reducing the incorporation of mineral‐derived N into soil food webs. We set up a field experiment in experimental grasslands with different levels of plant species and functional group richness. We labeled soil with 15NH4 15NO3 and analyzed the incorporation of mineral‐derived 15N into soil microorganisms and mesofauna over 3 months. Mineral‐derived N incorporation decreased over time in all investigated organisms. Plant species richness and presence of legumes reduced the uptake of mineral‐derived N into microorganisms. In parallel, the incorporation of mineral‐derived 15N into mesofauna species declined with time and decreased with increasing plant species richness in the secondary decomposer springtail Ceratophysella sp. Effects of both plant species richness and functional group richness on other mesofauna species varied with time. The presence of grasses increased the 15N incorporation into Ceratophysella sp., but decreased it in the primary decomposer oribatid mite Tectocepheus velatus sarekensis. The results highlight that mineral N is quickly channeled into soil animal food webs via microorganisms irrespective of plant diversity. The amount of mineral‐derived N incorporated into soil animals, and the plant community properties affecting this incorporation, differed markedly between soil animal taxa, reflecting species‐specific use of food resources. Our results highlight that plant diversity and community composition alter the competition for N in soil and change the transfer of N across trophic levels in soil food webs, potentially leading to changes in soil animal population dynamics and community composition. Sustaining high plant diversity may buffer detrimental effects of elevated N deposition on soil biota. 相似文献