全文获取类型
收费全文 | 885篇 |
免费 | 56篇 |
国内免费 | 1篇 |
出版年
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 18篇 |
2014年 | 30篇 |
2013年 | 46篇 |
2012年 | 56篇 |
2011年 | 47篇 |
2010年 | 19篇 |
2009年 | 25篇 |
2008年 | 28篇 |
2007年 | 40篇 |
2006年 | 35篇 |
2005年 | 36篇 |
2004年 | 31篇 |
2003年 | 43篇 |
2002年 | 32篇 |
2001年 | 23篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 6篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1975年 | 10篇 |
1973年 | 9篇 |
1971年 | 10篇 |
1970年 | 6篇 |
1969年 | 6篇 |
1968年 | 17篇 |
1967年 | 5篇 |
排序方式: 共有942条查询结果,搜索用时 21 毫秒
81.
Introduction
Recent studies suggest that heat is associated with an increase in the number of ambulance calls and emergency department visits. We investigated the association between heat and daily number of emergency department visits at the University Hospital of Verona during the warm seasons 2011–2012 and we assessed the magnitude of the impact in terms of attributable events, focusing on the role of age and triage codification.Materials and methods
We used a Poisson model to analyse the association between daily number of visits and daily mean apparent temperature, accounting for air pollution level and seasonality. The analyses were stratified by age group and were performed both on the total number of emergency department visits and on the subsample of high-priority visits. Impact estimates were obtained only for this subsample, using a Monte Carlo approach to account for sampling variability. Number of attributable events and attributable community rate were calculated.Results
We found a positive and immediate association between event occurrence and mean apparent temperatures exceeding a threshold located around 28–29°C. The estimated percent change in the total number of visits per 1°C increase of exposure above the threshold was equal to 3.75 (90% CI: 3.01; 4.49). Focusing only on high-priority visits, the estimated percent change was larger and the greatest effect was among children. We estimated that apparent temperatures above the threshold were responsible for 1177 high-priority visits during the study period. Due to the record high temperatures observed in 2012 in Italy and in Europe, the impact in 2012 was much larger than in 2011, and consisted in 34 high-priority visits every 10000 children, 30 every 10000 people aged 15–64, and 38 every 10000 people aged 65 and over.Discussion
Our results indicate that heat affects not only the elderly, but also children and non-elderly adults, stressing the need for developing public health preparedness plans for the entire community. 相似文献82.
83.
84.
There is an urgent need for animal models of autism spectrum disorder (ASD) to understand the underlying pathology and facilitate development and testing of new treatments. The synaptic growth‐associated protein‐43 (GAP43) has recently been identified as an autism candidate gene of interest. Our previous studies show many brain abnormalities in mice lacking one allele for GAP43 [GAP43 (+/?)] that are consistent with the disordered connectivity theory of ASD. Thus, we hypothesized that GAP43 (+/?) mice would show at least some autistic‐like behaviors. We found that GAP43 (+/?) mice, relative to wild‐type (+/+) littermates, displayed resistance to change, consistent with one of the diagnostic criteria for ASD. GAP43 (+/?) mice also displayed stress‐induced behavioral withdrawal and anxiety, as seen in many autistic individuals. In addition, both GAP43 (+/?) mice and (+/+) littermates showed low social approach and lack of preference for social novelty, consistent with another diagnostic criterion for ASD. This low sociability is likely because of the mixed C57BL/6J 129S3/SvImJ background. We conclude that GAP43 deficiency leads to the development of a subset of autistic‐like behaviors. As these behaviors occur in a mouse that displays disordered connectivity, we propose that future anatomical and functional studies in this mouse may help uncover underlying mechanisms for these specific behaviors. Strain‐specific low sociability may be advantageous in these studies, creating a more autistic‐like environment for study of the GAP43‐mediated deficits of resistance to change and vulnerability to stress. 相似文献
85.
Polyploidy is a prominent and significant force in plant evolution, taking place since ancient times and continuing until today. Recent cytogenetic studies in the genus Brachiaria using germplasm collected from wild African savannas in the 1980s revealed that most species and accessions within species are polyploid. Diploid, tetraploid, and pentaploid accessions have been found. We found asynchronous meiosis during microsporogenesis, followed by genome elimination, in two pentaploid (2n = 5x = 45) accessions (D53 and D71) of a hardy, invasive pasture grass, introduced from Africa to Brazil, Brachiaria decumbens. In these accessions, chromosomes paired as 18 bivalents and nine univalents during diakinesis, suggesting that these accessions resulted from a recent event of natural hybridization. The lack of chromosome associations in the genomes suggests that these accessions resulted from hybridization between two genotypes that are not closely related, with low genome affinity and with different meiotic rhythms. This supposition is reinforced by the meiotic behavior of the nine univalents, which were always laggard in relation to the other chromosomes and eliminated as micronuclei in microspores. The behavior of these accessions, which have an odd level of ploidy and confirmed genome elimination, supports the general assumption that a polyploid accession can undergo a new event of polyploidization by natural hybridization (neopolyploidyzation). This evidence for natural hybridization in Brachiaria shows that this is a wild genus in an ongoing evolutionary process. 相似文献
86.
87.
Ricci Giannina Campanini Emeline Boni Nishikaku Angela Satie Puccia Rosana Marques Mariângela Bialek Ralf Rodrigues Anderson Messias Batista Wagner Luiz 《Mycopathologia》2022,187(2-3):157-168
Mycopathologia - Paracoccidioidomycosis (PCM) is a systemic mycosis caused by a group of cryptic species embedded in the Paracoccidioides brasiliensis complex and Paracoccidioides lutzii. Four... 相似文献
88.
Actin depolymerizing factors (ADFs) have been recently implicated in plant defense against pathogenic fungi, associated with the cytoskeletal rearrangements that contribute to establish an effective barrier against fungal ingress. In this work, we identified a DNA fragment corresponding to a part of a gene predicted to encode an ADF-like protein in genotypes of Fragaria ananassa resistant to the fungus Colletotrichum acutatum. Bulked segregant analysis combined with AFLP was used to identify polymorphisms linked to resistance in hybrids derived from the cross between the resistant cultivar 'Sweet Charlie' and the susceptible cultivar 'Pájaro'. The sequence of one out of three polymorphic bands detected showed significant BLASTX hits to ADF proteins from other plants. Two possible exons were identified and bioinformatic analysis revealed the presence of the ADF homology domain with two actin-binding sites, an N-terminal phosphorylation site, and a nuclear localization signal. In addition to its possible application in strawberry breeding programs, these finding may contribute to investigate the role of ADFs in plant resistance against fungi. 相似文献
89.
J.V. Lee S. Lai M. Exner J. Lenz V. Gaia S. Casati P. Hartemann C. Lück B. Pangon M.L. Ricci M. Scaturro S. Fontana M. Sabria I. Sánchez S. Assaf S. Surman‐Lee 《Journal of applied microbiology》2011,110(4):1032-1044
Aims: To perform an international trial to derive alert and action levels for the use of quantitative PCR (qPCR) in the monitoring of Legionella to determine the effectiveness of control measures against legionellae. Methods and Results: Laboratories (7) participated from six countries. Legionellae were determined by culture and qPCR methods with comparable detection limits. Systems were monitored over ≥10 weeks. For cooling towers (232 samples), there was a significant difference between the log mean difference between qPCR (GU l?1) and culture (CFU l?1) for Legionella pneumophila (0·71) and for Legionella spp. (2·03). In hot and cold water (506 samples), the differences were less, 0·62 for Leg. pneumophila and 1·05 for Legionella spp. Results for individual systems depended on the nature of the system and its treatment. In cooling towers, Legionella spp. GU l?1 always exceeded CFU l?1, and usually Legionella spp. were detected by qPCR when absent by culture. The pattern of results by qPCR for Leg. pneumophila followed the culture trend. In hot and cold water, culture and qPCR gave similar results, particularly for Leg. pneumophila. There were some marked exceptions with temperatures ≥50°C, or in the presence of supplementary biocides. Action and alert levels for qPCR were derived that gave results comparable to the application of the European Guidelines based on culture. Algorithms are proposed for the use of qPCR for routine monitoring. Conclusions: Action and alert levels for qPCR can be adjusted to ensure public health is protected with the benefit that remedial actions can be validated earlier with only a small increase in the frequency of action being required. Significance and Impact of the Study: This study confirms it is possible to derive guidelines on the use of qPCR for monitoring the control of legionellae with consequent improvement to response and public health protection. 相似文献
90.
Tarabbo M Lapa D Castilletti C Tommaselli P Guarducci R Lucà G Emanuele A Zaccaria O La Gioia VF Girardi E Capobianchi MR Ippolito G 《PloS one》2011,6(1):e15933