全文获取类型
收费全文 | 164篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 2篇 |
理论与方法论 | 1篇 |
现状及发展 | 41篇 |
研究方法 | 19篇 |
综合类 | 102篇 |
自然研究 | 1篇 |
出版年
2013年 | 1篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 2篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 4篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 10篇 |
1969年 | 1篇 |
1968年 | 6篇 |
1967年 | 7篇 |
1966年 | 10篇 |
1965年 | 3篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有166条查询结果,搜索用时 15 毫秒
131.
Kulkarni SR Ofek EO Rau A Cenko SB Soderberg AM Fox DB Gal-Yam A Capak PL Moon DS Li W Filippenko AV Egami E Kartaltepe J Sanders DB 《Nature》2007,447(7143):458-460
Historically, variable and transient sources have both surprised astronomers and provided new views of the heavens. Here we report the discovery of an optical transient in the outskirts of the lenticular galaxy Messier 85 in the Virgo cluster. With a peak absolute R magnitude of -12, this event is distinctly brighter than novae, but fainter than type Ia supernovae (which are expected in a population of old stars in lenticular galaxies). Archival images of the field do not show a luminous star at that position with an upper limit in the g filter of about -4.1 mag, so it is unlikely to be a giant eruption from a luminous blue variable star. Over a two-month period, the transient source emitted radiation energy of almost 10(47) erg and subsequently faded in the optical sky. It is similar to, but six times more luminous at peak than, an enigmatic transient in the galaxy M31 (ref. 1). A possible origin of M85 OT2006-1 is a stellar merger. If so, searches for similar events in nearby galaxies will not only allow study of the physics of hyper-Eddington sources, but also probe an important phase in the evolution of stellar binary systems. 相似文献
132.
Many tasks require rapid and fine-tuned adjustment of motor performance based on incoming sensory information. This process of sensorimotor adaptation engages two parallel subcorticocortical neural circuits, involving the cerebellum and basal ganglia, respectively. How these distributed circuits are functionally coordinated has not been shown in humans. The cerebellum and basal ganglia show very similar convergence of input-output organization, which presents an ideal neuroimaging model for the study of parallel processing at a systems level. Here we used functional magnetic resonance imaging to measure the temporal coherence of brain activity during a tactile discrimination task. We found that, whereas the prefrontal cortex maintained a high level of activation, output activities in the cerebellum and basal ganglia showed different phasic patterns. Moreover, cerebellar activity significantly correlated with the activity of the supplementary motor area but not with that of the primary motor cortex; in contrast, basal ganglia activity was more strongly associated with the activity of the primary motor cortex than with that of the supplementary motor area. These results demonstrate temporally partitioned activity in the cerebellum and basal ganglia, implicating functional independence in the parallel subcortical outputs. This further supports the idea of task-related dynamic reconfiguration of large-scale neural networks. 相似文献
133.
Genome-wide association study identifies a common variant associated with risk of endometrial cancer
Spurdle AB Thompson DJ Ahmed S Ferguson K Healey CS O'Mara T Walker LC Montgomery SB Dermitzakis ET;Australian National Endometrial Cancer Study Group Fahey P Montgomery GW Webb PM Fasching PA Beckmann MW Ekici AB Hein A Lambrechts D Coenegrachts L Vergote I Amant F Salvesen HB Trovik J Njolstad TS Helland H Scott RJ Ashton K Proietto T Otton G;National Study of Endometrial Cancer Genetics Group Tomlinson I Gorman M Howarth K Hodgson S Garcia-Closas M Wentzensen N Yang H Chanock S Hall P 《Nature genetics》2011,43(5):451-454
Endometrial cancer is the most common malignancy of the female genital tract in developed countries. To identify genetic variants associated with endometrial cancer risk, we performed a genome-wide association study involving 1,265 individuals with endometrial cancer (cases) from Australia and the UK and 5,190 controls from the Wellcome Trust Case Control Consortium. We compared genotype frequencies in cases and controls for 519,655 SNPs. Forty seven SNPs that showed evidence of association with endometrial cancer in stage 1 were genotyped in 3,957 additional cases and 6,886 controls. We identified an endometrial cancer susceptibility locus close to HNF1B at 17q12 (rs4430796, P = 7.1 × 10(-10)) that is also associated with risk of prostate cancer and is inversely associated with risk of type 2 diabetes. 相似文献
134.
Bis JC Kavousi M Franceschini N Isaacs A Abecasis GR Schminke U Post WS Smith AV Cupples LA Markus HS Schmidt R Huffman JE Lehtimäki T Baumert J Münzel T Heckbert SR Dehghan A North K Oostra B Bevan S Stoegerer EM Hayward C Raitakari O Meisinger C Schillert A Sanna S Völzke H Cheng YC Thorsson B Fox CS Rice K Rivadeneira F Nambi V Halperin E Petrovic KE Peltonen L Wichmann HE Schnabel RB Dörr M Parsa A Aspelund T Demissie S Kathiresan S Reilly MP Taylor K Uitterlinden A Couper DJ Sitzer M 《Nature genetics》2011,43(10):940-947
Carotid intima media thickness (cIMT) and plaque determined by ultrasonography are established measures of subclinical atherosclerosis that each predicts future cardiovascular disease events. We conducted a meta-analysis of genome-wide association data in 31,211 participants of European ancestry from nine large studies in the setting of the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium. We then sought additional evidence to support our findings among 11,273 individuals using data from seven additional studies. In the combined meta-analysis, we identified three genomic regions associated with common carotid intima media thickness and two different regions associated with the presence of carotid plaque (P < 5 × 10(-8)). The associated SNPs mapped in or near genes related to cellular signaling, lipid metabolism and blood pressure homeostasis, and two of the regions were associated with coronary artery disease (P < 0.006) in the Coronary Artery Disease Genome-Wide Replication and Meta-Analysis (CARDIoGRAM) consortium. Our findings may provide new insight into pathways leading to subclinical atherosclerosis and subsequent cardiovascular events. 相似文献
135.
Yasuda K Miyake K Horikawa Y Hara K Osawa H Furuta H Hirota Y Mori H Jonsson A Sato Y Yamagata K Hinokio Y Wang HY Tanahashi T Nakamura N Oka Y Iwasaki N Iwamoto Y Yamada Y Seino Y Maegawa H Kashiwagi A Takeda J Maeda E Shin HD Cho YM Park KS Lee HK Ng MC Ma RC So WY Chan JC Lyssenko V Tuomi T Nilsson P Groop L Kamatani N Sekine A Nakamura Y Yamamoto K Yoshida T Tokunaga K Itakura M Makino H Nanjo K Kadowaki T Kasuga M 《Nature genetics》2008,40(9):1092-1097
We carried out a multistage genome-wide association study of type 2 diabetes mellitus in Japanese individuals, with a total of 1,612 cases and 1,424 controls and 100,000 SNPs. The most significant association was obtained with SNPs in KCNQ1, and dense mapping within the gene revealed that rs2237892 in intron 15 showed the lowest Pvalue (6.7 x 10(-13), odds ratio (OR) = 1.49). The association of KCNQ1 with type 2 diabetes was replicated in populations of Korean, Chinese and European ancestry as well as in two independent Japanese populations, and meta-analysis with a total of 19,930 individuals (9,569 cases and 10,361 controls) yielded a P value of 1.7 x 10(-42) (OR = 1.40; 95% CI = 1.34-1.47) for rs2237892. Among control subjects, the risk allele of this polymorphism was associated with impairment of insulin secretion according to the homeostasis model assessment of beta-cell function or the corrected insulin response. Our data thus implicate KCNQ1 as a diabetes susceptibility gene in groups of different ancestries. 相似文献
136.
Steinthorsdottir V Thorleifsson G Reynisdottir I Benediktsson R Jonsdottir T Walters GB Styrkarsdottir U Gretarsdottir S Emilsson V Ghosh S Baker A Snorradottir S Bjarnason H Ng MC Hansen T Bagger Y Wilensky RL Reilly MP Adeyemo A Chen Y Zhou J Gudnason V Chen G Huang H Lashley K Doumatey A So WY Ma RC Andersen G Borch-Johnsen K Jorgensen T van Vliet-Ostaptchouk JV Hofker MH Wijmenga C Christiansen C Rader DJ Rotimi C Gurney M Chan JC Pedersen O Sigurdsson G Gulcher JR Thorsteinsdottir U Kong A 《Nature genetics》2007,39(6):770-775
137.
Broderick P Carvajal-Carmona L Pittman AM Webb E Howarth K Rowan A Lubbe S Spain S Sullivan K Fielding S Jaeger E Vijayakrishnan J Kemp Z Gorman M Chandler I Papaemmanuil E Penegar S Wood W Sellick G Qureshi M Teixeira A Domingo E Barclay E Martin L Sieber O;CORGI Consortium Kerr D Gray R Peto J Cazier JB Tomlinson I Houlston RS 《Nature genetics》2007,39(11):1315-1317
To identify risk variants for colorectal cancer (CRC), we conducted a genome-wide association study, genotyping 550,163 tag SNPs in 940 individuals with familial colorectal tumor (627 CRC, 313 advanced adenomas) and 965 controls. We evaluated selected SNPs in three replication sample sets (7,473 cases, 5,984 controls) and identified three SNPs in SMAD7 (involved in TGF-beta and Wnt signaling) associated with CRC. Across the four sample sets, the association between rs4939827 and CRC was highly statistically significant (P(trend) = 1.0 x 10(-12)). 相似文献
138.
Fox TE Finnegan CM Blumenthal R Kester M 《Cellular and molecular life sciences : CMLS》2006,63(9):1017-1023
The era of sphingolipid-based therapeutics is upon us. A large body of work has been accumulating that demonstrates the distinct biological roles of sphingolipids in maintaining a homeostatic environment and in responding to environmental stimuli to regulate cellular processes. It is thus necessary to further investigate alterations in sphingolipid-metabolism in pathological conditions and, in turn, try to exploit altered sphingolipid-metabolizing enzymes and their metabolites as therapeutic targets. This review will examine how advances in the fields of drug delivery, drug discovery, synthetic chemistry, enzyme replacement therapy, immunobiology, infectious disease and nanotechnology have delivered the potential and promise of utilizing and/or targeting sphingolipid metabolites as therapies for diverse diseases. 相似文献
139.
Rapid responses of British butterflies to opposing forces of climate and habitat change. 总被引:32,自引:0,他引:32
M S Warren J K Hill J A Thomas J Asher R Fox B Huntley D B Roy M G Telfer S Jeffcoate P Harding G Jeffcoate S G Willis J N Greatorex-Davies D Moss C D Thomas 《Nature》2001,414(6859):65-69
Habitat degradation and climate change are thought to be altering the distributions and abundances of animals and plants throughout the world, but their combined impacts have not been assessed for any species assemblage. Here we evaluated changes in the distribution sizes and abundances of 46 species of butterflies that approach their northern climatic range margins in Britain-where changes in climate and habitat are opposing forces. These insects might be expected to have responded positively to climate warming over the past 30 years, yet three-quarters of them declined: negative responses to habitat loss have outweighed positive responses to climate warming. Half of the species that were mobile and habitat generalists increased their distribution sites over this period (consistent with a climate explanation), whereas the other generalists and 89% of the habitat specialists declined in distribution size (consistent with habitat limitation). Changes in population abundances closely matched changes in distributions. The dual forces of habitat modification and climate change are likely to cause specialists to decline, leaving biological communities with reduced numbers of species and dominated by mobile and widespread habitat generalists. 相似文献
140.
Dunlop MG Dobbins SE Farrington SM Jones AM Palles C Whiffin N Tenesa A Spain S Broderick P Ooi LY Domingo E Smillie C Henrion M Frampton M Martin L Grimes G Gorman M Semple C Ma YP Barclay E Prendergast J Cazier JB Olver B Penegar S Lubbe S Chander I Carvajal-Carmona LG Ballereau S Lloyd A Vijayakrishnan J Zgaga L Rudan I Theodoratou E;Colorectal Tumour Gene Identification 《Nature genetics》2012,44(7):770-776
We performed a meta-analysis of five genome-wide association studies to identify common variants influencing colorectal cancer (CRC) risk comprising 8,682 cases and 9,649 controls. Replication analysis was performed in case-control sets totaling 21,096 cases and 19,555 controls. We identified three new CRC risk loci at 6p21 (rs1321311, near CDKN1A; P = 1.14 × 10(-10)), 11q13.4 (rs3824999, intronic to POLD3; P = 3.65 × 10(-10)) and Xp22.2 (rs5934683, near SHROOM2; P = 7.30 × 10(-10)) This brings the number of independent loci associated with CRC risk to 20 and provides further insight into the genetic architecture of inherited susceptibility to CRC. 相似文献