全文获取类型
收费全文 | 121篇 |
免费 | 0篇 |
专业分类
系统科学 | 2篇 |
理论与方法论 | 1篇 |
现状及发展 | 33篇 |
研究方法 | 11篇 |
综合类 | 72篇 |
自然研究 | 2篇 |
出版年
2020年 | 1篇 |
2016年 | 2篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1992年 | 3篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有121条查询结果,搜索用时 421 毫秒
91.
辽宁本溪地区条带状铁矿(BIF)与其玄武质火山围岩之间的时空关联非常密切.对于玄武质火山围岩高场强元素(HFSE)的研究表明:wNb/wTa比值(7.00~19.93)表现出明显的分异,而wZr/wHf比值(33.46~38.28)则变化不大;从弓长岭到南芬、歪头山样品的wNb/wTa比值变化具有明显的循序性.这种高场强元素的迁移和分异特征反映出俯冲作用与盆地演化之间的关联.研究区玄武质火山围岩(wNb/wYb)N比值大于1(1.21~18.45,平均2.72),这进一步表明,其形成的构造背景为陆内弧后盆地提供了有利于BIF形成的条件. 相似文献
92.
Warren WC Hillier LW Marshall Graves JA Birney E Ponting CP Grützner F Belov K Miller W Clarke L Chinwalla AT Yang SP Heger A Locke DP Miethke P Waters PD Veyrunes F Fulton L Fulton B Graves T Wallis J Puente XS López-Otín C Ordóñez GR Eichler EE Chen L Cheng Z Deakin JE Alsop A Thompson K Kirby P Papenfuss AT Wakefield MJ Olender T Lancet D Huttley GA Smit AF Pask A Temple-Smith P Batzer MA Walker JA Konkel MK Harris RS Whittington CM Wong ES Gemmell NJ Buschiazzo E Vargas Jentzsch IM Merkel A 《Nature》2008,453(7192):175-183
We present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhibits a fascinating combination of reptilian and mammalian characters. For example, platypuses have a coat of fur adapted to an aquatic lifestyle; platypus females lactate, yet lay eggs; and males are equipped with venom similar to that of reptiles. Analysis of the first monotreme genome aligned these features with genetic innovations. We find that reptile and platypus venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved despite platypuses laying eggs; and immune gene family expansions are directly related to platypus biology. Expansions of protein, non-protein-coding RNA and microRNA families, as well as repeat elements, are identified. Sequencing of this genome now provides a valuable resource for deep mammalian comparative analyses, as well as for monotreme biology and conservation. 相似文献
93.
During oviposition the endoparasitic waspCampoletis sonorensis, introduces a polydnavirus into parasitized insects where viral gene expression is required for endoparasite survival. The polydnavirus is integrated into wasp chromosomal DNA and replicates only in the ovary. Ecdysteroids regulate the developmental expression of many insect genes and may regulate polydnavirus replication. Direct verification of viral replication was performed by dot blot hybridization and by amplifying DNA sequences containing the viral integration site; this junction fragment cannot be amplified from integrated virus. Thoracic ligations and in vitro ecdysteroid treatments of wasp ovaries support the hypothesis that polydnavirus DNA replication is regulated by ecdysteroid during parasite development. 相似文献
94.
Projected increase in continental runoff due to plant responses to increasing carbon dioxide 总被引:13,自引:0,他引:13
Betts RA Boucher O Collins M Cox PM Falloon PD Gedney N Hemming DL Huntingford C Jones CD Sexton DM Webb MJ 《Nature》2007,448(7157):1037-1041
In addition to influencing climatic conditions directly through radiative forcing, increasing carbon dioxide concentration influences the climate system through its effects on plant physiology. Plant stomata generally open less widely under increased carbon dioxide concentration, which reduces transpiration and thus leaves more water at the land surface. This driver of change in the climate system, which we term 'physiological forcing', has been detected in observational records of increasing average continental runoff over the twentieth century. Here we use an ensemble of experiments with a global climate model that includes a vegetation component to assess the contribution of physiological forcing to future changes in continental runoff, in the context of uncertainties in future precipitation. We find that the physiological effect of doubled carbon dioxide concentrations on plant transpiration increases simulated global mean runoff by 6 per cent relative to pre-industrial levels; an increase that is comparable to that simulated in response to radiatively forced climate change (11 +/- 6 per cent). Assessments of the effect of increasing carbon dioxide concentrations on the hydrological cycle that only consider radiative forcing will therefore tend to underestimate future increases in runoff and overestimate decreases. This suggests that freshwater resources may be less limited than previously assumed under scenarios of future global warming, although there is still an increased risk of drought. Moreover, our results highlight that the practice of assessing the climate-forcing potential of all greenhouse gases in terms of their radiative forcing potential relative to carbon dioxide does not accurately reflect the relative effects of different greenhouse gases on freshwater resources. 相似文献
95.
96.
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
97.
Common 5p15.33 and 6p21.33 variants influence lung cancer risk 总被引:1,自引:0,他引:1
Wang Y Broderick P Webb E Wu X Vijayakrishnan J Matakidou A Qureshi M Dong Q Gu X Chen WV Spitz MR Eisen T Amos CI Houlston RS 《Nature genetics》2008,40(12):1407-1409
We conducted a genome-wide association (GWA) study of lung cancer comparing 511,919 SNP genotypes in 1,952 cases and 1,438 controls. The most significant association was attained at 15q25.1 (rs8042374; P = 7.75 x 10(-12)), confirming recent observations. Pooling data with two other GWA studies (5,095 cases, 5,200 controls) and with replication in an additional 2,484 cases and 3,036 controls, we identified two newly associated risk loci mapping to 6p21.33 (rs3117582, BAT3-MSH5; P(combined) = 4.97 x 10(-10)) and 5p15.33 (rs401681, CLPTM1L; P(combined) = 7.90 x 10(-9)). 相似文献
98.
Di Bernardo MC Crowther-Swanepoel D Broderick P Webb E Sellick G Wild R Sullivan K Vijayakrishnan J Wang Y Pittman AM Sunter NJ Hall AG Dyer MJ Matutes E Dearden C Mainou-Fowler T Jackson GH Summerfield G Harris RJ Pettitt AR Hillmen P Allsup DJ Bailey JR Pratt G Pepper C Fegan C Allan JM Catovsky D Houlston RS 《Nature genetics》2008,40(10):1204-1210
We conducted a genome-wide association study of 299,983 tagging SNPs for chronic lymphocytic leukemia (CLL) and performed validation in two additional series totaling 1,529 cases and 3,115 controls. We identified six previously unreported CLL risk loci at 2q13 (rs17483466; P = 2.36 x 10(-10)), 2q37.1 (rs13397985, SP140; P = 5.40 x 10(-10)), 6p25.3 (rs872071, IRF4; P = 1.91 x 10(-20)), 11q24.1 (rs735665; P = 3.78 x 10(-12)), 15q23 (rs7176508; P = 4.54 x 10(-12)) and 19q13.32 (rs11083846, PRKD2; P = 3.96 x 10(-9)). These data provide the first evidence for the existence of common, low-penetrance susceptibility to a hematological malignancy and new insights into disease causation in CLL. 相似文献
99.
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
100.
Observations show that the seismic normal modes of the Earth at frequencies near 10 mHz are excited at a nearly constant level in the absence of large earthquakes. This background level of excitation has been called the 'hum' of the Earth, and is equivalent to the maximum excitation from a magnitude 5.75 earthquake. Its origin is debated, with most studies attributing the forcing to atmospheric turbulence, analogous to the forcing of solar oscillations by solar turbulence. Some reports also predicted that turbulence might excite the planetary modes of Mars to detectable levels. Recent observations on Earth, however, suggest that the predominant excitation source lies under the oceans. Here I show that turbulence is a very weak source, and instead it is interacting ocean waves over the shallow continental shelves that drive the hum of the Earth. Ocean waves couple into seismic waves through the quadratic nonlinearity of the surface boundary condition, which couples pairs of slowly propagating ocean waves of similar frequency to a high phase velocity component at approximately double the frequency. This is the process by which ocean waves generate the well known 'microseism peak' that dominates the seismic spectrum near 140 mHz (refs 11, 12), but at hum frequencies, the mechanism differs significantly in frequency and depth dependence. A calculation of the coupling between ocean waves and seismic modes reproduces the seismic spectrum observed. Measurements of the temporal correlation between ocean wave data and seismic data have confirmed that ocean waves, rather than atmospheric turbulence, are driving the modes of the Earth. 相似文献