全文获取类型
收费全文 | 112篇 |
免费 | 2篇 |
专业分类
系统科学 | 6篇 |
理论与方法论 | 1篇 |
现状及发展 | 25篇 |
研究方法 | 34篇 |
综合类 | 46篇 |
自然研究 | 2篇 |
出版年
2021年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 1篇 |
2012年 | 13篇 |
2011年 | 13篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 10篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 9篇 |
2001年 | 1篇 |
1997年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有114条查询结果,搜索用时 0 毫秒
81.
82.
A. C. Angela Bol 《Cellular and molecular life sciences : CMLS》1959,15(3):115-116
Zusammenfassung Das Männchen des dreistachligen Stichlings zeigt unmittelbar nach Balz und Befruchtung der Eier kein sexuelles Verhalten mehr. Die Erniedrigung der sexuellen Motivation wird nicht durch Balzhandlungen oder Befruchtung verursacht, sondern durch die Wahrnehmung der Eier im Nest (Beispiel einer «Endsituation»). 相似文献
83.
84.
85.
Reburial of fossil organic carbon in marine sediments 总被引:4,自引:0,他引:4
Marine sediments act as the ultimate sink for organic carbon, sequestering otherwise rapidly cycling carbon for geologic timescales. Sedimentary organic carbon burial appears to be controlled by oxygen exposure time in situ, and much research has focused on understanding the mechanisms of preservation of organic carbon. In this context, combustion-derived black carbon has received attention as a form of refractory organic carbon that may be preferentially preserved in soils and sediments. However, little is understood about the environmental roles, transport and distribution of black carbon. Here we apply isotopic analyses to graphitic black carbon samples isolated from pre-industrial marine and terrestrial sediments. We find that this material is terrestrially derived and almost entirely depleted of radiocarbon, suggesting that it is graphite weathered from rocks, rather than a combustion product. The widespread presence of fossil graphitic black carbon in sediments has therefore probably led to significant overestimates of burial of combustion-derived black carbon in marine sediments. It could be responsible for biasing radiocarbon dating of sedimentary organic carbon, and also reveals a closed loop in the carbon cycle. Depending on its susceptibility to oxidation, this recycled carbon may be locked away from the biologically mediated carbon cycle for many geologic cycles. 相似文献
86.
Angela J. Black Olga Klinkowska David G. McMillan Fiona J. McMillan 《Journal of forecasting》2014,33(8):627-639
This paper examines the relationship between stock prices and commodity prices and whether this can be used to forecast stock returns. As both prices are linked to expected future economic performance they should exhibit a long‐run relationship. Moreover, changes in sentiment towards commodity investing may affect the nature of the response to disequilibrium. Results support cointegration between stock and commodity prices, while Bai–Perron tests identify breaks in the forecast regression. Forecasts are computed using a standard fixed (static) in‐sample/out‐of‐sample approach and by both recursive and rolling regressions, which incorporate the effects of changing forecast parameter values. A range of model specifications and forecast metrics are used. The historical mean model outperforms the forecast models in both the static and recursive approaches. However, in the rolling forecasts, those models that incorporate information from the long‐run stock price/commodity price relationship outperform both the historical mean and other forecast models. Of note, the historical mean still performs relatively well compared to standard forecast models that include the dividend yield and short‐term interest rates but not the stock/commodity price ratio. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
87.
Rivière JB Mirzaa GM O'Roak BJ Beddaoui M Alcantara D Conway RL St-Onge J Schwartzentruber JA Gripp KW Nikkel SM Worthylake T Sullivan CT Ward TR Butler HE Kramer NA Albrecht B Armour CM Armstrong L Caluseriu O Cytrynbaum C Drolet BA Innes AM Lauzon JL Lin AE Mancini GM Meschino WS Reggin JD Saggar AK Lerman-Sagie T Uyanik G Weksberg R Zirn B Beaulieu CL;Finding of Rare Disease Genes 《Nature genetics》2012,44(8):934-940
Megalencephaly-capillary malformation (MCAP) and megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndromes are sporadic overgrowth disorders associated with markedly enlarged brain size and other recognizable features. We performed exome sequencing in 3 families with MCAP or MPPH, and our initial observations were confirmed in exomes from 7 individuals with MCAP and 174 control individuals, as well as in 40 additional subjects with megalencephaly, using a combination of Sanger sequencing, restriction enzyme assays and targeted deep sequencing. We identified de novo germline or postzygotic mutations in three core components of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway. These include 2 mutations in AKT3, 1 recurrent mutation in PIK3R2 in 11 unrelated families with MPPH and 15 mostly postzygotic mutations in PIK3CA in 23 individuals with MCAP and 1 with MPPH. Our data highlight the central role of PI3K-AKT signaling in vascular, limb and brain development and emphasize the power of massively parallel sequencing in a challenging context of phenotypic and genetic heterogeneity combined with postzygotic mosaicism. 相似文献
88.
Sung WK Zheng H Li S Chen R Liu X Li Y Lee NP Lee WH Ariyaratne PN Tennakoon C Mulawadi FH Wong KF Liu AM Poon RT Fan ST Chan KL Gong Z Hu Y Lin Z Wang G Zhang Q Barber TD Chou WC Aggarwal A Hao K Zhou W Zhang C Hardwick J Buser C Xu J Kan Z Dai H Mao M Reinhard C Wang J Luk JM 《Nature genetics》2012,44(7):765-769
To survey hepatitis B virus (HBV) integration in liver cancer genomes, we conducted massively parallel sequencing of 81 HBV-positive and 7 HBV-negative hepatocellular carcinomas (HCCs) and adjacent normal tissues. We found that HBV integration is observed more frequently in the tumors (86.4%) than in adjacent liver tissues (30.7%). Copy-number variations (CNVs) were significantly increased at HBV breakpoint locations where chromosomal instability was likely induced. Approximately 40% of HBV breakpoints within the HBV genome were located within a 1,800-bp region where the viral enhancer, X gene and core gene are located. We also identified recurrent HBV integration events (in ≥ 4 HCCs) that were validated by RNA sequencing (RNA-seq) and Sanger sequencing at the known and putative cancer-related TERT, MLL4 and CCNE1 genes, which showed upregulated gene expression in tumor versus normal tissue. We also report evidence that suggests that the number of HBV integrations is associated with patient survival. 相似文献
89.
90.
Haiman CA Chen GK Vachon CM Canzian F Dunning A Millikan RC Wang X Ademuyiwa F Ahmed S Ambrosone CB Baglietto L Balleine R Bandera EV Beckmann MW Berg CD Bernstein L Blomqvist C Blot WJ Brauch H Buring JE Carey LA Carpenter JE Chang-Claude J Chanock SJ Chasman DI Clarke CL Cox A Cross SS Deming SL Diasio RB Dimopoulos AM Driver WR Dünnebier T Durcan L Eccles D Edlund CK Ekici AB Fasching PA Feigelson HS Flesch-Janys D Fostira F Försti A Fountzilas G 《Nature genetics》2011,43(12):1210-1214
Estrogen receptor (ER)-negative breast cancer shows a higher incidence in women of African ancestry compared to women of European ancestry. In search of common risk alleles for ER-negative breast cancer, we combined genome-wide association study (GWAS) data from women of African ancestry (1,004 ER-negative cases and 2,745 controls) and European ancestry (1,718 ER-negative cases and 3,670 controls), with replication testing conducted in an additional 2,292 ER-negative cases and 16,901 controls of European ancestry. We identified a common risk variant for ER-negative breast cancer at the TERT-CLPTM1L locus on chromosome 5p15 (rs10069690: per-allele odds ratio (OR) = 1.18 per allele, P = 1.0 × 10(-10)). The variant was also significantly associated with triple-negative (ER-negative, progesterone receptor (PR)-negative and human epidermal growth factor-2 (HER2)-negative) breast cancer (OR = 1.25, P = 1.1 × 10(-9)), particularly in younger women (<50 years of age) (OR = 1.48, P = 1.9 × 10(-9)). Our results identify a genetic locus associated with estrogen receptor negative breast cancer subtypes in multiple populations. 相似文献