全文获取类型
收费全文 | 393篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
系统科学 | 3篇 |
理论与方法论 | 4篇 |
现状及发展 | 50篇 |
研究方法 | 58篇 |
综合类 | 203篇 |
自然研究 | 76篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 33篇 |
2011年 | 92篇 |
2010年 | 10篇 |
2009年 | 2篇 |
2008年 | 12篇 |
2007年 | 23篇 |
2006年 | 14篇 |
2005年 | 16篇 |
2004年 | 16篇 |
2003年 | 24篇 |
2002年 | 27篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1992年 | 7篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1970年 | 6篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1957年 | 3篇 |
排序方式: 共有394条查询结果,搜索用时 15 毫秒
151.
152.
The missing memristor found 总被引:17,自引:0,他引:17
Anyone who ever took an electronics laboratory class will be familiar with the fundamental passive circuit elements: the resistor, the capacitor and the inductor. However, in 1971 Leon Chua reasoned from symmetry arguments that there should be a fourth fundamental element, which he called a memristor (short for memory resistor). Although he showed that such an element has many interesting and valuable circuit properties, until now no one has presented either a useful physical model or an example of a memristor. Here we show, using a simple analytical example, that memristance arises naturally in nanoscale systems in which solid-state electronic and ionic transport are coupled under an external bias voltage. These results serve as the foundation for understanding a wide range of hysteretic current-voltage behaviour observed in many nanoscale electronic devices that involve the motion of charged atomic or molecular species, in particular certain titanium dioxide cross-point switches. 相似文献
153.
154.
155.
Hakonarson H Grant SF Bradfield JP Marchand L Kim CE Glessner JT Grabs R Casalunovo T Taback SP Frackelton EC Lawson ML Robinson LJ Skraban R Lu Y Chiavacci RM Stanley CA Kirsch SE Rappaport EF Orange JS Monos DS Devoto M Qu HQ Polychronakos C 《Nature》2007,448(7153):591-594
Type 1 diabetes (T1D) in children results from autoimmune destruction of pancreatic beta cells, leading to insufficient production of insulin. A number of genetic determinants of T1D have already been established through candidate gene studies, primarily within the major histocompatibility complex but also within other loci. To identify new genetic factors that increase the risk of T1D, we performed a genome-wide association study in a large paediatric cohort of European descent. In addition to confirming previously identified loci, we found that T1D was significantly associated with variation within a 233-kb linkage disequilibrium block on chromosome 16p13. This region contains KIAA0350, the gene product of which is predicted to be a sugar-binding, C-type lectin. Three common non-coding variants of the gene (rs2903692, rs725613 and rs17673553) in strong linkage disequilibrium reached genome-wide significance for association with T1D. A subsequent transmission disequilibrium test replication study in an independent cohort confirmed the association. These results indicate that KIAA0350 might be involved in the pathogenesis of T1D and demonstrate the utility of the genome-wide association approach in the identification of previously unsuspected genetic determinants of complex traits. 相似文献
156.
Genomes of all mammals encode apobec3 genes, which are thought to have a function in intrinsic cellular immunity to several viruses including human immunodeficiency virus type 1 (HIV-1). APOBEC3 (A3) proteins are packaged into virions and inhibit retroviral replication in newly infected cells, at least in part by deaminating cytidines on the negative strand DNA intermediates. However, the role of A3 in innate resistance to mouse retroviruses is not understood. Here we show that A3 functions during retroviral infection in vivo and provides partial protection to mice against infection with mouse mammary tumour virus (MMTV). Both mouse A3 and human A3G proteins interacted with the MMTV nucleocapsid in an RNA-dependent fashion and were packaged into virions. In addition, mouse A3-containing and human A3G-containing virions showed a marked decrease in titre. Last, A3(-/-) mice were more susceptible to MMTV infection, because virus spread was more rapid and extensive than in their wild-type littermates. 相似文献
157.
TJ Pugh SD Weeraratne TC Archer DA Pomeranz Krummel D Auclair J Bochicchio MO Carneiro SL Carter K Cibulskis RL Erlich H Greulich MS Lawrence NJ Lennon A McKenna J Meldrim AH Ramos MG Ross C Russ E Shefler A Sivachenko B Sogoloff P Stojanov P Tamayo JP Mesirov V Amani N Teider S Sengupta JP Francois PA Northcott MD Taylor F Yu GR Crabtree AG Kautzman SB Gabriel G Getz N Jäger DT Jones P Lichter SM Pfister TM Roberts M Meyerson SL Pomeroy YJ Cho 《Nature》2012,488(7409):106-110
158.
Zhang J Ding L Holmfeldt L Wu G Heatley SL Payne-Turner D Easton J Chen X Wang J Rusch M Lu C Chen SC Wei L Collins-Underwood JR Ma J Roberts KG Pounds SB Ulyanov A Becksfort J Gupta P Huether R Kriwacki RW Parker M McGoldrick DJ Zhao D Alford D Espy S Bobba KC Song G Pei D Cheng C Roberts S Barbato MI Campana D Coustan-Smith E Shurtleff SA Raimondi SC Kleppe M Cools J Shimano KA Hermiston ML Doulatov S Eppert K Laurenti E Notta F Dick JE Basso G Hunger SP Loh ML Devidas M Wood B Winter S 《Nature》2012,481(7380):157-163
159.
Zhang J Benavente CA McEvoy J Flores-Otero J Ding L Chen X Ulyanov A Wu G Wilson M Wang J Brennan R Rusch M Manning AL Ma J Easton J Shurtleff S Mullighan C Pounds S Mukatira S Gupta P Neale G Zhao D Lu C Fulton RS Fulton LL Hong X Dooling DJ Ochoa K Naeve C Dyson NJ Mardis ER Bahrami A Ellison D Wilson RK Downing JR Dyer MA 《Nature》2012,481(7381):329-334
Retinoblastoma is an aggressive childhood cancer of the developing retina that is initiated by the biallelic loss of RB1. Tumours progress very quickly following RB1 inactivation but the underlying mechanism is not known. Here we show that the retinoblastoma genome is stable, but that multiple cancer pathways can be epigenetically deregulated. To identify the mutations that cooperate with RB1 loss, we performed whole-genome sequencing of retinoblastomas. The overall mutational rate was very low; RB1 was the only known cancer gene mutated. We then evaluated the role of RB1 in genome stability and considered non-genetic mechanisms of cancer pathway deregulation. For example, the proto-oncogene SYK is upregulated in retinoblastoma and is required for tumour cell survival. Targeting SYK with a small-molecule inhibitor induced retinoblastoma tumour cell death in vitro and in vivo. Thus, retinoblastomas may develop quickly as a result of the epigenetic deregulation of key cancer pathways as a direct or indirect result of RB1 loss. 相似文献
160.