全文获取类型
收费全文 | 249篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
教育与普及 | 1篇 |
理论与方法论 | 2篇 |
现状及发展 | 28篇 |
研究方法 | 50篇 |
综合类 | 161篇 |
自然研究 | 8篇 |
出版年
2017年 | 1篇 |
2016年 | 2篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 27篇 |
2011年 | 40篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 23篇 |
2007年 | 27篇 |
2006年 | 18篇 |
2005年 | 24篇 |
2004年 | 23篇 |
2003年 | 17篇 |
2002年 | 18篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1959年 | 4篇 |
1958年 | 2篇 |
排序方式: 共有251条查询结果,搜索用时 859 毫秒
161.
162.
Safe handling of nanotechnology 总被引:7,自引:0,他引:7
Maynard AD Aitken RJ Butz T Colvin V Donaldson K Oberdörster G Philbert MA Ryan J Seaton A Stone V Tinkle SS Tran L Walker NJ Warheit DB 《Nature》2006,444(7117):267-269
163.
Graham J Davies Zahra F Ra Carl Anthony Philip Prewett Jing Peng Robert Nordon 《中国工程科学》2012,10(5):42-44
The concept of an integrated "lab on a chip" has long been a goal for the micro-electro-mechanical-systems(MEMS) community.This would entail the integration of not only the sampling and analysis of various functions,but also the ability to transmit this information off the chip to a central repository.This paper describes the initial steps in the fabrication of a "lab on a chip" which would continually analyze blood sampled via microneedles using techniques such as nano plasmonics,specifically,concentrations of glucose.The analysis could then be transmitted off the chip using digital signal processing.This paper describes the analysis and optimization of the microneedle shape and size and the fabrication of the resulting needles in silicon using deep reactive ion etching(DRIE).The paper also describes the opportunities for fabrication of such needles in alternative materials and describes the issues that still have to be overcome before such an integrated device is realized. 相似文献
164.
Northcott PA Shih DJ Peacock J Garzia L Morrissy AS Zichner T Stütz AM Korshunov A Reimand J Schumacher SE Beroukhim R Ellison DW Marshall CR Lionel AC Mack S Dubuc A Yao Y Ramaswamy V Luu B Rolider A Cavalli FM Wang X Remke M Wu X Chiu RY Chu A Chuah E Corbett RD Hoad GR Jackman SD Li Y Lo A Mungall KL Nip KM Qian JQ Raymond AG Thiessen NT Varhol RJ Birol I Moore RA Mungall AJ Holt R Kawauchi D Roussel MF Kool M Jones DT Witt H Fernandez-L A Kenney AM Wechsler-Reya RJ Dirks P Aviv T 《Nature》2012,488(7409):49-56
Medulloblastoma, the most common malignant paediatric brain tumour, is currently treated with nonspecific cytotoxic therapies including surgery, whole-brain radiation, and aggressive chemotherapy. As medulloblastoma exhibits marked intertumoural heterogeneity, with at least four distinct molecular variants, previous attempts to identify targets for therapy have been underpowered because of small samples sizes. Here we report somatic copy number aberrations (SCNAs) in 1,087 unique medulloblastomas. SCNAs are common in medulloblastoma, and are predominantly subgroup-enriched. The most common region of focal copy number gain is a tandem duplication of SNCAIP, a gene associated with Parkinson's disease, which is exquisitely restricted to Group 4α. Recurrent translocations of PVT1, including PVT1-MYC and PVT1-NDRG1, that arise through chromothripsis are restricted to Group 3. Numerous targetable SCNAs, including recurrent events targeting TGF-β signalling in Group 3, and NF-κB signalling in Group 4, suggest future avenues for rational, targeted therapy. 相似文献
165.
Treiber CD Salzer MC Riegler J Edelman N Sugar C Breuss M Pichler P Cadiou H Saunders M Lythgoe M Shaw J Keays DA 《Nature》2012,484(7394):367-370
Understanding the molecular and cellular mechanisms that mediate magnetosensation in vertebrates is a formidable scientific problem. One hypothesis is that magnetic information is transduced into neuronal impulses by using a magnetite-based magnetoreceptor. Previous studies claim to have identified a magnetic sense system in the pigeon, common to avian species, which consists of magnetite-containing trigeminal afferents located at six specific loci in the rostral subepidermis of the beak. These studies have been widely accepted in the field and heavily relied upon by both behavioural biologists and physicists. Here we show that clusters of iron-rich cells in the rostro-medial upper beak of the pigeon Columbia livia are macrophages, not magnetosensitive neurons. Our systematic characterization of the pigeon upper beak identified iron-rich cells in the stratum laxum of the subepidermis, the basal region of the respiratory epithelium and the apex of feather follicles. Using a three-dimensional blueprint of the pigeon beak created by magnetic resonance imaging and computed tomography, we mapped the location of iron-rich cells, revealing unexpected variation in their distribution and number--an observation that is inconsistent with a role in magnetic sensation. Ultrastructure analysis of these cells, which are not unique to the beak, showed that their subcellular architecture includes ferritin-like granules, siderosomes, haemosiderin and filopodia, characteristics of iron-rich macrophages. Our conclusion that these cells are macrophages and not magnetosensitive neurons is supported by immunohistological studies showing co-localization with the antigen-presenting molecule major histocompatibility complex class II. Our work necessitates a renewed search for the true magnetite-dependent magnetoreceptor in birds. 相似文献
166.
Blaga CI Xu J DiChiara AD Sistrunk E Zhang K Agostini P Miller TA DiMauro LF Lin CD 《Nature》2012,483(7388):194-197
Establishing the structure of molecules and solids has always had an essential role in physics, chemistry and biology. The methods of choice are X-ray and electron diffraction, which are routinely used to determine atomic positions with sub-?ngstr?m spatial resolution. Although both methods are currently limited to probing dynamics on timescales longer than a picosecond, the recent development of femtosecond sources of X-ray pulses and electron beams suggests that they might soon be capable of taking ultrafast snapshots of biological molecules and condensed-phase systems undergoing structural changes. The past decade has also witnessed the emergence of an alternative imaging approach based on laser-ionized bursts of coherent electron wave packets that self-interrogate the parent molecular structure. Here we show that this phenomenon can indeed be exploited for laser-induced electron diffraction (LIED), to image molecular structures with sub-?ngstr?m precision and exposure times of a few femtoseconds. We apply the method to oxygen and nitrogen molecules, which on strong-field ionization at three mid-infrared wavelengths (1.7, 2.0 and 2.3?μm) emit photoelectrons with a momentum distribution from which we extract diffraction patterns. The long wavelength is essential for achieving atomic-scale spatial resolution, and the wavelength variation is equivalent to taking snapshots at different times. We show that the method has the sensitivity to measure a 0.1?? displacement in the oxygen bond length occurring in a time interval of ~5?fs, which establishes LIED as a promising approach for the imaging of gas-phase molecules with unprecedented spatio-temporal resolution. 相似文献
167.
A selective jumonji H3K27 demethylase inhibitor modulates the proinflammatory macrophage response 总被引:1,自引:0,他引:1
L Kruidenier CW Chung Z Cheng J Liddle K Che G Joberty M Bantscheff C Bountra A Bridges H Diallo D Eberhard S Hutchinson E Jones R Katso M Leveridge PK Mander J Mosley C Ramirez-Molina P Rowland CJ Schofield RJ Sheppard JE Smith C Swales R Tanner P Thomas A Tumber G Drewes U Oppermann DJ Patel K Lee DM Wilson 《Nature》2012,488(7411):404-408
168.
Jäger S Cimermancic P Gulbahce N Johnson JR McGovern KE Clarke SC Shales M Mercenne G Pache L Li K Hernandez H Jang GM Roth SL Akiva E Marlett J Stephens M D'Orso I Fernandes J Fahey M Mahon C O'Donoghue AJ Todorovic A Morris JH Maltby DA Alber T Cagney G Bushman FD Young JA Chanda SK Sundquist WI Kortemme T Hernandez RD Craik CS Burlingame A Sali A Frankel AD Krogan NJ 《Nature》2012,481(7381):365-370
Human immunodeficiency virus (HIV) has a small genome and therefore relies heavily on the host cellular machinery to replicate. Identifying which host proteins and complexes come into physical contact with the viral proteins is crucial for a comprehensive understanding of how HIV rewires the host's cellular machinery during the course of infection. Here we report the use of affinity tagging and purification mass spectrometry to determine systematically the physical interactions of all 18 HIV-1 proteins and polyproteins with host proteins in two different human cell lines (HEK293 and Jurkat). Using a quantitative scoring system that we call MiST, we identified with high confidence 497 HIV-human protein-protein interactions involving 435 individual human proteins, with ~40% of the interactions being identified in both cell types. We found that the host proteins hijacked by HIV, especially those found interacting in both cell types, are highly conserved across primates. We uncovered a number of host complexes targeted by viral proteins, including the finding that HIV protease cleaves eIF3d, a subunit of eukaryotic translation initiation factor 3. This host protein is one of eleven identified in this analysis that act to inhibit HIV replication. This data set facilitates a more comprehensive and detailed understanding of how the host machinery is manipulated during the course of HIV infection. 相似文献
169.
170.