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排序方式: 共有59条查询结果,搜索用时 78 毫秒
21.
Chapman HN Hau-Riege SP Bogan MJ Bajt S Barty A Boutet S Marchesini S Frank M Woods BW Benner WH London RA Rohner U Szöke A Spiller E Möller T Bostedt C Shapiro DA Kuhlmann M Treusch R Plönjes E Burmeister F Bergh M Caleman C Huldt G Seibert MM Hajdu J 《Nature》2007,448(7154):676-679
Extremely intense and ultrafast X-ray pulses from free-electron lasers offer unique opportunities to study fundamental aspects of complex transient phenomena in materials. Ultrafast time-resolved methods usually require highly synchronized pulses to initiate a transition and then probe it after a precisely defined time delay. In the X-ray regime, these methods are challenging because they require complex optical systems and diagnostics. Here we propose and apply a simple holographic measurement scheme, inspired by Newton's 'dusty mirror' experiment, to monitor the X-ray-induced explosion of microscopic objects. The sample is placed near an X-ray mirror; after the pulse traverses the sample, triggering the reaction, it is reflected back onto the sample by the mirror to probe this reaction. The delay is encoded in the resulting diffraction pattern to an accuracy of one femtosecond, and the structural change is holographically recorded with high resolution. We apply the technique to monitor the dynamics of polystyrene spheres in intense free-electron-laser pulses, and observe an explosion occurring well after the initial pulse. Our results support the notion that X-ray flash imaging can be used to achieve high resolution, beyond radiation damage limits for biological samples. With upcoming ultrafast X-ray sources we will be able to explore the three-dimensional dynamics of materials at the timescale of atomic motion. 相似文献
22.
CH Wu C Fallini N Ticozzi PJ Keagle PC Sapp K Piotrowska P Lowe M Koppers D McKenna-Yasek DM Baron JE Kost P Gonzalez-Perez AD Fox J Adams F Taroni C Tiloca AL Leclerc SC Chafe D Mangroo MJ Moore JA Zitzewitz ZS Xu LH van den Berg JD Glass G Siciliano ET Cirulli DB Goldstein F Salachas V Meininger W Rossoll A Ratti C Gellera DA Bosco GJ Bassell V Silani VE Drory RH Brown JE Landers 《Nature》2012,488(7412):499-503
Amyotrophic lateral sclerosis (ALS) is a late-onset neurodegenerative disorder resulting from motor neuron death. Approximately 10% of cases are familial (FALS), typically with a dominant inheritance mode. Despite numerous advances in recent years, nearly 50% of FALS cases have unknown genetic aetiology. Here we show that mutations within the profilin 1 (PFN1) gene can cause FALS. PFN1 is crucial for the conversion of monomeric (G)-actin to filamentous (F)-actin. Exome sequencing of two large ALS families showed different mutations within the PFN1 gene. Further sequence analysis identified 4 mutations in 7 out of 274 FALS cases. Cells expressing PFN1 mutants contain ubiquitinated, insoluble aggregates that in many cases contain the ALS-associated protein TDP-43. PFN1 mutants also display decreased bound actin levels and can inhibit axon outgrowth. Furthermore, primary motor neurons expressing mutant PFN1 display smaller growth cones with a reduced F/G-actin ratio. These observations further document that cytoskeletal pathway alterations contribute to ALS pathogenesis. 相似文献
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Neutralization of Graffi leukaemia virus 总被引:1,自引:0,他引:1
25.
Marion Depla Rustem Uzbekov Christophe Hourioux Emmanuelle Blanchard Amélie Le Gouge Ludovic Gillet Philippe Roingeard 《Cellular and molecular life sciences : CMLS》2010,67(18):3151-3161
Hepatitis C virus (HCV) release is linked to the formation of lipid droplet (LD) clusters in the perinuclear area of infected
cells, induced by the core protein. We used electron microscopy (EM) to monitor and compare the number and size of LD in cells
producing the mature and immature forms of the HCV core protein, and 3D EM to reconstruct whole cells producing the mature
core protein. Only the mature protein coated the LD and induced their clustering and emergence from endoplasmic reticulum
membranes enriched in this protein. We found no particular association between LD clusters and the centrosome in reconstructed
cells. The LD clustering induced by the mature core protein was associated with an increase in LD synthesis potentially due,
at least in part, to the ability of this protein to coat the LD. These observations provide useful information for further
studies of the mechanisms involved in HCV-induced steatosis. 相似文献
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Gezari S Chornock R Rest A Huber ME Forster K Berger E Challis PJ Neill JD Martin DC Heckman T Lawrence A Norman C Narayan G Foley RJ Marion GH Scolnic D Chomiuk L Soderberg A Smith K Kirshner RP Riess AG Smartt SJ Stubbs CW Tonry JL Wood-Vasey WM Burgett WS Chambers KC Grav T Heasley JN Kaiser N Kudritzki RP Magnier EA Morgan JS Price PA 《Nature》2012,485(7397):217-220
The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant galaxies. Previous candidate flares have had declining light curves in good agreement with expectations, but with poor constraints on the time of disruption and the type of star disrupted, because the rising emission was not observed. Recently, two 'relativistic' candidate tidal disruption events were discovered, each of whose extreme X-ray luminosity and synchrotron radio emission were interpreted as the onset of emission from a relativistic jet. Here we report a luminous ultraviolet-optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696. The observed continuum is cooler than expected for a simple accreting debris disk, but the well-sampled rise and decay of the light curve follow the predicted mass accretion rate and can be modelled to determine the time of disruption to an accuracy of two days. The black hole has a mass of about two million solar masses, modulo a factor dependent on the mass and radius of the star disrupted. On the basis of the spectroscopic signature of ionized helium from the unbound debris, we determine that the disrupted star was a helium-rich stellar core. 相似文献
28.
Fatality in mice due to oversaturation of cellular microRNA/short hairpin RNA pathways 总被引:2,自引:0,他引:2
Grimm D Streetz KL Jopling CL Storm TA Pandey K Davis CR Marion P Salazar F Kay MA 《Nature》2006,441(7092):537-541
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