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71.
Cruz FW Burns SJ Karmann I Sharp WD Vuille M Cardoso AO Ferrari JA Dias PL Viana O 《Nature》2005,434(7029):63-66
During the last glacial period, large millennial-scale temperature oscillations--the 'Dansgaard/Oeschger' cycles--were the primary climate signal in Northern Hemisphere climate archives from the high latitudes to the tropics. But whether the influence of these abrupt climate changes extended to the tropical and subtropical Southern Hemisphere, where changes in insolation are thought to be the main direct forcing of climate, has remained unclear. Here we present a high-resolution oxygen isotope record of a U/Th-dated stalagmite from subtropical southern Brazil, covering the past 116,200 years. The oxygen isotope signature varies with shifts in the source region and amount of rainfall in the area, and hence records changes in atmospheric circulation and convective intensity over South America. We find that these variations in rainfall source and amount are primarily driven by summer solar radiation, which is controlled by the Earth's precessional cycle. The Dansgaard/Oeschger cycles can be detected in our record and therefore we confirm that they also affect the tropical hydrological cycle, but that in southern subtropical Brazil, millennial-scale climate changes are not as dominant as they are in the Northern Hemisphere. 相似文献
72.
Carcinogenicity of the herbicide maleic hydrazide 总被引:1,自引:0,他引:1
73.
74.
Presley JF Ward TH Pfeifer AC Siggia ED Phair RD Lippincott-Schwartz J 《Nature》2002,417(6885):187-193
Cytosolic coat proteins that bind reversibly to membranes have a central function in membrane transport within the secretory pathway. One well-studied example is COPI or coatomer, a heptameric protein complex that is recruited to membranes by the GTP-binding protein Arf1. Assembly into an electron-dense coat then helps in budding off membrane to be transported between the endoplasmic reticulum (ER) and Golgi apparatus. Here we propose and corroborate a simple model for coatomer and Arf1 activity based on results analysing the distribution and lifetime of fluorescently labelled coatomer and Arf1 on Golgi membranes of living cells. We find that activated Arf1 brings coatomer to membranes. However, once associated with membranes, Arf1 and coatomer have different residence times: coatomer remains on membranes after Arf1-GTP has been hydrolysed and dissociated. Rapid membrane binding and dissociation of coatomer and Arf1 occur stochastically, even without vesicle budding. We propose that this continuous activity of coatomer and Arf1 generates kinetically stable membrane domains that are connected to the formation of COPI-containing transport intermediates. This role for Arf1/coatomer might provide a model for investigating the behaviour of other coat protein systems within cells. 相似文献
75.
Abrupt variations of the radiolarian fauna at Mid-Pleistocene climate transition in the South China Sea 总被引:2,自引:0,他引:2
Based on a detailed study of the radiolarian fauna, the abundance pattern of planktic foraminifera as well as on isotope and
sedimentological records, the Mid-Pleistocene climate transition as a multiple transition phenomenon could be recognized at
Core 17957-2 from the South China Sea. Distinct changes in the radiolarian/foraminfera ratio, the coarse fraction and the
radiolarian assemblages can be related to the global climate cooling observed at the Mid-Pleistocene revolution (MPR) around
900 ka. A pronounced southward shift of the North Equatorial Current that leads to lower sea-surface temperatures in the South
China Sea is documented by the shift of tropical to subtropical radiolarian assemblages at 900 ka. Increasing radiolarian
abundance after the MPR can be interpreted as a result of stronger upwelling and nutrient supply. These abrupt variations
could result from the northern trade wind system and East Asian monsoon circulation. 相似文献
76.
Luther S Fenton FH Kornreich BG Squires A Bittihn P Hornung D Zabel M Flanders J Gladuli A Campoy L Cherry EM Luther G Hasenfuss G Krinsky VI Pumir A Gilmour RF Bodenschatz E 《Nature》2011,475(7355):235-239
Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult, because of the nonlinear interaction of excitation waves in a heterogeneous anatomical substrate. In the absence of a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation. Here we establish the relationship between the response of the tissue to an electric field and the spatial distribution of heterogeneities in the scale-free coronary vascular structure. We show that in response to a pulsed electric field, E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density ρ(E) and a characteristic time, τ, for tissue depolarization that obeys the power law τ?∝?E(α). These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore, efficient termination of fibrillation. Using this control strategy, we demonstrate low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques. 相似文献
77.
Berger MF Lawrence MS Demichelis F Drier Y Cibulskis K Sivachenko AY Sboner A Esgueva R Pflueger D Sougnez C Onofrio R Carter SL Park K Habegger L Ambrogio L Fennell T Parkin M Saksena G Voet D Ramos AH Pugh TJ Wilkinson J Fisher S Winckler W Mahan S Ardlie K Baldwin J Simons JW Kitabayashi N MacDonald TY Kantoff PW Chin L Gabriel SB Gerstein MB Golub TR Meyerson M Tewari A Lander ES Getz G Rubin MA Garraway LA 《Nature》2011,470(7333):214-220
78.
Direct generation of functional dopaminergic neurons from mouse and human fibroblasts 总被引:2,自引:0,他引:2
79.
Fernando Bartolomé Úrsula Muñoz Noemí Esteras Carolina Alquezar Andrea Collado Félix Bermejo-Pareja Ángeles Martín-Requero 《Cellular and molecular life sciences : CMLS》2010,67(24):4257-4268
Statins may exert beneficial effects on Alzheimer’s disease (AD) patients. Based on the antineoplastic and apoptotic effects
of statins in a number of cell types, we hypothesized that statins may be able to protect neurons by controlling the regulation
of cell cycle and/or apoptosis. A growing body of evidence indicates that neurodegeneration involves the cell-cycle activation
in postmitotic neurons. Failure of cell-cycle control is not restricted to neurons in AD patients, but occurs in peripheral
cells as well. For these reasons, we studied the role of simvastatin (SIM) on cell survival/death in lymphoblasts from AD
patients. We report here that SIM induces apoptosis in AD lymphoblasts deprived of serum. SIM interacts with PI3K/Akt and
ERK1/2 signaling pathways thereby decreasing the serum withdrawal-enhanced levels of the CDK inhibitor p21Cip1 (p21) and restoring the vulnerability of AD cells to trophic factor deprivation. 相似文献
80.
Alais S Soto-Rifo R Balter V Gruffat H Manet E Schaeffer L Darlix JL Cimarelli A Raposo G Ohlmann T Leblanc P 《Cellular and molecular life sciences : CMLS》2012,69(8):1331-1352
The cellular prion protein PrP(C)/CD230 is a GPI-anchor protein highly expressed in cells from the nervous and immune systems and well conserved among vertebrates. In the last decade, several studies suggested that PrP(C) displays antiviral properties by restricting the replication of different viruses, and in particular retroviruses such as murine leukemia virus (MuLV) and the human immunodeficiency virus type 1 (HIV-1). In this context, we previously showed that PrP(C) displays important similarities with the HIV-1 nucleocapsid protein and found that PrP(C) expression in a human cell line strongly reduced HIV-1 expression and virus production. Using different PrP(C) mutants, we report here that the anti-HIV-1 properties are mostly associated with the amino-terminal 24-KRPKP-28 basic domain. In agreement with its reported RNA chaperone activity, we found that PrP(C) binds to the viral genomic RNA of HIV-1 and negatively affects its translation. Using a combination of biochemical and cell imaging strategies, we found that PrP(C) colocalizes with the virus assembly machinery at the plasma membrane and at the virological synapse in infected T cells. Depletion of PrP(C) in infected T cells and microglial cells favors HIV-1 replication, confirming its negative impact on the HIV-1 life cycle. 相似文献