全文获取类型
收费全文 | 722篇 |
免费 | 34篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 37篇 |
2020年 | 17篇 |
2019年 | 25篇 |
2018年 | 30篇 |
2017年 | 15篇 |
2016年 | 28篇 |
2015年 | 34篇 |
2014年 | 50篇 |
2013年 | 58篇 |
2012年 | 60篇 |
2011年 | 49篇 |
2010年 | 32篇 |
2009年 | 24篇 |
2008年 | 46篇 |
2007年 | 36篇 |
2006年 | 33篇 |
2005年 | 26篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 4篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1965年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有757条查询结果,搜索用时 15 毫秒
81.
82.
Moussaïd M Guillot EG Moreau M Fehrenbach J Chabiron O Lemercier S Pettré J Appert-Rolland C Degond P Theraulaz G 《PLoS computational biology》2012,8(3):e1002442
In human crowds as well as in many animal societies, local interactions among individuals often give rise to self-organized collective organizations that offer functional benefits to the group. For instance, flows of pedestrians moving in opposite directions spontaneously segregate into lanes of uniform walking directions. This phenomenon is often referred to as a smart collective pattern, as it increases the traffic efficiency with no need of external control. However, the functional benefits of this emergent organization have never been experimentally measured, and the underlying behavioral mechanisms are poorly understood. In this work, we have studied this phenomenon under controlled laboratory conditions. We found that the traffic segregation exhibits structural instabilities characterized by the alternation of organized and disorganized states, where the lifetime of well-organized clusters of pedestrians follow a stretched exponential relaxation process. Further analysis show that the inter-pedestrian variability of comfortable walking speeds is a key variable at the origin of the observed traffic perturbations. We show that the collective benefit of the emerging pattern is maximized when all pedestrians walk at the average speed of the group. In practice, however, local interactions between slow- and fast-walking pedestrians trigger global breakdowns of organization, which reduce the collective and the individual payoff provided by the traffic segregation. This work is a step ahead toward the understanding of traffic self-organization in crowds, which turns out to be modulated by complex behavioral mechanisms that do not always maximize the group's benefits. The quantitative understanding of crowd behaviors opens the way for designing bottom-up management strategies bound to promote the emergence of efficient collective behaviors in crowds. 相似文献
83.
Talior-Volodarsky I Randhawa VK Zaid H Klip A 《The Journal of biological chemistry》2008,283(37):25115-25123
Insulin induces GLUT4 translocation to the muscle cell surface. Using differential amino acid labeling and mass spectrometry, we observed insulin-dependent co-precipitation of actinin-4 (ACTN4) with GLUT4 (Foster, L. J., Rudich, A., Talior, I., Patel, N., Huang, X., Furtado, L. M., Bilan, P. J., Mann, M., and Klip, A. (2006) J. Proteome Res. 5, 64-75). ACTN4 links F-actin to membrane proteins, and actin dynamics are essential for GLUT4 translocation. We hypothesized that ACTN4 may contribute to insulin-regulated GLUT4 traffic. In L6 muscle cells insulin, but not platelet-derived growth factor, increased co-precipitation of ACTN4 with GLUT4. Small interfering RNA-mediated ACTN4 knockdown abolished the gain in surface-exposed GLUT4 elicited by insulin but not by platelet-derived growth factor, membrane depolarization, or mitochondrial uncoupling. In contrast, knockdown of alpha-actinin-1 (ACTN1) did not prevent GLUT4 translocation by insulin. GLUT4 colocalized with ACTN4 along the insulin-induced cortical actin mesh and ACTN4 knockdown prevented GLUT4-actin colocalization without impeding actin remodeling or Akt phosphorylation, maintaining GLUT4 in a tight perinuclear location. We propose that ACTN4 contributes to GLUT4 traffic, likely by tethering GLUT4 vesicles to the cortical actin cytoskeleton. 相似文献
84.
Selective regulation of the perinuclear distribution of glucose transporter 4 (GLUT4) by insulin signals in muscle cells 总被引:1,自引:0,他引:1
Insulin regulates glucose transporter 4 (GLUT4) availability at the surface of muscle and adipose cells. In L6 myoblasts, stably expressed GLUT4myc is detected mostly in a perinuclear region. In unstimulated cells, about half of perinuclear GLUT4myc colocalizes with the transferrin receptor (TfR). Insulin stimulation selectively decreased the perinuclear colocalization of GLUT4myc with TfR determined by 3D-reconstruction of fluorescence images. Perinuclear GLUT4myc adopted two main distributions defined morphometrically as 'conical' and 'concentric'. Insulin rapidly reduced the proportion of cells with conical in favor of concentric perinuclear GLUT4myc distributions in association with the gain in surface GLUT4myc. Upon removal of insulin, the GLUT4myc perinuclear distribution and surface levels reversed in parallel. In contrast, hypertonicity (which like insulin elevates surface GLUT4myc) did not elicit perinuclear GLUT4myc redistribution. Insulin also caused redistribution of perinuclear vesicle-associated membrane protein-2 (VAMP2), without alteration of perinuclear TfR and VAMP3. Inhibitory mutants of phosphatidylinositol-3 kinase (Deltap85) or Akt substrate AS160 (AS160-4P) prevented insulin-mediated perinuclear GLUT4myc redistribution. Tetanus toxin expression did not prevent the perinuclear GLUT4myc redistribution, suggesting that redistribution is independent of GLUT4myc fusion with the plasma membrane. We propose that insulin causes selective, dynamic relocalization of perinuclear GLUT4myc and VAMP2 and perinuclear GLUT4myc redistribution is a direct target of insulin-derived signals. 相似文献
85.
Lucia Acebey Amira Apaza Rosy de Michel Stephan Beck Valérie Jullian Grace Ruiz Alberto Gimenez Séverine Chevalley Michel Sauvain 《Biodiversity and Conservation》2008,17(8):1853-1859
Developing countries with a rich biodiversity want to control the use of this natural patrimony, especially in the research
of natural compounds of pharmaceutical interest. Here we present the organization of six permanent plots in a mountain tropical
forest on the east side of the Andean Cordillera in Bolivia, and their role in the discovery of plants with antiplasmodial
or antileishmanial activities. Permanent plots are widely used in ecological survey, but rarely in bioprospecting. This set-up
allows Bolivian authorities to control the bioprospecting, and facilitates further chemical studies on the bioactive plants.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Lucia Acebey and Amira Apaza have contributed equally to this work. 相似文献
86.
87.
Parkinson’s disease (PD) is a movement disorder associated with genetic and age related causes. Although autosomal recessive early onset PD linked to parkin mutations does not exhibit α-Synuclein accumulation, while autosomal dominant and sporadic PD manifest with α-Synuclein inclusions, loss of dopaminergic substantia nigra neurons is a common denominator in PD. Here we show that decreased parkin ubiquitination and loss of parkin stability impair interaction with Beclin-1 and alter α-Synuclein degradation, leading to death of dopaminergic neurons. Tyrosine kinase inhibition increases parkin ubiquitination and interaction with Beclin-1, promoting autophagic α-Synuclein clearance and nigral neuron survival. However, loss of parkin via deletion increases α-Synuclein in the blood compared to the brain, suggesting that functional parkin prevents α-Synuclein release into the blood. These studies demonstrate that parkin ubiquitination affects its protein stability and E3 ligase activity, possibly leading to α-Synuclein sequestration and subsequent clearance. 相似文献
88.
Sarah O. Makled Amira M. Hamdan Abdel-Fattah M. El-Sayed 《Probiotics and antimicrobial proteins》2020,12(2):365-374
A 50-day feeding trial was conducted to evaluate the effects of dietary supplementation of a novel marine psychrotrophic bacterium, Psychrobacter maritimus 相似文献
89.
90.