全文获取类型
收费全文 | 6306篇 |
免费 | 450篇 |
国内免费 | 5篇 |
出版年
2023年 | 46篇 |
2022年 | 73篇 |
2021年 | 156篇 |
2020年 | 102篇 |
2019年 | 131篇 |
2018年 | 167篇 |
2017年 | 138篇 |
2016年 | 225篇 |
2015年 | 304篇 |
2014年 | 349篇 |
2013年 | 493篇 |
2012年 | 546篇 |
2011年 | 500篇 |
2010年 | 310篇 |
2009年 | 289篇 |
2008年 | 359篇 |
2007年 | 384篇 |
2006年 | 333篇 |
2005年 | 288篇 |
2004年 | 248篇 |
2003年 | 239篇 |
2002年 | 218篇 |
2001年 | 78篇 |
2000年 | 64篇 |
1999年 | 63篇 |
1998年 | 53篇 |
1997年 | 46篇 |
1996年 | 37篇 |
1995年 | 25篇 |
1994年 | 26篇 |
1993年 | 20篇 |
1992年 | 41篇 |
1991年 | 39篇 |
1990年 | 43篇 |
1989年 | 24篇 |
1988年 | 30篇 |
1987年 | 19篇 |
1986年 | 25篇 |
1985年 | 33篇 |
1984年 | 27篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1972年 | 7篇 |
排序方式: 共有6761条查询结果,搜索用时 15 毫秒
1.
2.
Neurons in the visual cortex are responsive to the presentation of oriented and curved line segments, which are thought to act as primitives for the visual processing of shapes and objects. Prolonged adaptation to such stimuli gives rise to two related perceptual effects: a slow change in the appearance of the adapting stimulus (perceptual drift), and the distortion of subsequently presented test stimuli (adaptational aftereffects). Here we used a psychophysical nulling technique to dissociate and quantify these two classical observations in order to examine their underlying mechanisms and their relationship to one another. In agreement with previous work, we found that during adaptation horizontal and vertical straight lines serve as attractors for perceived orientation and curvature. However, the rate of perceptual drift for different stimuli was not predictive of the corresponding aftereffect magnitudes, indicating that the two perceptual effects are governed by distinct neural processes. Finally, the rate of perceptual drift for curved line segments did not depend on the spatial scale of the stimulus, suggesting that its mechanisms lie outside strictly retinotopic processing stages. These findings provide new evidence that the visual system relies on statistically salient intrinsic reference stimuli for the processing of visual patterns, and point to perceptual drift as an experimental window for studying the mechanisms of visual perception. 相似文献
3.
Alba Luengo Zhaoqi Li Dan Y. Gui Lucas B. Sullivan Maria Zagorulya Brian T. Do Raphael Ferreira Adi Naamati Ahmed Ali Caroline A. Lewis Craig J. Thomas Stefani Spranger Nicholas J. Matheson Matthew G. Vander Heiden 《Molecular cell》2021,81(4):691-707.e6
- Download : Download high-res image (172KB)
- Download : Download full-size image
4.
Background
NOL7 is a candidate tumor suppressor that localizes to a chromosomal region 6p23. This locus is frequently lost in a number of malignancies, and consistent loss of NOL7 through loss of heterozygosity and decreased mRNA and protein expression has been observed in tumors and cell lines. Reintroduction of NOL7 into cells resulted in significant suppression of in vivo tumor growth and modulation of the angiogenic phenotype. Further, NOL7 was observed to localize to the nucleus and nucleolus of cells. However, the mechanisms regulating its subcellular localization have not been elucidated. 相似文献5.
6.
Cristina Cereda Emanuela Leoni Pamela Milani Orietta Pansarasa Giuliano Mazzini Stefania Guareschi Elena Alvisi Andrea Ghiroldi Luca Diamanti Stefano Bernuzzi Mauro Ceroni Emanuela Cova 《PloS one》2013,8(10)
Several lines of evidence support the hypothesis of a toxic role played by wild type SOD1 (WT-SOD1) in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). In this study we investigated both distribution and expression profile of WT-SOD1 in leukocytes from 19 SALS patients and 17 healthy individuals. Immunofluorescence experiments by confocal microscopy showed that SOD1 accumulates in the nuclear compartment in a group of SALS subjects. These results were also confirmed by western blot carried out on soluble nuclear and cytoplasmic fractions, with increased nuclear SOD1 level (p<0.05). In addition, we observed the presence of cytoplasmic SOD1 aggregates in agreement with an increased amount of the protein recovered by the insoluble fraction. A further confirmation of the overall increased level of SOD1 has been obtained from single cells analysis using flow cytometry as cells from SALS patients showed an higher SOD1 protein content (p<0.05). These findings add further evidence to the hypothesis of an altered WT-SOD1 expression profile in peripheral blood mononuclear cells (PBMCs) from patients with ALS suggesting that WT-SOD1 species with different degrees of solubility could be involved in the pathogenesis of the disease. 相似文献
7.
Controlled generation of reactive oxygen species orchestrates numerous physiological signaling events (Finkel, T. (2011) Signal transduction by reactive oxygen species. J. Cell Biol. 194, 7–15). A major cellular target of reactive oxygen species is the thiol side chain (RSH) of Cys, which may assume a wide range of oxidation states (i.e. −2 to +4). Within this context, Cys sulfenic (Cys-SOH) and sulfinic (Cys-SO2H) acids have emerged as important mechanisms for regulation of protein function. Although this area has been under investigation for over a decade, the scope and biological role of sulfenic/sulfinic acid modifications have been recently expanded with the introduction of new tools for monitoring cysteine oxidation in vitro and directly in cells. This minireview discusses selected recent examples of protein sulfenylation and sulfinylation from the literature, highlighting the role of these post-translational modifications in cell signaling. 相似文献
8.
9.
10.
Here we report massive seed predation of Pseudobombax grandiflorum (Bombacaceae) by Botogeris versicolurus (Psittacidae) in a forest fragment in Brazil. The intensity of seed predation was very high when compared to other studies in continuous forest, perhaps resulting from a scarcity of resources in such areas. This scarcity may limit the range of parrot's diet to a few plant species. It suggests that studies of Psittacidae seed predation may be important for conservation of some plants in fragments. 相似文献