全文获取类型
收费全文 | 20485篇 |
免费 | 1943篇 |
国内免费 | 2300篇 |
专业分类
24728篇 |
出版年
2024年 | 76篇 |
2023年 | 325篇 |
2022年 | 668篇 |
2021年 | 1110篇 |
2020年 | 806篇 |
2019年 | 989篇 |
2018年 | 814篇 |
2017年 | 662篇 |
2016年 | 912篇 |
2015年 | 1342篇 |
2014年 | 1543篇 |
2013年 | 1608篇 |
2012年 | 1968篇 |
2011年 | 1761篇 |
2010年 | 1111篇 |
2009年 | 1011篇 |
2008年 | 1144篇 |
2007年 | 995篇 |
2006年 | 913篇 |
2005年 | 788篇 |
2004年 | 692篇 |
2003年 | 692篇 |
2002年 | 610篇 |
2001年 | 382篇 |
2000年 | 322篇 |
1999年 | 260篇 |
1998年 | 164篇 |
1997年 | 146篇 |
1996年 | 126篇 |
1995年 | 104篇 |
1994年 | 135篇 |
1993年 | 77篇 |
1992年 | 82篇 |
1991年 | 71篇 |
1990年 | 57篇 |
1989年 | 49篇 |
1988年 | 42篇 |
1987年 | 32篇 |
1986年 | 25篇 |
1985年 | 42篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Yanyu Wang Sarah A. Jenkins Chunfang Gu Ankita Shree Margarita Martinez-Moczygemba Jennifer Herold Marina Botto Rick A. Wetsel Yi Xu 《PLoS pathogens》2016,12(6)
Spores of Bacillus anthracis, the causative agent of anthrax, are known to persist in the host lungs for prolonged periods of time, however the underlying mechanism is poorly understood. In this study, we demonstrated that BclA, a major surface protein of B. anthracis spores, mediated direct binding of complement factor H (CFH) to spores. The surface bound CFH retained its regulatory cofactor activity resulting in C3 degradation and inhibition of downstream complement activation. By comparing results from wild type C57BL/6 mice and complement deficient mice, we further showed that BclA significantly contributed to spore persistence in the mouse lungs and dampened antibody responses to spores in a complement C3-dependent manner. In addition, prior exposure to BclA deletion spores (ΔbclA) provided significant protection against lethal challenges by B. anthracis, whereas the isogenic parent spores did not, indicating that BclA may also impair protective immunity. These results describe for the first time an immune inhibition mechanism of B. anthracis mediated by BclA and CFH that promotes spore persistence in vivo. The findings also suggested an important role of complement in persistent infections and thus have broad implications. 相似文献
992.
Lifang Zou Guihua Tu Wei Xie Shiyao Wen Qiuyu Xie Shuangmei Liu Guilin Li Yun Gao Hong Xu Shouyu Wang Yun Xue Bing Wu Qiulan Lv Mofeng Ying Xi Zhang Shangdong Liang 《Purinergic signalling》2016,12(1):127-137
Adenosine triphosphate (ATP) acts on P2X receptors to initiate signal transmission. P2X7 receptors play a role in the pathophysiological process of myocardial ischemic injury. Long noncoding RNAs (lncRNAs) participate in numerous biological functions independent of protein translation. LncRNAs are implicated in nervous system diseases. This study investigated the effects of NONRATT021972 small interference RNA (siRNA) on the pathophysiologic processes mediated by P2X7 receptors in stellate ganglia (SG) after myocardial ischemic injury. Our results demonstrated that the expression of NONRATT021972 in SG was significantly higher in the myocardial ischemic (MI) group than in the control group. Treatment of MI rats with NONRATT021972 siRNA, the P2X7 antagonist brilliant blue G (BBG), or P2X7 siRNA improved the histology of injured ischemic cardiac tissues and decreased the elevated concentrations of serum myocardial enzymes, creatine kinase (CK), CK isoform MB (CK-MB), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) compared to the MI rats. NONRATT021972 siRNA, BBG, or P2X7 siRNA treatment in MI rats decreased the expression levels of P2X7 immunoreactivity, P2X7 messenger RNA (mRNA), and P2X7 protein, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and phosphorylated p38 mitogen-activated protein kinase (p38 MAPK) in the SG compared to MI rats. NONRATT021972 siRNA treatment prevented the pathophysiologic processes mediated by P2X7 receptors in the SG after myocardial ischemic injury. 相似文献
993.
Yi He Germaine G. Cornelissen-Guillaume Junyun He Abba J. Kastin Laura M. Harrison 《Chronobiology international》2016,33(5):553-560
Autophagy is essential for normal cellular survival and activity. Circadian rhythms of autophagy have been studied in several peripheral organs but not yet reported in the brain. Here, we measured the circadian rhythm of autophagy-related proteins in mouse hippocampus and tested the effect of sleep fragmentation (SF). Expressions of the autophagy-related proteins microtubule‐associated protein 1 light chain 3 (LC3) and beclin were determined by western blotting and immunohistochemistry. Both the hippocampal LC3 signal and the ratio of its lipid-conjugated form LC3-II to its cytosolic form LC3-I showed a 24 h rhythm. The peak was seen at ZT6 (1 pm) and the nadir at ZT16 (1 am). The LC3 immunoreactivity in hippocampal CA1 pyramidal neurons also distributed differently, with more diffuse cytoplasmic appearance at ZT16. Chronic SF had a mild effect to disrupt the 24 h rhythm of LC3 and beclin expression. Interestingly, a greater effect of SF was seen after 24 h of recovery sleep when LC3-II expression was attenuated at both the peak and trough of circadian activities. Overall, the results show for the first time that the hippocampus has a distinct rhythm of autophagy that can be altered by SF. 相似文献
994.
995.
Yakun Hu Libing Deng Jie Zhang Xin Fang Puming Mei Xuebing Cao Jiari Lin Yi Wei Xiong Zhang Renshi Xu 《Molecular neurobiology》2016,53(7):4302-4318
996.
997.
998.
999.
Polybissilsesquioxanes with single‐handed helical morphologies attracted much attention during the last decade, which could be applied as asymmetric catalysts and chiral stationary phases. Herein, a pair of chiral biphenylene‐bridged bissilsesquioxanes were synthesized. They self‐assembled into helical bundles in ethanol, behavior that was confirmed in field emission scanning electron microscopy images. Circular dichroism analysis indicated that the biphenylene groups twisted in a single‐handed fashion. Single‐handed helical polybissilsesquioxane bundles were prepared via polycondensation of the bissilsesquioxanes, using a self‐templating approach. Because of the shrinkage that occurred during polycondensation, the helical pitches of the bundles were shorter than those of their corresponding organic self‐assemblies. The wide‐angle X‐ray diffraction pattern indicated that there were no π–π interactions among the diphenylene groups. The circular dichroism spectra indicated that the chirality was successfully transferred from the bissilsesquioxane self‐assemblies to the polybissilsesquioxane. The polybissilsesquioxanes displayed a capacity for the adsorption of nitrobenzene and had potential application for enantioseparation. Chirality 28:44–48, 2016. © 2015 Wiley Periodicals, Inc. 相似文献
1000.
Identification and Characterization of Pothos latent virus Causing Necrotic Ringspots and Line Patterns on Lisianthus (Eustoma grandiflorum) in Taiwan 下载免费PDF全文
Lisianthus (Eustoma grandiflorum) grown in screenhouses in Taiwan showed ringspots and concentric line patterns on leaves. A virus having isometric particles approximately 30–32 nm in diameter was isolated from affected lisianthus. Combined results of biological, cytological, serological, molecular and phylogenetic analyses show that the virus can be identified as Pothos latent virus (PoLV), genus Aureusvirus, family Tombusviridae. Inoculating the virus on non‐infected lisianthus plants reproduced the symptoms previously observed in the field. So, this is the first report of PoLV causing disease in lisianthus and the first report of the virus in Taiwan. 相似文献