全文获取类型
收费全文 | 133856篇 |
免费 | 8992篇 |
国内免费 | 8381篇 |
出版年
2023年 | 1568篇 |
2022年 | 1749篇 |
2021年 | 3440篇 |
2020年 | 2969篇 |
2019年 | 3792篇 |
2018年 | 3535篇 |
2017年 | 2873篇 |
2016年 | 3571篇 |
2015年 | 5979篇 |
2014年 | 9373篇 |
2013年 | 10250篇 |
2012年 | 7109篇 |
2011年 | 8401篇 |
2010年 | 6318篇 |
2009年 | 6668篇 |
2008年 | 7036篇 |
2007年 | 7218篇 |
2006年 | 5968篇 |
2005年 | 5510篇 |
2004年 | 4591篇 |
2003年 | 4133篇 |
2002年 | 3720篇 |
2001年 | 2647篇 |
2000年 | 2342篇 |
1999年 | 2369篇 |
1998年 | 2112篇 |
1997年 | 1734篇 |
1996年 | 1611篇 |
1995年 | 1957篇 |
1994年 | 1860篇 |
1993年 | 1709篇 |
1992年 | 1590篇 |
1991年 | 1305篇 |
1990年 | 1099篇 |
1989年 | 1058篇 |
1988年 | 1023篇 |
1987年 | 899篇 |
1986年 | 763篇 |
1985年 | 1031篇 |
1984年 | 1387篇 |
1983年 | 910篇 |
1982年 | 1120篇 |
1981年 | 949篇 |
1980年 | 760篇 |
1979年 | 729篇 |
1978年 | 469篇 |
1977年 | 406篇 |
1976年 | 386篇 |
1974年 | 268篇 |
1973年 | 276篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Silkworm hemolymph contains unique proteins that exhibit anti-apoptotic activity in mammalian cells. Among them, 30 K protein, which is one of the major anti-apoptotic molecules in silkworm hemolymph, has been well investigated. However, little is known about the biological functions of storage protein 1 (SP1), another main protein in silkworm hemolymph. In this study, the anti-apoptotic and anti-oxidative activities of SP1 were analyzed. A stable cell line expressing SP1 was constructed, which showed strong anti-apoptotic effect induced by staurosporine treatment. In addition, the cell line exhibited resistance to oxidative stress caused by hydrogen peroxide. For practical applications of SP1, recombinant SP1 was produced in Escherichia coli, and the supplementation of recombinant SP1 into culture medium exhibited anti-apoptotic and anti-oxidative activities. In addition, SP1 was found to be a cell-penetrating protein and localized in the cytosol as well as on the plasma membrane. The findings showed that SP1 itself is not an anti-oxidant; rather, it mediates intracellular anti-oxidative activity. In conclusion, the cellular resistance of SP1 to apoptosis and oxidative stress will provide a new strategy that could be utilized in the bio-industry for the production of biologics as well as for the development of anti-aging cosmetics. 相似文献
2.
3.
4.
5.
6.
Feng Xue Zhoushan Wu Jinrong Tong Jialun Zheng 《Bioscience, biotechnology, and biochemistry》2017,81(10):1891-1898
This study investigated the effects of high-intensity ultrasound and glycosylation on the structural and interfacial properties of the Maillard reaction conjugates of buckwheat protein isolate (BPI). The covalent attachment of dextran to BPI was confirmed by examination of the Fourier-transform infrared spectra. Emulsifying properties of the conjugates obtained by ultrasound treatment were improved as compared to those obtained by classical heating. Structural feature analyses suggested that conjugates obtained by ultrasound treatment had less α-helix and more random coil, higher surface hydrophobicity and less compact tertiary structure as compared to those obtained by classical heating. The surface activity measurement revealed that the BPI–dextran conjugates obtained by ultrasound treatment were closely packed and that each molecule occupied a small area of the interface. Combination of ultrasonic treatment and glycosylation was proved to be an efficient way to develop new stabilizers and thickening agents for food in this study. 相似文献
7.
8.
Maria Weinert Tharakeswari Selvakumar Travis S. Tierney Kambiz N. Alavian 《Journal of visualized experiments : JoVE》2015,(96)
Degeneration of mesencephalic dopaminergic (mesDA) neurons is the pathological hallmark of Parkinson’s diseae. Study of the biological processes involved in physiological functions and vulnerability and death of these neurons is imparative to understanding the underlying causes and unraveling the cure for this common neurodegenerative disorder. Primary cultures of mesDA neurons provide a tool for investigation of the molecular, biochemical and electrophysiological properties, in order to understand the development, long-term survival and degeneration of these neurons during the course of disease. Here we present a detailed method for the isolation, culturing and maintenance of midbrain dopaminergic neurons from E12.5 mouse (or E14.5 rat) embryos. Optimized cell culture conditions in this protocol result in presence of axonal and dendritic projections, synaptic connections and other neuronal morphological properties, which make the cultures suitable for study of the physiological, cell biological and molecular characteristics of this neuronal population. 相似文献
9.
Brain energy disorders and oxidative stress due to chronic hypoperfusion were considered to be the major risk factors in the pathogenesis of dementia. In previous studies, we have demonstrated that acupuncture treatment improved cognitive function of VaD patients and multi-infarct dementia (MID) rats. Acupuncture therapy also increased the activities of glycometabolic enzymes in the brain. But it is not clear whether acupuncture treatment compensates neuronal energy deficit after cerebral ischemic through enhancing the activities of glucose metabolic enzymes and preserving mitochondrial function, and whether acupuncture neuroprotective effect is associated with activations of mitochondrial antioxidative defense system. So, the effect of acupuncture therapy on cognitive function, cerebral blood flow (CBF), mitochondrial respiratory function and oxidative stress in the brain of MID rats was investigated in this study. The results showed that acupuncture treatment significantly improved cognitive abilities and increased regional CBF of MID rats. Acupuncture elevated the activities of total SOD, CuZnSOD and MnSOD, decreased the level of malondialdehyde (MDA) and superoxide anion, regulated the ratio of reduced glutathione (GSH) and oxidized glutathione (GSSG) in mitochondria, and raised the level of the respiratory control index (RCI) and P/O ratio and the activities of mitochondrial respiratory enzymes of MID rats. These results indicated that acupuncture treatment improved cognitive function of MID rats; and this improvement might be due to increased CBF, which ameliorated mitochondrial dysfunction induced by ischemia and endogenous oxidative stress system of brain. 相似文献
10.
B. Oderfeld-Nowak W. Jegliski M. Skup J. Skangiel-Kramska M. Zaremba D. Koczyk 《Journal of neurochemistry》1993,61(1):116-119
Abstract: The glial fibrillary acidic protein (GFAP) content was investigated using immunoblotting techniques in the septum and hippocampus of the rat after bilateral lateral fimbria transection. Seven days after surgery GFAP content increased significantly both in the septum (140% of control) and hippocampus (120% in dorsal, the less denervated, and 145% in the most denervated ventral part), indicating the occurrence of reactive gliosis. The GM1 treatment caused statistically significant attenuation of GFAP increment in all hippocampal parts. In contrast, GM1 treatment has no influence on the increase of GFAP content in the septum. Results suggest a differential effect of GM1 on the two gliotic reactions formed as a consequence of the lesion at the level of the source of innervation (septum) and the target (hippocampus). 相似文献