全文获取类型
收费全文 | 353篇 |
免费 | 23篇 |
出版年
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 8篇 |
2012年 | 11篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 15篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1967年 | 2篇 |
1963年 | 2篇 |
1959年 | 2篇 |
1955年 | 2篇 |
1953年 | 3篇 |
1925年 | 1篇 |
1918年 | 1篇 |
排序方式: 共有376条查询结果,搜索用时 46 毫秒
71.
Evidence of Increased Oxidative Damage in Both Sporadic and Familial Amyotrophic Lateral Sclerosis 总被引:22,自引:13,他引:9
Robert J. Ferrante Susan E. Browne Leslie A. Shinobu Allen C. Bowling M. Jay Baik Usha MacGarvey Neil W. Kowall †Robert H. Brown Jr. M. Flint Beal 《Journal of neurochemistry》1997,69(5):2064-2074
Abstract: Some cases of autosomal dominant familial amyotrophic lateral sclerosis (FALS) are associated with mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1), suggesting that oxidative damage may play a role in ALS pathogenesis. To further investigate the biochemical features of FALS and sporadic ALS (SALS), we examined markers of oxidative damage to protein, lipids, and DNA in motor cortex (Brodmann area 4), parietal cortex (Brodmann area 40), and cerebellum from control subjects, FALS patients with and without known SOD mutations, SALS patients, and disease controls (Pick's disease, progressive supranuclear palsy, diffuse Lewy body disease). Protein carbonyl and nuclear DNA 8-hydroxy-2'-deoxyguanosine (OH8 dG) levels were increased in SALS motor cortex but not in FALS patients. Malondialdehyde levels showed no significant changes. Immunohistochemical studies showed increased neuronal staining for hemeoxygenase-1, malondialdehyde-modified protein, and OH8 dG in both SALS and FALS spinal cord. These studies therefore provide further evidence that oxidative damage may play a role in the pathogenesis of neuronal degeneration in both SALS and FALS. 相似文献
72.
The role of mitochondrial dysfunction and neuronal nitric oxide in animal models of neurodegenerative diseases 总被引:8,自引:0,他引:8
Jörg B. Schulz Russell T. Matthews Thomas Klockgether Johannes Dichgans M. Flint Beal 《Molecular and cellular biochemistry》1997,174(1-2):193-197
Excitotoxicity, mitochondrial dysfunction and free radical induced oxidative damage have been implicated in the pathogenesis of several different neurodegenerative diseases, such as amyotrophic lateral sclerosis, Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease. Much of the interest in the association of neurodegeneration with mitochondrial dysfunction and oxidative damage emerged from animal studies using mitochondrial toxins. Within mitochondria 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), acts to inhibit NADH-coenzyme Q reductase (complex I) of the electron transport chain. MPTP produces Parkinsonism in humans, primates, and mice. Similarly, lesions produced by the reversible inhibitor of succinate dehydrogenase (complex II), malonate, and the irreversible inhibitor, 3-nitropropionic acid (3-NP), closely resemble the histologic, neurochemical and clinical features of HD in both rats and non-human primates. The interruption of oxidative phosphorylation results in decreased levels of ATP. A consequence is partial neuronal depolarization and secondary activation of voltage-dependent NMDA receptors, which may result in excitotoxic neuronal cell death (secondary excitotoxicity). The increase in intracellular Ca2+ concentration leads to an actiation of Ca2+ dependent enzymes, including the constitutive neuronal nitric oxide synthase (cnNOS) which produces NO·. NO· may react with the superoxide anion to form peroxynitrite. We show that systemic administration of 7-nitroindazole (7-NI), a relatively specific inhibitor of cnNOS in vivo. attenuates lesions produced by striatal malonate injections or systemic treatment with 3-NP or MPTP. Furthermore 7-NI attenuated increases in lactate production and hydroxyl radical and 3-nitrotyrosine generation in vivo, which may be a consequence of peroxynitrite formation. Our results suggest that neuronal nitric oxide synthase inhibitors may be useful in the treatment of neurologic diseases in which excitotoxic mechanisms play a role. (Mol Cell Biochem 174: 193–197, 1997) 相似文献
73.
74.
Marie-Josee MF Lemoy Angela Colagross Schouten Don R Canfield 《Comparative medicine》2016,66(1):59-62
Bioabsorbable hemostatic agents such as oxidized regenerated cellulose are widely used to control intraoperative diffuse capillary bleeding. Compared with electrocautery or ligation, oxidized regenerated cellulose has the advantage of controlling bleeding without occluding the vessel lumen or causing thermal injuries to adjacent tissue. Although the manufacturer recommends removal of the material once hemostasis is achieved, oxidized regenerated cellulose is a bioabsorbable hemostatic agent and is often left in the surgical bed to prevent subsequent bleeding after surgical closure. However, noninvasive imaging techniques have revealed granulomatous foreign-body reactions that mimic infection or tumor recurrence. We present a case report of sterile peritonitis and granuloma formation secondary to the presence of oxidized regenerated cellulose after intestinal resection to excise a colonic adenocarcinoma in an aged rhesus macaque.Bioabsorbable hemostatic agents such as oxidized regenerated cellulose (for example, Surgicel) are widely used to control intraoperative diffuse capillary bleeding. Compared with electrocautery or ligation, oxidized regenerated cellulose has the advantage of controlling bleeding without occluding the vessel lumen or causing thermal injuries to adjacent tissue.16Oxidized regenerated cellulose is formed by dissolving the α-cellulose of decomposed wood pulp in an alkaline solution and subsequently regenerating it as a continuous fiber. This fiber is then woven into a gauze and oxidized.17,22 Oxidized regenerated cellulose is supplied as a substrate that is flexible, malleable, and trimable.16The mechanism of hemostasis of oxidized regenerated cellulose is reportedly associated with its caustic activity.2 The oxidation of cellulose produces a low-pH organic acid that reacts with blood, thus forming an artificial clot and causing platelet aggregation.18Although the manufacturer recommends the removal of oxidized regenerated cellulose once hemostasis is achieved,8 the product, a bioabsorbable hemostatic agent, is often left in situ within the surgical bed to prevent bleeding after surgical procedures. The biodegradation and elimination of oxidized regenerated cellulose from the tissue occurs in 2 phases.14 Polyanhydroglucuronic acid, the major functional unit of oxidized regenerated cellulose, is readily soluble. This acid is degraded extracellulary and systematically cleared from the system approximately 18 h after implantation.13,14 The remaining fibrous residue, however, requires macrophage phagocytosis for clearance and can be observed within macrophages for at least 48 h after implantation.13 Unfortunately, these fibrous residues have a prolonged degradation, and their persistence for as long as 7 mo after surgery has been confirmed histologically.7Despite the biocompatibility of oxidized regenerated cellulose, granulomatous foreign-body reactions that imitate infection or tumor recurrence have been revealed by using noninvasive imaging techniques.1,11,12,15,17,18,22 Here we describe a case of peritonitis and granuloma formation secondary to the presence of oxidized regenerated cellulose after an intestinal resection to excise a colonic adenocarcinoma in an aged rhesus macaque. 相似文献
75.
76.
Satria P. Sajuthi Neeraj K. Sharma Jeff W. Chou Nicholette D. Palmer David R. McWilliams John Beal Mary E. Comeau Lijun Ma Jorge Calles-Escandon Jamehl Demons Samantha Rogers Kristina Cherry Lata Menon Ethel Kouba Donna Davis Marcie Burris Sara J. Byerly Maggie C. Y. Ng Nisa M. Maruthur Sanjay R. Patel Lawrence F. Bielak Leslie A. Lange Xiuqing Guo Michèle M. Sale Kei Hang K. Chan Keri L. Monda Gary K. Chen Kira Taylor Cameron Palmer Todd L. Edwards Kari E. North Christopher A. Haiman Donald W. Bowden Barry I. Freedman Carl D. Langefeld Swapan K. Das 《Human genetics》2016,135(8):869-880
77.
78.
Chloroplast ontogeny has been examined in 42-day etiolated triploid aspen callus (Populus tremuloides Michx.) subjected to two different light conditions. White and low-intensity red illumination showed little differences in their stimulatory effects on plastid development, the red light-irradiated plastids developing only slightly more slowly. Asynchronous plastid development was noted in both lighting systems. Etioplasts contained an interconnected tubular net, phytoferritin aggregates, electron-transparent vesicles which seem to invaginate from the inner plastid membrane, membrane-bound homogeneous spheroids and starch grains. Irradiation caused various morphological changes within the proplastids; the tubular complex became transformed into the more ordered prolamellar body-like structure from which radiated membrane-bound sacs filled with electron-dense material. These sacs, characterized as thylakoid precursors, were transformed into a thylakoidal system typical of mature chloroplasts. This ontogenetic scheme represents an additional pathway for the development of photosynthetic lamellae. Other light-induced changes in the developing plastid include disappearance of phytoferritin particles and homogeneous spheroids, decrease in starch content, and appearance of osmiophilic droplets. 相似文献
79.
80.
A combination iron-mordant fixative in which propionic acid is substituted for acetic acid has been found useful in preparing small plant chromosomes for carmine stained squashes. Propionic acid is better than acetic acid because it holds more iron in stable solution. The fixative is a 3:1 mixture of 95% alcohol and pure propionic acid which contains 400 mg. of Fe(OH)3 per 100 ml. of propionic acid. The latter is previously prepared by dissolving the dry freshly prepared Fe(OH)3 in it. To each 10 ml. vial of fixative is added a few drops of carmine stain. Standard aceto-carmine squashes of material fixed in this mixture show quick intense staining and are especially useful for differentiated chromosomes at mitotic prophase. 相似文献