首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   94篇
  免费   27篇
  2021年   4篇
  2017年   2篇
  2016年   2篇
  2015年   3篇
  2014年   6篇
  2013年   4篇
  2012年   9篇
  2011年   4篇
  2010年   6篇
  2009年   2篇
  2008年   1篇
  2007年   3篇
  2006年   2篇
  2005年   4篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  2001年   1篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1995年   3篇
  1992年   2篇
  1990年   1篇
  1988年   3篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1978年   4篇
  1977年   3篇
  1975年   1篇
  1974年   2篇
  1973年   4篇
  1972年   3篇
  1971年   1篇
  1970年   3篇
  1969年   2篇
  1967年   3篇
  1966年   1篇
  1965年   3篇
  1962年   4篇
  1960年   2篇
  1959年   1篇
  1958年   2篇
  1957年   1篇
  1956年   2篇
  1938年   1篇
排序方式: 共有121条查询结果,搜索用时 328 毫秒
71.
THE LOCALIZATION OF ENZYME ACTIVITIES IN THE RAT BRAIN   总被引:5,自引:5,他引:5       下载免费PDF全文
Studies with rat brain illustrate the usefulness of formol-calcium-fixed tissue for studying both enzymatic "chemoarchitectonics" and intracellular organelles. Unembedded frozen sections and polyvinyl alcohol-embedded sections may be used to demonstrate the activities of DPNH-tetrazolium reductase localized in mitochondria and ergastoplasm, TPNH-tetrazolium reductase localized in mitochondria, ATPase (and/or apyrase or ADPase) in cell membranes, and acid phosphatase in lysosomes.1 Among the observations recorded are: (1) the presence of lysosomes in all cells of the brain; (2) the presence of numerous large lysosomes near the nuclei of capillary endothelial cells; (3) a polarized arrangement of large lysosomes in epithelial cells of the ependyma and choroid plexus; (4) the presence of ATPase activity in the cell membranes of some neurons; (5) the presence of either an apyrase or combination of ATPase and ADPase in the cell membranes of neuroglia and capillaries; (6) the presence of both DPNH- and TPNH-tetrazolium reductase activities in neuroglia; (7) the presence of DPNH- and TPNH-tetrazolium reductase activities in mitochondria and of DPNH-tetrazolium reductase activity in Nissl substance. The possible functional significance of these localizations is briefly discussed, as is their relation to "quantitative histochemistry" data available in the literature.  相似文献   
72.
73.
A major challenge in controlling overabundant wildlife is monitoring their populations, particularly as they decline to very low density. Camera traps and wildlife detector dogs are increasingly being used for this purpose. We compared the cost-effectiveness of these two approaches for detecting feral cats (Felis catus) on two pastoral properties in Hawke's Bay, North Island, New Zealand. One property was subject to intensive pest removal, while the other had no recent history of pest control. Camera traps and wildlife detector dogs detected cats at similar rates at both sites. The operating costs of each method were also comparable. We identify a number of advantages and disadvantages of each technique, and suggest priorities for further research.  相似文献   
74.
The peroxidatic activity of hemoglobin permitted visualization of its uptake by rat hepatocytes by means of the Graham-Karnovsky 3,3'-diaminobenzidine (DAB) procedure. Lysosomes were visualized by their acid phosphatase, β-glucuronidase, and glucosaminidase activities. When large doses of rat, cow, or human hemoglobin are intravenously injected, or when hemoglobinemia is induced by injection of distilled water, DAB-positive hemoglobin is engulfed by pinocytosis. Pinocytotic vacuoles become digestive vacuoles ("phagolysosomes") by fusion with lysosomes of the dense body type that have moved from their pericanalicular position. By 16–24 hr after even massive amounts of hemoglobin (400 mg/100 g), the protein is barely demonstrable in hepatocytes. At the lowest doses of injected hemoglobin (15 mg/100 g body weight), DAB-positive vacuoles are demonstrable only in the Kupffer cells.  相似文献   
75.
76.
Thymus glands of chicks with leukemia induced by BAI strain A (myeloblastosis) virus were fixed in cold 4 per cent formaldehyde-sucrose. Frozen sections were incubated in the ATPase medium of Wachstein and Meisel and studied by light microscopy and electron microscopy. The ATPase activity of the virus is localized to the outermost membrane of the virus. The membrane of the blast-like cells of the thymus cortex from which the virus emerges, by budding, also possesses such activity. It appears likely that the outermost membrane of the virus is derived from the plasma membrane of these cells.  相似文献   
77.
Further characterization of HeLa S3 plasma membrane ghosts   总被引:1,自引:1,他引:0  
A plasma membrane fraction of HeLa S3 cells, consisting of ghosts, is characterized more fully. A simple procedure is described which permits light and electron microscope study of the plasma membrane fraction through the entire depth of the final product pellet and through large areas parallel to the surface. Contamination by nuclei is 0.14%, too little for DNA detection by the diphenylamine reaction. Contamination by rough endoplasmic reticulum and ribosomes is small, a single ghost containing about 3% of the RNA in a single cell. Mitochondria were not encountered. Electron microscopy also shows (a) small vesicles associated with the outer surface of the ghosts, and (b) a filamentous web at the inner face of the ghost membrane. Sodium dodecyl sulfate (SDS)-polyacrylamide gel analysis shows that of the many Coomassie Blue-stained bands two were prominent. One, 43,000 daltons, co-migrated with purified rabbit muscle actin and constituted about 7.5% of the plasma membrane protein. The other major band, 34,000 daltons, was concentrated in the plasma membrane fraction. Two major glycoproteins detected by autoradiography of [14C]fucose-labeled glycoproteins on the gels, had apparent molecular weights of 35,000 daltons and 32,000 daltons. These major bands did not stain with Coomassie Blue. There were many other minor glycoprotein bands in the 200,000- to 80,000-dalton range. Ouabain-sensitive, Na+, K+-adenosine triphosphatase (ATPase) activity of the ghost fraction is purified 9.1 (+/- 2.2) times over the homogenate; recover of the activity is 12.0 (+/- 3.8%) of the homogenate. Enrichment and recovery of fucosylglycoprotein parallel those for ouabain-sensitive Na+, K+-ATPase activity. Fucosyl glycoprotein is recovered more than the enzyme activity in a smooth membrane vesicle fraction probably containing the bulk of plasma membrane not recovered as ghosts.  相似文献   
78.
Cytochemical contributions to differentiating GERL from the Golgi apparatus   总被引:31,自引:0,他引:31  
Synopsis Recent studies from our laboratory are described which deal with endocrine cells (insulinoma, -cells of the pancreas, thyroid epithelial cells), pancreatic exocrine cells, and hepatocytes. These emphasize the importance of the hydrolase-rich specialized region of endoplasmic reticulum, known as GERL, in secretory cells. Also reviewed in this paper are the varied molecular transformations which apparently occur in GERL in different cell types, as reported from other laboratories as well as our own. Evidence of the continuity of GERL with rough endoplasmic reticulum is presented. Two hydrolytic enzyme activities in GERL, in addition to acid phosphatase activity, are recorded. Finally, the use of cytochemical staining procedures in the study of microperoxisomes is briefly described. The Histochemical Journal lecture 1976. Delivered to the Histochemistry and Cytochemistry Section of the Royal Microscopical Society on 14 September 1976  相似文献   
79.
In dorsal root ganglia and peripheral nerve of the rat and other species, nucleoside phosphatase and unspecific cholinesterase reaction products are found in the plasma membranes and spaces between them at two sites: (1) Schwann cell-axon interfaces and mesaxons of unmyelinated fibers, and (2) sheath cell-perikaryon interfaces and interfaces between adjacent sheath cells. Acetylcholinesterase reaction product is found in the perikaryon (within the endoplasmic reticulum) and the axon (axoplasmic surface). Nucleoside phosphatase reaction product is also found in the numerous vacuoles at the surface of perineurium cells, ganglion sheath cells, and cells surrounding some ganglion blood vessels. Nucleoside phosphatase activities in the sections fail to respond, in the manner described for "transport ATPase," to diisopropylphosphofluoridate, sodium and potassium ions, and ouabain. Nucleoside diphosphates are hydrolyzed more slowly than triphosphates in unmyelinated fibers, and are not hydrolyzed at the perikaryon surface. Nucleoside monophosphates are either not hydrolyzed or hydrolyzed very slowly. In contrast to these localizations, which are believed to demonstrate sites of enzyme activity, it is considered likely that diffusion artifacts account for the nucleoside phosphatase reaction product frequently found along the outer surfaces of myelinated fibers and within vacuoles at the Schwann cell surfaces of these fibers. The diffuse reaction product seen in basement membranes of ganglion and nerve may also be artifact.  相似文献   
80.
We previously reported that some cattle affected by bovine spongiform encephalopathy (BSE) showed distinct molecular features of the protease-resistant prion protein (PrPres) in Western blot, with a 1–2 kDa higher apparent molecular mass of the unglycosylated PrPres associated with labelling by antibodies against the 86–107 region of the bovine PrP protein (H-type BSE). By Western blot analyses of PrPres, we now showed that the essential features initially described in cattle were observed with a panel of different antibodies and were maintained after transmission of the disease in C57Bl/6 mice. In addition, antibodies against the C-terminal region of PrP revealed a second, more C-terminally cleaved, form of PrPres (PrPres #2), which, in unglycosylated form, migrated as a ≈ 14 kDa fragment. Furthermore, a PrPres fragment of ≈7 kDa, which was not labelled by C-terminus-specific antibodies and was thus presumed to be a product of cleavage at both N- and C-terminal sides of PrP protein, was also detected. Both PrPres #2 and ≈7 kDa PrPres were detected in cattle and in C57Bl/6 infected mice. These complex molecular features are reminiscent of findings reported in human prion diseases. This raises questions regarding the respective origins and pathogenic mechanisms in prion diseases of animals and humans.Key Words: prion, BSE, Creutzfeldt-Jakob, Gerstmann-Sträussler-Scheinker, Western blot, amyloid  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号