全文获取类型
收费全文 | 85篇 |
免费 | 0篇 |
专业分类
现状及发展 | 27篇 |
研究方法 | 11篇 |
综合类 | 47篇 |
出版年
2018年 | 1篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有85条查询结果,搜索用时 31 毫秒
1.
Summary 2-Halogeno-ethanols change the active site structure of -chymotrypsin more rapidly and effectively than ethanol, 1-propanol and urea, probably before producing an extensive conformation change. 相似文献
2.
Powerful radio jets from active galactic nuclei are thought to be powered by the accretion of material onto the supermassive black hole (the 'central engine'). M87 is one of the closest examples of this phenomenon, and the structure of its jet has been probed on a scale of about 100 Schwarzschild radii (R(s), the radius of the event horizon). However, the location of the central black hole relative to the jet base (a bright compact radio 'core') remains elusive. Observations of other jets indicate that the central engines are located about 10(4)-10(6)R(s) upstream from the radio core. Here we report radio observations of M87 at six frequencies that allow us to achieve a positional accuracy of about 20?microarcseconds. As the jet base becomes more transparent at higher frequencies, the multifrequency position measurements of the radio core enable us to determine the upstream end of the jet. The data reveal that the central engine of M87 is located within 14-23R(s) of the radio core at 43?GHz. This implies that the site of material infall onto the black hole and the eventual origin of the jet reside in the bright compact region seen on the image at 43?GHz. 相似文献
3.
Onouchi Y Gunji T Burns JC Shimizu C Newburger JW Yashiro M Nakamura Y Yanagawa H Wakui K Fukushima Y Kishi F Hamamoto K Terai M Sato Y Ouchi K Saji T Nariai A Kaburagi Y Yoshikawa T Suzuki K Tanaka T Nagai T Cho H Fujino A Sekine A Nakamichi R Tsunoda T Kawasaki T Nakamura Y Hata A 《Nature genetics》2008,40(1):35-42
Kawasaki disease is a pediatric systemic vasculitis of unknown etiology for which a genetic influence is suspected. We identified a functional SNP (itpkc_3) in the inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) gene on chromosome 19q13.2 that is significantly associated with Kawasaki disease susceptibility and also with an increased risk of coronary artery lesions in both Japanese and US children. Transfection experiments showed that the C allele of itpkc_3 reduces splicing efficiency of the ITPKC mRNA. ITPKC acts as a negative regulator of T-cell activation through the Ca2+/NFAT signaling pathway, and the C allele may contribute to immune hyper-reactivity in Kawasaki disease. This finding provides new insights into the mechanisms of immune activation in Kawasaki disease and emphasizes the importance of activated T cells in the pathogenesis of this vasculitis. 相似文献
4.
T. Aoyagi T. Wada F. Kojima M. Nagai S. Harada T. Takeuchi K. Isse M. Ogura M. Hamamoto K. Tanaka T. Nagao 《Cellular and molecular life sciences : CMLS》1992,48(7):656-659
Previously we reported that there is a kallikrein deficiency in the cerebral tissue of patients with Alzheimer-type dementia. The present study was performed to investigate protease changes in the serum of these patients. The results showed that the kallikrein activity was normal, but that the activities of plasmin and urokinase were significantly low. The present findings indicate a derangement in the clotting and fibrinolytic systems in Alzheimer patients. 相似文献
5.
Spectroscopic studies have provided extensive information on the primary process of visual pigments and photoexcitation of chlorophyll as well as their effects on photoreactivity on the higher-order structures of protein has been observed only rarely. Resonance Raman spectroscopy can reveal the vibrational frequencies of the chromophore in a molecule provided the excitation wavelength is in the absorption band of that molecule. As the visible absorption bands of haemproteins are due to pi pi* transitions of the porphyrin ring, we can selectively observe the vibrational frequencies of iron porphyrin during in situ interactions with immediate amino acid residues of protein when the wavelength of excitation light is close to the Soret or Q band. Correlation of some vibrational frequencies of haem with the oxidation and spin states of the haem iron has been studied in detail and an empirical rules has been established. This method is therefore especially suitable for the study of an effect of higher-order structures of protein on the chromophore. We report here a photoreaction facilitated by a particular quaternary structure of protein--in various haemoglobins resonance Raman spectroscopy showed that reversible photoreduction of haem took place in the T state but not the R state. 相似文献
6.
Free fatty acids regulate insulin secretion from pancreatic beta cells through GPR40 总被引:32,自引:0,他引:32
Itoh Y Kawamata Y Harada M Kobayashi M Fujii R Fukusumi S Ogi K Hosoya M Tanaka Y Uejima H Tanaka H Maruyama M Satoh R Okubo S Kizawa H Komatsu H Matsumura F Noguchi Y Shinohara T Hinuma S Fujisawa Y Fujino M 《Nature》2003,422(6928):173-176
Diabetes, a disease in which carbohydrate and lipid metabolism are regulated improperly by insulin, is a serious worldwide health issue. Insulin is secreted from pancreatic beta cells in response to elevated plasma glucose, with various factors modifying its secretion. Free fatty acids (FFAs) provide an important energy source as nutrients, and they also act as signalling molecules in various cellular processes, including insulin secretion. Although FFAs are thought to promote insulin secretion in an acute phase, this mechanism is not clearly understood. Here we show that a G-protein-coupled receptor, GPR40, which is abundantly expressed in the pancreas, functions as a receptor for long-chain FFAs. Furthermore, we show that long-chain FFAs amplify glucose-stimulated insulin secretion from pancreatic beta cells by activating GPR40. Our results indicate that GPR40 agonists and/or antagonists show potential for the development of new anti-diabetic drugs. 相似文献
7.
Summary Bilateral lesions of the suprachiasmatic nucleus of the hypothalamus of rats abolished circadian rhythms of oxygen consumption and of the respiratory quotient (RQ). The RQ remained constant at a level intermediate between the maximum (about 1.0) and minimum (about 0.9) values in control animals. 相似文献
8.
T. Aoyagi T. Wada M. Nagai F. Kojima S. Harada T. Takeuchi H. Takahashi K. Hirokawa T. Tsumita 《Cellular and molecular life sciences : CMLS》1990,46(1):94-97
Summary We examined the changes in the intracerebral activities, at the time of postmortem autopsy, in patients with Alzheimer's disease. When compared with the control group, the activity of kallikrein-like enzyme was significantly decreased, while prolyl endopeptidase activity increased, in the patients group. Aprotinin inhibited 50% of the activity of the former enzyme at 2×10–7M. Taken together with the results of a multivariate study, the above findings may indicate that intracerebral kallikrein deficiency plays an important role in the pathogenesis of Alzheimer's disease. 相似文献
10.
Zusammenfassung Mit Hilfe einer Nährlösung, in der 2prozentiges Glyzerin den Zucker ersetzte, wurde ein neues und vereinfachendes Verfahren gefunden, die durch Acriflavin bedingte Induktion der Atmungsunfähigkeit von Hefe zu prüfen. Während die normalen, das heisst atmungsfähigen Zellen sich in dieser Nährlösung vermehren, tun dies die atmungsunfähigen Zellen nie. Eine bemerkenswerte Zunahme der atmungsunfähigen Zellen wurde bei normalen Hefekulturen in Glyzerin-Nährlösung nach Zusatz von verschiedenen Konzentrationen von Acriflavin trotz der nachteiligen Bedingungen beobachtet. 相似文献