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   192篇
  免费   10篇
  2018年   1篇
  2016年   1篇
  2014年   2篇
  2013年   85篇
  2012年   7篇
  2011年   4篇
  2010年   2篇
  2008年   4篇
  2007年   2篇
  2006年   4篇
  2005年   4篇
  2004年   3篇
  2002年   3篇
  2001年   4篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1994年   2篇
  1992年   5篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1987年   3篇
  1986年   4篇
  1985年   4篇
  1984年   3篇
  1983年   2篇
  1982年   5篇
  1981年   4篇
  1980年   3篇
  1979年   4篇
  1978年   4篇
  1977年   3篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1970年   2篇
  1969年   2篇
  1968年   1篇
排序方式: 共有202条查询结果,搜索用时 203 毫秒
111.
In the screening of actinomycetes’ culture filtrate for inhibitor of subtilisin and various microbial alkaline proteinases, a novel inhibitor was found in a cultured broth of strain WT-27. This inhibitor was named as MAPI, abbreviation of microbial alkaline proteinase inhibitor.Judging from the morphological and physiological properties of the actinomycetes which produced MAPI, this strain was identified as Streptomyces nigrescens.

For the production of MAPI, this strain was aerobically cultured at 25 ~ 27%C in a jar fermentor which contained an optimum medium consisting of polypepton 3 %, meat extract 1%, glucose 1%, NaCl 0.1%, K2HPO4 0.1% and MnSO4·nH2O 0.0001%, pH 7.0. The production of MAPI reached its maximum after 21 ~ 24 hr cultivation.

MAPI had an inhibitory activity against various microbial alkaline proteinases, α-chymotrypsin and papain but not against trypsin, kallikrein, thermolysin, or pepsin.  相似文献   
112.
A novel enzyme, which was named Nα-benzyloxycarbonyl amino acid urethane hydrolase II, was purified from a cell-free extract of Lactobacillus fermenti 36 ATCC 9338. The enzyme catalyzed the stoichiometric hydrolysis of Nα-benzyloxycarbonyl arginine to form benzyl alcohol and arginine. The enzyme was purified 106-fold with an activity yield of 3%. The purified enzyme was homogeneous by disc gel electrophoresis. The molecular weight of the native enzyme is about 200,000 by gel filtration, and a molecular weight of 27,000 was found for the reduced and denaturated enzyme by gel electrophoresis in sodium dodecyl sulfate. The isoelectric point of the enzyme was 5.0, it was inhibited by disodium ethylenediamine tetraacetate and p-chloromercuribenzoate, and the presence of a divalent cation, i.e. Co2+, is essential for its activity.  相似文献   
113.
The exchange reaction of the peptide NH protons of a microbial protease inhibitor (Streptomyces subtilisin inhibitor) with deuterium atoms in 2H2O (p2H 6.8) has been studied by proton magnetic resonance in the temperature range 56-71 degrees C. Both slowly and rapidly exchanging processes have been observed. The number of slowly exchanging protons is estimated to be 25 +/- 2 per subunit of the protein molecule. The decay of the slowly exchanging proton signals follows a single time-exponential function at each temperature. The observed first-order rate constants have been analyzed to give the denaturated fraction of the protein as a function of temperature with a consequent enthalpy (56 kcal/mol) and an entropy (137 cal/degree per mol) of denaturation. The results indicate the high conformational stability of this protein against heat denaturation.  相似文献   
114.
115.
116.
The MAP kinase pathway is one of the most important pathways involved in cell proliferation and differentiation, and its components are promising targets for antitumor drugs. Design and synthesis of a novel MEK inhibitor, based on the 3D-structural information of the target enzyme, and then multidimensional optimization including metabolic stability, physicochemical properties and safety profiles were effectively performed and led to the identification of a clinical candidate for an orally available potent MEK inhibitor, CH4987655, possessing a unique 3-oxo-oxazinane ring structure at the 5-position of the benzamide core structure. CH4987655 exhibits slow dissociation from the MEK enzyme, remarkable in vivo antitumor efficacy both in mono- and combination therapy, desirable metabolic stability, and insignificant MEK inhibition in mouse brain, implying few CNS-related side effects in human. An excellent PK profile and clear target inhibition in PBMC were demonstrated in a healthy volunteer clinical study.  相似文献   
117.

Background

Apoptosis is thought to play a role in the pathogenesis of severe dengue and the release of cell-free DNA into the circulatory system in several medical conditions. Therefore, we investigated circulating DNA as a potential biomarker for severe dengue.

Methods and Findings

A direct fluorometric degradation assay using PicoGreen was performed to quantify cell-free DNA from patient plasma. Circulating DNA levels were significantly higher in patients with dengue virus infection than with other febrile illnesses and healthy controls. Remarkably, the increase of DNA levels correlated with the severity of dengue. Additionally, multivariate logistic regression analysis showed that circulating DNA levels independently correlated with dengue shock syndrome.

Conclusions

Circulating DNA levels were increased in dengue patients and correlated with dengue severity. Additional studies are required to show the benefits of this biomarker in early dengue diagnosis and for the prognosis of shock complication.  相似文献   
118.

Background

Green tea has become renowned for its health benefits. In this study, we investigated the anti-stress effect of two kinds of green tea against a mental stress task load.

Methods

Warm water, ordinary green tea (Sagara), and shaded white tea, which contains more amino acid components than Sagara, were used as test samples in a randomized cross-over design study. Eighteen students (nine male and nine female) participated in three experimental trials on different days at intervals of seven days. Saliva was collected before beverage intake and after performing the mental stress load tasks. Concentration of chromogranin A (CgA) in the saliva was used as an index of autonomic nervous system activity.

Results

CgA level increased after the mental tasks, but intake of green tea inhibited this increase; the anti-stress effect was even greater after consumption of shaded white tea. Intake of shaded white tea also lowered Total Mood Disturbance (TMD) score on the Profile of Mood States (POMS); subjects in this condition tended to perform more calculations in the arithmetic task than those in the warm water treatment condition.

Conclusions

Salivary CgA concentration levels increased after mental stress load tasks, but ingestion of green tea inhibited this increase. This anti-stress effect was larger after the consumption of shaded white tea than after Sagara. Shaded white tea intake also lowered TMD score (POMS) and tended to improve performance on an arithmetic task compared to warm water, suggesting that shaded white tea might also improve mood during and after mental stress load.  相似文献   
119.
Synthesis of trehalose from maltose by a coupled enzyme system with trehalose Phosphorylase and maltose Phosphorylase has been studied. Trehalose Phosphorylase was partially purified from Euglena gracilis and maltose Phosphorylase was obtained from Lactobacillus brevis. The optimum pH of the reaction was 6.5~7.0 and the reaction rate was faster in the rection mixture containing a low concentration of phosphate. The final ratio of conversion (the ratio of trehalose to maltose) in the pH range between 6.0 and 8.0 was about 60%.

Immobilized maltose and trehalose Phosphorylase in κ-carageenan could be used without any appreciable loss of activity for batch reactions at least 10 times.  相似文献   
120.
A tissue-type transglutaminase (TGase) was purified from liver tissue of the red sea bream, Pagrus major, by ion-exchange chromatography and heparin-Sepharose affinity chromatography. Its activity was assessed using a fluorometric assay to measure the incorporation of monodansylcadaverine into N,N′-dimethyl casein. The molecular mass of purified TGase was estimated to be 78kDa by SDS–polyacrylamide gel electrophoresis. The enzyme required Ca2+ to express its activity, although 10 mM Sr2+ also activated the enzyme fully. TGase activity was maximal at pH 9.0–9.5, and the enzyme was strongly inhibited by sulfhydryl reagents. The purified enzyme catalyzed the cross-linking of myosin heavy chain obtained from Alaska pollack, resulting in gelation of an actomyosin solution. The partial amino acid sequence of this fish TGase showed divisionally significant similarity to TGase from guinea pig liver.  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