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   806篇
  免费   62篇
  国内免费   19篇
  2023年   2篇
  2022年   9篇
  2021年   11篇
  2020年   20篇
  2019年   25篇
  2018年   33篇
  2017年   20篇
  2016年   21篇
  2015年   18篇
  2014年   28篇
  2013年   63篇
  2012年   26篇
  2011年   35篇
  2010年   24篇
  2009年   29篇
  2008年   51篇
  2007年   41篇
  2006年   36篇
  2005年   28篇
  2004年   31篇
  2003年   33篇
  2002年   27篇
  2001年   23篇
  2000年   20篇
  1999年   16篇
  1998年   22篇
  1997年   30篇
  1996年   19篇
  1995年   16篇
  1994年   15篇
  1993年   13篇
  1992年   13篇
  1991年   8篇
  1990年   9篇
  1989年   5篇
  1988年   6篇
  1987年   3篇
  1986年   6篇
  1985年   11篇
  1984年   12篇
  1983年   2篇
  1982年   4篇
  1981年   3篇
  1980年   5篇
  1979年   5篇
  1978年   4篇
  1977年   2篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有887条查询结果,搜索用时 15 毫秒
41.
The autoproteolytic processing of mature aspartic proteinase from sunflower seeds was investigated. The mature aspartic proteinase (48 kDa) was processed at N65s-D66s in the plant-specific region of the enzyme to form 34-kDa and 14-kDa subunits. The next step was the hydrolysis of the A25s-Q26s and N97s-E98s bonds to form a 39-kDa enzyme that consisted of 29-kDa and 9-kDa disulfide-bonded subunits. Finally, bonds including V1s-M2s, M2s-S3s, C100s-D101s, and D101s-R102s were cleaved to form non-covalently bound subunits (29 kDa and 9 kDa) by eliminating the disulfide bonds in the plant-specific region of the protein.  相似文献   
42.
The effects of adrenalectomy on growth, some enzyme activities in the liver and kidney, and urinary excretion of urea, creatinine and creatine were investigated in rats fed the 10% casein diets containing 7% glycine with or without l-arginine and l-methionine (10C, 10C7G and 10C7ArgMet).

Body weight gains of the intact 10C and 10C7GArgMet groups were almost same as the corresponding adrenalectomized groups. The body weight of the adrenalectomized 10C7G group was extremely decreased though that of the intact 10C7G group was maintained almost constant; but the decrease was recovered by the administration of hydrocortisone. The activities of liver arginase and carbamylphosphate synthetase were not affected by those diets. Liver serine dehydratase and ornithine δ-aminotransferase activities were increased in the intact 10C7G and 10C7GArgMet groups, but these increases were depressed by adrenalectomy. Glutamate-pyruvate transminase activities in the liver of intact 10C7G and 10C7GArgMet groups were also enhanced, but were extremely decreased in the corresponding adrenalectomized groups. Kidney transamidinase activity was not affected by adrenalectomy. The amount of urinary excreted urea was almost unchanged by adrenalectomy, but was increased by hydrocortisone administration. The amounts of excreted creatine of the adrenalectomized groups were generally larger than the corresponding intact groups, but slightly decreased by the administration of hydrocortisone. The amount of excreted creatinine was not generally affected by adrenalectomy.  相似文献   
43.
Objective The aim of this study was to clarify the clinical role of TMPRSS4 expression in cervical squamous cell carcinoma (CSCC) and to investigate the role of TMPRSS4 in predicting outcomes of patients with CSCC. Methods The retrospective study enrolled 87 patients diagnosed with CSCC between 2004 and 2006. TMPRSS4 expression in CSCC was assessed by immunohistochemistry, and data on clinical variables were collected by retrospective chart review. The impact of TMPRSS4 expression on 5-year disease-free survival (DFS) and 5-year overall survival (OS) was assessed by Kaplan–Meier analysis and Cox proportional hazards modeling. Results The high expression of TMPRSS4 was 63.2% in 87 patients with CSCC, and 17.5% in 40 patients with benign cervical disease (P < 0.001). High TMPRSS4 expression was significantly associated with tumor grade (P = 0.005), lymph node metastasis (P = 0.004), and deep cervical stromal invasion (P = 0.025). Patients with high expression of TMPRSS4 had shorter OS and DFS than those with low expression (P = 0.0205 and P = 0.0318, respectively). In multivariate Cox regression analysis, high expression of TMPRSS4 was a potential prognostic indicator for OS (P = 0.041) and DFS (P = 0.015). Conclusion Our findings suggest that TMPRSS4 might play an important role in the progression of CSCC. TMPRSS4 could be a potential prognostic marker of CSCC.  相似文献   
44.
Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1–3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds.Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.  相似文献   
45.
Plant secretome comprises dozens of secreted proteins. However, little is known about the composition of the whole secreted peptide pools and the proteases responsible for the generation of the peptide pools. The majority of studies focus on target detection and characterization of specific plant peptide hormones. In this study, we performed a comprehensive analysis of the whole extracellular peptidome, using moss Physcomitrella patens as a model. Hundreds of modified and unmodified endogenous peptides that originated from functional and nonfunctional protein precursors were identified. The plant proteases responsible for shaping the pool of endogenous peptides were predicted. Salicylic acid (SA) influenced peptide production in the secretome. The proteasome activity was altered upon SA treatment, thereby influencing the composition of the peptide pools. These results shed more light on the role of proteases and posttranslational modification in the “active management” of the extracellular peptide pool in response to stress conditions. It also identifies a list of potential peptide hormones in the moss secretome for further analysis.  相似文献   
46.
47.
48.
A method to the study of -casein proteolysis by aspartic proteinases is developed. The 3% trichloroacetic acid-soluble peptides of -casein digested with cardosin A were separated by capillary zone electrophoresis under different experimental conditions in an uncoated fused silica capillary. The best separation was at pH 3.01, 30 kV and 30 °C.  相似文献   
49.
The peptides formed upon action of purified cardoon rennet on the Ala189-Phe190-Leu191-Leu192-Tyr193 -casein fragment were separated by capillary electrophoresis in an uncoated fused silica capillary. There was a linear correlation between electrophoretic mobility and Z/M2/3 (Z, net charge; M, molecular mass) under all experimental conditions tested; under the optimal condicitions, 25 kV and 40 °C, the correlation coefficient was 0.994. The reported method is fast (migration times less than 7 min) and may be used to study the action of aspartic proteinases on the C-terminal domain of -casein and thus to help elucidate their effect on cheese quality.  相似文献   
50.
Trypsin, chymotrypsin, cathepsins B and D, aminopeptidase and carboxypeptidases A and B were detected in body extracts of the storage mite Acarus farris (Oudemans) (Astigmata: Acaridae). Faeces-enriched medium exhibited higher (10-50-fold) specific protease activity rates than those measured with mite body extracts for trypsin, chymotrypsin and carboxypeptidases A and B, suggesting that they are involved in mite digestion. However, the activity of cathepsin B was only three-fold higher in faecal than in body extracts, indicating that its presence in the lumen of the digestive tract is low compared to that of serine proteases. The activity of aminopeptidases was higher in mite bodies, indicating that they might be membrane bound. Cathepsin D activity was only detected in body extracts, indicating that this enzyme is not a digestive protease in this species. Zymograms resolved three major bands of gelatinolytic activity, but at least one protease form was only present in body extracts. Protease inhibitors of different specificity were tested in vivo to establish their potential as control agents. The development of A. farris was significantly retarded when the immature stages were fed on artificial diet containing inhibitors of serine and cysteine proteases and aminopeptidases, whereas no such effect was found with inhibitors of aspartyl proteases and carboxypeptidases. Interestingly, the most significant effects on A. farris occurred when a combination of inhibitors targeting different enzyme classes was supplied mixed in the diet, suggesting a synergistic toxicity. Several plant lectins were also tested, but only wheat germ agglutinin and concanavalin-A affected development.  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