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   503篇
  免费   46篇
  549篇
  2023年   4篇
  2022年   12篇
  2021年   10篇
  2020年   11篇
  2019年   12篇
  2018年   20篇
  2017年   19篇
  2016年   20篇
  2015年   35篇
  2014年   35篇
  2013年   42篇
  2012年   49篇
  2011年   35篇
  2010年   22篇
  2009年   20篇
  2008年   20篇
  2007年   28篇
  2006年   23篇
  2005年   24篇
  2004年   27篇
  2003年   23篇
  2002年   17篇
  2001年   7篇
  2000年   3篇
  1999年   3篇
  1998年   7篇
  1997年   4篇
  1996年   1篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1978年   1篇
  1977年   1篇
  1874年   1篇
排序方式: 共有549条查询结果,搜索用时 0 毫秒
131.
132.
Liquid chromatography-mass spectrometry was applied to determine the action pattern of different chondroitin lyases. Two commercial enzymes, chondroitinase ABC (Proteus vulgaris) and chondroitinase ACII (Arthrobacter aurescens), having action patterns previously determined by viscosimetry and gel electrophoresis were first examined. Next, the action patterns of recombinant lyases, chondroitinase ABC from Bacteroides thetaiotaomicron (expressed in Escherichia coli) and chondroitinase AC from Flavobacterium heparinum (expressed in its original host), were examined. Chondroitin sulfate A (CS-A, also known as chondroitin-4-sulfate) was used as the substrate for these four lyases. Aliquots taken at various time points were analyzed. The products of chondroitinase ABC (P. vulgaris) and chondroitinase AC (F. heparinum) contained unsaturated oligosaccharides of sizes ranging from disaccharide to decasaccharide, demonstrating that both are endolytic enzymes. The products afforded by chondroitinase ABC (B. thetaiotaomicron) and chondroitinase ACII (A. aurescens) contained primarily unsaturated disaccharide. These two exolytic enzymes showed different minor products, suggesting some subtle specificity differences between the actions of these two exolytic lyases on chondroitin sulfate A.  相似文献   
133.
134.
135.
136.
Objective: We examined the relationship between income and education level with BMI and waist circumference to provide further understanding of the relationship between socioeconomic status and obesity and to identify the presence of sex differences. Research Methods and Procedures: A total of 7962 people ≥20 years of age (3597 men; 4365 women) who participated in the 1998 Korean National Health and Nutrition Examination Survey provided data including height, weight, waist circumference, education, and income level. We examined adjusted BMI and waist circumference according to level of income and education and the association between income and education with obesity and abdominal obesity by multiple logistic regression analysis. Results: In men, significant dose‐response relationships were noted between income and obesity (trend, p < 0.05) and abdominal obesity (trend, p < 0.05). Compared with the lowest income group, the adjusted odds ratios (ORs) (95% confidence interval) of the highest income group for obesity and abdominal obesity were 1.65 (1.18 to 2.32) and 1.37 (0.94 to 1.98), respectively. However, income was not associated with obesity or abdominal obesity in the fully adjusted models in women. With regard to education, women showed significantly decreased ORs, with inverse trends for obesity and abdominal obesity across all education levels. Compared with the lowest education group, the adjusted ORs (95% confidence interval) for obesity and abdominal obesity were 0.66 (0.57 to 0.76) and 0.40 (0.35 to 0.45), respectively, among women with 7 to 12 years of schooling and 0.27 (0.21 to 0.34) and 0.15 (0.12 to 0.18), respectively, among women with 13 or more years of schooling. Discussion: Socioeconomic difference has a considerable impact on the prevalence of obesity among the Korean population, and the patterns differ substantially across sex.  相似文献   
137.
Human mesenchymal stem cells (hMSC), that have been reported to be present in bone marrow, adipose tissues, dermis, muscles, and peripheral blood, have the potential to differentiate along different lineages including those forming bone, cartilage, fat, muscle, and neuron. Therefore, hMSC are attractive candidates for cell and gene therapy. The optimal conditions for hMSC expansion require medium supplemented with fetal bovine serum (FBS). Some forms of cell therapy will involve multiple doses, raising a concern over immunological reactions caused by medium-derived FBS proteins. In this study, we cultured human adipose stromal cells (hADSC) and bone marrow stroma cells (HBMSC) in human serum (HS) during their isolation and expansion, and demonstrated that they maintain their proliferative capacity and ability for multilineage differentiation and promote engraftment of peripheral blood-derived CD34(+) cells mobilized from bone marrow in NOD/SCID mice. Our results indicate that hADSC and hBMSC cultured in HS can be used for clinical trials of cell and gene therapies, including promotion of engraftment after allogeneic HSC transplantation.  相似文献   
138.
Microglia are cells from non-neuronal lineages that reside in the central nervous system. In zebrafish, early macrophages migrate from the yolk sac to the brain and retina at 26-30 hour post fertilization (hpf) and transform into microglia at 55-60 hpf. The migration of macrophages into the central nervous system requires signaling by macrophage colony stimulating factor-1 receptor (csf-1r), which is encoded by the gene fms. In this study, we show that the targeted knockdown of csf-1r with morpholino oligonucleotides delays migration of macrophages from the yolk sac to the retina, and this delay in macrophage migration results in microphthalmia, delay in cell cycle withdrawal among retinal progenitors and the absence of neuronal differentiation. When embryos were allowed to survive beyond the time when morpholino-dependent translation inhibition is lost, microglia re-occupy the retina and neuronal differentiation partially recovers. Our data demonstrate that microglia are required for normal retinal growth and neurogenesis. This study provides new insight into the neurogenic role of microglia during retinal development in zebrafish.  相似文献   
139.
140.
Monooctanoyl phloroglucinol with anti-microbial activities was synthesized from phloroglucinol (50 mM) and vinyl octanoate (150 mM) with agitation at 40 °C using 10 mg lipase AK (Pseudomonas fluorescens) in acetonitrile (1 ml, aw=0.07). The yield was approximately 70% as conversion rate of phloroglucinol over 3 days. The product, at 205 g ml–1, was bacteriocidal against Escherichia coli and Staphylococcus epidermidis.  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