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   62篇
  免费   1篇
  2016年   3篇
  2015年   6篇
  2014年   1篇
  2013年   6篇
  2012年   2篇
  2011年   2篇
  2010年   2篇
  2009年   1篇
  2008年   4篇
  2007年   1篇
  2005年   1篇
  2004年   4篇
  2003年   1篇
  2002年   5篇
  2001年   2篇
  2000年   1篇
  1999年   1篇
  1996年   1篇
  1995年   1篇
  1988年   1篇
  1987年   1篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1979年   2篇
  1976年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1969年   1篇
  1967年   1篇
排序方式: 共有63条查询结果,搜索用时 15 毫秒
51.
It is well known that the Wilms' tumor gene WT1 plays an important role in cell proliferation and differentiation, and in organ development. In this study, to examine the role of the WT1 gene in lineage determination, fetal liver cells from LacZ-transgenic mice, in which WT1 expression was marked by the expression of the LacZ gene driven by WT1 promoter, were FACS-sorted according to LacZ expression of high (LacZ(++)) or undetectable (LacZ(-)) levels, which paralleled endogenous WT1 expression levels. LacZ(++) fetal liver cells were enriched by hepatocyte and endothelial progenitor cells. These results indicated that WT1 expression is a common marker of both hepatocyte and endothelial progenitors. These results also implied a role of the WT1 gene in lineage determination.  相似文献   
52.
The Wilms' tumor gene WT1 is overexpressed in various types of solid tumors, including lung and breast cancer and WT1 protein is a tumor antigen for these malignancies. In phase I clinical trials of WT1 peptide-based cancer immunotherapy, two patients with advanced lung cancer were intradermally injected with 0.3 mg of an HLA-A*2402-restricted, 9-mer WT1 peptide emulsified with Montanide ISA51 adjuvant. Consecutive WT1 vaccination at 2-week intervals resulted in a reduction in tumor markers such as chorio-embryonic antigen (CEA) and sialyl Lewis (x) (SLX) and by a transient decrease in tumor size. No adverse effects except for local erythema at the injection sites of WT1 vaccine were observed. These results provided us with the first clinical evidence demonstrating that WT1 peptide-based immunotherapy should be a promising treatment for patients with lung cancer.  相似文献   
53.
Although the status of Crinoidea (sea lilies and featherstars) as sister group to all other living echinoderms is well-established, relationships among crinoids, particularly extant forms, are debated. All living species are currently placed in Articulata, which is generally accepted as the only crinoid group to survive the Permian–Triassic extinction event. Recent classifications have recognized five major extant taxa: Isocrinida, Hyocrinida, Bourgueticrinina, Comatulidina and Cyrtocrinida, plus several smaller groups with uncertain taxonomic status, e.g., Guillecrinus, Proisocrinus and Caledonicrinus. Here we infer the phylogeny of extant Crinoidea using three mitochondrial genes and two nuclear genes from 59 crinoid terminals that span the majority of extant crinoid diversity. Although there is poor support for some of the more basal nodes, and some tree topologies varied with the data used and mode of analysis, we obtain several robust results. Cyrtocrinida, Hyocrinida, Isocrinida are all recovered as clades, but two stalked crinoid groups, Bourgueticrinina and Guillecrinina, nest among the featherstars, lending support to an argument that they are paedomorphic forms. Hence, they are reduced to families within Comatulida. Proisocrinus is clearly shown to be part of Isocrinida, and Caledonicrinus may not be a bourgueticrinid. Among comatulids, tree topologies show little congruence with current taxonomy, indicating that much systematic revision is required. Relaxed molecular clock analyses with eight fossil calibration points recover Articulata with a median date to the most recent common ancestor at 231–252 mya in the Middle to Upper Triassic. These analyses tend to support the hypothesis that the group is a radiation from a small clade that passed through the Permian–Triassic extinction event rather than several lineages that survived. Our tree topologies show various scenarios for the evolution of stalks and cirri in Articulata, so it is clear that further data and taxon sampling are needed to recover a more robust phylogeny of the group.  相似文献   
54.
An endopeptidase was purified and characterized from green leaves of cucumber (Cucumis sativus L. suyo). The purified enzyme, a basic amino acid-specific endopeptidase with a pI of 5.0, was a monomeric protein of 80 kDa whose pH optimum was 9.5. Inhibitor analysis suggested that it was a serine endopeptidase and contained sulfhydryl groups essential for catalytic activity. Analysis of internal amino acid sequences of the endopeptidase showed no significant similarity to other proteins. Its activity was inhibited by L-Arg and guanidino compounds having high hydrophobicity, as well as divalent cations such as Mg2+ and Ca2+. The K(i) values of L-Arg and Mg2+, which are also likely in vivo inhibitors, were 3.5 and 10 mM, respectively. Inhibition by L-Arg and Mg2+ was additive, and more than 70% of the activity was reversibly inhibited under their physiologically significant concentrations. These results suggest that the enzyme is possibly regulated by L-Arg and/or guanidino compounds, and by divalent cations in vivo.  相似文献   
55.
56.
Nitrate reductase (NR) from the leaves of Hordeum distichumwas very susceptible to inactivation by barley leaf thiol proteinase,trypsin, and papain. A cytochrome c reductase species with amolecular weight of about 40,000 was derived from the NR complexby the proteolytic actions. The barley proteinase seemed toattack the Mo+-containing component of NR, just like trypsinand papain. It showed a preference for the alanine and tryptophanesters among the carbobenzoxyamino acid-nitrophenylesters tested. In vivo NR activity in the presence of leupeptin was fairlyhigher than that in its absence. Leupeptin also protected NRfrom its cleavage to small cytochrome c reductase species, suggestingthat the barley proteinase may play a role in the in vivo changein NR activity. (Received May 21, 1984; Accepted September 10, 1984)  相似文献   
57.
Chopped maize stover, ammoniated at ambient and elevated temperatures or steam treated, was evaluated with four Cheviot crossbred wethers fitted with permanent rumen fistulae in a 4 × 4 Latin square design. Treatments were: (i) control, 60% H2O, ensiled for at least 40 days; (ii) 3% NH3, 60% H2O for 30 days at 21°C; (iii) 3% NH3, 60% H2O for 12 h at 90°C; (iv) steamed at 16.2 kg/cm2 and 213°C for 4 min. The sheep received two meals per day at a restricted level of 90% of lowest ad libitum intake. The markers 51Cr-EDTA (100 μ ci) and 103Ru-phenanthroline complex (10 μ ci) were used for the liquid and particulate phases, respectively. Samples for rumen metabolites were collected in each period at 0, 0.5, 1.0, 2.0, 3.0, 4.0, 6.0 and 8.0 h after the morning meal. On the following day, a mixture of the markers in 200 ml of demineralized water was infused into the rumen in a single dose and rumen fluid was sampled at specific times for 4 days.Rumen fluid pH tended to be lower with ammoniated stovers. High NH3-N levels were maintained with ammoniated stovers, indicating gradual release of nitrogen. Total VFA tended to increase more with the thermoammoniated stover. Molar proportions of propionate increased (P < 0.05) and butyrate decreased (P < 0.05) with ammoniation. In contrast, steam treatment increased (P < 0.05) molar proportions of acetate and butyrate. The largest decrease (P < 0.05) for C2 : C3 acids occurred with thermoammoniated stover. Treatments with NH3 or steam increased (P < 0.05) dilution rate. Mean retention time of particulate matter was decreased (P < 0.05) by treatment, being shortest with steamed material.  相似文献   
58.
Alloxan diabetic rats with fasting blood glucose levels above 300 mg/100 ml were treated with oral administration of water-in-oil-in-water (W/O/W) insulin emulsions at a dose of 50 U/100 g body weight, three times daily for 10 to 14 days. The course of diabetes was followed by determinations of glucose levels in blood and urine. During treatment with oral W/O/W insulin emulsions, daily excretion of urinary glucose decreased by about 30 to 40% (2 to 3 g/day) in all of the five rats studied, and returned to the pre-treatment levels after the treatment being discontinued. During treatment, a significant reduction in fasting blood glucose levels was observed in 4 out of 5 rats, giving the decrease by 18 to 44%. Quantitative estimates suggested that the effectiveness of 50 U/100 g of oral W/O/W insulin emulsions was comparable to that after intramuscular regular insulin at a dose of 0.5 U/100 g. Although oral W/O/W insulin emulsions are still of low efficiency, these results would indicate that diabetes can be controlled by effective oral insulin preparations.  相似文献   
59.
60.
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