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   178篇
  免费   15篇
  国内免费   2篇
  2021年   6篇
  2020年   1篇
  2019年   2篇
  2018年   5篇
  2017年   6篇
  2016年   1篇
  2015年   6篇
  2014年   7篇
  2013年   11篇
  2012年   12篇
  2011年   9篇
  2010年   15篇
  2009年   11篇
  2008年   8篇
  2007年   4篇
  2006年   8篇
  2005年   6篇
  2004年   3篇
  2003年   2篇
  2002年   4篇
  2001年   3篇
  2000年   1篇
  1999年   2篇
  1998年   7篇
  1997年   7篇
  1996年   4篇
  1995年   1篇
  1994年   4篇
  1993年   4篇
  1992年   3篇
  1991年   5篇
  1990年   4篇
  1988年   4篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1979年   1篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1969年   1篇
  1950年   1篇
排序方式: 共有195条查询结果,搜索用时 203 毫秒
141.
Biofilms are a natural form of cell immobilization that result from microbial attachment to solid supports. Biofilm reactors with polypropylene composite-supports containing up to 25% (w/w) of various agricultural materials (corn hulls, cellulose, oat hulls, soybean hulls or starch) and nutrients (soybean flour or zein) were used for ethanol production. Pure cultures ofZymomonas mobilis, ATCC 31821 orSaccharomyces cerevisiae ATCC 24859 and mixed cultures with either of these ethanol-producing microorganisms and the biofilm-formingStreptomyces viridosporus T7A ATCC 39115 were evaluated. An ethanol productivity of 374g L–1 h–1 (44% yield) was obtained on polypropylene composite-supports of soybean hull-zein-polypropylene by usingZ. mobilis, whereas mixed-culture fermentations withS. viridosporus resulted in ethanol productivity of 147.5 g L–1 h–1 when polypropylene composite-supports of corn starch-soybean flour were used. WithS. cerevisiae, maximum productivity of 40 g L–1 h–1 (47% yield) was obtained on polypropylene composite-supports of soybean hull-soybean flour, whereas mixed-culture fermentation withS. viridosporus resulted in ethanol productivity of 190g L–1 h–1 (35% yield) when polypropylene composite-supports of oat hull-polypropylene were used. The maximum productivities obtained without supports (suspension culture) were 124 g L–1 h–1 and 5 g L–1 h–1 withZ. mobilis andS. cerevisiae, respectively. Therefore, forZ. mobilis andS. cerevisiae, ethanol productivities in biofilm fermentations were three- and eight-fold higher than suspension culture fermentations, respectively. Biofilm formation on the chips was detected by weight change and Gram staining of the support material at the end of the fermentation. The ethanol production rate and concentrations were consistently greater in biofilm reactors than in suspension cultures.This is Journal Paper No. J-16356 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 3253  相似文献   
142.
Dyar JJ  Shade J 《Plant physiology》1974,53(4):666-668
Benzimidazole has been studied previously by certain investigators as a growth regulator. This compound was found to promote various phases of growth in the gametophyte of the fern Thelypteris felix-mas. Concentrations of benzimidazole in the order of 0.01 mm, 0.02 mm, and 0.1 mm stimulated cell division, an increase in body size, and also rhizoid lengths of the gametophyte. A concentration of 1.0 mm was always inhibitory.  相似文献   
143.
An artificial maize seed bioassay was developed to evaluate potential resistance factors against the rice weevil, Sitophilus oryzae. Weevils reared in artificial seeds compared to those reared in whole maize seeds: (i) developed faster, (ii) had similar within-seed developmental mortalities, (iii) were lighter in weight upon emergence and (iv) oviposited the same number of eggs. Using this bioassay we found that E-64, a cysteine protease inhibitor, decreased the number of emerged adults per seed and delayed within-seed developmental time, suggesting that the rice weevil utilizes a cysteine protease to digest its dietary protein. Weevils fed inhibitors of trypsin and chymotrypsin, Bowman-Birk and Kunitz inhibitors respectively, developed normally. Para-amino-l-phenylalanine (PAPA), a non-protein amino acid implicated as an insect resistance factor in Vigna vexillata, was lethal at dietary levels of 0.2% (w/w) and higher. An extract from Amaranthus caudatus seeds delayed the developmental time of the rice weevil at dietary levels of 0.2% (w/w) and increased mortality at dietary levels of 1.0% (w/w). Several proteins tested, including Griffonia simplicifolia agglutinin II, phytohemagglutinin extract containing common bean -amylase inhibitor, pokeweed agglutinin, Bacillus thuringiensis CRY1A/CRY1B endotoxin, and an -amylase inhibitor from wheat, had no effect on the rice weevil. The artificial maize seed bioassay was adapted by pelleting the seed for use with an ultrasonic insect feeding monitor to determine the finding activity of rice weevils as they developed from egg hatch to pupation.  相似文献   
144.
The cowpea bruchid, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae: Bruchini), is a worldwide pest of stored cowpea grain [ Vigna unguiculata (L.) Walp. (Leguminosae)], causing tens of millions of dollars' worth of damage annually. One method of managing this pest involves planting cultivars whose seeds are resistant to bruchids. Despite extensive research, we still do not know the mechanism by which TVu 2027, the original resistant cowpea line, resists C. maculatus . Using micro-CAT (computerized axial tomography) scan imaging, we visualized the feeding patterns of bruchids living and growing within cowpea seeds. We present evidence that an interior zone in TVu 2027 seeds is responsible for the high mortality and developmental delays experienced by avirulent larval bruchids. We observed that both virulent as well as avirulent bruchid strains have different feeding patterns in TVu 2027 seeds compared to susceptible seeds. It appears that the resistance factor is most concentrated in a zone in each cotyledon adjacent to the air space separating the two seed halves.  相似文献   
145.
The aim of the study was to validate a nonradioactive method for relative blood flow measurements in severely injured lungs that avoids labor-intensive tissue processing. The use of fluorescent-labeled microspheres was compared with the standard radiolabeled-microsphere method. In seven sheep, lung injury was established by using oleic acid. Five pairs of radio- and fluorescent-labeled microspheres were injected before and after established lung injury. Across all animals, 175 pieces were selected randomly. The radioactivity of each piece was determined by using a scintillation counter. The fluorescent dye was extracted from each piece with a solvent without digestion or filtering. The fluorescence was determined with an automated fluorescent spectrophotometer. Perfusion was calculated for each piece from both the radioactivity and fluorescence and volume normalized. Correlations between flow determined by the two methods were in the range from 0.987 +/- 0.007 (SD) to 0.991 +/- 0.002 (SD) after 9 days of soaking. Thus the fluorescent microsphere technique is a valuable tool for investigating regional perfusion in severely injured lungs and can replace radioactivity.  相似文献   
146.
Abstract We used a network of 20 carbon dioxide- and octenol-supplemented light traps to sample adult mosquitoes throughout Russell Island in southern Moreton Bay, south-east Queensland. Between February and April 2001, an estimated 1365 564 adult female mosquitoes were collected. In contrast to an average catch of 9754 female mosquitoes per trap night on Russell Island, reference traps set on Macleay Island and on the mainland returned average catches of 3172 and 222, respectively. On Russell Island, Ochlerotatus vigilax (Skuse), Coquillettidia linealis (Skuse), Culex annulirostris Skuse and Verrallina funerea (Theobald), known or suspected vectors of Ross River (RR) and/or Barmah Forest (BF) viruses, comprised 89.6% of the 25 taxa collected. When the spatial distributions of the above species were mapped and analysed using local spatial statistics, all were found to be present in highest numbers towards the southern end of the island during most of the 7 weeks. This indicated the presence of more suitable adult harbourage sites and/or suboptimal larval control efficacy. As immature stages and the breeding habitat of Cq. linealis are as yet undescribed, this species in particular presents a considerable impediment to proposed development scenarios. The method presented here of mapping the numbers of mosquitoes throughout a local government area allows specific areas that have high vector numbers to be defined.  相似文献   
147.
Determination of predictive biomarkers by immunohistochemistry (IHC) relies on antibodies with high selectivity. RNA in situ hybridization (RNA ISH) may be used to confirm IHC and may potentially replace it if suitable antibodies are not available or are insufficiently selective to discriminate closely related protein isoforms. We validated RNA ISH as specificity control for IHC and as a potential alternative method for selecting patients for treatment with MET inhibitors. MET, the HGF receptor, is encoded by the MET proto-oncogene that may be activated by mutation or amplification. MET expression and activity were tested in a panel of control cell lines. MET could be detected in formalin fixed paraffin, embedded (FFPE) samples by IHC and RNA ISH, and this was confirmed by sandwich immunoassays of fresh frozen samples. Gastric cancer cell lines with high MET expression and phosphorylation of tyrosine-1349 respond to the MET inhibitor, BAY-853474. High expression and phosphorylation of MET is a predictive biomarker for response to MET inhibitors. We then analyzed MET expression and activity in a matched set of FFPE vs. fresh frozen tumor samples consisting of 20 cases of gastric cancer. Two of 20 clinical samples investigated exhibited high MET expression with RNA ISH and IHC. Both cases were shown by sandwich immunoassays to exhibits strong functional activity. Expression levels and functional activity in these two cases were in a range that predicted response to treatment. Our findings indicate that owing to its high selectivity, RNA ISH can be used to confirm findings obtained by IHC and potentially may replace IHC for certain targets if no suitable antibodies are available. RNA ISH is a valid platform for testing predictive biomarkers for patient selection.  相似文献   
148.
149.
Galectins, beta-galactoside-binding lectins, are extensively distributed in the animal kingdom and share some basic molecular properties. Galectin-3, a member of this family, is generally associated with differentiation, morphogenesis, and metastasis. In this study, galectin-3 was isolated from ovine placental cotyledons round the middle of the gestation period by lactose extraction followed by affinity chromatography on lactosyl-agarose, and separated from galectin-1 by size exclusion chromatography on a Superose 12 column. Under native conditions this lectin behaved as a monomer with an apparent molecular weight of approximately 29,000 and an isoelectric point of 9.0. The partial amino acid sequence of the peptides obtained by tryptic digestion of this protein followed by HPLC separation showed striking homology with other members of the galectin-3 subfamily. Furthermore, ovine placental galectin-3 exhibited specific mitogenic activity toward rat spleen mononuclear cells. Besides, this protein strongly reacted with a rabbit antiserum raised against a chicken galectin. Results obtained by Western blot analysis showed that its expression was greatly decreased in term placenta with respect to the middle of the gestation period, suggesting a regulated expression throughout development.   相似文献   
150.
不孕不育患者解脲脲原体菌株血清型别的检测   总被引:2,自引:0,他引:2  
本文以解脲脲原体标准菌株1-14型免疫家获得UU1-14型抗血清。用IDT法对48株自不孕不育患者分离的地方株作分型试验。结果在1.2.4.5.6.7.8和12血八个清型中出现强阳性反应,其中4型最多。另有4株混合型。对四种血清型无反应。  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