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   238篇
  免费   8篇
  2023年   1篇
  2022年   1篇
  2019年   2篇
  2018年   1篇
  2017年   4篇
  2016年   3篇
  2015年   8篇
  2014年   6篇
  2013年   10篇
  2012年   21篇
  2011年   24篇
  2010年   12篇
  2009年   8篇
  2008年   15篇
  2007年   15篇
  2006年   13篇
  2005年   10篇
  2004年   20篇
  2003年   12篇
  2002年   20篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   1篇
  1997年   3篇
  1996年   5篇
  1995年   5篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1990年   3篇
  1989年   1篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1982年   3篇
  1980年   1篇
  1978年   1篇
排序方式: 共有246条查询结果,搜索用时 31 毫秒
51.
Hebeloma vinosophyllum (Basidiomycota, Agaricales), a member of the ammonia fungi, occurred on the ground in the close vicinity of the decomposed carcass of a jungle crow,Corvus macrorhynchos, in a forest dominated byQuercus spp. in Urawa, Saitama Pref., central Japan. This is the first report of an ammonia fungus occurring at the site of a decomposed wild bird carcass.  相似文献   
52.
As a step to develop a cryopreservation method for zebrafish oocytes, we investigated the cryobiological properties of immature oocytes at stage III by examining their ability to mature and to develop into hatching embryos after fertilization. When oocytes were chilled at −5 °C for 30 min, the maturation rate decreased, but the rates of fertilization and hatching were not significantly different from those of controls. When oocytes were exposed to hypotonic solutions for 60 min at 25 °C, the rates of maturation, fertilization, and hatching decreased in a solution with 0.16 Osm/kg or below. When oocytes were exposed to hypertonic solutions (containing sucrose) at 25 °C for 30 min, the maturation rate decreased in solution with 0.51 Osm/kg, whereas the hatching rate decreased with lower osmolality (0.40 Osm/kg). In an experiment on the toxicity of cryoprotectants (∼10%, at 25 °C), it was found that glycerol and ethylene glycol were toxic both by the assessment of maturation and hatching. Propylene glycol, DMSO and methanol were less toxic by the assessment of maturation, but were found to be toxic by the assessment of hatching. Methanol was the least toxic, but it was less effective to make a solution vitrify than propylene glycol. Therefore, a portion of methanol was replaced with propylene glycol. The replacement increased the toxicity, but could be effective to reduce chilling injury at −5 °C. These results clarified the sensitivity of immature oocytes to various cryobiological properties accurately, which will be useful for realizing cryopreservation of zebrafish oocytes.  相似文献   
53.
54.
55.
56.
Rat CD4+ T cells were divided into two distinct subsets by a monoclonal antibody RTH-1 recognizing a unique epitope on rat CD45R. Cellular distribution of OX-22- and RTH-1-defined antigens was the same. However, OX-22 and RTH-1 recognized different epitopes that exist on rat CD45R. The expression of IL-4 gene was detected only in RTH-1low CD4+ T cell subset upon various stimulations. In contrast, the expression of IL-2 and IFN-γ gene varied depending upon the nature of stimuli. The increased cell surface expression of CD44 was detected in RTH-1high CD4+ T cell subset. Conversely the increased expression of CD2 was detected in RTH-1low CD4+ T cell subset. The expression of CD3 and LFA-1 was not significantly different between RTH-1high and RTH-1low subsets.  相似文献   
57.
Summary The gene braB, encoding the Na-coupled carrier for branched-chain amino acids in Pseudomonas aeruginosa PAO, was cloned on cosmid pMMB34. The cosmid clones carrying the braB gene were identified as those that restored growth at low leucine concentration and Na-dependent leucine transport activity to P. aeruginosa PAO3536 defective in the transport of branched-chain amino acids. Determination of the nucleotide sequence of the DNA fragment shows that the braB gene comprises 1311 bp and encodes a hydrophobic protein of 437 amino acids with a calculated Mr of 45279. The hydropathy profile suggests that there exist in the carrier protein 12 hydrophobic segments long enough to traverse the membrane. The amino acid sequence shows a high degree of homology with thebrnQ product, a branched-chain amino acid carrier of Salmonella typhimurium, while no homology in the nucleotide sequences is found in the braB and brnQ genes.  相似文献   
58.
1-Phenyl-N-methyl-1,2,3,4-tetrahydroisoquinoline and 1-phenyl-1,2,3,4-tetrahydroisoquinoline were detected for the first time in parkinsonian human brain using gas chromatography-tandem mass spectrometry (GC-MS-MS). Since these compounds are structural analogues of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) that produces parkinsonism in humans, they might be candidates for endogenous MPTP-like neurotoxins.  相似文献   
59.
We developed a rapid and simple method for the screening of antiviral agents against herpes simplex virus (HSV) in a model of gastrointestinal herpetic infection in vitro. This method was based on inhibition of HSV-induced cytopathogenicity in gastric adenocarcinoma MKN-28 cells, as monitored by an MTT colorimetric assay. From the various compounds that were evaluated for their activity against HSV-1 and HSV-2, brivudine (BVDU) emerged as the most effective. When the 50% effective concentration (EC50) values of the antiherpes agents in MKN-28 cells were compared with those in human embryo lung MRC-5 cells, all compounds, except for BVDU, showed higher EC50 values in MKN-28 cells. For BVDU the EC50 values in MKN-28 cells were 0.8 (HSV-1) and 0.036 (HSV-2) times the EC50 values in MRC-5 cells. Thus BVDU was 27.5 times more active against HSV-2 in MKN-28 cells than in MRC-5 cells. The MKN-28 gastric cancer cells may be useful for the rapid screening of anti-HSV agents and, in particular, those that may be useful in therapy of gastrointestinal HSV infections in gastrointestinal herpetic infection.  相似文献   
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