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   472篇
  免费   46篇
  2023年   3篇
  2021年   6篇
  2019年   3篇
  2018年   5篇
  2017年   5篇
  2016年   3篇
  2015年   19篇
  2014年   16篇
  2013年   23篇
  2012年   25篇
  2011年   26篇
  2010年   16篇
  2009年   12篇
  2008年   17篇
  2007年   16篇
  2006年   9篇
  2005年   20篇
  2004年   14篇
  2003年   9篇
  2002年   12篇
  2001年   19篇
  2000年   18篇
  1999年   16篇
  1998年   9篇
  1997年   7篇
  1996年   5篇
  1995年   9篇
  1994年   6篇
  1993年   7篇
  1992年   7篇
  1991年   8篇
  1990年   6篇
  1989年   8篇
  1988年   12篇
  1987年   19篇
  1986年   7篇
  1985年   13篇
  1984年   3篇
  1983年   3篇
  1982年   8篇
  1981年   9篇
  1980年   8篇
  1979年   3篇
  1978年   6篇
  1977年   11篇
  1976年   4篇
  1973年   3篇
  1972年   7篇
  1969年   2篇
  1966年   4篇
排序方式: 共有518条查询结果,搜索用时 140 毫秒
511.
Summary Mouse monoclonal antibodies to carcinoembryogenic antigen (CEA) obtained by the somatic cell hybridization technique of Köhler and Milstein were used in a modified enzyme bridge immunoperoxidase staining method. Both high and low affinity antibodies were tested and their staining properties compared with those of a commercial polyvalent rabbit antiserum. The staining pattern of neoplastic epithelial cells in all seven antibodies in samples of primary adenocarcinoma of the colon was similar, indicating that no gross differences were found in the exposure of the different antigenic determinants of CEA in formalin fixed tissue. The background staining of the monoclonal antibodies was negligible. It is concluded that monoclonal antibodies are superior to conventional antisera in immunoperoxidase staining of CEA.  相似文献   
512.
Amylolytic lactic acid bacteria in fish silage   总被引:2,自引:1,他引:1  
An ∝aL-amylase activity has been observed in lactic acid bacteria occurring initially in fermented fish silage. The organisms belong to the genus Leuconostoc . The main fraction of the amylolytic enzyme produced by one of the isolated bacteria is cell-bound and is released into the medium at a late stage of growth. Treating cells with ultrasound or Triton X-100 increases enzyme activity in the culture filtrate. The pH range for enzyme activity is 5.0–7.0, with an optimum at pH 6.0. The enzyme is extremely labile at pH 8.0 and is inactivated at temperatures above 50°C at pH 5.8. Two enzyme fractions were found by isoelectric focusing, the main one at pH 5.00 and another at pH 4.5. Chromatography on DEAE cellulose gave two active peaks.  相似文献   
513.
Summary Three families with infants affected with campomelic dysplasia, a genetically determined mesenchymal disease frequently associated with sex reversal were studied. Two XY famales with ovarian gonadal differentiation and typical clinical features of campomelic dysplasia could be tested for H-Y antigen and were found to be H-Y negative.  相似文献   
514.
The size distributions of electrophoretically isolated subfractions of the very low density human plasma lipoproteins have been determined using electron microscopy. The primary and secondary particles observed in plasma of normal subjects after fat ingestion appear to have similar size distributions. Particles produced by corn oil feeding can be fixed by the osmium tetroxide reaction while those produced by butter fat feeding could not be fixed or made visible by this technique. Good agreement between particle size as measured by electron microscopy and particle size as predicted by ultra-centrifugal analysis was obtained.  相似文献   
515.
Metabolically stable consortia of anaerobic bacteria obtained by enrichment of sediment samples with 3,4,5-trimethoxybenzoate (TMBA), 3,4,5-trihydroxybenzoate (gallate [GA]), or 5-chlorovanillin (CV) were used to study the anaerobic transformation of a series of chloroveratroles, chloroguaiacols, and chlorocatechols used as cosubstrates. Experiments were carried out with growing cultures, and the following pathways were demonstrated for metabolism of the growth substrates: (i) TMBA produced GA, which was further degraded without the formation of aromatic intermediates; (ii) GA formed pyrogallol, which was stable to further transformation; and (iii) CV was degraded by a series of steps involving de-O-methylation, oxidation of the aldehyde group, and decarboxylation to 3-chlorocatechol before ring cleavage. Mono-de-O-methylation of the cosubstrates occurred rapidly in the order 4,5,6-trichloroguaiacol greater than 3,4,5-trichloroguaiacol approximately 3,4,5-trichloroveratrole approximately tetrachloroveratrole greater than tetrachloroguaiacol and was concomitant with degradation of the growth substrates. For the polymethoxy compounds--chloroveratroles, 1,2,3-trichloro-4,5,6-trimethoxybenzene, and 4,5,6-trichlorosyringol--de-O-methylation took place sequentially. The resulting chlorocatechols were stable to further transformation until the cultures had exhausted the growth substrates; selective dechlorination then occurred with the formation of 3,5-dichlorocatechol from 3,4,5-trichlorocatechol and of 3,4,6-trichlorocatechol from tetrachlorocatechol. 2,4,5-, 2,4,6-, and 3,4,5-trichoroanisole and 2,3,4,5-tetrachloroanisole were de-O-methylated, but the resulting chlorophenols were resistant to dechlorination. These results extend those of a previous study with spiked sediment samples and their endogenous microflora and illustrate some of the transformations of chloroguaiacols and chlorocatechols which may be expected to occur in anaerobic sediments.  相似文献   
516.
517.
As a means of characterizing the distal long arm of chromosome 5, in particular, the region spanning 5q23-->q31, we analyzed somatic cell hybrids prepared from cells with overlapping chromosomal rearrangements. In one hybrid, the derivative chromosome 5 from a patient with acute myeloid leukemia (AML) de novo, whose bone marrow cells had a balanced translocation, t(5;7)(q31;q22), involving chromosome band 5q31, was isolated in a somatic cell hybrid (B294). In addition, we prepared somatic cell hybrids from a lymphoblastoid cell line (CC) derived from a patient who has a constitutional interstitial deletion of chromosome 5 spanning 5q23.1-->q31.1. By a combination of Southern hybridization analysis and fluorescent in situ hybridization, we constructed a map dividing 5q23-->q31 into four regions. We can assign genes to these regions and relate them to anonymous RFLP markers that have been genetically mapped.  相似文献   
518.
Recent chromosome walking experiments have identified a candidate gene (ZFY) for the testis-determining factor on the human Y chromosome (Page et al., 1987). We report here the regional assignments of the ZFY gene and related sequences in the human and the mouse. By in situ hybridization, we assigned ZFX and ZFY to human chromosome bands Xp21 and Yp11.3, respectively. Although the mouse harbors two Zfy genes, only one site at band A1 of its Y chromosome was significantly labeled. The mouse Zfx gene and the Zfa gene on chromosome 10 were assigned to bands XD and 10B5, respectively. These assignments of the ZFX gene in human and mouse add another marker to the conserved syntenic group for evaluating the evolutionary relationship of the human and mouse X chromosomes.  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