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   1028763篇
  免费   119465篇
  国内免费   644篇
  2018年   8373篇
  2016年   11990篇
  2015年   17640篇
  2014年   20461篇
  2013年   28753篇
  2012年   32548篇
  2011年   32472篇
  2010年   21938篇
  2009年   20334篇
  2008年   29305篇
  2007年   30193篇
  2006年   28298篇
  2005年   27330篇
  2004年   27236篇
  2003年   26247篇
  2002年   25700篇
  2001年   42989篇
  2000年   43467篇
  1999年   35116篇
  1998年   13563篇
  1997年   14084篇
  1996年   13492篇
  1995年   12839篇
  1994年   12696篇
  1993年   12465篇
  1992年   29844篇
  1991年   28826篇
  1990年   28358篇
  1989年   27525篇
  1988年   25524篇
  1987年   24846篇
  1986年   23011篇
  1985年   23105篇
  1984年   19320篇
  1983年   16929篇
  1982年   13536篇
  1981年   12143篇
  1980年   11525篇
  1979年   18859篇
  1978年   14989篇
  1977年   13623篇
  1976年   12826篇
  1975年   13997篇
  1974年   15062篇
  1973年   14946篇
  1972年   13570篇
  1971年   12594篇
  1970年   10771篇
  1969年   10278篇
  1968年   9253篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Anaerobic ureolytic bacteria from caecal content and soft faeces of rabbit   总被引:2,自引:0,他引:2  
Forty strains of ureolytic bacteria were isolated from the caecal content and soft faeces of seven rabbits by the anaerobic roll tube method and were characterized. The isolates were identified with Clostridium coccoides, Cl. innocuum, Peptostreptococcus productus, P. micros, Peptococcus magnus, Fusobacterium russii and Fusobacterium sp. Urease activity of representative strains of the various species was also determined. The study indicated that strongly-ureolytic anaerobic bacteria are present in the caecum of the rabbit.  相似文献   
952.
953.
These siblings of a Czech family aged 21, 19 and 6 years, respectively, with congenital dyserythropoietic anemia, type II, (HEMPAS) are reported. In two elder siblings ferrokinetic studies revealed a rapid plasma 59Fe clearance, markedly decreased erythrocyte incorporation and shortened 51Cr red-cell survival. Direct anti-globulin test was found positive in one of them. Further investigations revealed low values of blood plasma cholesterol, total lipids, beta-lipoproteins, beta-carotine and vitamin E and A as well as low values of the prothrombin complex. Liver biopsy demonstrated siderosis and disseminated intravascular coagulation in the liver in both patients. The possible reasons for these humoral aberrations are discussed.  相似文献   
954.
955.
The Pig chromosomes that contain rDNA sites displayed a polymorphism in the distribution of the genes among the nucleolar organizers located on pairs Nos. 8 and 10. Two, or more often three, active sites were observed in the chromosomes of lymphocytes stimulated with phytohemagglutinin. Only 5% of the metaphases showed a 4th small active site. At the onset of stimulation most cells contained one-two nucleoli; four nucleoli were never observed. After prolonged stimulation, the number of nuclei containing three nucleoli increased. A 4th small nucleolus appeared in a few cells, presumably formed by activation of the smallest rDNA site.  相似文献   
956.
J L Weber  E Cutz 《CMAJ》1980,123(2):112-117
  相似文献   
957.
Treatment of bacteriological-grade plastic with concentrated sulphuric acid is a well known technique which increases the wettability of the surface and renders it suitable for eukaryotic cell adhesion. We have noticed that these substrata present a distinctive surface topography in the presence of a serum supplement under normal culture conditions. The adsorbed serum layer is comprised of fine furrows and ridges and the influence of adherent cells on this layer leads to minute tears and distortions in the direction of the corrugations. This provides a novel system for the investigation of cell spreading and locomotion by scanning electron microscopy.  相似文献   
958.
Abstract In a 2-year field survey, the phylloplane mycoflora on the haulm base of wheat was studied by the dilution plate technique. No significant colonisation was registered before the end of May. Cladosporium spp., 'white' and 'red' yeasts were found to be the most abundant fungi.  相似文献   
959.
Cellular fatty acid composition of Leuconostoc oenos   总被引:3,自引:0,他引:3  
The cellular fatty acid composition of 70 lactic acid bacteria was examined by capillary gas chromatography. Fifty-four Leuconostoc oenos strains, including three reference, type strains from the other Leuconostoc spp., nine Pediococcus spp. and two Lactobacillus spp. were studied. Eighteen fatty acids were determined, of which 10 were identified by gas chromatography-mass spectrometry. The relative percentages of the 18 fatty acids of the Leuconostoc strains were analyzed numerically and grouped using the unweighted pair-group method. Results show that four clusters could be defined at r = 0.920, with five strains unassigned. The major fatty acids of the Leuc. oenos strains were found to be palmitic acid (C16:0), palmitoleic acid (C16:1–9), oleic acid (C18: 1–9), vaccenic acid (C18: 1–11), dihyrosterculic acid (C19-cyclopropane-9) and lactobacillic acid (C19-cyclopropane-11). It was mainly on the basis of the amounts of oleic acid and the C19-cyclopropane fatty acids that the strains of Leuc. oenos could be distinguished from each other. This is the first report of the occurrence of dihydrosterculic acid in lactic acid bacteria. For the majority of Leuc. oenos strains, the result obtained with the cellular fatty acid analysis confirmed the phenotypic relationships.  相似文献   
960.
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