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   4600篇
  免费   504篇
  国内免费   4篇
  2021年   74篇
  2019年   48篇
  2018年   72篇
  2017年   54篇
  2016年   101篇
  2015年   120篇
  2014年   162篇
  2013年   198篇
  2012年   251篇
  2011年   259篇
  2010年   190篇
  2009年   133篇
  2008年   265篇
  2007年   239篇
  2006年   175篇
  2005年   180篇
  2004年   179篇
  2003年   162篇
  2002年   165篇
  2001年   98篇
  2000年   85篇
  1999年   90篇
  1998年   65篇
  1997年   54篇
  1996年   56篇
  1995年   48篇
  1994年   41篇
  1993年   46篇
  1992年   81篇
  1991年   86篇
  1990年   70篇
  1989年   73篇
  1988年   85篇
  1987年   53篇
  1986年   59篇
  1985年   51篇
  1984年   59篇
  1983年   49篇
  1982年   36篇
  1981年   39篇
  1980年   48篇
  1979年   49篇
  1978年   48篇
  1976年   45篇
  1975年   33篇
  1974年   34篇
  1973年   42篇
  1972年   33篇
  1970年   33篇
  1969年   33篇
排序方式: 共有5108条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
Summary The inheritance of both the mitochondrial DNA (mtDNA) and the nuclear-encoded extrachromosomal ribosomal DNA (rDNA) has been studied in the myxomycete, Didymium iridis, by DNA-DNA hybridization of labeled probes to total DNA at various stage of the life cycle. Both the mtDNA and rDNA populations rapidly become homogeneous in individuals, but there is a qualitative difference in the patterns of inheritance of these two molecules. One parental rDNA type was preferentially inherited in all crosses; selective replication of this molecule is tentatively proposed as the mechanism of inheritance. In contrast, either parental mtDNA type could be inherited. Since the inherited population of parental mtDNA molecules are not partitioned into cells in this coenocytic organism, no known mechanism of inheritance can explain the rapid and apparently random loss of one parental mtDNA type in individuals.  相似文献   
46.
Membrane associated nitrate reductase (NR) was detected in plasma membrane (PM) fractions isolated by aqueous two-phase partitioning from barley (Hordeum vulgare L. var CM 72) roots. The PM associated NR was not removed by washing vesicles with 500 millimolar NaCl and 1 millimolar EDTA and represented up to 4% of the total root NR activity. PM associated NR was stimulated up to 20-fold by Triton X-100 whereas soluble NR was only increased 1.7-fold. The latency was a function of the solubilization of NR from the membrane. NR, solubilized from the PM fraction by Triton X-100 was inactivated by antiserum to Chlorella sorokiniana NR. Anti-NR immunoglobulin G fragments purified from the anti-NR serum inhibited NO3 uptake by more than 90% but had no effect on NO2 uptake. The inhibitory effect was only partially reversible; uptake recovered to 50% of the control after thorough rinsing of roots. Preimmune serum immunoglobulin G fragments inhibited NO3 uptake 36% but the effect was completely reversible by rinsing. Intact NR antiserum had no effect on NO3 uptake. The results present the possibility that NO3 uptake and NO3 reduction in the PM of barley roots may be related.  相似文献   
47.
48.
Twelve loci form a continuous linkage map for human chromosome 18   总被引:7,自引:0,他引:7  
We have constructed a primary genetic map of human chromosome 18 consisting of 11 DNA markers and one serological marker (JK). Two of these loci define highly polymorphic VNTR systems. The markers define a continuous genetic linkage map of 97 cM in males and 205 cM in females; female genetic distances in a panel of 59 three-generation families were consistently about twice those observed in males. The high odds in support of the linear order of the markers on this recombination map, and the extent of coverage of chromosome 18, indicate that this map will permit efficient linkage studies of human genetic diseases that may be segregating on chromosome 18 and will provide anchor points for development of high-resolution maps for this chromosome.  相似文献   
49.
An antimicrobial peptide designated pediocin AcH was isolated from Pediococcus acidilactici strain H. The pediocin AcH was purified by ion exchange chromatography. The molecular weight of pediocin AcH was determined by SDS-PAGE to be about 2700 daltons. Pediocin AcH was sensitive to proteolytic enzymes, resistant to heat and organic solvents, and active over a wide range of pH. Pediocin AcH exhibited inhibition against several food spoilage bacteria and foodborne pathogens including Staphylococcus aureus, Clostridium perfringens and Listeria monocytogenes. It was bactericidal to sensitive cells and acted very rapidly. The bactericidal effect was not produced by either cell lysis or apparent loss of membrane permeability.  相似文献   
50.
Sixty-nine strains of bacteria isolated from murcha and ragi (amylase starters) were studied. These came from 14 different amylase starters from Java, Bali, and Nepal and were isolated from dilution plates incubated under aerobic and anaerobic conditions. Most belonged to Pediococcus , probably P. pentosaceus , and to Streptococcus faecalis. None were able to attack starch although they are used in starch fermentations. When inoculated on rice as pure cultures most of them failed to show visible growth unless yeasts and moulds were added at the same time. The roles of these bacteria are unknown but they may produce secondary products from the glucose formed by the amylolytic yeasts and moulds always found in the starters.  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