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   224篇
  免费   9篇
  233篇
  2021年   3篇
  2017年   4篇
  2016年   3篇
  2015年   5篇
  2014年   5篇
  2013年   4篇
  2012年   5篇
  2011年   7篇
  2010年   12篇
  2009年   15篇
  2008年   9篇
  2007年   8篇
  2006年   8篇
  2005年   12篇
  2004年   8篇
  2003年   5篇
  2002年   4篇
  2001年   3篇
  1999年   4篇
  1998年   5篇
  1997年   4篇
  1996年   2篇
  1995年   3篇
  1994年   5篇
  1993年   2篇
  1992年   3篇
  1988年   5篇
  1987年   4篇
  1986年   3篇
  1980年   2篇
  1979年   4篇
  1978年   2篇
  1977年   4篇
  1976年   3篇
  1974年   2篇
  1971年   2篇
  1970年   2篇
  1966年   2篇
  1964年   1篇
  1962年   1篇
  1959年   2篇
  1958年   2篇
  1957年   3篇
  1956年   6篇
  1955年   5篇
  1954年   3篇
  1953年   5篇
  1952年   4篇
  1949年   1篇
  1948年   2篇
排序方式: 共有233条查询结果,搜索用时 15 毫秒
61.
Research laboratories studying the genetics of companion animals have no database tools specifically designed to aid in the management of the many kinds of data that are generated, stored and analyzed. We have developed a relational database, "DOG-SPOT," to provide such a tool. Implemented in MS-Access, the database is easy to extend or customize to suit a lab's particular needs. With DOG-SPOT a lab can manage data relating to dogs, breeds, samples, biomaterials, phenotypes, owners, communications, amplicons, sequences, markers, genotypes and personnel. Such an integrated data structure helps ensure high quality data entry and makes it easy to track physical stocks of biomaterials and oligonucleotides.  相似文献   
62.
Photosynthetic down-regulation and/or inhibition under water stress conditions are determinants for plant growth, survival and yield in drought-prone areas. Current knowledge about the sequence of metabolic events that leads to complete inhibition of photosynthesis under severe water stress is reviewed. An analysis of published data reveals that a key regulatory role for Rubisco in photosynthesis is improbable under water stress conditions. By contrast, the little data available for other Calvin cycle enzymes suggest the possibility of a key regulatory role for some enzymes involved in the regeneration of RuBP. There are insufficient data to determine the role of photophosphorylation. Several important gaps in our knowledge of this field are highlighted. The most important is the remarkable scarcity of data about the regulation/inhibition of photosynthetic enzymes other than Rubisco under water stress. Consequently, new experiments are urgently needed to improve our current understanding of photosynthetic down-regulation under water stress. A second gap is the lack of knowledge of photosynthetic recovery after irrigation of plants which have been subjected to different stages of water stress. This knowledge is necessary in order to match physiological down-regulation by water stress with controlled irrigation programmes.  相似文献   
63.
64.
Levels of carbonic anhydrase activity were determined on a total (60 EUmg?1 protein), external (7.36 EU), internal (50.14 EU) and protoplast (15.63 EU) basis for Ranunculus penicillatus (Dumort.) Bab ssp. pseudofluitans (Syme) S. Webster, a freshwater aquatic macrophyte, by conventional electrometric methods. The site of activity of ‘external’ carbonic anhydrase (CA) has been visualized using 5-Dimethylaminonapthalene-1- sulphonamide (DNSA)-CA fluorescent complex formation, and is postulated to be closely associated with the epidermal cell wall. The photosynthetic rate of R. penicillatus ssp. pseudofluitans at pH 9.0 is in excess of the uncatalysed rate of production of CO2 from HCO?3, and this plant is therefore using HCO?3 for photosynthesis. The possible contribution of CA activity to inorganic carbon assimilation, and specifically to transport of HCO?3, in submerged aquatic plants is discussed.  相似文献   
65.
Hydroxyurea was used to study the proliferation rate of haemopoietic stem cells (CFUJ in normal mice, after irradiation or transplantation into irradiated recipients. It was demonstrated that the proliferation rate of endogenous CFUS (endo-CFU,) and exogenous CFUS (exo-CFUs) are identical. After irradiation (650 R) the surviving endo-CFUs begin to proliferate immediately. By contrast exo-CFU, transplanted into the irradiated recipient mouse (850 R), begin to proliferate only after about 30 hr. However, injection of isoproterenol (which stimulates adenyl cyclase) or dibutyryl cyclic adenosine 3′,5′-monophosphate shortly after marrow cell graft, triggers the transplanted CFUS into cell cycle as shown by an almost immediately increased sensitivity to hydroxyurea. Isoproterenol is capable of inducing DNA synthesis also in stem cells of normal mice but it takes about 20 hr before CFU, become to be increasingly sensitive to hydroxyurea.  相似文献   
66.
67.
68.
69.
70.
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