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   4233篇
  免费   222篇
  2022年   22篇
  2021年   40篇
  2020年   25篇
  2019年   54篇
  2018年   57篇
  2017年   51篇
  2016年   65篇
  2015年   105篇
  2014年   136篇
  2013年   380篇
  2012年   200篇
  2011年   220篇
  2010年   122篇
  2009年   136篇
  2008年   219篇
  2007年   254篇
  2006年   253篇
  2005年   228篇
  2004年   234篇
  2003年   254篇
  2002年   216篇
  2001年   100篇
  2000年   109篇
  1999年   102篇
  1998年   75篇
  1997年   61篇
  1996年   45篇
  1995年   40篇
  1994年   30篇
  1993年   33篇
  1992年   49篇
  1991年   47篇
  1990年   39篇
  1989年   43篇
  1988年   26篇
  1987年   26篇
  1986年   28篇
  1985年   36篇
  1984年   26篇
  1983年   22篇
  1982年   18篇
  1981年   19篇
  1980年   19篇
  1978年   17篇
  1977年   18篇
  1976年   11篇
  1975年   25篇
  1974年   13篇
  1973年   18篇
  1966年   10篇
排序方式: 共有4455条查询结果,搜索用时 15 毫秒
101.
Two new non-protein amino acids, Nδ-benzoyl-l-ornithine and Nδ-benzoyl-l-γ-hydroxyornithine have been characterized from the seeds of Vicia pseudo-orobus.  相似文献   
102.
Catharanthine and akuammicine, together with ajmalicine and strictosidine, were isolated from a culture strain of Catharanthus roseus suspension cells. The biosynthetic capability of the cultured cells to produce akuammicine, catharanthine and vindoline was confirmed by feeding experiments with dl-tryptophan-[3-14C] to yield the radioactive alkaloids.  相似文献   
103.
104.
The physiological action of CCC for leaves of Kyoho grapes wasstudied. Leaves from the lower to upper positions of the primaryshoots and (primary) lateral shoots showed uneven photosyntheticactivities with peaks. The photosynthetic activity of each leaffrom both shoots was increased by treatment with CCC, whereasrespiratory activity was not affected with CCC. In the primaryshoots, CCC treatment increased the contents of chlorophylla and b in the leaves, but in the lateral shoots only chlorophyllb contents were increased. Dry weights of the leaves from thelateral shoots increased with CCC, but those of leaves locatedin the vicinity of nodes bearing the fruit clusters varied slightlyor were almost the same as the dry weight of non-treated leaves.Leaf thickness was increased by CCC and paralleled the variationin dry weight. The leaf area was decreased by CCC. (Received April 19, 1980; )  相似文献   
105.
106.
The membrane potential generated at pH 8.5 by K+-depleted and Na+-loaded Vibrioalginolyticus is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na+-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na+ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na+-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na+ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na+ chemical gradient.  相似文献   
107.
108.
Adenosie, AMP, ADP and ATP activated adenylate cyclase in pig skin (epidermis) slices resulting in the accumulation of cyclic AMP. This effect was highly potentiated by the addition of the cyclic AMP-phophodiesterase inhibitor, papaverine. But another inhibitor, theophylline, strongly blocked the activation of adenylate cyclase by adenosine and adenine nucleotides. Theophylline apparently competed with adenosine for the cell suface receptor. Like theophylline, the addition of adenine alone caused no accumulation of cyclic AMP, but it significantly inhibited the stimulatory effect of adenosine. Guanosine, or guanine, cytidine, uridine, or thymidine nucleotides has no effect on the accumulation of cyclic AMP. Among other adenine nucleotides was tested, adenosine 5′-monophosphoramidate, but not adenosine 5′-monosulfate, significantly increased cyclic AMP especially with the addition of papaverine. Neither 2′- nor 3′-adenylic acid were effective. Our data indicate that pig epidermis has four specific and independent adenylate cyclase systems for adenosine (and adenine nucleotides), histamine, epinephrine and prostaglandin E.  相似文献   
109.
110.
A male infant with monosomy 21.   总被引:2,自引:0,他引:2  
A male infant with total monosomy 21 identified by Q-, G- and R-banding is described. His main symptoms are hypertonia, micrognathia, microphthalmus, imperforate anus, ambiguous external genitalia, floating and malopposed thumbs, overlying fingers, right clubfoot and growth retardation. Both parents are phenotypically as well as karotypically normal.  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