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   294035篇
  免费   34641篇
  国内免费   152篇
  2018年   2413篇
  2016年   3111篇
  2015年   4076篇
  2014年   4957篇
  2013年   6783篇
  2012年   7782篇
  2011年   7990篇
  2010年   5257篇
  2009年   5080篇
  2008年   7199篇
  2007年   7378篇
  2006年   7261篇
  2005年   6968篇
  2004年   6847篇
  2003年   6668篇
  2002年   6519篇
  2001年   17270篇
  2000年   17455篇
  1999年   13312篇
  1998年   3870篇
  1997年   4138篇
  1996年   3856篇
  1995年   3490篇
  1994年   3473篇
  1993年   3544篇
  1992年   10392篇
  1991年   10321篇
  1990年   9806篇
  1989年   9641篇
  1988年   8992篇
  1987年   8359篇
  1986年   7561篇
  1985年   7411篇
  1984年   5834篇
  1983年   5085篇
  1982年   3621篇
  1981年   3185篇
  1980年   3043篇
  1979年   5352篇
  1978年   4122篇
  1977年   3756篇
  1976年   3305篇
  1975年   3783篇
  1974年   3954篇
  1973年   3895篇
  1972年   3425篇
  1971年   3185篇
  1970年   2829篇
  1969年   2742篇
  1968年   2415篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
983.
984.
985.
986.
The adaptation to a high protein diet of the concentration and mRNA level of a trypsin-sensitive, cholecystokinin-releasing peptide (monitor peptide), which was proposed to be the mediator of the cholecystokinin release in response to protein intake, was investigated in the rat pancreas. Adult rats were placed on one of two isocaloric diets. One group was fed a 22% casein diet (control diet) and the other a 64% casein diet (high-protein diet) for 14 days. In order to quantify the monitor peptide separately from pancreatic secretory trypsin inhibitor (PSTI-II), which is highly similar in its amino acid and mRNA nucleotide sequences to the monitor peptide but has less cholecystokinin-releasing activity, we used specific assay methods: HPLC was used for determining the monitor peptide concentration in zymogen granules and a synthetic oligonucleotide probe for determining the mRNA of the monitor peptide in the pancreas. The concentrations in the zymogen granules and the mRNA levels in the pancreas of the two peptides increased in parallel during the adaptation to the high protein diet, indicating that these two peptides were under the same control during the adaptation. The concentration and mRNA level of the monitor peptide, which were measured after 0, 3, and 14 days, increased throughout the experiment period, as did the concentration of trypsin. This suggested that the monitor peptide and trypsin may respond to similar signals during the adaptation to a high protein diet and that this apparent coordination may facilitate the adaptation of the pancreas to the diet.  相似文献   
987.
It is established that insulin enhances the ability of the loach liver plasma membranes to phosphorylate lactate dehydrogenase. In the case of insulin-treated plasma membranes the amount of incorporated 32P is more than 4 times higher than that of the basal level. It is concluded that insulin-stimulated plasma membrane-dependent phosphorylation of the enzyme is one of the possible molecular mechanisms of hormone action on intracellular metabolism.  相似文献   
988.
Restriction fragments' length polymorphism in the region of apolipoprotein A-I (apo A-I) gene was investigated in Novosibirsk (Siberia, USSR) population. Correlation between PstI apo A-I alleles (2,2 kb-P1; 3,3 kb-P2) and total cholesterol, triglycerides, high density polyproteins cholesterol, and apolipoprotein A-I level was analysed. A tendency to increase in cholesterol index of atherogenicity and to decrease in high density lipoproteins cholesterol as well as apolipoprotein A-I level was shown to occur for P1P2 genotype patients.  相似文献   
989.
Sixteen raptors, including one eagle, two falcons, five hawks and eight owls, were found to have developmental ocular lesions. The most common lesion was microphthalmia. Other findings included cataract, microphakia, retinal dysplasia, malformation of the ciliary body, choroid and pecten, and lentoid formation. Specific causes for these lesions could not be determined. It is hypothesized that developmental ocular disease probably is more common than available reports indicate.  相似文献   
990.
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