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   293407篇
  免费   34614篇
  国内免费   151篇
  2018年   2403篇
  2016年   3091篇
  2015年   4038篇
  2014年   4922篇
  2013年   6754篇
  2012年   7715篇
  2011年   7929篇
  2010年   5210篇
  2009年   5044篇
  2008年   7170篇
  2007年   7330篇
  2006年   7213篇
  2005年   6928篇
  2004年   6797篇
  2003年   6623篇
  2002年   6473篇
  2001年   17271篇
  2000年   17454篇
  1999年   13314篇
  1998年   3868篇
  1997年   4132篇
  1996年   3856篇
  1995年   3492篇
  1994年   3472篇
  1993年   3544篇
  1992年   10401篇
  1991年   10327篇
  1990年   9812篇
  1989年   9647篇
  1988年   8997篇
  1987年   8367篇
  1986年   7571篇
  1985年   7417篇
  1984年   5841篇
  1983年   5082篇
  1982年   3620篇
  1981年   3181篇
  1980年   3034篇
  1979年   5353篇
  1978年   4116篇
  1977年   3755篇
  1976年   3302篇
  1975年   3786篇
  1974年   3953篇
  1973年   3897篇
  1972年   3423篇
  1971年   3188篇
  1970年   2824篇
  1969年   2746篇
  1968年   2413篇
排序方式: 共有10000条查询结果,搜索用时 5 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