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   814393篇
  免费   96485篇
  国内免费   330篇
  911208篇
  2018年   7269篇
  2016年   9910篇
  2015年   13899篇
  2014年   16098篇
  2013年   22627篇
  2012年   25188篇
  2011年   25242篇
  2010年   16701篇
  2009年   15596篇
  2008年   21921篇
  2007年   23030篇
  2006年   21360篇
  2005年   21140篇
  2004年   21084篇
  2003年   20060篇
  2002年   19223篇
  2001年   33613篇
  2000年   33997篇
  1999年   27412篇
  1998年   10137篇
  1997年   10510篇
  1996年   10138篇
  1995年   9708篇
  1994年   9728篇
  1993年   9492篇
  1992年   23752篇
  1991年   23308篇
  1990年   22946篇
  1989年   22190篇
  1988年   20898篇
  1987年   19917篇
  1986年   18634篇
  1985年   18844篇
  1984年   15774篇
  1983年   13857篇
  1982年   10820篇
  1981年   9970篇
  1980年   9406篇
  1979年   15767篇
  1978年   12168篇
  1977年   11247篇
  1976年   10642篇
  1975年   11743篇
  1974年   12387篇
  1973年   12359篇
  1972年   11487篇
  1971年   10271篇
  1970年   8882篇
  1969年   8503篇
  1968年   7681篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Argon laser surgery is an effective treatment for ectasias and congenital port-wine stains; however, its use in children under the age of 13 is controversial. This paper reviews 202 children under the age of 13 who underwent argon laser treatments for congenital port-wine stains, spider angiomas, epidermal nevi, and lentigines. The clinical characteristics of port-wine stains in 170 children are discussed. Good to excellent results (moderate to complete clearing) in port-wine stains were obtained in 60 percent of patients and seemed to correlate best with lack of blanchability on pressure. Hypertrophic scarring was seen in only 7 children, all of whom had undressed wounds; no significant scarring has been seen in any subsequent child who had maintained a dressed wound postoperatively.  相似文献   
62.
63.
64.
65.
66.
67.
68.
Isopropanol administered in a large (6 g/kg, orally) as well as in a lower dose (1 g/kg, I.P.) is slowly oxidized into acetone by the intact rat. Using two inhibitors, 3 amino-1,2,4-triazole and pyrazole, investigations on the hepatic enzymatic system involved in the oxidation of isopropanol show that catalase does not play an important part in this pathway, contrary to alcohol dehydrogenase which is the major enzyme responsible for this oxidation. Although isopropanol oxidation is mainly catalysed in the liver through alcohol dehydrogenase, no alteration of the hepatic extramitochondrial redox state occurs after the administration of a large as well as of a lower dose of isopropanol. From these experiments it may be concluded that alterations of the liver NAD+/NADH ratio, which seem to play an important part in the ethanol induced fatty liver, are not involved in the isopropanol induced one.  相似文献   
69.
70.
An agar-degrading marine bacterium identified as a Microscilla species was isolated from coastal California marine sediment. This organism harbored a single 101-kb circular DNA plasmid designated pSD15. The complete nucleotide sequence of pSD15 was obtained, and sequence analysis indicated a number of genes putatively encoding a variety of enzymes involved in polysaccharide utilization. The most striking feature was the occurrence of five putative agarase genes. Loss of the plasmid, which occurred at a surprisingly high frequency, was associated with loss of agarase activity, supporting the sequence analysis results.  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