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   878252篇
  免费   91846篇
  国内免费   643篇
  970741篇
  2018年   8615篇
  2017年   8284篇
  2016年   11489篇
  2015年   14570篇
  2014年   17421篇
  2013年   24904篇
  2012年   28058篇
  2011年   28875篇
  2010年   19666篇
  2009年   18256篇
  2008年   25618篇
  2007年   26603篇
  2006年   24955篇
  2005年   23950篇
  2004年   23649篇
  2003年   22881篇
  2002年   22327篇
  2001年   41417篇
  2000年   40742篇
  1999年   32572篇
  1998年   11322篇
  1997年   11566篇
  1996年   10946篇
  1995年   10050篇
  1994年   9621篇
  1993年   9659篇
  1992年   25872篇
  1991年   25213篇
  1990年   24347篇
  1989年   23872篇
  1988年   21875篇
  1987年   20682篇
  1986年   19212篇
  1985年   18986篇
  1984年   15451篇
  1983年   13524篇
  1982年   10182篇
  1981年   9111篇
  1980年   8459篇
  1979年   14290篇
  1978年   11262篇
  1977年   10124篇
  1976年   9618篇
  1975年   10728篇
  1974年   11418篇
  1973年   11282篇
  1972年   10314篇
  1971年   9215篇
  1970年   8060篇
  1969年   7858篇
排序方式: 共有10000条查询结果,搜索用时 46 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.
Reconstruction of bony structures of the face is always a problem as big as the defect and the function that must be replaced. Everything from simple grafts to sophisticated distant bone flaps has been used. Based on the studies of Cutting et al., Psillakis et al., and Casanova et al., we have developed the full-thickness galeoparietal bone flap, initially for mandibular reconstruction, but of great use for all maxillofacial reconstructions. From July of 1987 to December of 1988, 14 patients have been operated on. The experience with this flap is shown in four patients as follows: primary reconstruction of a mandible as a result of ameloblastoma, secondary reconstruction of a mandible with associated old fractures and malalignment of segments, bilateral malar reconstruction in a patient with Treacher Collins syndrome, and severe sequelae of an already treated Romberg case. Small variations could be made to best accommodate the technique used to the defect we were treating. Some technical details, the experience, the results, and possible sequelae or complications are also discussed.  相似文献   
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.
The Saccharomyces cerevisiae SSU1 gene was isolated based on its ability to complement a mutation causing sensitivity to sulfite, a methionine intermediate. SSU1 encodes a deduced protein of 458 amino acids containing 9 or 10 membrane-spanning domains but has no significant similarity to other proteins in public databases. An Ssu1p-GEP fusion protein was localized to the plasma membrane. Multicopy suppression analysis, undertaken to explore relationships among genes previously implicated in sulfite metabolism, suggests a regulatory pathway in which SSU1 acts downstream of FZF1 and SSU3, which in turn act downstream of GRR1.  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