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   896097篇
  免费   83007篇
  国内免费   1049篇
  980153篇
  2018年   19506篇
  2017年   18188篇
  2016年   18075篇
  2015年   14254篇
  2014年   16532篇
  2013年   23699篇
  2012年   30643篇
  2011年   39950篇
  2010年   30407篇
  2009年   25774篇
  2008年   34136篇
  2007年   36865篇
  2006年   23717篇
  2005年   23446篇
  2004年   23408篇
  2003年   22782篇
  2002年   22073篇
  2001年   35042篇
  2000年   34442篇
  1999年   27626篇
  1998年   10230篇
  1997年   10314篇
  1996年   9893篇
  1995年   9083篇
  1994年   8759篇
  1993年   8793篇
  1992年   22372篇
  1991年   21993篇
  1990年   21396篇
  1989年   20851篇
  1988年   19110篇
  1987年   18353篇
  1986年   17106篇
  1985年   16967篇
  1984年   13967篇
  1983年   12211篇
  1982年   9251篇
  1981年   8368篇
  1980年   7769篇
  1979年   12946篇
  1978年   10211篇
  1977年   9202篇
  1976年   8808篇
  1975年   9833篇
  1974年   10488篇
  1973年   10358篇
  1972年   10021篇
  1971年   8983篇
  1970年   7393篇
  1969年   7255篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
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   
72.
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   
73.
74.
75.
76.
77.
78.
79.
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   
80.
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