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   762850篇
  免费   90045篇
  国内免费   348篇
  2018年   6719篇
  2016年   8996篇
  2015年   12303篇
  2014年   14359篇
  2013年   20423篇
  2012年   22846篇
  2011年   23560篇
  2010年   16058篇
  2009年   14954篇
  2008年   21126篇
  2007年   21970篇
  2006年   20508篇
  2005年   19743篇
  2004年   19425篇
  2003年   18826篇
  2002年   18376篇
  2001年   32679篇
  2000年   32823篇
  1999年   26132篇
  1998年   9557篇
  1997年   10178篇
  1996年   9553篇
  1995年   8985篇
  1994年   8824篇
  1993年   8987篇
  1992年   22293篇
  1991年   21994篇
  1990年   21260篇
  1989年   20793篇
  1988年   19394篇
  1987年   18770篇
  1986年   17502篇
  1985年   17476篇
  1984年   14689篇
  1983年   12647篇
  1982年   9818篇
  1981年   8819篇
  1980年   8509篇
  1979年   14017篇
  1978年   11162篇
  1977年   10244篇
  1976年   9782篇
  1975年   10623篇
  1974年   11487篇
  1973年   11294篇
  1972年   10417篇
  1971年   9461篇
  1970年   8215篇
  1969年   8016篇
  1968年   7507篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
81.
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   
82.
83.
84.
85.
86.
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   
87.
88.
89.
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   
90.
Expression of the glycoprotein clusterin is markedly increased following tissue injury. One function of clusterin is to promote cell interactions which are perturbed in these pathologic settings. Clusterin causes cell aggregation and adhesion in vitro yet the molecular mechanism for this effect is not known. In order to identify the active site(s) of clusterin, 34 peptides, each 15 amino acid residues in length, were synthesized from hydrophilic regions of human clusterin. When studied individually, none of the peptides caused aggregation of LLC-PK1 cells, a porcine renal epithelial cell line. However, two out of the 34 peptides inhibited clusterin-induced cell aggregation in a dose-dependent manner. Scrambled versions of these two 'active' peptides did not inhibit cell aggregation. Seven peptides promoted cell adhesion. In conclusion, these findings provide evidence for novel amino acid sequences mediating clusterin-induced renal cell interactions.  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