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   762028篇
  免费   85074篇
  国内免费   335篇
  847437篇
  2018年   6759篇
  2016年   9179篇
  2015年   12201篇
  2014年   14371篇
  2013年   20619篇
  2012年   23138篇
  2011年   23605篇
  2010年   16052篇
  2009年   14956篇
  2008年   21506篇
  2007年   22078篇
  2006年   20942篇
  2005年   19912篇
  2004年   19837篇
  2003年   18966篇
  2002年   18519篇
  2001年   32037篇
  2000年   32129篇
  1999年   26168篇
  1998年   9527篇
  1997年   9935篇
  1996年   9457篇
  1995年   8692篇
  1994年   8687篇
  1993年   8642篇
  1992年   21974篇
  1991年   21436篇
  1990年   21144篇
  1989年   20823篇
  1988年   19478篇
  1987年   18624篇
  1986年   17302篇
  1985年   17303篇
  1984年   14294篇
  1983年   12525篇
  1982年   9631篇
  1981年   8580篇
  1980年   8295篇
  1979年   13876篇
  1978年   10886篇
  1977年   9840篇
  1976年   9515篇
  1975年   10287篇
  1974年   11214篇
  1973年   11002篇
  1972年   10140篇
  1971年   9135篇
  1970年   8047篇
  1969年   7740篇
  1968年   7225篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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.
69.
The frequency of cytokine-producing CD4-/CD8- mononuclear cells was assessed in patients of different age groups (29 infants, aged 1-5 years; 30 schoolchildren, aged 6-14 years, 26 adults, aged > 15 years) with acute Plasmodium falciparum malaria, from Gabon. Fifteen patients were followed up before antimalarial treatment (day 0), during parasite clearance (day 3) and after resolution of parasitemia (day 10). By using flow cytometry for intracellular detection of cytokines, a striking expansion of CD4-/CD8- cells producing the type 1 cytokines interleukin (IL)-2-/interferon (IFN)-gamma+, IL-2+/IFN-gamma+ and IL-2+/IFN-gamma- was observed in adults as compared with children. Type 2 cytokine expression (IL-4+/IFN-gamma-, IL-13+/IFN-gamma-) and type 0 cells (IL-4+/IFN-gamma+, IL-13+/IFN-gamma+) were not significantly different between the three age groups. Patients with severe malaria had a significantly increased frequency of type 2 cytokine-producing CD4-/CD8- cells. Drug-induced clearance of parasitemia was characterized by a decrease of IL-2+/IFN-gamma- and type 2 cytokine expressing CD4-/CD8- cells and by a gradual increase of IL-10+/IFN-gamma- expression. The type 1/type 2 dichotomy observed within the CD4-/CD8- cell population is likely to be of significance in the host response against P. falciparum malaria.  相似文献   
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