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   360420篇
  免费   41100篇
  国内免费   166篇
  2018年   3358篇
  2017年   3167篇
  2016年   4714篇
  2015年   6709篇
  2014年   7780篇
  2013年   10968篇
  2012年   12412篇
  2011年   12549篇
  2010年   8431篇
  2009年   7436篇
  2008年   10888篇
  2007年   11305篇
  2006年   10525篇
  2005年   10276篇
  2004年   10331篇
  2003年   9977篇
  2002年   9862篇
  2001年   14826篇
  2000年   14778篇
  1999年   12017篇
  1998年   4610篇
  1997年   4584篇
  1996年   4341篇
  1995年   4194篇
  1994年   4163篇
  1993年   4040篇
  1992年   10201篇
  1991年   9728篇
  1990年   9515篇
  1989年   9232篇
  1988年   8640篇
  1987年   8259篇
  1986年   7474篇
  1985年   7656篇
  1984年   6385篇
  1983年   5584篇
  1982年   4537篇
  1981年   3978篇
  1980年   3789篇
  1979年   6314篇
  1978年   4785篇
  1977年   4490篇
  1976年   4160篇
  1975年   4472篇
  1974年   4847篇
  1973年   4932篇
  1972年   4510篇
  1971年   4193篇
  1970年   3549篇
  1969年   3447篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
991.
The position of the dorsum directly influences the apparent size of the nasal base: the higher the bridge, the smaller the nasal base seems. This powerful optical illusion provides the surgeon with an alternate strategy for creating harmony in the nose with a low, straight dorsum and a disproportionately large nasal base. Instead of reducing the lower nose, the surgeon can augment the upper nose (and make whatever nasal base changes are independently necessary). This alternate strategy limits the amount of nasal skeletal reduction necessary, thereby limiting the potential for postoperative change and soft-tissue distortion and directly increasing the surgeon's control over the result.  相似文献   
992.
A field isolate of Desulfovibrio desulfuricans was grown in defined medium in a two-stage continuous culture apparatus with different concentrations of phosphate in the feed medium. The first state (V1) was operated as a conventional chemostat (D = 0.045 h−1) that was limited in energy source (lactate) or phosphate. The second stage (V2) received effluent from V1 but no additional nutrients, and contained a healthy population of transiently starved or resting cells. An increase in the concentration of phosphate in the medium fed to V1 resulted in increased corrosion rates of carbon steel in both V1 and V2. Despite the more rapid corrosion observed in growing cultures relative to that in resting cultures, corrosion products that were isolated under strictly anaerobic conditions from the two culture modes had similar bulk compositions which varied with the phosphate content of the medium. Crystalline mackinawite (Fe9S8), vivianite [Fe3(PO4)2 · 8H2O], and goethite [FeO(OH)] were detected in amounts which varied with the culture conditions. Chemical analyses indicated that the S in the corrosion product was almost exclusively in the form of sulfides, while the P was present both as phosphate and as unidentified components, possibly reduced P species. Some differential localization of S and P was observed in intact corrosion products. Cells from lactate-limited, but not from phosphate-limited, cultures contained intracellular granules that were enriched in P and Fe. The results are discussed in terms of several proposed mechanisms of microbiologically influenced corrosion.  相似文献   
993.
994.
995.
996.
997.
998.
999.
The carpal tunnel syndrome can cause severe pain and disability, both of which are avoidable if the condition is diagnosed and treated early in its course. Two sets of circumstances—delay in the correct diagnosis and recurrence of symptoms after an apparently successful operation—may give rise to problems in these aspects of management and delay recovery.  相似文献   
1000.
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