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   325715篇
  免费   37937篇
  国内免费   716篇
  2018年   3111篇
  2016年   4088篇
  2015年   5558篇
  2014年   6553篇
  2013年   9213篇
  2012年   10314篇
  2011年   10364篇
  2010年   6968篇
  2009年   6250篇
  2008年   8934篇
  2007年   9329篇
  2006年   8701篇
  2005年   8347篇
  2004年   8393篇
  2003年   8100篇
  2002年   7963篇
  2001年   14424篇
  2000年   14414篇
  1999年   11602篇
  1998年   4099篇
  1997年   4217篇
  1996年   3878篇
  1995年   3867篇
  1994年   3882篇
  1993年   3745篇
  1992年   9872篇
  1991年   9449篇
  1990年   9258篇
  1989年   8969篇
  1988年   8374篇
  1987年   8007篇
  1986年   7226篇
  1985年   7335篇
  1984年   6050篇
  1983年   5310篇
  1982年   4174篇
  1981年   3690篇
  1980年   3512篇
  1979年   6094篇
  1978年   4544篇
  1977年   4269篇
  1976年   3962篇
  1975年   4294篇
  1974年   4651篇
  1973年   4709篇
  1972年   4352篇
  1971年   4065篇
  1970年   3435篇
  1969年   3333篇
  1968年   2961篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
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   
952.
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   
953.
954.
955.
956.
957.
958.
959.
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   
960.
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