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   6405篇
  免费   0篇
电工技术   2篇
化学工业   29篇
能源动力   2篇
轻工业   5篇
石油天然气   4篇
无线电   3篇
一般工业技术   16篇
冶金工业   6336篇
自动化技术   8篇
  2024年   2篇
  2019年   1篇
  2017年   1篇
  2011年   1篇
  2010年   2篇
  2009年   1篇
  2008年   1篇
  2007年   4篇
  2006年   2篇
  2005年   4篇
  2004年   7篇
  2003年   5篇
  2002年   1篇
  2001年   2篇
  1999年   179篇
  1998年   2022篇
  1997年   1131篇
  1996年   726篇
  1995年   370篇
  1994年   327篇
  1993年   386篇
  1992年   41篇
  1991年   93篇
  1990年   68篇
  1989年   77篇
  1988年   76篇
  1987年   84篇
  1986年   74篇
  1985年   69篇
  1984年   3篇
  1983年   12篇
  1982年   34篇
  1981年   44篇
  1980年   38篇
  1979年   2篇
  1978年   17篇
  1977年   159篇
  1976年   317篇
  1975年   13篇
  1966年   1篇
  1965年   1篇
  1955年   7篇
排序方式: 共有6405条查询结果,搜索用时 0 毫秒
81.
The purpose of this study was to assess the safety and efficacy of percutaneous transluminal cerebral balloon angioplasty (PTCBA) of extra- and intra-cranial arteries by investigating procedural outcome. Eighty haemodynamically significant extra- and intra-cranial lesions (% diameter stenosis > 70) in 74 clinically symptomatic patients were treated by elective and initial PTCBA between March 1991 and February 1996 and thereafter followed. Death, stroke, surgery, or repeated angioplasty of restenosis or new lesions were regarded as cerebral events after the initial PTCBA. The procedural and clinical success rates were 81 % (65 of 80) and 81 % (60 of 74), respectively. Progressively ischaemic symptoms disappeared completely after clinically successful dilatation. Angiographic restenosis rate at 3 months was 22 %(14 of 65). By life-table method, the death/stroke risk was 16 %, and any cerebral event risk was 49 % at 2 years following PTCBA, respectively. The most common of first cerebral events presented was repeated angioplasty of restenosis. In conclusion, PTCBA has great efficacy in decreasing recurrent neurological symptoms and produces a favourable short-term outcome, whereas restenosis limits long-term benefit.  相似文献   
82.
83.
84.
Low frequency impedance measurements of pure egg lecithin (phosphatidylcholine) bilayers have revealed the presence of four layers which can be attributed to the acyl chain, carbonyl, glycerol bridge and phosphatidylcholine regions of the lecithin molecule. Measurements on bilayers formed in the presence of unoxidised-cholesterol revealed that cholesterol molecules were located in the hydrocarbon region of the bilayer with its hydroxyl groups aligned with the carbonyl region of the lecithin molecules. Measurements of oxidised-cholesterol lecithin bilayers revealed that these molecules protruded less into the hydrocarbon region and their polar hydroxyl group aligned with the glycerol bridge region of the lecithin molecule.  相似文献   
85.
86.
87.
88.
OBJECTIVE: To review the results of surgical management of heterotopic ossification about the elbow in burned patients. DESIGN: Retrospective analysis with long-term patient follow-up. MATERIALS AND METHODS: Eleven patients with 16 elbows requiring surgery were admitted between January 1, 1982 and December 31, 1993. A posterior approach to the elbow with release of the encased ulnar nerve +/- anterior transposition and transolecranon osteotomy to access extensive bone formation in the olecranon fossa was employed. Eight patients (11 elbows) were available for long-term follow-up conducted at mean 50 +/- 13 months after surgery. Long-term follow-up consisted of measurement of range of elbow motion, as well as clinical assessment of ulnar nerve function. MAIN RESULTS: For the 11 elbows examined postoperatively, the mean range of motion preoperatively in flexion-extension was 11 degrees +/- 5 degrees compared to 89 degrees +/- 12 degrees postoperatively (p < 0.001). Three patients with poor long-term results had ankylosis of the joint preoperatively. Of four patients with ulnar nerve paresis preoperatively, none had ulnar nerve dysfunction at follow-up. Of 16 elbows operated on, four (25%) had postoperative complications. Two suffered soft-tissue breakdown with hardware exposure requiring abdominal flap closure, one early failure of olecranon fixation, and one late infected hardware. CONCLUSIONS: Surgery for both limited range of motion as well as ulnar nerve compression is effective in cases of heterotopic ossification about the elbows of burned patients. Early operative intervention is indicated in progressive disease, particularly ulnar nerve palsy, if soft-tissue quality is adequate. Complications with 25% of elbows suggest that use of olecranon osteotomy for joint access may warrant review.  相似文献   
89.
90.
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