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   2252篇
  免费   8篇
化学工业   56篇
金属工艺   4篇
机械仪表   3篇
建筑科学   1篇
矿业工程   1篇
能源动力   5篇
轻工业   24篇
无线电   9篇
一般工业技术   13篇
冶金工业   2133篇
自动化技术   11篇
  2022年   2篇
  2021年   6篇
  2020年   3篇
  2019年   4篇
  2018年   5篇
  2017年   5篇
  2016年   4篇
  2015年   2篇
  2014年   2篇
  2013年   9篇
  2012年   4篇
  2011年   17篇
  2010年   7篇
  2009年   3篇
  2008年   3篇
  2007年   2篇
  2006年   5篇
  2005年   2篇
  2004年   5篇
  2003年   6篇
  2002年   7篇
  2001年   2篇
  1999年   66篇
  1998年   690篇
  1997年   377篇
  1996年   253篇
  1995年   151篇
  1994年   115篇
  1993年   129篇
  1992年   15篇
  1991年   19篇
  1990年   24篇
  1989年   25篇
  1988年   33篇
  1987年   29篇
  1986年   17篇
  1985年   17篇
  1984年   2篇
  1983年   6篇
  1982年   10篇
  1981年   10篇
  1980年   15篇
  1979年   2篇
  1978年   5篇
  1977年   37篇
  1976年   97篇
  1975年   5篇
  1972年   1篇
  1971年   1篇
  1955年   2篇
排序方式: 共有2260条查询结果,搜索用时 0 毫秒
11.
12.
SR Babyar 《Canadian Metallurgical Quarterly》1996,76(3):226-38; discussion 239-47
BACKGROUND AND PURPOSE: Scapular excursion and the wrist speed were studied before and after instruction and practice designed to achieve symmetrical scapular movement. SUBJECTS: Subjects were 10 female and 6 male patients, aged 44 to 78 years (chi=60.3, SD=11.2), with diagnosed shoulder pathologies. METHODS: Subjects were videotaped performing a reaching task. Pain status was monitored. The subjects were instructed to make the scapular movement symmetrical. They then repeated the task, while being videotaped, to monitor the effect of instruction. RESULTS: Individuals with asymmetric upper-extremity starting positions had excessive vertical motion of the involved scapula, which they controlled after instruction. Peak wrist speed of the involved upper extremity was lower only after instruction. CONCLUSION AND DISCUSSION: Even in the absence of biomechanical factors or pain, excessive scapular vertical motion appears to occur in the involved upper extremities of individuals recovering from unilateral shoulder problems. Improved scapular control can follow simple verbal instruction and practice, with a slight decrement in wrist speed.  相似文献   
13.
A polysaccharide containing D-galactose, 2-deoxy-2-N-acetylamino-D-galactose and 3,6-dideoxy-3-N-(D-3-hydroxybutyryl)amino-D-galactose, probably corresponding to the lipopolysaccharide side chain, was obtained from an aqueous phenol extract of isolated cell walls from Acinetobacter baumannii strain O2. By means of NMR studies and chemical degradations, the repeating unit of the polymer was identified as a branched hexasaccharide of the structure shown, where Fuc3N represents 3-amino-3,6-dideoxygalactose and R represents D-3-hydroxybutyryl. Serological tests indicated that the polymer corresponded to the O2 antigen.  相似文献   
14.
There is little information on the possible value of screening children who are liable to haemoglobinopathies as part of pre-operative assessment for dental treatment under general anaesthesia. The present retrospective investigation examined, first, the number of patients having low haemoglobin levels among 1000 patients who had undergone haematological investigation prior to general anaesthesia in a dental outpatient unit, and, secondly, the subsequent clinical management of these patients. Haemoglobin levels of 10.0 g/dl or less were found in 31 children: 13 Asian, 7 Afro-Caribbean, 5 Mediterranean, 3 Arabic, 1 white Caucasian and 2 Oriental children. In addition, 17 patients had sickle-cell trait and 2 had beta-thalassaemia trait, but there was no relationship between the presence of haemoglobinopathy and low levels of haemoglobin. The planned general anaesthesia was undertaken for 22 of the 31 children who had low levels of haemoglobin and for the 19 children with haemoglobinopathy. Only 6 children ultimately did not undergo general anaesthesia, all failing to return. It is concluded that pre-anaesthetic haematological assessment of children needing minor dental surgery is rarely of any significant clinical value.  相似文献   
15.
AIM: To assess the efficacy of cisapride in reducing ileus persisting to the tenth postoperative day after neonatal abdominal surgery. METHODS: A prospective, randomised, double blind trial comparing rectal cisapride (1.4-2.3 mg/kg/day) with placebo over seven days was undertaken in 33 neonates. RESULTS: Seven of 12 (58%) patients receiving placebo and eight of 11 (73%) receiving cisapride achieved a first sustained feed during treatment. Of those receiving cisapride, the first sustained feed occurred at 2.3 days (SEM 0.6) compared with 4.7 days (SEM 0.8) with placebo. By the seventh day the mean daily net enteral balance was 69 (SEM 18) ml/kg in the cisapride subgroup and 17 (SEM 8) ml/kg for those receiving placebo. Stool was passed on 6.3 (SEM 0.4) treatment days in the cisapride subgroup compared with 4.1 (SEM 1.0) treatment days in the placebo subgroup. CONCLUSION: Cisapride is effective in neonates with a prolonged ileus after abdominal surgery.  相似文献   
16.
Ionomeric composites based on sepiolite and hydrogenated poly(styrene butadiene) block copolymer were obtained and characterized from a microstructural and electrical point of view. Before blending, because of the high silanol group concentration in the sepiolite, the latter could be organophilized with suitable coupling agents. The resulting materials were easily processed into thin films or membranes 0.2–0.4 mm thick, their conductivity in some cases approaching 10?1 S/cm. Their suitability for film formation and good electrical properties indicate potential applications as electrolytes in polymer fuel cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3512–3519, 2002  相似文献   
17.
18.
19.
Shock increases mortality from brain injuries, but the mechanism is poorly understood. We hypothesized that brain injury followed by shock and resuscitation leads to a secondary reperfusion injury mediated in part by polymorphonuclear leukocytes (PMNs). To validate this hypothesis, we studied cerebral perfusion pressure (CPP), intracranial pressure (ICP), cerebral blood flow (CBF), cortical water content (CWC), and hemodynamic variables in a porcine model of focal cryogenic brain injury and hemorrhagic shock. Cerebral PMN accumulation (CPMN) in the injured and uninjured hemispheres was determined histologically from the total PMNs in five high-power fields (400x). Twenty-nine mature swine were randomized to four groups. Group 1, the control group, was instrumented only. Group 2 animals had a brain injury alone and were studied for 24 hours. Group 3 animals had a brain injury and hemorrhagic shock. Group 4 animals had hemorrhagic shock alone. Brain injury followed by shock caused a significantly greater ICP and a significantly lower CBF than brain injury or shock alone. There was no significant difference in CPP between groups after resuscitation. The CWC of the lesioned area was similar in both brain-injured groups but was significantly increased when compared with the controls and the shock-only group. The CWC of the nonlesioned hemisphere was higher in group 3 than in group 2. The CPMN in both hemispheres in group 3 was significantly greater than in either group 2 or group 4. There was a significant positive correlation between CPMN and both ICP and CWC, and a significant negative correlation between CPMN and CBF. These data suggest an association between CPMN accumulation and secondary brain injury.  相似文献   
20.
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