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   926篇
  免费   2篇
  国内免费   1篇
化学工业   8篇
金属工艺   6篇
机械仪表   1篇
建筑科学   1篇
轻工业   6篇
水利工程   1篇
石油天然气   2篇
无线电   6篇
一般工业技术   15篇
冶金工业   871篇
原子能技术   4篇
自动化技术   8篇
  2023年   1篇
  2021年   2篇
  2018年   1篇
  2016年   1篇
  2015年   1篇
  2014年   1篇
  2013年   2篇
  2012年   1篇
  2011年   4篇
  2010年   5篇
  2009年   4篇
  2008年   6篇
  2007年   3篇
  2006年   5篇
  2005年   4篇
  2003年   5篇
  2002年   2篇
  2001年   2篇
  2000年   3篇
  1999年   32篇
  1998年   262篇
  1997年   162篇
  1996年   101篇
  1995年   45篇
  1994年   47篇
  1993年   60篇
  1992年   4篇
  1991年   7篇
  1990年   1篇
  1989年   5篇
  1988年   7篇
  1987年   4篇
  1986年   7篇
  1985年   11篇
  1982年   3篇
  1981年   3篇
  1980年   13篇
  1978年   3篇
  1977年   26篇
  1976年   65篇
  1959年   1篇
  1955年   1篇
  1939年   2篇
  1930年   1篇
  1929年   1篇
  1923年   2篇
排序方式: 共有929条查询结果,搜索用时 906 毫秒
181.
During a 12-week intervention, opioid dependent participants (N = 120) maintained on thrice-a-week (M, W, F) buprenorphine plus therapist and computer-based counseling were randomized to receive: (a) medication contingencies (MC = thrice weekly dosing schedule vs. daily attendance and single-day 50% dose reduction imposed upon submission of an opioid and/or cocaine positive urine sample); (b) voucher contingency (VC = escalating schedule for opioid and/or cocaine negative samples with reset for drug-positive samples); or (c) standard care (SC), with no programmed consequences for urinalysis results. VC resulted in better 12-week retention (85%) compared to MC (58%; p = 0.009), but neither differed from SC (76% retained). After adjusting for baseline differences in employment, and compared to SC, the MC group achieved 1.5 more continuous weeks of combined opioid/cocaine abstinence (p = 0.030), while the VC group had 2 more total weeks of abstinence (p = 0.048). Drug use results suggest that both the interventions were efficacious, with effects primarily in opioid rather than cocaine test results. Findings should be interpreted in light of the greater attrition associated with medication-based contingencies versus the greater monetary costs of voucher-based contingencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
182.
Adequate exposure of the mitral valve can be difficult to obtain through a median sternotomy. A variety of techniques have been described to facilitate exposure in this situation. This report describes the use of trans-aortic technique which allows easy and accurate division of the mitral subvalvar apparatus. The mitral valve can then be approached through a left atriotomy, everted and the excision completed.  相似文献   
183.
184.
Photorelaxation elicited by ultraviolet light (366 nm) was investigated on isolated rat thoracic aorta and trachealis. Rat tracheal smooth muscle but not aorta did not show UV-induced photorelaxation. Both streptozotocin, NO-carrying molecule and N omega-nitro-L-arginine, NO2-carrying molecule significantly enhanced photorelaxation, concentration-dependently, in rat trachealis and aorta. Methylene blue (10 microM) inhibited the potentiation action of streptozotocin and N omega-nitro-L-arginine in both tissues. Superoxide dismutase (300 U/ml) enhanced streptozotocin- and N omega-nitro-L-arginine-potentiated photorelaxation in rat trachealis, while pyrogallol (0.1 mM), a potent O2- generating agent, inhibited streptozotocin-potentiated photorelaxation in trachealis. Streptozotocin was much more effective than N omega-nitro-L-Arginine in potentiating of photorelaxation elicited by UV light in both tissues. From these findings, we conclude that streptozotocin and N omega-nitro-L-arginine produce EDRF like labile substance(s) by UV irradiation.  相似文献   
185.
186.
BACKGROUND: We developed a method of closed-chest cardiopulmonary bypass to arrest and protect the heart with cardioplegic solution. This method was used in 54 dogs and the results were retrospectively analyzed. METHODS: Bypass cannulas were placed in the right femoral vessels. A balloon occlusion catheter was passed via the left femoral artery and positioned in the ascending aorta. A pulmonary artery vent was placed via the jugular vein. In 17 of the dogs retrograde cardioplegia was provided with a percutaneous coronary sinus catheter. RESULTS: Cardiopulmonary bypass time was 111 +/- 27 minutes (mean +/- standard deviation) and cardiac arrest time was 66 +/- 21 minutes. Preoperative cardiac outputs were 2.9 +/- 0.70 L/min and postoperative outputs were 2.9 +/- 0.65 L/min (p = not significant). Twenty-one-French and 23F femoral arterial cannulas that allowed coaxial placement of the ascending aortic balloon catheter were tested in 3 male calves. Line pressures were higher, but not clinically limiting, with the balloon catheter placed coaxially. CONCLUSIONS: Adequate cardiopulmonary bypass and cardioplegia can be achieved in the dog without opening the chest, facilitating less invasive cardiac operations. A human clinical trial is in progress.  相似文献   
187.
The Mitek Mini GII anchor is showcased as a relatively new device that provides a rapid, simple method for bony reattachment; here, it is introduced for the fixation of flexor or extensor tendons at their insertion. Transosseous tunnels with limited visualization, pull-out sutures, and external devices can now be avoided if desired. Applications for soft-tissue fixation should in no way be limited to the small bones of the hand. Expense of the apparatus remains its only major drawback.  相似文献   
188.
189.
190.
The gait patterns of eighteen patients who had had a single infarct due to obstruction of the middle cerebral artery were evaluated within one week after the patients had resumed independent walking and before a gait rehabilitation program had been initiated. Gait was analyzed with use of motion analysis, force-plate recordings, and dynamic surface electromyographic studies of the muscles of the lower extremities. The patterns of motion of the lower extremity on the hemiplegic side had a stronger association with the clinical severity of muscle weakness than with the degree of spasticity, balance control, or phasic muscle activity. There was a delay in the initiation of flexion of the hip during the pre-swing phase, and flexion of the hip and knee as well as dorsiflexion of the ankle progressed only slightly during the swing phase. During the stance phase, there was decreased extension of the hip that was related to decreased muscle effort and a coupling between flexion of the knee and dorsiflexion of the ankle. The abnormal patterns of motion altered the velocity, the length of the stride, the cadence, and all phases of the gait cycle. The duration of the pre-swing phase was prolonged for the patients who had the slowest gait velocities. There also were abnormal movements of the upper extremity, the trunk, the pelvis, and the lower extremity on the unaffected side in an effort to compensate for the decreased velocity on the hemiplegic side. As velocity improved, these abnormal movements decreased. Therefore, the goal of therapy should be to improve muscle strength and coordination on the hemiplegic side, especially during the pre-swing phase.  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