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   1749篇
  免费   3篇
电工技术   1篇
化学工业   12篇
金属工艺   1篇
机械仪表   1篇
轻工业   1篇
无线电   5篇
一般工业技术   4篇
冶金工业   1724篇
原子能技术   1篇
自动化技术   2篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2016年   2篇
  2007年   1篇
  2005年   2篇
  2004年   1篇
  2003年   2篇
  1999年   56篇
  1998年   573篇
  1997年   295篇
  1996年   199篇
  1995年   83篇
  1994年   81篇
  1993年   98篇
  1992年   12篇
  1991年   31篇
  1990年   22篇
  1989年   22篇
  1988年   18篇
  1987年   23篇
  1986年   21篇
  1985年   26篇
  1984年   1篇
  1983年   5篇
  1982年   5篇
  1981年   9篇
  1980年   19篇
  1979年   1篇
  1978年   5篇
  1977年   39篇
  1976年   88篇
  1975年   4篇
  1962年   1篇
  1955年   1篇
排序方式: 共有1752条查询结果,搜索用时 811 毫秒
991.
The aim of this paper was to review the world's literature regarding port site recurrences. A Medline search was performed for all port site recurrences published in the literature. These reports were analysed and port site recurrences studied to determine initial stage of cancers, time to recurrence and whether the port site was an isolated site of recurrence or part of widespread intra-abdominal disease. The possible aetiologies were similarly reviewed and several recent basic science reports assessed. To date, 93 port site recurrences have been published. These have occurred with colorectal cancers as well as ovarian, gastric, pancreatic and other malignancies. Often, these recurrences are isolated and most standard means of prevention of cell dissemination may not prevent their occurrence. Possible mechanisms include aerosolisation of tumour cells, exfoliation, and changes in immune function. Port site recurrences continue to be reported. Their aetiology is unclear but the occurrence is of concern and requires continued scrutiny for laparoscopic oncologic surgery.  相似文献   
992.
PURPOSE: To study the intraocular pharmacokinetics of intravenously administered ciprofloxacin following eye trauma. METHODS: Twenty-three New Zealand albino rabbits and 12 Yorkshire pigs each received a surgically induced scleral injury to the right eye. Following repair, each rabbit received a single 30-mg intravenous infusion of ciprofloxacin. Each pig received either two 200-mg doses or two 400-mg doses of intravenous ciprofloxacin given 12 hours apart. Vitreous and serum samples were harvested at 0.5, 1, 4, 6, and 12 hours after antibiotic administration in rabbits and 1 hour after the second dose in pigs. Bioassays for ciprofloxacin were performed on each sample, and results were statistically compared by t test. The untraumatized left eye in each animal served as a control. RESULTS: The mean vitreous concentration of ciprofloxacin in traumatized rabbit eyes was 0.37 microgram/ml. This level was sustained above levels in control eyes (0.18 microgram/ml) for at least 4 hours following antibiotic administration. In control eyes, intravitreal levels peaked at 1 hour. Mean vitreous concentrations +/- SD in traumatized pig eyes were 0.091 +/- 0.017 microgram/ml in swine that had received 200-mg doses of ciprofloxacin vs 0.312 +/- 0.153 microgram/ml in swine that had received 400-mg doses (P = .02). Mean vitreous concentrations of ciprofloxacin in control eyes were not affected by increasing dosage. CONCLUSION: In both animal models, experimental surgical trauma increased intravitreal ciprofloxacin delivery. In addition, systemically administered ciprofloxacin achieved intravitreous levels exceeding minimum inhibitory concentrations for common ocular pathogens, suggesting a role for ciprofloxacin in the prophylaxis of posttraumatic endophthalmitis.  相似文献   
993.
994.
995.
The influence of posture and age on urinary protein excretion was studied in 120 normal men volunteers. The supine excretion rate was less than 140 mug/min in all but two people (median value 38 mug/min) and tended to increase with age. The excretion rate decreased on quiet standing in 80% of people, which corresponded to a fall in creatinine-clearance. In the remaining 20% protein excretion increased on standing but generally remained within normal limits and was dissociated from changes in creatinine clearances. This increase was more prevalent in younger people and may represent a phenomenon analogous to orthostatic proteinuria, differing only quantitatively.  相似文献   
996.
A battery of subjective and electrophysiologic auditory and vestibular tests were administered to 22 patients with neurologically confirmed brain-stem lesions to investigate the interrelationships between the test results. Acoustic-reflex and simultaneous midplane binaural loudness-balance abnormalities were related to N2 and N3 abnormalities on the brain-stem evoked-response measures. Unilateral abnormalities in low-redundancy speech tests, prolonged auditory reaction times, and reduced loudness growth on the alternate binaural loudness-balance test were related to ipsilateral N4 abnormalities or contralateral N5 abnormalities on the brain-stem evoked-response measures.  相似文献   
997.
998.
A paper clip applied to the tails of rats induced gnawing and eating, which decreased in latency and increased in duration with experience. With sustained pressure to the tail, rats learned a new habit in order to gain access to wood chips on which to gnaw. That these are also properties of behavior elicited by electrical brain stimulation suggests that both manipulations may act through the same mechanism. These results support the hypothesis that a nonspecific arousing stimulus can be a sufficient condition for establishing learned habits.  相似文献   
999.
The materials of clinical observations of 103 patients with pseudarthrosis and unhealing crural fractures, in whom 104 operations of compression-distraction osteosynthesis were accomplished, are analysed. The results of the treatment in various groups of patients are described.  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