全文获取类型
收费全文 | 2025篇 |
免费 | 18篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 155篇 |
金属工艺 | 21篇 |
机械仪表 | 16篇 |
建筑科学 | 44篇 |
矿业工程 | 3篇 |
能源动力 | 11篇 |
轻工业 | 74篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 176篇 |
一般工业技术 | 223篇 |
冶金工业 | 1169篇 |
原子能技术 | 7篇 |
自动化技术 | 124篇 |
出版年
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 29篇 |
2013年 | 42篇 |
2012年 | 24篇 |
2011年 | 38篇 |
2010年 | 36篇 |
2009年 | 40篇 |
2008年 | 45篇 |
2007年 | 43篇 |
2006年 | 32篇 |
2005年 | 31篇 |
2004年 | 41篇 |
2003年 | 21篇 |
2002年 | 21篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 62篇 |
1998年 | 377篇 |
1997年 | 213篇 |
1996年 | 123篇 |
1995年 | 96篇 |
1994年 | 55篇 |
1993年 | 87篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 30篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 27篇 |
1976年 | 82篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1971年 | 6篇 |
1968年 | 7篇 |
排序方式: 共有2043条查询结果,搜索用时 15 毫秒
151.
152.
Osteopetrosis or Albers-Schonberg disease is a rare hereditary disorder of osteoclast function in which resorption of bone is diminished, resulting in abnormally dense bones. The condition is known to occur in at least four recognizable clinical patterns, each of which is variable. The optimal treatment of fractures and of bone deformity in these patients has not previously been made clear. To determine appropriate orthopedic management of the condition, we conducted a survey of the membership of the Pediatric Orthopedic Society of North America. The combined experience of 57 surgeons who treated 79 patients with osteopetrosis was compiled. Four femoral neck fractures treated by closed reduction and internal fixation had a satisfactory result, but three treated nonoperatively developed varus and required osteotomy. A total of 20 hips was treated for coxa vara by various means, none of which was free of complications. Valgus osteotomy, when used as the primary treatment for coxa vara, was the most consistently satisfactory procedure, whereas in situ pinning failed in two of three hips. Fourteen subtrochanteric fractures and 31 other fractures of the femur were treated. Good results were reported with traction or casting or both in the majority of those fractures. Twenty-nine tibia fractures were treated successfully, the majority by nonoperative means. Upper extremity fractures healed well with closed reduction and casting. Vertebral fractures, spondylolysis, and back pain were most frequently treated without surgery. 相似文献
153.
Measurements of relaxation times for passivation, by means of a.c. impedance measurements, have been made and a correlation with susceptibility to stress corrosion cracking obtained, for low carbon steels in carbonate/bicarbonate solutions at 70°C. 相似文献
154.
155.
Paul Kay Alona Armstrong Adrian McDonald Daniel Parsons Jim Best Jeff Peakall rew Walker Miles Foulger Sarah Gledhill & Martin Tillotson 《Water and Environment Journal》2009,23(1):52-62
Residuum lodges comprise small dams constructed on feeder streams immediately before they enter a reservoir, behind which ponds form, where sediment is deposited. Despite their construction on many impoundment reservoirs (IRE) and catchwaters, little research has previously investigated their efficacy at removing sediments from feeder streams. The current pilot study has, therefore, been carried out at an IRE supplying Halifax, West Yorkshire, UK, where a residuum lodge was recently cleaned out. Sediment concentrations reaching the reservoir were reduced by up to 42% although no certain impacts were noted on the other water quality variables that were measured. Moreover, it was found that the clearance operation did not result in the release of excessive quantities of sediment into the reservoir. It was estimated that the cleared residuum lodge would take 12 years to refill. A survey of other residuum lodges in the Yorkshire region showed there to be considerable differences in their remaining capacities. 相似文献
156.
A statistical algorithm has been developed to compensate for the fixed-pattern noise associated with spatial nonuniformity and temporal drift in the response of focal-plane array infrared imaging systems. The algorithm uses initial scene data to generate initial estimates of the gain, the offset, and the variance of the additive electronic noise of each detector element. The algorithm then updates these parameters by use of subsequent frames and uses the updated parameters to restore the true image by use of a least-mean-square error finite-impulse-response filter. The algorithm is applied to infrared data, and the restored images compare favorably with those restored by use of a multiple-point calibration technique. 相似文献
157.
158.
159.
EL Code CL Crespi BW Penman FJ Gonzalez TK Chang DJ Waxman 《Canadian Metallurgical Quarterly》1997,25(8):985-993
In situ hybridization was combined with serotonin (5-hydroxytryptamine, 5-HT) or tyrosine hydroxylase immunocytochemistry and with Fluoro-Gold retrograde labeling of bulbo-spinal pathways in order to investigate the expression of GAP-43 mRNA in monoamine cell groups of the adult rat brain stem. Consistent with previous reports, GAP-43 mRNA was observed in serotonin and dopamine cell groups in the pons. In addition, GAP-43 expressing cells were observed in all the major monoamine cell groups in the medulla. Thus the B1, B2 and B3 serotonin cell groups all showed high GAP-43 expression in all contained many GAP-43 expressing serotonin cells with spinal cord projections. The A1, A2, A5 and A6 noradrenaline cell groups also showed high GAP-43 expression, although cells with spinal cord projections were largely restricted to the A5 group and A6 subcoeruleus region. In all areas, GAP-43 expressing cells with spinal cord projections were also observed which were not serotonergic or noradrenergic. 相似文献
160.
Significant cleavage by hammerhead ribozymes requires activation by divalent metal ions. Several models have been proposed to account for the influence of metal ions on hammerhead activity. A number of recent papers have presented data that have been interpreted as supporting a one-metal-hydroxide-ion mechanism. In addition, a solvent deuterium isotope effect has been taken as evidence against a proton transfer in the rate-limiting step of the cleavage reaction. We propose that these data are more easily explained by a two-metal-ion mechanism that does not involve a metal hydroxide, but does involve a proton transfer in the rate-limiting step. 相似文献