全文获取类型
收费全文 | 749篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 5篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 3篇 |
轻工业 | 5篇 |
无线电 | 1篇 |
一般工业技术 | 6篇 |
冶金工业 | 717篇 |
自动化技术 | 11篇 |
出版年
2020年 | 1篇 |
2017年 | 1篇 |
2014年 | 1篇 |
2012年 | 4篇 |
2011年 | 1篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2005年 | 1篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 19篇 |
1998年 | 188篇 |
1997年 | 114篇 |
1996年 | 63篇 |
1995年 | 42篇 |
1994年 | 44篇 |
1993年 | 52篇 |
1992年 | 10篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 20篇 |
1976年 | 52篇 |
1972年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有751条查询结果,搜索用时 15 毫秒
91.
MK Strecker-McGraw ML Lorenz M Hendrickson SG Jolley WP Tunell 《Canadian Metallurgical Quarterly》1998,33(11):1623-1627
PURPOSE: There is a paucity of quantitative and reproducible follow-up data on childhood operations for gastroesophageal reflux disease (GERD). With the development of minimally invasive techniques for antireflux operations in children, there is a need to quantitatively determine immediate outcomes for such operations performed by laparotomy for comparison. METHODS: A retrospective review of 385 children (age range, 1 week to 15 years) who had a primary antireflux operation in a Children's or University Hospital performed by laparotomy between 1983 and 1997, and who also had an extended esophageal pH study performed within the first 12 postoperative weeks, was conducted. The operations performed included Nissen fundoplication (n = 135), Thal fundoplication (n = 195), and Boerema gastropexy (n = 55). An immediate postoperative failure of the operation to control GERD was defined as an abnormal esophageal pH score persisting up to the twelfth postoperative week. RESULTS: Eleven patients (2.9%) were classified as having an immediate postoperative failure of their operation to control GERD. An additional three patients had an abnormal esophageal pH score 2 weeks postoperatively, which subsequently reverted to a normal esophageal pH score by 12 weeks. The immediate postoperative failure rate was 1.5% (2 of 135) for the Nissen fundoplication, 1.5% (3 of 195) for the Thal fundoplication, and 10.9% (6 of 55) for the Boerema gastropexy. A higher failure rate (five patients, 36%) was seen for the first 14 patients who underwent a Boerema gastropexy during the learning curve period for this operation before 1985, and by excluding these patients the failure rate was 2.4% (1 of 41) after 1985. There was no significantly increased probability of immediate postoperative failure in patients with central nervous system disorders, prematurity, repaired esophageal atresia, or gastric emptying abnormalities. Only 5 (36%) of the 14 children with persisting symptoms suggestive of GERD had immediate postoperative failure of their operation. CONCLUSIONS: Extended esophageal pH monitoring during the first 12 postoperative weeks is a helpful tool to assess the immediate outcome of antireflux operations in children because clinical symptoms alone may be unreliable. The immediate failure rate for an antireflux operation performed in children by laparotomy is very low and seems to be unaffected by comorbid factors. 相似文献
92.
93.
94.
R van der Weide KJ Zuiderveld WP Mali MA Viergever 《Canadian Metallurgical Quarterly》1998,17(5):831-841
Coil embolization is a safe treatment for cerebral aneurysms only if the width of the neck in relation to the fundus of the aneurysm is small. Therefore, accurate visualization of the aneurysmal neck is required both in the diagnostic process and during the intervention. Conventional digital subtraction angiography (DSA) is still the preferred modality for the examination of cerebrovascular abnormalities like aneurysms, but it often does not provide the required morphological characteristics due to the suboptimal selection of projection angles and resulting overprojections of surrounding vasculature. This paper presents a method for performing a computer-assisted calculation of the optimal projection angles for DSA by post-processing computed tomographic angiography (CTA) volume data using ray-casting techniques and a combination of image processing algorithms. By means of phantom studies, retrospective simulations of angiograms, and in vivo applications of calculated optimal viewing angles, it is demonstrated that the proposed method results in better angiographic projections of the neck of saccular aneurysms with small neck-fundus ratio than those acquired at standard angles prescribed by clinical protocols. 相似文献
95.
KP Braun RA de Graaf WP Vandertop RH Gooskens KA Tulleken K Nicolay 《Canadian Metallurgical Quarterly》1998,40(6):832-839
The severity and progression of ventricular enlargement, the occurrence of cerebral edema, and the localization of ischemic metabolic changes were investigated in a rat model of hydrocephalus, using in vivo 1H MR spectroscopic imaging (SI) and diffusion weighted MRI (DW MRI). Hydrocephalic rats were studied 1, 2, 4, and 8 weeks after injection of kaolin into the cisterna magna. Parametric images of the apparent diffusion coefficient (ADC) revealed a varying degree of ventriculomegaly in all rats, with different time courses of ventricular expansion. Extracellular white matter edema was observed during the early stages of hydrocephalus, most extensively in cases of progressive ventriculomegaly. In gray matter regions, ADC values were not changed, compared with controls. In case of fatal hydrocephalus, high lactate levels were observed throughout the whole brain. In all other rats, at all time points after kaolin injection, lactate was detected only in voxels containing cerebrospinal fluid. This suggests accumulation of lactate in the ventricles, and/or an ongoing periventricular production of lactate as a consequence of cerebral ischemia in experimental hydrocephalus. 相似文献
96.
97.
WP Goldman JD Baty VD Buckles S Sahrmann JC Morris 《Canadian Metallurgical Quarterly》1998,55(5):674-680
We evaluated the data of the National Collegiate Athletic Association Injury Surveillance System on collegiate wrestling with a focus on musculoskeletal injuries. Over 800,000 athlete-exposures during an 11-year period compose these data. Findings particular to wrestling and a comparison with other collegiate sports are included. Collegiate wrestling had a relatively high rate of injury at 9.6 injuries per 1000 athlete-exposures. It was second to spring football in total injury rate. Most injuries in this study were not serious, with 6.3% resulting in surgery and 37.6% resulting in a week or more off from wrestling. There was only one catastrophic, nonfatal injury. The knee, shoulder, and ankle were the most commonly injured regions, and injuries to them were often the more serious. Sprains, strains, and contusions were the most common injury types. Takedowns and sparring were the most common activities at the time of injury. Mechanism of injury was evaluated; rotation about a planted foot and contact with environmental objects were identified as areas needing further attention. Illegal action accounted for only 4.6% of injuries in competition. Competition had a significantly higher injury rate than practice, but the injury profiles of these two areas showed both to be equally important. The preseason and regular season had higher injury rates than the postseason, but, again, the injury profiles of these periods were similar. Injury percentages were similar among the 10 weight classes. 相似文献
98.
99.
WP Maksymowych C Gorodezky A Olivo C Alaez C Wong R Burgos-Vargas J Sanchez-Corona C Ramos-Remus AS Russell 《Canadian Metallurgical Quarterly》1997,24(5):904-907
OBJECTIVE: HLA class II encoded factors may influence the phenotype of ankylosing spondylitis (AS). These include HLA DRB1*07 for peripheral arthritis, and polymorphism of the HLA-linked LMP2 locus and HLA DRB1*08 for acute anterior uveitis (AAU). We studied the relationship between DRB1*08 and disease phenotype in additional populations of individuals with AS. METHODS: The patient population included 385 unrelated HLA-B27 positive individuals with AS. These included 204 Caucasians and 2 populations of Mexican Mestizo with AS: 106 with predominately adult onset disease from Guadalajara and 75 with predominately juvenile onset disease from Mexico City. The control population of 428 individuals included 210 random and 36 HLA-B27 positive unrelated Canadian Caucasians and 173 random and 9 HLA-B27 positive Mexican Mestizo from Mexico City. DRB1*08 typing was by sequence specific polymerase chain reaction. RESULTS: A significantly higher prevalence of DRB1*08 was observed in Mexican patients with juvenile onset disease (44.9%) and especially those with undifferentiated spondyloarthropathy (55.6%) compared to normal unrelated Mexican Mestizo (25.4%) (p < 0.01 for both) and in patients with undifferentiated spondyloarthropathy versus B27 controls (11.1%) (p = 0.03), although no significant differences were observed in within patient group comparisons based on phenotypic features of disease such as AAU and age at onset. No significant relationship between DRB1*08 and disease phenotype was evident in Caucasian individuals. CONCLUSION: Our data suggest DRB1*08 may influence the phenotype of spondyloarthritis in Mexican Mestizo, but do not support the view that DRB1*08 influences the development of AAU, as reported in a Japanese population. 相似文献
100.