全文获取类型
收费全文 | 2254篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 8篇 |
金属工艺 | 1篇 |
矿业工程 | 1篇 |
轻工业 | 1篇 |
无线电 | 5篇 |
一般工业技术 | 1篇 |
冶金工业 | 2237篇 |
自动化技术 | 2篇 |
出版年
2023年 | 1篇 |
2011年 | 1篇 |
2006年 | 2篇 |
2003年 | 5篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 70篇 |
1998年 | 736篇 |
1997年 | 371篇 |
1996年 | 267篇 |
1995年 | 131篇 |
1994年 | 112篇 |
1993年 | 120篇 |
1992年 | 19篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1983年 | 3篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 67篇 |
1976年 | 160篇 |
1975年 | 3篇 |
1964年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有2256条查询结果,搜索用时 31 毫秒
11.
HE Montgomery P Clarkson CM Dollery K Prasad MA Losi H Hemingway D Statters M Jubb M Girvain A Varnava M World J Deanfield P Talmud JR McEwan WJ McKenna S Humphries 《Canadian Metallurgical Quarterly》1997,96(3):741-747
PURPOSE: To determine the radiologic characteristics of cystic dystrophy of the duodenal wall. MATERIALS AND METHODS: Ten patients with cystic dystrophy of the duodenal wall and chronic pancreatitis underwent ultrasonography (US) (n = 10), computed tomography (CT) (n = 10), endoscopic US (n = 5), and endoscopic retrograde cholangiopancreatography (ERCP) (n = 9). Cystic dystrophy of the duodenal wall was classified as either cystic or solid. The imaging findings were retrospectively analyzed and compared with findings at pancreatoduodenectomy (n = 10). RESULTS: The more frequent cystic type (n = 7) of cystic dystrophy of the duodenal wall was characterized by the presence of easily recognizable cystic lesions (diameter, more than 1 cm), located within the thickened wall of the second portion of the duodenum. The solid type (n = 3) of cystic dystrophy of the duodenal wall demonstrated fibrous thickening of the duodenal wall within which small cysts (diameter, less than 1 cm) were present. The intraduodenal cysts were usually elongated or bilobate with a thick wall. The thickening of the duodenal wall appeared as a solid layer between the duodenal lumen and the pancreas, hypoechoic at US, isoattenuating at unenhanced CT, and hypoattenuating in the early phase (after initiation of infusion of contrast material) and isoattenuating in the late phase (after completion of infusion) at contrast material-enhanced CT. Findings at retrospective analysis of CT and endoscopic US images were characteristic. CONCLUSION: Imaging modalities, notably CT and endoscopic US, helped establish the diagnosis of cystic dystrophy of the duodenal wall. 相似文献
12.
Pregnant Sprague-Dawley rats were administered primidone (PRM) by oral gavage on gestation days 8-17 in doses of 0.40, and 80 mg/kg. Although these doses of PRM did not produce significant differences in litter size, birth weight, mortality, date of attainment of developmental landmarks or measures of preweaning reflex and motor development, there were a number of significant differences that developed as the animals approached and entered adulthood. When tested as adults, the 80 mg/kg male rats showed a deficit in the performance of an eight-arm radial maze task. These same animals showed a significant reduction in open field activity when tested as adults. In addition, both male and female PRM-treated animals showed reduced body weights at different periods corresponding to onset of sexual maturation during development. These findings are consistent with the larger body of literature reporting on the neurobehavioral teratology of phenobarbital, including its ability to produce lesions in the hippocampus and endocrine dysfunction resulting in reproductive deficits. These results suggest that PRM produces its adverse effects as a result of its metabolism to phenobarbital, which in turn affects the limbic system. 相似文献
13.
C Sergi K Jundt S Seipp T Goeser L Theilmann G Otto HF Otto WJ Hofmann 《Canadian Metallurgical Quarterly》1998,29(6):861-871
BACKGROUND/AIMS: The aim of the study was to assess the impact factor of HCV and HGV in fulminant hepatic failure. METHODS: The 5'-untranslated regions of HCV RNA and HGV RNA and a segment of the core antigen sequence of HBV were amplified after extracting the nucleic acids from snap-frozen tissue aliquots from explanted livers of 26 consecutive patients undergoing orthotopic liver transplantation for fulminant hepatic failure preoperatively diagnosed as either autoimmune (n=2), HAV/HBV (n=8), toxic (n=4) or aetiologically unknown (n=12). RESULTS: HCV RNA was detected in five of 26 (19.2%) livers with fulminant hepatic failure. All five HCV RNA-positive livers belonged to the group of non-toxic, non-autoimmune liver failure (n=20), three of them were found in the group of liver failure with unknown aetiology (n=12) and two in the group of HBV-associated liver failure (n=7), making an HCV incidence of 25%, 25% and 28.6%, in the different groups, respectively. HGV RNA was detected in 10 of 17 (58.8%) explants and in all four groups of fulminant hepatic failure as defined preoperatively. HBV DNA was identified in six livers of 26 patients (23.1%) with fulminant hepatic failure. Neither HCV RNA nor HBV DNA was detected in the livers of patients with toxic or autoimmune fulminant hepatic failure. CONCLUSIONS: These results indicate that HBV and HCV, but not HGV, play an aetiologic role in fulminant hepatic failure. HCV-positive cases were concentrated either in the group of otherwise unexplained fulminant hepatic failure or in the group of HBV fulminant hepatic failure. HGV-positive cases, on the other hand, were found within all four preoperatively defined groups, indicating a role as cofactor rather than as single aetiologic agent. 相似文献
14.
15.
The non-sulphonylurea hypoglycaemic agent repaglinide is about one order of magnitude less potent, in terms of insulinotropic efficiency, than S3075, another meglitinide analogue. In the present study, the effects of these two drugs upon 86Rb outflow, 45Ca efflux and insulin release from prelabelled rat pancreatic islets were investigated in a perifusion system. At a concentration of 10 microM, which is sufficient to evoke a maximal secretory response in incubated islets, both agents inhibited 86Rb efflux from islets perifused in the absence of D-glucose, and stimulated both 45Ca efflux and insulin release from islets perifused in the presence of 6 mM D-glucose. The stimulation of 45Ca efflux from prelabelled islets was suppressed in the absence of extracellular Ca2+. The cationic and secretory response to repaglinide differed, however, from that evoked by S3075, in persisting for at least 20 min after removal of the drug from the perifusion medium, whilst the changes in 86Rb outflow, 45Ca efflux and insulin release caused by S3075 were rapidly reversible. These findings indicate that there is no parallel between the insulinotropic efficiency of distinct meglitinide analogues, and the reversibility of their functional effects. Since a comparable dissociation was recently documented in the case of hypoglycaemic sulphonylureas, the present observations reinforce the view that distinct molecular determinants may rule the relative insulinotropic potency of sulphonylureas and structurally related meglitinide analogues, on one hand, and the reversibility of their biological action, on the other hand. 相似文献
16.
17.
18.
19.
20.
Carotid and vertebral artery dissections typically occur in young adults after major trauma, although they can arise spontaneously or after trivial injury. Many patients with carotid dissections have minor symptoms such as a subject bruit or Horner's syndrome. Cephalic pain is also frequent and often inaugural in carotid dissection. However, extracranial dissection is a well recognised cause of ischaemic stroke. The diagnosis of dissection was based on angiographic findings. Noninvasive imaging also allows prompt and reliable diagnosis. Our goal was to demonstrate the spectrum of neuroradiologic (CT, MR and angiographic) findings in craniocervical arterial dissection and compare the diagnostic utility of CT, MR, MR angiography. Clinical data imaging studies, and outcome were reviewed and compared with the results in four patients with carotid artery dissection. 相似文献