全文获取类型
收费全文 | 577755篇 |
免费 | 5923篇 |
国内免费 | 1536篇 |
专业分类
电工技术 | 10389篇 |
综合类 | 390篇 |
化学工业 | 87657篇 |
金属工艺 | 27136篇 |
机械仪表 | 19874篇 |
建筑科学 | 11605篇 |
矿业工程 | 4939篇 |
能源动力 | 14287篇 |
轻工业 | 35677篇 |
水利工程 | 7255篇 |
石油天然气 | 16913篇 |
武器工业 | 36篇 |
无线电 | 62495篇 |
一般工业技术 | 126368篇 |
冶金工业 | 97983篇 |
原子能技术 | 16418篇 |
自动化技术 | 45792篇 |
出版年
2021年 | 5543篇 |
2020年 | 4275篇 |
2019年 | 5431篇 |
2018年 | 9773篇 |
2017年 | 9968篇 |
2016年 | 10637篇 |
2015年 | 6254篇 |
2014年 | 10575篇 |
2013年 | 26878篇 |
2012年 | 16203篇 |
2011年 | 21261篇 |
2010年 | 17067篇 |
2009年 | 19210篇 |
2008年 | 19652篇 |
2007年 | 19223篇 |
2006年 | 16717篇 |
2005年 | 14881篇 |
2004年 | 14302篇 |
2003年 | 14089篇 |
2002年 | 13389篇 |
2001年 | 13215篇 |
2000年 | 12597篇 |
1999年 | 12582篇 |
1998年 | 29747篇 |
1997年 | 21096篇 |
1996年 | 16108篇 |
1995年 | 12225篇 |
1994年 | 10904篇 |
1993年 | 11031篇 |
1992年 | 8365篇 |
1991年 | 8043篇 |
1990年 | 8128篇 |
1989年 | 7685篇 |
1988年 | 7365篇 |
1987年 | 6729篇 |
1986年 | 6520篇 |
1985年 | 7222篇 |
1984年 | 6781篇 |
1983年 | 6241篇 |
1982年 | 5788篇 |
1981年 | 5906篇 |
1980年 | 5646篇 |
1979年 | 5769篇 |
1978年 | 5878篇 |
1977年 | 6354篇 |
1976年 | 7791篇 |
1975年 | 5205篇 |
1974年 | 5116篇 |
1973年 | 5216篇 |
1972年 | 4546篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
981.
Effect of sliding speed on adhesive wear of binary Al-Si alloys 总被引:2,自引:0,他引:2
982.
F Chiarella E Santoro S Domenicucci A Maggioni C Vecchio 《Canadian Metallurgical Quarterly》1998,81(7):822-827
Left ventricular (LV) thrombosis can be found in patients with acute myocardial infarction (AMI). No wide multicenter trial on AMI has provided information about LV thrombosis until now. The protocol of the GISSI-3 study included the search for the presence of LV thrombosis in patients from 200 coronary care units that did not specifically focus on LV thrombosis. We examined the GISSI-3 database results related to 8,326 patients at low to medium risk for LV thrombi in which a predischarge echocardiogram (9 +/- 5 days) was available. LV thrombosis was found in 427 patients (5.1%): 292 of 2,544 patients (11.5%) with anterior AMI and in 135 of 5,782 patients (2.3%) with AMI in other sites (p <0.0001). The incidence of LV thrombosis was higher in patients with ejection fraction < or = 40% (151 of 1,432 [10.5%] vs 276 of 6,894 [4%]; p <0.0001) both in the total population and in the subgroup with anterior AMI (106 of 597 [17.8%] vs 186 of 1,947 [9.6%]; p <0.0001). Multivariate analysis showed that only the Killip class > I and early intravenous beta-blocker administration were independently associated with higher LV thrombosis risk in the subgroup of patients with anterior AMI (odds ratio 1.75, 95% confidence interval 1.28 to 2.39; odds ratio 1.32, 95% confidence interval 1.02 to 1.72, respectively). In patients with anterior AMI, oral beta-blocker therapy given or not given after early intravenous beta-blocker administration does not influence the occurrence of LV thrombosis. The rate of LV thrombosis was similar in patients treated or not treated with nitrates and lisinopril both in the total population and in patients with anterior and nonanterior AMI. In conclusion, in the GISSI-3 population at low to medium risk for LV thrombi, the highest rate of occurrence of LV thrombosis was found among patients with anterior AMI and an ejection fraction < 40%. Killip class > I and the early intravenous beta-blocker administration were the only variables independently associated with a higher predischarge incidence of LV thrombosis after anterior AMI. 相似文献
983.
984.
985.
986.
Y Kimura S Takishita H Muratani K Kinjo Y Shinzato A Muratani K Fukiyama 《Canadian Metallurgical Quarterly》1998,37(9):736-745
We performed a cross-sectional survey of stroke and acute myocardial infarction (AMI) in Okinawa, Japan with a census population of about 1.2 million. A total of 3,644 cases of first-ever stroke and 898 cases of initial acute myocardial infarction (AMI) were detected. The age-adjusted annual incidence rate for stroke was 105 per 100,000 standard population of Japan, and that of AMI was 26. The case-fatality rate of stroke within 28 days of onset was 12.8%, and that of AMI was 22.2%. Of the stroke cases, 51.4% were diagnosed as brain infarction, 38.7% as brain hemorrhage, and 9.3% as subarachnoid hemorrhage. The diagnosis of stroke subtypes were confirmed by computed tomography or magnetic resonance imaging in 98.4% of all stroke cases. In Okinawa, the incidence rate of AMI was still considerably lower than that in the Western population, and the rate of stroke was similar to that in the Western population. 相似文献
987.
K Okawa T Aoki K Sano S Harihara A Kitano T Kuroki 《Canadian Metallurgical Quarterly》1998,93(12):2405-2410
OBJECTIVE: We examined the clinical characteristics of ulcerative colitis patients who demonstrated endoscopically discontinuous lesions at the mouth of the appendix. METHODS: Of patients with initial or recurrent active ulcerative colitis who underwent total colonoscopy during the past 3 yr at Osaka City General Hospital, we selected those who had skip lesions in the mouth of the appendix before treatment, and examined their gender, age, disease type, sites of lesions, inflammatory reaction, severity of disease, effects of treatment, and posttreatment course. RESULTS: Discontinuous lesions at the mouth of the appendix were found in 10 patients, who had the following common clinical features: the major lesion was usually present in the lower part of the large bowel including the rectum, many of the patients had suffered an initial attack only, all patients had mild disease, and many of the patients responded quite satisfactorily to treatment with salicylazosulfapyridine. CONCLUSION: Numerous patients with ulcerative colitis with discontinuous lesions at the mouth of the appendix were observed and their clinical characteristics were examined. Determination of the clinical significance of skip lesions in the appendix will contribute to elucidation of the pathogenesis of ulcerative colitis. 相似文献
988.
989.
EA Ismail IS Shabani M Badawi H Sanaa S Madi A Al-Tawari H Nadi M Zaki Q Al-saleh 《Canadian Metallurgical Quarterly》1998,13(10):488-492
We studied Guillain-Barré syndrome, affecting children 12 years old or less, throughout Kuwait, in the period between January 1, 1992, and March 31, 1997. Nineteen children had the diagnostic criteria of Guillain-Barré syndrome, with an overall annual incidence rate of 0.95/100,000 population at risk. Female patients outnumbered male patients with a sex ratio of 1.4:1. There was a clustering of cases in winter and spring and in the year 1996. The disease symptoms were relatively severe in our patients because only 16% (3 of 19) of them were able to walk at the height of their illness, whereas the rest were bed or chair bound or needed assisted ventilation. Two patients had the electrodiagnostic features of axonal neuropathy and both had residual deficits on follow-up, whereas the rest recovered fully. All the patients received intravenous immunoglobulin. The mean time to walk unaided was 23.5 days (range, 2-84 days) after intravenous immunoglobulin and excluding the two patients with axonal neuropathy, and full recovery was achieved in a mean time of 103 days (range, 30-300 days). Contrary to previous studies, we found no correlation between oral polio vaccine administration and Guillain-Barré syndrome in 2 successive years (1995 and 1996) during a nationwide campaign targeting children less than 5 years old. 相似文献
990.