全文获取类型
收费全文 | 7264篇 |
免费 | 48篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 49篇 |
综合类 | 2篇 |
化学工业 | 747篇 |
金属工艺 | 65篇 |
机械仪表 | 66篇 |
建筑科学 | 158篇 |
矿业工程 | 7篇 |
能源动力 | 62篇 |
轻工业 | 282篇 |
水利工程 | 29篇 |
石油天然气 | 10篇 |
无线电 | 364篇 |
一般工业技术 | 569篇 |
冶金工业 | 4592篇 |
原子能技术 | 20篇 |
自动化技术 | 293篇 |
出版年
2021年 | 25篇 |
2020年 | 26篇 |
2019年 | 27篇 |
2018年 | 26篇 |
2017年 | 29篇 |
2016年 | 39篇 |
2015年 | 25篇 |
2014年 | 52篇 |
2013年 | 164篇 |
2012年 | 80篇 |
2011年 | 129篇 |
2010年 | 75篇 |
2009年 | 85篇 |
2008年 | 118篇 |
2007年 | 100篇 |
2006年 | 79篇 |
2005年 | 112篇 |
2004年 | 102篇 |
2003年 | 103篇 |
2002年 | 100篇 |
2001年 | 85篇 |
2000年 | 64篇 |
1999年 | 182篇 |
1998年 | 1291篇 |
1997年 | 798篇 |
1996年 | 525篇 |
1995年 | 363篇 |
1994年 | 263篇 |
1993年 | 321篇 |
1992年 | 98篇 |
1991年 | 106篇 |
1990年 | 101篇 |
1989年 | 114篇 |
1988年 | 110篇 |
1987年 | 95篇 |
1986年 | 72篇 |
1985年 | 86篇 |
1984年 | 46篇 |
1983年 | 48篇 |
1982年 | 72篇 |
1981年 | 63篇 |
1980年 | 64篇 |
1979年 | 44篇 |
1978年 | 41篇 |
1977年 | 146篇 |
1976年 | 225篇 |
1975年 | 57篇 |
1974年 | 38篇 |
1973年 | 40篇 |
1972年 | 21篇 |
排序方式: 共有7315条查询结果,搜索用时 0 毫秒
1.
OA al-Swayeh MS al-Humayyd AA Mustafa AS al-Tuwaijri RS al-Rashed AT Ali 《Canadian Metallurgical Quarterly》1997,12(7):481-489
Recent evidence suggests that oxygen-derived free radicals are involved in mediating gastric microvascular and parenchymal cell injuries induced by ischaemia and reperfusion. Therefore, the effect of the locally acting anti-ulcer drug, sucralfate, was studied on ischaemia and reperfusion (e.g. induced gastric lesions, intraluminal bleeding, changes in vascular permeability and non-protein sulfhydryl levels in the rat stomach). Allopurinol was used as a known standard antioxidant drug. Rats were subjected to 30 min of gastric ischaemia in the presence of 100 mmol/L hydrochloric acid and reperfusion periods of 15, 30 or 60 min duration. The gastric lesions were assessed microscopically under an inverted microscope. The vascular permeability was quantified by measuring the extravasated Evans blue in the stomach. There were significantly greater numbers of gastric lesions, intraluminal bleeding and leakage of Evans blue during all reperfusion periods as compared with those of ischaemia, with maximum effects occurring at 60 min following reperfusion. Pretreatment with sucralfate (31.25-250 mg/kg, p.o.) or allopurinol (12.5-50 mg/kg, i.p.) 30 min before the procedure, dose-dependently reduced the gastric lesions, intraluminal bleeding, and decreased the vascular permeability induced by ischaemia and reperfusion. Furthermore, sucralfate dose-dependently reverses the ischaemia and reperfusion-induced depletion of mucosal non-protein sulfhydryl levels and inhibited the superoxide radical production in both cell-free xanthine-xanthine oxidase and in the stimulated polymorphonuclear cellular systems. These results suggest that the protection produced by sucralfate against gastric injury may be due to its antioxidant effects. 相似文献
2.
Rolandic discharge (RD), noted in the electroencephalography (EEG) of patients with benign epilepsy in childhood with centrotemporal spikes (BECCT) has several unique features. One feature is that the amount or frequency of RDs does not correlate well with the incidence of seizures in BECCT although it is a key finding in the diagnosis of this epileptic syndrome. In this study, we examined the efficacy of antiepileptic drugs focusing on the disappearance of RDs in relationship with seizure control. Forty patients with BECCT who were not medically treated prior to this study were randomly sorted into three groups. Twenty patients were assigned for clonazepam (CZP) treatment, 10 patients for valproate (VPA) and the remaining 10 patients for carbamazepine (CBZ). Each drug was administered for 4 consecutive weeks. EEGs were recorded twice during the study, before and 4 weeks after the medication trial. The effects of each treatment on RDs were assessed. RDs disappeared in 15 of the 20 cases treated with CZP (75%) within 4 weeks while the same was observed in only one of the 10 cases treated with VPA (10%). CBZ failed to demonstrate any effect on RD. In the group treated with CZP, there were no differences in seizure incidence, seizure type and blood concentration of CZP between the patients whose RDs disappeared and those whose RDs remained. 相似文献
3.
4.
Vascular injuries may occur as complications of elbow dislocation and usually involve the brachial artery. A case report is presented in which only the radial artery was compromised as a result of the dislocation. 相似文献
5.
6.
7.
8.
The separate contributions of impellers and stators to suction are studied by means of interaction models. From these, suction can be predicted when interchangeable components are used in any combination, and in either direction of impeller rotation. Methods are devised by which numerical values of the impeller and stator terms can be simply assigned. The resulting model provides good agreement with experiment. The influence of variability in component geometry is reflected in the model parameters. Possible applications of the model are suggested. 相似文献
9.
10.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples. 相似文献