全文获取类型
收费全文 | 100579篇 |
免费 | 8268篇 |
国内免费 | 5513篇 |
专业分类
电工技术 | 2235篇 |
技术理论 | 5篇 |
综合类 | 8598篇 |
化学工业 | 10349篇 |
金属工艺 | 21235篇 |
机械仪表 | 4929篇 |
建筑科学 | 23805篇 |
矿业工程 | 3019篇 |
能源动力 | 1518篇 |
轻工业 | 3472篇 |
水利工程 | 2222篇 |
石油天然气 | 3245篇 |
武器工业 | 639篇 |
无线电 | 1221篇 |
一般工业技术 | 10968篇 |
冶金工业 | 15261篇 |
原子能技术 | 551篇 |
自动化技术 | 1088篇 |
出版年
2024年 | 258篇 |
2023年 | 1132篇 |
2022年 | 2615篇 |
2021年 | 3121篇 |
2020年 | 3064篇 |
2019年 | 2516篇 |
2018年 | 2242篇 |
2017年 | 3288篇 |
2016年 | 3411篇 |
2015年 | 3733篇 |
2014年 | 6176篇 |
2013年 | 5913篇 |
2012年 | 7297篇 |
2011年 | 8129篇 |
2010年 | 6130篇 |
2009年 | 6296篇 |
2008年 | 5268篇 |
2007年 | 6629篇 |
2006年 | 6033篇 |
2005年 | 5083篇 |
2004年 | 4270篇 |
2003年 | 3622篇 |
2002年 | 3117篇 |
2001年 | 2645篇 |
2000年 | 2289篇 |
1999年 | 1908篇 |
1998年 | 1521篇 |
1997年 | 1364篇 |
1996年 | 1169篇 |
1995年 | 902篇 |
1994年 | 772篇 |
1993年 | 572篇 |
1992年 | 468篇 |
1991年 | 314篇 |
1990年 | 273篇 |
1989年 | 249篇 |
1988年 | 153篇 |
1987年 | 96篇 |
1986年 | 40篇 |
1985年 | 44篇 |
1984年 | 36篇 |
1983年 | 32篇 |
1982年 | 38篇 |
1981年 | 25篇 |
1980年 | 50篇 |
1979年 | 19篇 |
1978年 | 4篇 |
1975年 | 4篇 |
1964年 | 4篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
Ramazan Kahraman 《Journal of Materials Engineering and Performance》2002,11(1):46-50
The objective of this study was to evaluate the effectiveness of sodium benzoate as an inhibitor to slow down or prevent atmospheric
corrosion/discoloration of the local mild steel during storage in the Arabian Gulf region. Test specimens were prepared from
locally produced reinforcing steel products. The inhibitor solution was applied on steel specimens at a concentration of 100
mM for 1 day at room temperature. Wooden exposure racks were used to hold as-received and inhibitor-treated specimens during
atmospheric exposure for different periods. Corrosion was evaluated through weight loss determination and electrochemical
technique. As expected, the Arabian Gulf atmosphere was corrosive on the as-received local mild steel. On the other hand,
treatment of steel with sodium benzoate lowered its corrosion rate during initial days of its exposure to atmosphere. However,
atmospheric corrosion inhibition performance of sodium benzoate deteriorated with exposure time after 30 or more days of atmospheric
exposure, and the corrosion rates of sodium benzoate-treated specimens reached that of the unprotected specimens at the end
of 90 days of atmospheric exposure. 相似文献
112.
On the basis of generalization of the results of investigation of the operation of rodlike elements of composite materials, we make a conclusion that the influence of various factors on the deformability of these elements is studied incompletely. The comparison of the stress-strain states for different models of concrete and reinforced-concrete elements makes it possible to describe the effect of longitudinal reinforcement (coefficient of reinforcement, strength and deformation characteristics) on the critical level of strains in the cross section. According to the results of our investigations, we give recommendations concerning the evaluation of the critical value of the coefficient of reinforcement above which one may observe the effect of reinforcement on the deformability of the analyzed sections. It is shown that the compression strength of the brittle base of the composite with inhomogeneous structure decreases as a result of the fracture processes. It is also demonstrated that the existing procedure used for the evaluation of the indicated decrease in strength requires significant improvement. The problem of evaluation of the ultimate value of the coefficient of reinforcement is also analyzed. 相似文献
113.
Rotating-bending uniaxial fatigue tests and micro-fatigue crack initiation tests were carried out using a permanent mold cast
(PMC) and semi-solid die cast (SDC) with Al−7%Si−0.35%Mg composition in order to examine the relationship between solidification
structures and fatigue behaviors. The crack length was measured using a replication method. Fatigue strength was improved
in SDC, which was almost consistent with the predicted fatigue strength using the size of Si particle cluster. Resistance
to fatigue crack initiation and fatigue strength were improved in SDC owing to the finer Si cluster and to higher ultimate
tensile strength. Fatigue crack in PMC was preferentially initiated at pores. For SDC, the fatigue crack was initiated at
the Si particle/matrix interface, and then sucessively grew along eutectic cell boundaries. 相似文献
114.
纤维混凝土在水工建筑工程中的应用(上) 总被引:1,自引:0,他引:1
概述改性混凝土垢发展情况,介绍纤维混凝土在国内外水工建筑物上的应用实例,提出钢纤维增强钢筋混凝土水工建筑结构强度计算方法。包括受弯构件正截面强度,斜截面抗剪强度的计算;重点介绍了网状钢纤维增强混凝土(FOC)在水工建筑物上的应用,包括在渡槽,闸门,小型拦河坝,轻型岸型等工程上的应用实例,T新梁正斜截面的强度计算,板材承载力计算的方法。 相似文献
115.
研究结果表明 :水胶比、胶凝材料用量、钢纤维掺量、矿渣代水泥量对钢纤维砼强度影响显著。当矿渣取代水泥 10 %时 ,钢纤维砼强度最高。经试验选择出一个具有良好和易性和较高强度 (118MPa)的钢纤维砼配合比 ,为掺磨细矿渣的中含量超短异形钢纤维砼的设计和施工提供了试验依据 相似文献
116.
采用自行开发研制的超音速电弧喷设备,在45钢表面制成了钛铝合金复合涂层。并利用金相显微镜、X射线衍射仪、扫描电镜、电子探针,对涂层的成分、相结构、显微组织及其结合强度、显微硬度进行了研究。结果表明,利用超音速电弧喷涂设备,可以在45钢表面形成 度高、孔隙率低,结合强度较好和硬度高的Ti-Al合金涂层。 相似文献
117.
118.
钢纤维喷射混凝土作为面板材料的可行性研究 总被引:3,自引:2,他引:1
钢纤维混凝土作为一种新型增强材料,以其较好的受力变形特性在水利水电,交通,海岸防护,港口及军事等诸多工程中得到了广泛的应用。针对混凝土面板堆石坝面板的受力变形特点,为改善水布垭面板堆石坝面板的受力条件,提高其防渗能力,同时方便施工,现提出采用钢纤维喷射混凝土作为水布垭面板堆石坝面板材料的新构想,并通过对钢纤维喷射混凝土的物理力学特性及堆石坝面板受力变形进行分析,为钢纤维喷射混凝土在水布垭面板堆石坝面板中的实际应用提出了建议方案。 相似文献
119.
Wang Hai-dou Xu Bin-shi Wei Shi-cheng Zhang Xian-cheng Jin Guo Jiang Yi 《中南工业大学学报(英文版)》2005,12(2):30-33
The guide-pieces, used in the process line of steel rolling, were the important components. The guidepieces, which were slide
contacting with the rolled-piece, had a high temperature and high speed. The wear was very serious. The results from failure
analysis showed that there were three failure forms in the guide-pieces: the first was the wear during heat friction, the
second was the heat fatigue under the cycle of deep heating and deep cooling, and the third was the impact rupture. Among
them, the wear was the main reason. To the wear of guidepieces, there were four mechanisms, namely abrasive wear, adhesive
wear, fatigue wear and corrosion wear. The failure analysis to the guide-piece laid the foundation for its remanufacturing.
Foundation item: Project(50235030) supported by the National Natural Science Foundation of China 相似文献
120.
轻型钢骨结构低层住宅设计荷载分析 总被引:1,自引:0,他引:1
本文讨论了北美低层钢骨结构住宅结构设计的荷载问题,包括各类荷载的取值和计算方法,以及荷载组合模式,并提出了在我国相关规范没有出台前,在国内进行设计时应该注意的一些问题。 相似文献