全文获取类型
收费全文 | 40148篇 |
免费 | 3820篇 |
国内免费 | 1922篇 |
专业分类
电工技术 | 2466篇 |
技术理论 | 3篇 |
综合类 | 2691篇 |
化学工业 | 6560篇 |
金属工艺 | 2196篇 |
机械仪表 | 2422篇 |
建筑科学 | 2972篇 |
矿业工程 | 1140篇 |
能源动力 | 1119篇 |
轻工业 | 2627篇 |
水利工程 | 775篇 |
石油天然气 | 2516篇 |
武器工业 | 380篇 |
无线电 | 4908篇 |
一般工业技术 | 4754篇 |
冶金工业 | 1784篇 |
原子能技术 | 404篇 |
自动化技术 | 6173篇 |
出版年
2024年 | 240篇 |
2023年 | 829篇 |
2022年 | 1514篇 |
2021年 | 2069篇 |
2020年 | 1526篇 |
2019年 | 1150篇 |
2018年 | 1367篇 |
2017年 | 1426篇 |
2016年 | 1180篇 |
2015年 | 1671篇 |
2014年 | 2157篇 |
2013年 | 2412篇 |
2012年 | 2725篇 |
2011年 | 2945篇 |
2010年 | 2613篇 |
2009年 | 2182篇 |
2008年 | 2316篇 |
2007年 | 2075篇 |
2006年 | 2010篇 |
2005年 | 1746篇 |
2004年 | 1138篇 |
2003年 | 961篇 |
2002年 | 930篇 |
2001年 | 805篇 |
2000年 | 800篇 |
1999年 | 972篇 |
1998年 | 756篇 |
1997年 | 595篇 |
1996年 | 571篇 |
1995年 | 470篇 |
1994年 | 394篇 |
1993年 | 260篇 |
1992年 | 238篇 |
1991年 | 174篇 |
1990年 | 128篇 |
1989年 | 100篇 |
1988年 | 87篇 |
1987年 | 53篇 |
1986年 | 48篇 |
1985年 | 37篇 |
1984年 | 31篇 |
1983年 | 28篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Temperature control curve is the key to achieving temperature control and crack prevention of high concrete dam during construction,and its rationality depends on the accurate measurement of temperature stress.With the simulation testing machine for the temperature stress,in the present study,we carried out the deformation process tests of concrete under three temperature curves:convex,straight and concave.Besides,we not only measured the early-age elastic modulus,creep parameters and stress process,but also proposed the preferred type.The results show that at early age,higher temperature always leads to greater elastic modulus and smaller creep.However,the traditional indoor experiments have underestimated the elastic modulus and creep development at early age,which makes the calculated value of temperature stress too small,thus increasing the cracking risk.In this study,the stress values of the three curves calculated based on the strain and early-age parameters are in good agreement with the temperature stress measured by the temperature stress testing machine,which verifies the method accuracy.When the temperature changes along the concave curve,the law of stress development is in consistent with that of strength.Under this condition,the stress fluctuation is small and the crack prevention safety of the concave type is higher,so the concave type is better.The test results provide a reliable basis and support for temperature control curve design and optimization of concrete dams. 相似文献
62.
Multibody System Dynamics - A recursive rotational-coordinate-based formulation of a planar Euler–Bernoulli beam is developed, where large displacements, deformations, and rotations are... 相似文献
63.
While the significance of oscillator dynamics and coupling structure to synchronization behaviors has been well addressed in the literature, little attention has been paid to the possible influence of coupling functions. In the present paper, adopting the scheme of dual-channel time-delayed couplings, we investigate how the synchronization behaviors of networked chaotic oscillators are influenced by parameters in the coupling functions. It is found that, with the introduction of the second coupling channel, the synchronization region, as calculated according to the method of master stability function (MSF), can be largely modified. In particular, by a slight change of the time delay, it is found that the synchronization region can be significantly adjusted, or even switched from non-existing to existing. We demonstrate this interesting phenomenon for both situations of processing and propagation induced time delays, as well as for different coupling functions. Our studies shed new light on the mechanism of chaos synchronization, and may potentially be used for the control of complex network dynamics. 相似文献
64.
张帆 《吉林化工学院学报》2015,(7):76-79
采用目标追求的入世、出世量表筛选出入世水平高组(70名)和低组(72)大学生,出世水平高组(68名)和低组(71名)大学生,探讨不同入世、出世水平大学生在奖学金申请、选修课和求职应聘三种决策任务领域上的框架效应及其在性别上的特点。结果发现:(1)不同出入世水平大学生在决策任务上的框架效应特点不同,入世水平高分组和低分组、出世水平高分组和低分组在奖学金申请问题上均出现了经典的框架效应;(2)在奖学金申请问题上,男性被试和女性被试的选择出现了明显的经典的框架效应。 相似文献
65.
Substrate pretreatment affects the porosity of thin nickel electrolytic coatings which is a combined function of the composition and the roughness of the substrate surface. Electropolishing the substrate surface is an effective method of reducing coating porosity, whereas coatings plated on either electroetched or mechanically ground substrates are relatively porous owing to the remaining oxide layer on the substrate and the increased roughness of the substrate. For nickel coatings plated on mechanically ground rough substrates, the relationship between nickel porosity, apparent coating thickness and substrate roughness has been examined. 相似文献
66.
研究了Sr元素(加入量分别为0.03%、0.06%、0.09%、0.12%和0.18%)对含Fe量为1.2%的ZL102合金的组织和性能的影响。研究发现,随着Sr元素的加入,合金中粗大的针状Fe相开始出现断裂分叉现象,同时针状Fe相的长度也随Sr元素加入量的增加而减小,但Sr对Fe相的针状形貌没有明显改变。随着Sr元素加入量逐渐增加,合金的抗拉强度和伸长率均呈现出先增后减的变化趋势。当Sr元素加入量达到0.12%时,合金材料的综合力学性能最佳。 相似文献
67.
Fan Jinglian Zhao Muyue Xu Guofu Central-South University of Technology Changsha China 《中国有色金属学会会刊》1993,(3)
The breakage mechanism of W-Ni-Fe alloy in the process of electro-heat upsetting studied both theoretically and experimetnally, and also the behaviors of crack formation and propagation were analysed. Alloy suffers from corrosion and thermal-mechanical fatigue mutual function. Simultaneously, the practical ways to improve the anvil life was discussed. 相似文献
68.
69.
70.