全文获取类型
收费全文 | 72818篇 |
免费 | 5886篇 |
国内免费 | 3642篇 |
专业分类
电工技术 | 3542篇 |
技术理论 | 3篇 |
综合类 | 5881篇 |
化学工业 | 8257篇 |
金属工艺 | 5064篇 |
机械仪表 | 9090篇 |
建筑科学 | 7501篇 |
矿业工程 | 2094篇 |
能源动力 | 2272篇 |
轻工业 | 7170篇 |
水利工程 | 1067篇 |
石油天然气 | 1870篇 |
武器工业 | 696篇 |
无线电 | 3384篇 |
一般工业技术 | 8723篇 |
冶金工业 | 5344篇 |
原子能技术 | 790篇 |
自动化技术 | 9598篇 |
出版年
2024年 | 336篇 |
2023年 | 1239篇 |
2022年 | 2477篇 |
2021年 | 2657篇 |
2020年 | 2636篇 |
2019年 | 2306篇 |
2018年 | 2239篇 |
2017年 | 2652篇 |
2016年 | 2799篇 |
2015年 | 3027篇 |
2014年 | 3993篇 |
2013年 | 4223篇 |
2012年 | 4837篇 |
2011年 | 5564篇 |
2010年 | 3838篇 |
2009年 | 3967篇 |
2008年 | 3630篇 |
2007年 | 4267篇 |
2006年 | 3853篇 |
2005年 | 3532篇 |
2004年 | 2884篇 |
2003年 | 2639篇 |
2002年 | 2122篇 |
2001年 | 1645篇 |
2000年 | 1385篇 |
1999年 | 1199篇 |
1998年 | 1012篇 |
1997年 | 841篇 |
1996年 | 711篇 |
1995年 | 589篇 |
1994年 | 515篇 |
1993年 | 404篇 |
1992年 | 309篇 |
1991年 | 221篇 |
1990年 | 230篇 |
1989年 | 179篇 |
1988年 | 156篇 |
1987年 | 95篇 |
1986年 | 86篇 |
1985年 | 57篇 |
1984年 | 72篇 |
1982年 | 52篇 |
1980年 | 54篇 |
1979年 | 49篇 |
1965年 | 46篇 |
1964年 | 68篇 |
1963年 | 54篇 |
1959年 | 39篇 |
1958年 | 40篇 |
1955年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
阐述了冶金设备齿轮减速器润滑问题的重要性,分析了齿轮润滑的主要状态和润滑对齿轮传动的影响,简述了冶金设备齿轮减速机的工作特点及对润滑油性能的要求和选用。 相似文献
62.
In Part I of this paper, a theoretical basis is presented using a two-degrees-of-freedom model. In this second part of the study, the passive control and the two types of semiactive controls introduced in Part I are examined numerically for a taut cable experiencing wind-induced galloping motion. The passive and the semiactive control schemes for taut cables show a good similarity with the results obtained for the two-degrees-of-freedom model. The potential of using these control schemes in practical applications to flexible structures is demonstrated. 相似文献
63.
64.
In this work we present the discrete models for dynamic fracture of structures built of brittle materials. The models construction is based on Voronoi cell representation of the heterogeneous structure, with the beam lattice network used to model the cohesive and compressive forces between the neighboring cells. Each lattice component is a geometrically exact shear deformable beam which can describe large rigid body motion and the most salient fracture mechanisms. The latter can be represented through the corresponding form of the beam constitutive equations, which are derived either at microscale with random distribution of material properties or at a mesoscale with average deterministic values. The proposed models are also placed within the framework of dynamics, where special attention is paid to constructing the lattice network mass matrix as well as the corresponding time-stepping schemes. Numerical simulations of compression and bending tests is given to illustrate the models performance. 相似文献
65.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
66.
随着设备高速化的日益发展,传统的螺杆设计方法及相应的供送特性评价体系已显落后。参照蜗型凸轮动力学性能的评价方法,建立了高速供送螺杆的动态性能评价体系,为高速化供送螺杆的设计提供了性能参照指标。 相似文献
67.
The ability to accurately and reliably predict whether an older adult will commit suicide has eluded clinicians and researchers. A random national sample of psychologists who work with older adults was surveyed regarding their perception of 36 risk factors for completed suicide and indirect self-destructive behavior in older adults. This study produced a profile of psychologists' assessment and treatment practices when working with suicidal older adults. Determining what psychologists consider to be the most salient risk factors for completed suicide is important in identifying a minimum standard that clinicians should follow when assessing older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
69.
A modified rainflow counting method 总被引:1,自引:0,他引:1
Nie Hong 《International Journal of Fatigue》1991,13(6):465-469
The rainflow counting method is commonly recognized to be a good cyclic counting method in fatigue life prediction and for testing engineering components and structures. However, it has some shortcomings, which are pointed out in this paper in connection with the analysis of the stress-strain response. A modified rainflow counting method is presented. Case studies show that all the cycles really existing in the stress-strain response that cannot be counted by the rainflow counting method can be counted by the modified rainflow counting method. So it can be said that the modified rainflow counting method is a more reasonable cycling counting method than the traditional rainflow counting method. 相似文献
70.
正压冲固基础海洋平台冰激振动动力响应 总被引:1,自引:0,他引:1
正压冲固基础海洋平台是一种新型平台桩基结构形式。采用三维有限元的数值分析方法,建立了正压冲固平台的三维有限元模型。基于冰激强迫振动理论提出动冰载荷的计算方法,根据海冰破碎长度和冰速确定冰载周期,冰强度限制的水平冰力作为冰力峰值,得到的动冰载荷用于正压冲固平台的动力响应分析,并依照规范计算了6倍桩径处刚性固定时的动力响应。三维有限元方法计算得到的动力响应大于6倍桩径刚性固定时的计算结果,结构安全性评估偏于安全。 相似文献