全文获取类型
收费全文 | 11712篇 |
免费 | 1961篇 |
国内免费 | 517篇 |
专业分类
电工技术 | 294篇 |
综合类 | 1023篇 |
化学工业 | 451篇 |
金属工艺 | 2262篇 |
机械仪表 | 963篇 |
建筑科学 | 1049篇 |
矿业工程 | 4026篇 |
能源动力 | 190篇 |
轻工业 | 200篇 |
水利工程 | 223篇 |
石油天然气 | 883篇 |
武器工业 | 98篇 |
无线电 | 328篇 |
一般工业技术 | 778篇 |
冶金工业 | 569篇 |
原子能技术 | 50篇 |
自动化技术 | 803篇 |
出版年
2024年 | 40篇 |
2023年 | 110篇 |
2022年 | 320篇 |
2021年 | 452篇 |
2020年 | 518篇 |
2019年 | 346篇 |
2018年 | 337篇 |
2017年 | 419篇 |
2016年 | 479篇 |
2015年 | 477篇 |
2014年 | 811篇 |
2013年 | 698篇 |
2012年 | 1095篇 |
2011年 | 983篇 |
2010年 | 692篇 |
2009年 | 762篇 |
2008年 | 658篇 |
2007年 | 769篇 |
2006年 | 702篇 |
2005年 | 537篇 |
2004年 | 492篇 |
2003年 | 456篇 |
2002年 | 363篇 |
2001年 | 333篇 |
2000年 | 262篇 |
1999年 | 221篇 |
1998年 | 157篇 |
1997年 | 138篇 |
1996年 | 125篇 |
1995年 | 108篇 |
1994年 | 82篇 |
1993年 | 49篇 |
1992年 | 46篇 |
1991年 | 33篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 18篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1984年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1964年 | 4篇 |
1962年 | 2篇 |
1961年 | 2篇 |
1959年 | 2篇 |
1958年 | 3篇 |
1956年 | 4篇 |
1955年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
2.
3.
4.
针对朱仙庄矿 84 15工作面切眼特殊的地质条件 ,介绍了高强锚杆 (索 )支护技术成功应用于特厚极软煤层的经验 ,并对巷道支护成本进行了分析 相似文献
5.
Stepanov G. V. Kharchenko V. V. Babutskii A. I. Romanov S. V. Feofentov N. A. Kravchenko I. V. 《Strength of Materials》2004,36(3):321-326
The procedure for calculating the life of header – steam generator connector weld joints is proposed. It allows for running out the material plasticity reserve upon static cyclic elastoplastic loading as well as operating conditions, local stress concentrations, and residual stresses after welding. 相似文献
6.
电梯门机控制系统的运行曲线设计 总被引:1,自引:0,他引:1
为了实现电梯轿厢门的开门和关门快速且平稳地运行,介绍了一种基于高性能微型机的门机控制系统结构和门位移的检测原理,以门位移量作为控制系统的反馈量,对门机运行速度进行了分区设计。在高速附近的变化区,门机速度匀速变化时,进行了门机开门和关门控制曲线的计算,推导出运行位移与门机速度具有二次曲线的关系,进而对微型机控制的软件流程进行了设计,达到了门机高低速运行的平稳过渡。最后,给出了实际运行系统的主电路电压波形。 相似文献
7.
对省煤器开裂管进行了化学成分及宏、微观分析。分析结果表明,在高温高压条件下,在其焊缝溶合区出现粗大的魏氏组织,管材中的珠光体组织产生了不同程度的球化,而母材组织又存在严重的带状组织。在过热条件下熔合区极易出现裂纹,并由此快速扩展,造成省煤器管开裂。 相似文献
8.
When humans plan to execute a tool-use action, they can only specify the bodily movement parameters by taking into account the external target or goal of the tool-use action and the target-movement mapping implemented by the tool. In this study, the authors used the movement precuing method to investigate how people prepare for actions made with tools. More specifically, they asked whether people would be able to specify the spatial target and the target-movement mapping of the tool-use action independently of each other, and to what degree they would be able to prepare these components in advance. In 3 experiments, they precued either the target or the target-movement mapping of tool-use actions involving either a compatible or an incompatible target-movement mapping. Results indicate that participants benefit from partial advance information about the target-movement mapping, whereas no significant effects were found for precuing the spatial target of the action. These results occurred regardless of whether the target-movement mapping was compatible or incompatible and provide evidence for the notion that the target-movement mapping of a tool-use action is part of its cognitive representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Seeing a talker's face influences auditory speech recognition, but the visible input essential for this influence has yet to be established. Using a new seamless editing technique, the authors examined effects of restricting visible movement to oral or extraoral areas of a talking face. In Experiment 1, visual speech identification and visual influences on identifying auditory speech were compared across displays in which the whole face moved, the oral area moved, or the extraoral area moved. Visual speech influences on auditory speech recognition were substantial and unchanging across whole-face and oral-movement displays. However, extraoral movement also influenced identification of visual and audiovisual speech. Experiments 2 and 3 demonstrated that these results are dependent on intact and upright facial contexts, but only with extraoral movement displays. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
焊接方法对双相不锈钢焊接接头力学性能的影响 总被引:2,自引:0,他引:2
研究了不同焊接方法对SAF2205双相不锈钢板焊接接头金相组织和力学性能的影响,结果表明,采用不同焊接方法得到的焊接接头的铁素体与奥氏体两相比例不同,使焊接接头的力学性能存在较大差异,对实际生产中SAF2205双相不锈钢的焊接具有一定的指导意义。 相似文献