全文获取类型
收费全文 | 488篇 |
免费 | 25篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 49篇 |
综合类 | 27篇 |
化学工业 | 35篇 |
金属工艺 | 19篇 |
机械仪表 | 57篇 |
建筑科学 | 10篇 |
矿业工程 | 7篇 |
能源动力 | 16篇 |
轻工业 | 4篇 |
石油天然气 | 7篇 |
武器工业 | 3篇 |
无线电 | 104篇 |
一般工业技术 | 48篇 |
冶金工业 | 4篇 |
原子能技术 | 5篇 |
自动化技术 | 134篇 |
出版年
2023年 | 1篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 37篇 |
2013年 | 26篇 |
2012年 | 19篇 |
2011年 | 46篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 32篇 |
2007年 | 46篇 |
2006年 | 31篇 |
2005年 | 18篇 |
2004年 | 25篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 18篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1964年 | 1篇 |
排序方式: 共有529条查询结果,搜索用时 0 毫秒
31.
This study considered whether the distinction between core and peripheral criteria for behavioral addiction, previously drawn with respect to computing activities in general, applies in the specific area of Massively Multiplayer Online Game playing. Questionnaire items were administered over the Internet to 442 game players. Factor-analysis of the data supported the previous findings for computing in general. An addiction factor loaded on items tapping previously identified core criteria (conflict, withdrawal symptoms, relapse and reinstatement and behavioral salience) and a (non-pathological) engagement factor loaded on items tapping previously identified peripheral criteria (cognitive salience, tolerance and euphoria). Analysis of response frequencies supported the existence of a developmental process whereby peripheral criteria are met before core criteria. Players who might be considered addicted using a monothetic classification system involving only the core criteria were shown to spend a significantly greater amount of time playing per week than those endorsing only the peripheral criteria. It is concluded that the study supports the idea that it is inappropriate to use some of the previously used criteria for addiction when researching or diagnosing computer-related addictions. Implications of the present findings for Internet-mediated data collection methodologies are also discussed. 相似文献
32.
何丽娅 《南京邮电学院学报(自然科学版)》2007,27(6):72-75,80
分析了UMTS/WCDMA系统所产生的干扰对PAM—IR-UWB系统的影响,推导出了UWB系统在存在UMTS干扰下的误比特率公式,解析分析了UWB发射信号的基本参数与抗UMTS干扰能力之间的关系。数值计算和仿真验证了分析的正确性和UWB系统抗UMTS干扰的能力。 相似文献
33.
34.
齿轮箱箱体表面的振动信号包含了丰富的内部状态信息,因此成为系统动态特性辨识和结构故障诊断的主要依据。考虑到啮合刚度,以及加工误差或齿面缺陷的激励作用,从内部激励源到表面拾振点之间形成了多级、多界面的振动传递过程,沿不同路径的传播、衰减特性直接决定了振动信号采集的质量。建立某单级齿轮箱的有限元模型,通过模态叠加法完成了该结构的冲击响应分析,研究了沿不同传播路径的界面传播与衰减情况,并通过振动幅值能量和能量传播损耗率两个参数实现了衰减特性的定量分析。最终通过齿轮箱试验台的脉冲响应试验,验证了数值仿真的准确性,并建立了可信的齿轮箱冲击振动衰减规律。 相似文献
35.
Monomethylhydrazine (MMH) is currently the most widely used hypergolic propellant, due to its high performance and low ignition delay. However, its toxicity is a major concern. The present work aims at developing high‐performance hypergolic fuels that are based on tertiary amine azide functionality. A number of potential amine azide candidates have been proposed, and some of their physical and chemical properties have been computed using state‐of‐the‐art molecular modeling techniques. Gas‐phase heats of formation have been calculated using the CBS‐QB3 method, and the first‐principle COSMO‐RS method has been used to compute heats of vaporization and vapor pressures. A density correlation, based on molecular‐volume calculation, has been established to predict the densities of the candidate molecules. Finally, the liquid‐phase heats of formation and densities have been used to predict the specific and density impulses of the proposed candidate molecules. The results show that many of the molecules proposed here have much higher density impulse than that of MMH, and may be considered for experimental studies. 相似文献
36.
Abstract— In this paper, the perception of flicker in time‐sequential or field‐sequential 3‐D LC TVs driven by LED backlights is described. The seriousness of the perceived flicker and its influence on visual discomfort is investigated for various backlight operational modes. Results show that display backlights presenting different temporal light distribution have significant contribution to flicker visibility and visual discomfort. The display dimension, 2‐D or 3‐D, affects visual discomfort but not flicker visibility. The relationship between visual discomfort and flicker visibility is proportional when rendering 2‐D images, but not in the case of 3‐D images. Finally, a simple model is presented to evaluate visual discomfort related to flicker in 2‐D rendering. 相似文献
37.
38.
《Journal of the European Ceramic Society》2019,39(5):1893-1899
The Young modulus of partially and fully sintered alumina ceramics, obtained by firing to different temperatures (range 1200–1600°C), has been determined via impulse excitation, and the evolution of Young’s modulus of partially sintered alumina with temperature has been monitored from room temperature to 1600°C. As expected, the room-temperature Young modulus of the partially sintered materials is lower than all theoretical predictions. With increasing temperature Young’s modulus decreases, until the original firing temperature is exceeded and sintering (densification) continues, resulting in a steep Young’s modulus increase. During heating and cooling the temperature dependence obeys a master curve for alumina, unless the temperature of the original firing is excessively low. 相似文献
39.
介绍一种控制算法及在温度控制中的应用,它用系统的脉冲响应建立“预测模型”,这样的模型包含了关于系统动态的主要信息.温度过程的脉冲响应容易在线测取,故而省去了费力很大的“建模”工作.现场整定参数只有一个,使用方便,该算法仿真和试用结果令人满意 相似文献
40.
Wang Yong Huang Qibai Zhou Minggang Zhang Yongbo 《International Journal of Mechanics and Materials in Design》2006,3(1):1-6
The nonlinear force induced by spring and damping of 2-degree-of-freedom locally nonlinear vibrating system is regarded as
applied force, and its mathematical model is established in this paper. Then impulse response temporal method of linear vibrating
system is applied in the system, the response of locally nonlinear vibrating system is obtained by convolution integration
between unit impulse response of corresponding linear system and equivalent nonlinear force, and numerical simulation of the
model is attained. Finally, the feasibility of the new method on the domain of locally nonlinear vibrating system is verified
by comparing the results, which supplies a new method to solve approximately vibration response of locally nonlinear vibrating
systems. 相似文献