全文获取类型
收费全文 | 4767篇 |
免费 | 246篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 65篇 |
综合类 | 3篇 |
化学工业 | 815篇 |
金属工艺 | 104篇 |
机械仪表 | 65篇 |
建筑科学 | 274篇 |
矿业工程 | 30篇 |
能源动力 | 111篇 |
轻工业 | 569篇 |
水利工程 | 29篇 |
石油天然气 | 17篇 |
无线电 | 460篇 |
一般工业技术 | 747篇 |
冶金工业 | 683篇 |
原子能技术 | 53篇 |
自动化技术 | 991篇 |
出版年
2023年 | 40篇 |
2022年 | 47篇 |
2021年 | 120篇 |
2020年 | 89篇 |
2019年 | 114篇 |
2018年 | 149篇 |
2017年 | 145篇 |
2016年 | 171篇 |
2015年 | 134篇 |
2014年 | 180篇 |
2013年 | 296篇 |
2012年 | 240篇 |
2011年 | 289篇 |
2010年 | 211篇 |
2009年 | 221篇 |
2008年 | 250篇 |
2007年 | 214篇 |
2006年 | 195篇 |
2005年 | 171篇 |
2004年 | 155篇 |
2003年 | 110篇 |
2002年 | 142篇 |
2001年 | 66篇 |
2000年 | 67篇 |
1999年 | 71篇 |
1998年 | 153篇 |
1997年 | 107篇 |
1996年 | 97篇 |
1995年 | 61篇 |
1994年 | 74篇 |
1993年 | 70篇 |
1992年 | 36篇 |
1991年 | 34篇 |
1990年 | 31篇 |
1989年 | 40篇 |
1988年 | 21篇 |
1987年 | 29篇 |
1986年 | 31篇 |
1985年 | 35篇 |
1984年 | 40篇 |
1983年 | 27篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 26篇 |
1979年 | 23篇 |
1978年 | 12篇 |
1977年 | 23篇 |
1976年 | 27篇 |
1975年 | 11篇 |
1974年 | 14篇 |
排序方式: 共有5016条查询结果,搜索用时 62 毫秒
81.
Ye Cai ré Zimmermann Arndt Bauer Fritz Aldinger 《Journal of the American Ceramic Society》2003,86(9):1598-1600
Precursor-derived Si-C-N ceramics after creep testing in air were characterized using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). XRD analysis showed that the crept Si-C-N ceramics were covered by an α-cristobalite layer. TEM observations revealed that the precipitated nanocrystallites in the crept Si-C-N ceramics were β-SiC. Between α-cristobalite and crept Si-C-N ceramic, there was an intermediate zone in which Si2 N2 O nanocrystallites were distributed homogeneously. Moreover, Si2 N2 O nanocrystallites were often found covering the surface of nanosized gas channels in the crept Si-C-N ceramics, where no α-cristobalite phase was detected. Based on these observations, a two-step oxidation mechanism of Si-C-N ceramics during creep testing in air was proposed. 相似文献
82.
83.
Tom Oomen 《International journal of control》2014,87(7):1406-1422
Sampled-data control systems occasionally exhibit aliased resonance phenomena within the control bandwidth. The aim of this paper is to investigate the aspect of these aliased dynamics with application to a high performance industrial nano-positioning machine. This necessitates a full sampled-data control design approach, since these aliased dynamics endanger both the at-sample performance and the intersample behaviour. The proposed framework comprises both system identification and sampled-data control. In particular, the sampled-data control objective necessitates models that encompass the intersample behaviour, i.e., ideally continuous time models. Application of the proposed approach on an industrial wafer stage system provides a thorough insight and new control design guidelines for controlling aliased dynamics. 相似文献
84.
越来越高的汽车发动机温度对在汽车中使用的胶管和胶带用聚合物提出了更严格的要求。本综述了胶管和胶带中使用的聚合物,并针对提高耐热、耐屈挠疲劳和耐臭氧老化性能讨论了每一种聚合物用的硫化体系和防老剂搭配。 相似文献
85.
86.
87.
Information technology (IT) development in global organisations relies heavily on the transfer of tacit and complex knowledge from onshore units to offshore subsidiaries. A central concern of such organisations is the development of social capital, which is known to facilitate the smooth transfer of knowledge. However, only a few studies in IS research have explicitly examined the role of social capital for knowledge transfer in an IT offshoring context. In this paper, we argue that such knowledge transfer mechanisms can be understood better by considering social capital in concert with knowledge senders' efficacy and outcome expectations, two of the potentially key motivational drivers of knowledge transfer. We develop our arguments through a qualitative case study of a large German multinational company. German IT developers in this firm provided in‐depth accounts of their experience with offshore colleagues in an Indian captive subsidiary unit. Drawing on our analysis, we develop a model that depicts the influence of social capital, efficacy and outcome expectations on onshore IT developers' ability and willingness to transfer knowledge to offshore colleagues. Through the model, we also explain how social capital, efficacy and outcome expectations are interrelated and generate three interlocked, self‐reinforcing circles of knowledge transfer success in IT offshoring relationships. 相似文献
88.
Ilaria Pasciuto Sergio Ausejo Juan Tomás Celigüeta Ángel Suescun Aitor Cazón 《Multibody System Dynamics》2014,32(1):27-53
In this paper, we present a novel method to predict human motion, seeking to combine the advantages of both data-based and knowledge-based motion prediction methods. Our method relies on a database of captured motions for reference and introduces knowledge in the prediction in the form of a motion control law, which is followed while resembling the actually performed reference motion. The prediction is carried out by solving an optimization problem in which the following conditions are imposed to the motion: must fulfill the goals of the task; resemble the reference motion selected from the database; follow a knowledge-based dynamic motion control law; and ensure the dynamic equilibrium of the human model, considering its interactions with the environment. In this work, we apply the proposed method to a database of clutch pedal depression motions, and we present the results for three predictions. The method is validated by comparing the results of the prediction to motions actually performed in similar conditions. The predicted motions closely resemble the motions in the validation database and no significant differences have been noted either in the motion’s kinematics or in the motion’s dynamics. 相似文献
89.
Software development is a fast-paced environment where developers need constant update to ever-changing technologies. Furthermore, process improvement initiatives have been proven useful in increasing the productivity of a software organization. As such, these organizations need to decide where to invest their training budget. As a result, training in technological update to their workforce or training in process conformance with its productive processes become conflicting alternatives. This paper presents a system dynamics simulation of a software factory product line. The objective of this simulation is to understand the changes in behavior when selecting either one of the above-training alternatives. The system dynamics model was validated with an expert panel, and the simulation results have been empirically validated—using statistical process control—against the performance baseline of a real software development organization. With the simulation under statistical control and performing like the baseline, the independent variables representing process conformance (process training) and technology skills (skills training) were modified to study their impact on product defects and process stability. Our results show that while both variables have positive impact on defects and process stability, investment in process training results in a process with less variation and with fewer defects. 相似文献
90.
A high pressure differential scanning calorimeter (DSC) and a Fourier transform infrared (FTIR) spectrometer with a prism liquid cell (PLC) were used to monitor the reaction kinetics of styrene-unsaturated polyester resins at elevated curing temperatures and pressures. The thermal method is easy to perform but provides only an overall reaction exotherm. The spectroscopic method can detect the detailed reaction mechanism of copolymerizations. It is, however, less quantitative and the calculation is much more time-consuming compared to the thermal analysis. Reactions of two unsaturated polyester resins with different molecular structure were measured by these two methods. Results showed that applying cure pressure on unsaturated polyester resins reduced the reaction rate but increased the final conversion. The styrene reaction was enhanced more than the polyester reaction at high curing temperatures. 相似文献