全文获取类型
收费全文 | 456篇 |
免费 | 28篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 10篇 |
综合类 | 3篇 |
化学工业 | 179篇 |
金属工艺 | 8篇 |
机械仪表 | 6篇 |
建筑科学 | 12篇 |
矿业工程 | 1篇 |
能源动力 | 35篇 |
轻工业 | 62篇 |
水利工程 | 8篇 |
石油天然气 | 4篇 |
无线电 | 20篇 |
一般工业技术 | 60篇 |
冶金工业 | 6篇 |
原子能技术 | 4篇 |
自动化技术 | 69篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 23篇 |
2021年 | 51篇 |
2020年 | 29篇 |
2019年 | 36篇 |
2018年 | 42篇 |
2017年 | 52篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 27篇 |
2013年 | 49篇 |
2012年 | 28篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 19篇 |
2008年 | 13篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
排序方式: 共有487条查询结果,搜索用时 0 毫秒
1.
Time delays are encountered in many physical systems, and they usually threaten the stability and performance of closed-loop systems. The problem of determining all stabilising proportional-integral-derivative (PID) controllers for systems with perturbed delays is less investigated in the literature. In this study, the Rekasius substitution is employed to transform the system parameters to a new space. Then, the singular frequency (SF) method is revised for the Rekasius transformed system. A novel technique is presented to compute the ranges of time delay for which stable PID controller exists. This stability range cannot be readily computed from the previous methods. Finally, it is shown that similar to the original SF method, finite numbers of singular frequencies are sufficient to compute the stable regions in the space of time delay and controller coefficients. 相似文献
2.
A new nano-thermo-mechanical data storage memory is presented which combines two technologies of thermal actuation and buckling beam memory. The memory design is resistant in high radiation environments, making it a reliable memory for spacecraft computer systems. This memory has a data storage density, write/erase speed, and power consumption comparable with current memories. An integrated thermal–mechanical simulation of buckling in nano-mechanical memory is performed to optimize the design parameters. The preliminary system is a bridge with lengths of 20–40 μm, a width of 1 μm, and a thickness of 0.3 μm, in air with a pressure of 5 kPa. The simulation of high energy particle collisions shows radiation does not cause undesired buckling for silicon and silicon carbide bits, which makes the memory applicable for Jovian exploration. Optimization simulations are performed for silicon, silicon carbide, and kapton with various dimensions and actuation heating rates. The current work suggests the length of 20 μm for the bridge to balance the write time and the storage density. Among the beams with the fixed dimensions, kapton shows the fastest write time, with the lowest energy cost. However, high energy electron collision causes buckling in kapton, limiting its use in high radiation applications. The results show that silicon and silicon carbide based systems are viable for use in the extreme radiation environments that will be encountered in future space exploration missions. 相似文献
3.
4.
We propose a (t, m)?(s, n) threshold quantum secret sharing protocol between multiparty (m members in group 1) and multiparty (n members in group 2) using a sequence of Greenberger–Horne–Zeilinger (GHZ) states, which is useful and efficient when the parties of communication are not all present. In the protocol, Alice prepares a sequence of GHZ states in one of the eight different states and sends the last two particles to the first agent while other members encode their information on the sequence via unitary transformations. Finally the last member in group 2 measures the qubits. It is shown that this scheme is safe. 相似文献
5.
6.
Wireless Personal Communications - The beacon order and Superframe order parameter values, as defined by the IEEE 802.15.4 standard specification, constrain the number of data packets that can be... 相似文献
7.
Nafiseh Masaeli Hamid Haj Seyed Javadi Elham Noori 《Wireless Personal Communications》2013,72(4):2721-2740
Cluster-based routing protocols are one of the most favorable approaches for energy management in wireless sensor networks. The selection of the best cluster heads (CHs), as well as the formation of optimal clusters, is an NP-hard problem. The present study proposes an optimal solution for CHs selection to generate a network topology with optimized network performance. The problem is formulated as facility location problem and a linear programming model is used to solve the optimization problem. Results of analysis o the network simulator (NS2) indicate that applying this method in cluster-based routing protocols prolongs 16 % of the network lifetime, increases 15.5 % of data transmission and improves 5.5 % of throughput, as compared to the results of current heuristic methods such as LEACH, DEEC and EDFCM protocols. 相似文献
8.
Studies on the behavior of the vestibulo-ocular reflex (VOR) reveal that the monocular reflex gain is adjusted according to target position relative to each eye. In this paper, we present a nonlinear approach in modeling the viewing-context dependency of the slow-phase angular VOR. We show that including appropriate nonlinearities in the responses of premotor neurons in the brainstem is sufficient to account for the online modulation of the VOR with target position. This approach allows very complex behaviors in response to sensory patterns without resorting to currently assumed cortical computations. A local premotor topology with nonlinear properties has repercussions in the study of all ocular reflexes, since it implies context dependent dynamics in all behavioral responses (pursuit, optokinetic, VOR, saccades, etc.) that share this network. Local nonlinearities in spinal circuits could similarly influence the context dependence of other motor systems (such as stretch reflex modulation during rhythmic walking). 相似文献
9.
Tianhe Huang Guan Wang Mohammad-Ali Shahbazi Yuancheng Bai Jingrui Zhang Guobing Feng Elham Asadian Fatemeh Ghorbani-Bidkorpeh Zhiyuang Yang Yuanai Li Qingqing Huo Yingxin Liu Dongfei Liu 《Advanced functional materials》2023,33(2):2210627
A versatile surface decoration strategy to efficiently encapsulate water-soluble peptides is developed. By assembling peptide molecules into nanoparticles, diverse physiochemical properties of these compacted molecules are equalized to the surface properties of nanoparticles. Primarily driven by the generic electrostatic attractions, the surface of as-prepared peptide nanoparticles is decorated with charged amino acids-grafted poly(lactic-co-glycolic acid). This adsorbed polymer layer versatilely blocks the phase transfer of peptide nanoparticles by increasing their affinity to the dispersed phase solvent molecules. Attributed to the ultrahigh encapsulation efficiencies (> 96%), the peptide mass fraction inside the obtained microcomposites is higher than 48%. The plasma calcium level has been efficiently reduced for ≈3 weeks with only one single injection of salmon calcitonin-encapsulated microcomposite in osteoporotic rats. Similarly, one single injection of exenatide-encapsulated microcomposites efficiently controls the glycemic level in type 2 diabetic rats for up to 3 weeks. Overall, the developed versatile surface decoration strategy efficiently encapsulates peptides and improves their pharmacokinetic features, regardless of the molecular structure of peptide cargos. 相似文献
10.
Mazaheri Kalahroudi Parisa Yaghoubi Elham Barekatain Behrang 《Photonic Network Communications》2021,41(1):78-92
Photonic Network Communications - Based on the recent research, the communication cost has been the most important open issue in network on chip (NoC). In other words, the lower the communication... 相似文献