全文获取类型
收费全文 | 327篇 |
免费 | 25篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 128篇 |
金属工艺 | 8篇 |
机械仪表 | 8篇 |
建筑科学 | 9篇 |
能源动力 | 20篇 |
轻工业 | 57篇 |
无线电 | 27篇 |
一般工业技术 | 51篇 |
冶金工业 | 5篇 |
原子能技术 | 1篇 |
自动化技术 | 33篇 |
出版年
2023年 | 3篇 |
2022年 | 32篇 |
2021年 | 43篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 9篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 19篇 |
2012年 | 18篇 |
2011年 | 24篇 |
2010年 | 10篇 |
2009年 | 19篇 |
2008年 | 16篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1995年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有352条查询结果,搜索用时 15 毫秒
1.
Results of a study on the modifying mechanical properties of loose optical‐fiber poly(butylene terephthalate) (PBT) tubes, produced during the standard industrial extrusion process, show that heat treatment make the structure of their material to change. The study comprised measurements of mechanical strengths properties of the tubes (tensile strength, compression strength, kinking) and determination of tube material structure [by differential thermal analysis (DTA), wide angle X‐ray scattering analysis (WAXD), and scanning electron microscopy (SEM)]. Results of the study allowed observation that the annealing at 70°C for 34 h of the tubes caused the crystalline α phase to increase in the tube material from ~28.5% to ~31.5% and the structure of the existing crystallites to become more perfect. This made the values of certain mechanical properties of the tubes to increase even by as much as 30%. The tubes following such thermal treatment could be used in cables exposed to heavy‐duty operation in arduous environments, where a larger margin from the standpoint of mechanical properties is required. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2130–2134, 2002 相似文献
2.
The article proposes an analytical method for determining occupancy distribution and blocking probability in systems which are offered overflow traffic composed of multi-service traffic streams. The described analytical model enables determination of parameters of traffic overflowed from primary groups in hierarchically constructed telecommunication networks. The proposed method is based on an appropriate modification of the Kaufman-Roberts recursion for the full-availability group with multi-rate traffic and uses the modified Fredericks & Hayward’s approximation. Additionally, an approximate method for dimensioning systems with multi-service overflow traffic is also presented. The analytical results of the blocking probability and the results obtained in the dimensioning processes calculated using the presented methodology are compared with the data obtained from the system simulation process. 相似文献
3.
Teresa Mikołajczyk Grażyna Janowska Mariusz Wójcik Maciej Boguń Andrzej Kurzak 《应用聚合物科学杂志》2008,109(4):2513-2521
The rheological properties of spinning solutions of polyacrylonitrile in dimethyl formamide (DMF) containing various amounts of a ferromagnetic nanoaddition were investigated. The porous structure, the strength and thermal properties of fibers obtained from these solutions were assessed, as well as the uniformity of the nanoaddition distribution on the fiber surface was estimated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
4.
5.
We consider deterministic distributed broadcasting on multiple access channels in the framework of adversarial queuing. Packets
are injected dynamically by an adversary that is constrained by the injection rate and the number of packets that may be injected
simultaneously; the latter we call burstiness. A protocol is stable when the number of packets in queues at the stations stays
bounded. The maximum injection rate that a protocol can handle in a stable manner is called the throughput of the protocol.
We consider adversaries of injection rate 1, that is, of one packet per round, to address the question if the maximum throughput
1 can be achieved, and if so then with what quality of service. We develop a protocol that achieves throughput 1 for any number
of stations against leaky-bucket adversaries. The protocol has
O(n2+\textburstiness){\mathcal{O}(n^2+\text{burstiness})} packets queued simultaneously at any time, where n is the number of stations; this upper bound is proved to be best possible. A protocol is called fair when each packet is
eventually broadcast. We show that no protocol can be both stable and fair for a system of at least two stations against leaky-bucket adversaries. We study in detail small systems of exactly
two and three stations against window adversaries to exhibit differences in quality of broadcast among classes of protocols.
A protocol is said to have fair latency if the waiting time of packets is
O(\textburstiness){\mathcal{O}(\text{burstiness})}. For two stations, we show that fair latency can be achieved by a full sensing protocol, while there is no stable acknowledgment
based protocol. For three stations, we show that fair latency can be achieved by a general protocol, while no full sensing
protocol can be stable. Finally, we show that protocols that either are fair or do not have the queue sizes affect the order
of transmissions cannot be stable in systems of at least four stations against window adversaries. 相似文献
6.
Mariusz Janiak Krzysztof Tchoń 《Systems & Control Letters》2011,60(8):625-631
This paper addresses the constrained motion planning problem for nonholonomic systems represented by driftless control systems with output. The problem consists in defining a control function driving the system output to a desirable point at a given time instant, whereas state and control variables remain over the control horizon within prescribed bounds. The state and control constraints are handled by extending the control system with a pair of state equations driven by the violation of constraints, and adding regularizing perturbations. For the regularized system a Jacobian motion planning algorithm is designed, called imbalanced. Solutions of example constrained motion planning problems for the rolling ball illustrate the theoretical concepts. 相似文献
7.
8.
9.
Mariusz Pyrz 《Optimization and Engineering》2004,5(1):45-57
The optimal truss design using problem-oriented evolutionary algorithm is presented in the paper. The minimum weight structures subjected to stress and displacement constraints are searched. The discrete design variables are areas of members, selected from catalogues of available sections. The integration of the problem specific knowledge into the optimization procedure is proposed. The heuristic rules based on the concept of fully stressed design are introduced through special genetic operators, which use the information concerning the stress distribution of structural members. Moreover, approximated solutions obtained by deterministic, sequential discrete optimization methods are inserted into the initial population. The obtained hybrid evolutionary algorithm is specialized for truss design. Benchmark problems are calculated in numerical examples. The knowledge about the problem integrated into the evolutionary algorithm can enhance considerably the effectiveness of the approach and improve significantly the convergence rate and the quality of the results. The advantages and drawbacks of the proposed method are discussed. 相似文献
10.
Mariusz Banaszkiewicz 《热应力杂志》2017,40(6):690-703
The article presents a novel algorithm for robust calculation of thermal stresses in steam turbine components during transient operating conditions. Stress calculations are performed in 2 steps: in the first step an unsteady radial temperature distribution in the component model is computed, and based on this thermal stresses at critical locations are determined in the second step. The radial temperature distribution is obtained by solving the Fourier-Kirchhoff equation for a cylinder or sphere by means of a finite difference method. The thermal stresses are computed using the Duhamel integral and Green functions evaluated with a constant heat transfer coe?cient and used with an equivalent steam temperature obtained from the surface heat flux. 相似文献