全文获取类型
收费全文 | 1064篇 |
免费 | 59篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 280篇 |
金属工艺 | 21篇 |
机械仪表 | 38篇 |
建筑科学 | 28篇 |
矿业工程 | 3篇 |
能源动力 | 37篇 |
轻工业 | 20篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 85篇 |
一般工业技术 | 309篇 |
冶金工业 | 44篇 |
原子能技术 | 20篇 |
自动化技术 | 214篇 |
出版年
2024年 | 2篇 |
2023年 | 16篇 |
2022年 | 49篇 |
2021年 | 48篇 |
2020年 | 31篇 |
2019年 | 32篇 |
2018年 | 26篇 |
2017年 | 35篇 |
2016年 | 42篇 |
2015年 | 34篇 |
2014年 | 47篇 |
2013年 | 64篇 |
2012年 | 66篇 |
2011年 | 84篇 |
2010年 | 45篇 |
2009年 | 53篇 |
2008年 | 64篇 |
2007年 | 59篇 |
2006年 | 49篇 |
2005年 | 41篇 |
2004年 | 43篇 |
2003年 | 34篇 |
2002年 | 27篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1125条查询结果,搜索用时 15 毫秒
1.
We study the computational complexity of the qualitative algebra which is a temporal constraint formalism that combines the point algebra, the point-interval algebra and Allen's interval algebra. We identify all tractable fragments and show that every other fragment is NP-complete. 相似文献
2.
Sorin Manolache Petru Eles Zebo Peng 《International journal of parallel programming》2007,35(2):125-156
As feature sizes shrink, transient failures of on-chip network links become a critical problem. At the same time, many applications
require guarantees on both message arrival probability and response time. We address the problem of transient link failures
by means of temporally and spatially redundant transmission of messages, such that designer-imposed message arrival probabilities
are guaranteed. Response time minimisation is achieved by a heuristic that statically assigns multiple copies of each message
to network links, intelligently combining temporal and spatial redundancy. Concerns regarding energy consumption are addressed
in two ways. First, we reduce the total amount of transmitted messages, and, second, we minimise the application response
time such that the resulted time slack can be exploited for energy savings through voltage reduction. The advantages of the
proposed approach are guaranteed message arrival probability and guaranteed worst case application response time. 相似文献
3.
Prediction of Undrained Sinkhole Collapse 总被引:2,自引:0,他引:2
Charles E. Augarde Andrei V. Lyamin Scott W. Sloan 《Canadian Metallurgical Quarterly》2003,129(3):197-205
Sinkholes are surface depressions or shafts resulting from the collapse of a submerged cavity in soil. The cavities that lead to sinkholes form as a result of underlying geology in limestone areas, or as a result of human activity such as mining or leakage from a sewer. The formation of sinkholes is often sudden and can lead to extensive damage and loss of life, especially in urban areas. Much of the literature on the subject of sinkhole formation is empirical in nature, often being associated with specific locations. This paper presents the results of a study, using numerical modeling, of the undrained stability of the submerged cavities that lead to sinkhole formation. Finite-element limit analysis techniques (using programs developed at the University of Newcastle) are used to obtain upper and lower bound values of a suitable load parameter, which bracket the exact solution. The results are compared to analytical solutions, both from literature and derived independently. 相似文献
4.
Marcus T. Schmitz Bashir M. Al-Hashimi Petru Eles 《Design Automation for Embedded Systems》2002,6(4):401-424
In this paper, we introduce the LOPOCOS (Low Power Co-synthesis) system, a prototype CAD tool for system level co-design. LOPOCOS targets the design of energy-efficient embedded systems implemented as heterogeneous distributed architectures. In particular, it is designed to solve the specific problems involved in architectures that include dynamic voltage scalable (DVS) processors. The aim of this paper is to demonstrate how LOPOCOS can support the system designer in identifying energy-efficient hardware/software implementations for the desired embedded systems. Hence, highlighting the necessary optimization steps during design space exploration for DVS enable architectures. The optimization steps carried out in LOPOCOS involve component allocation and task/communication mapping as well as scheduling and dynamic voltage scaling. LOPOCOS has the following key features, which contribute to this energy efficiency. During the voltage scaling valuable power profile information of task execution is taken into account, hence, the accuracy of the energy estimation is improved. A combined optimization for scheduling and communication mapping based on genetic algorithm, optimizes simultaneously execution order and communication mapping towards the utilization of the DVS processors and timing behaviour. Furthermore, a separation of task and communication mapping allows a more effective implementation of both task and communication mapping optimizationsteps. Extensive experiments are conducted to demonstrate the efficiency of LOPOCOS. We report up to 38% higher energy reductions compared to previous co-synthesis techniques for DVS systems. The investigations include a real-life example of an optical flow detection algorithm. 相似文献
5.
We have measured the heat capacities of3He films and liquid3He in porous Vycor glass at 10 to 600 mK. With increasing the film thickness from 1 to 3 atomic layers, the specific heat evolves gradually from that typical to solid to that of liquid3He. At about 2 atomic layers, however, its low-temperature part is nearly temperature-independent; we interpret this as a result of gradual freezing of spins in an amorphous solid3He film with decreasing the temperature. The contribution of liquid3He in the center of the Vycor pores can be described as the specific heat of bulk liquid3He at corresponding pressures in the range 0 to 28 bar. The thickness of amorphous solid on the pore walls increases with external pressure roughly linearly. Preplating the walls with4He allows to determine the positions of3He atoms contributing to the surface specific heat at 10 to 50 mK. In addition, the contribution from the specific heat of3 He -4He mixing at 100 to 600 mK is discussed as a function of pressure and amount of4He.0n leave from ISSP Acad. Sci. of Russia, Chernogolovka, Russia 相似文献
6.
7.
Sergei Zinovyev Andrei Shelepchikov Pietro Tundo 《Applied catalysis. B, Environmental》2007,72(3-4):289-298
A multipurpose study deals with the transfer hydrogenolysis of 1,3,5-trichlorobenzene to benzene in the 2-propanol–Raney nickel system in the presence of KOH. At 70 °C, no reaction occurs without KOH or with weaker bases, e.g. amines or poorly soluble inorganic bases; however saturated KOH as well as water over 1% suppress the reaction rate, presumably due to the competitive adsorption of these species on the catalyst. The catalytic activity also drops with time because of the deposition of the solid KCl on the catalyst but can be recovered at washing the catalyst with water. The deactivation by KCl can be mitigated with the addition of promoters, e.g. quaternary ammonium salts (Aliquat 336, CTAC) or trioctylamine. Aliquat 336 also promotes hydrodechlorination in the hydrothermal system using a 10% solution of 2-propanol in water, Raney nickel and potassium carbonate as base at 150–200 °C and 10–20 bar. Under these conditions, hexachlorobenzene was also selectively dechlorinated to benzene. 相似文献
8.
Comparative adsorption and precipitation squeezes carried out on field core materials demonstrate that significant lifetime enhancement is achievable for precipitation squeeze with respect to more conventional adsorption squeeze. Coreflood tests have been carried out under reservoir conditions (135°C) employing a poly-phosphinocarboxylate (PPCA) as the scales inhibitor. Field treatment simulations, carried out starting from coreflood data and considering the characteristics of a North Sea formation taken as the reference, confirmed the higher performance, in term of squeeze lifetime, of the precipitation squeeze with respect to adsorption. The results pointed out the importance of choosing the appropriate formulation once the operative conditions are known, in order to promote the inhibitor precipitation into the formation. Some implications of these results for the optimization of the precipitation squeeze technology for field applications, with particular emphasis to formation damage, are also discussed. 相似文献
9.
In order to predict wax deposition problems the key parameter is the wax diffusion coefficient. While it is quite easy to find measured diffusivity values for well-defined compounds at quite low concentrations, very few experimental data are available for wax diffusivity in oil. Most of the literature data are estimated by interpolating experimental data obtained by loop tests and then they are affected by a noticeable uncertainty. In fact this parameter collects the whole uncertainty of the test and the paradoxical situation is that the key parameter ends to be the most error-affected or to be used as a pivotable parameter in “predictive” models. This article describes an experimental procedure to determine the overall diffusivity coefficient of waxes into the oil; the main advantage of this technique is that it allows the direct measure of diffusivity on the oil. Besides it is a very simple and straightforward technique. Results obtained were used to gain insight into the deposition process; the conclusion was that, due to the counter-intuitive diffusivity dependence on temperature, it is likely that noncompositional models available at present are structurally incorrect. 相似文献
10.
Anatoly M. Dolgonosov Ruslan Kh. Khamizov Anna N. Krachak Andrei G. Prudkovsky 《Reactive and Functional Polymers》1995,28(1)
A model for multispecies ion-exchange kinetics based on the Nernst-Planck equation is suggested. It is analyzed in comparison with the “locally-determinate” model described by Hwang and Helfferich [1]. The model makes possible simple computation. The conditions for the occurrence of unusual kinetic curves with a maximum are clarified. The proposed model is developed for different types of kinetic problems and verified by the experimental investigation of a kinetics in ternary systems. 相似文献