全文获取类型
收费全文 | 3991篇 |
免费 | 206篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 32篇 |
综合类 | 3篇 |
化学工业 | 1087篇 |
金属工艺 | 50篇 |
机械仪表 | 76篇 |
建筑科学 | 168篇 |
矿业工程 | 7篇 |
能源动力 | 151篇 |
轻工业 | 600篇 |
水利工程 | 52篇 |
石油天然气 | 23篇 |
无线电 | 306篇 |
一般工业技术 | 526篇 |
冶金工业 | 232篇 |
原子能技术 | 13篇 |
自动化技术 | 875篇 |
出版年
2024年 | 5篇 |
2023年 | 48篇 |
2022年 | 144篇 |
2021年 | 181篇 |
2020年 | 124篇 |
2019年 | 124篇 |
2018年 | 143篇 |
2017年 | 114篇 |
2016年 | 164篇 |
2015年 | 114篇 |
2014年 | 160篇 |
2013年 | 341篇 |
2012年 | 265篇 |
2011年 | 370篇 |
2010年 | 214篇 |
2009年 | 208篇 |
2008年 | 218篇 |
2007年 | 193篇 |
2006年 | 154篇 |
2005年 | 109篇 |
2004年 | 121篇 |
2003年 | 92篇 |
2002年 | 87篇 |
2001年 | 49篇 |
2000年 | 46篇 |
1999年 | 50篇 |
1998年 | 67篇 |
1997年 | 48篇 |
1996年 | 44篇 |
1995年 | 37篇 |
1994年 | 28篇 |
1993年 | 21篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1967年 | 3篇 |
1955年 | 1篇 |
排序方式: 共有4201条查询结果,搜索用时 15 毫秒
1.
ABSTRACTThis paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR . In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs. 相似文献
2.
In this article, a general synthesis method is proposed for the design of discontinuous feedback strategies leading to asymptotically stabilizing sliding regimes. The method is applicable to the class of nonlinear dynamical systems possessing constant equilibrium points. A family of nonlinear stabilizing sliding manifolds, parametrized by generic desired equilibrium point, is specified on the basis of the extended linearization approach. Some examples including simulations are presented for illustrative purposes.
Editor: S. Zak 相似文献
3.
Miguel Palomino Narciso Martí-Oliet Alberto Verdejo 《Electronic Notes in Theoretical Computer Science》2005,124(1):3
This paper is an introduction to rule-based programming in Maude. We illustrate in particular the use of operator attributes to structure the state of a system, and the difference between equations and rules. We use well-known mathematical games and puzzles for our examples illustrating the expressive power of Maude. 相似文献
4.
Luiz Antonio Alcântara Pereira Miguel Hiroo Hirata Nelson Manzanares Filho 《Journal of Wind Engineering & Industrial Aerodynamics》2004,92(6):477-491
Two-dimensional, unsteady flow around bodies of complex geometry (or multiple bodies) at high Reynolds number is simulated using the vortex method. This method is modified to take into account the sub-grid scale phenomena through a second order velocity structure function model adapted to the Lagrangian scheme. The dynamics of the body wake is computed using the convection-diffusion splitting algorithm; the convection process is carried out with a Lagrangian Adams-Bashforth time-marching scheme and the diffusion process is simulated using the random walk method. The pressure distribution is obtained using an integral equation derived from the pressure Poisson equation, which was first developed for a single body. Results for the numerical simulation around a linear cascade of airfoils are presented. As the flow is periodic in the y direction, the discrete vortex shedding need only be considered for a reference airfoil. The flow characteristics around the NACA 65-410 series airfoils are calculated and comparisons are made with results available in the literature. 相似文献
5.
Bedload Transport in Alluvial Channels 总被引:1,自引:0,他引:1
Miguel Bravo-Espinosa W. R. Osterkamp Vicente L. Lopes 《Canadian Metallurgical Quarterly》2003,129(10):783-795
Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams. 相似文献
6.
Ana Mafalda RibeiroJosé Miguel Loureiro 《Chemical engineering science》2002,57(9):1621-1626
The system ASC carbon filter/cyanogen chloride was studied by simulation. Three filter configurations and several models, taking into account Langmuir adsorption and second-order reaction between the adsorbed toxic vapour and the active metal on the surface, were developed.The effects of axial dispersion, number of reaction units, film mass transfer units and intraparticle mass transfer resistance on the breakthrough time were studied.Simulation results show that a complex model should be used in order to predict with reasonable accuracy the protection imparted by these filters. 相似文献
7.
Miguel J. Bagajewicz Vasilios Manousiouthakis 《American Institute of Chemical Engineers》1992,38(11):1769-1800
This article introduces the “state space” conceptual framework to process synthesis, which is used to provide a novel representation of a distillation network as a composite heat- and mass-exchange network. This representation suggests that distillation network synthesis may best be viewed as an interacting heat- and mass-exchange network synthesis problem. In that regard, familiar tools (such as pinch diagrams) from both heat-exchange network (HEN) and mass-exchange network (MEN) synthesis are shown to be of use in arriving at energy-efficient distillation network designs. Examples of propylene-propane and solvent-water separations are used to illustrate the proposed conceptual framework. 相似文献
8.
9.
Jos A.D. Muoz Antn Alvarez Jorge Ancheyta Miguel A. Rodríguez Gustavo Marroquín 《Catalysis Today》2005,109(1-4):214-218
The present paper focuses on the study of process alternatives for heat integration of a heavy crude oil hydrotreatment plant. Experimental information obtained from a pilot scale, kinetics and reactor modeling tools, and a commercial process simulator were employed to develop mass and energy balances. Four study cases, which employ a combination of quenching and heat exchangers, were identified and evaluated. The results indicated that the case with two quenches with hydrogen and three heat exchangers is the best process heat integration (PHI) option from an energetic point of view. 相似文献
10.
A population balance method in which continuum and discrete phases are integrated is developed to simulate the evolution of polydisperse population of bubbles in a turbulent pipeline flow. The investigation is focused on the effect of the coalescence efficiency on this evolution. A dilute system of bubbles under microgravity conditions is considered. It is found that if the initial coalescence efficiency is low, a slight increase produces a significant effect on the bubble coalescence rate, and thus on the evolution of the population. If, however, the initial coalescence efficiency is high, its increase results in a marginal effect on the way the population evolves. The results of simulations are validated against experimental data on the population mean. 相似文献