全文获取类型
收费全文 | 620篇 |
免费 | 22篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 167篇 |
金属工艺 | 12篇 |
机械仪表 | 16篇 |
建筑科学 | 19篇 |
能源动力 | 40篇 |
轻工业 | 70篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 22篇 |
一般工业技术 | 91篇 |
冶金工业 | 81篇 |
原子能技术 | 7篇 |
自动化技术 | 104篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 12篇 |
2021年 | 32篇 |
2020年 | 15篇 |
2019年 | 24篇 |
2018年 | 22篇 |
2017年 | 19篇 |
2016年 | 25篇 |
2015年 | 13篇 |
2014年 | 25篇 |
2013年 | 36篇 |
2012年 | 35篇 |
2011年 | 38篇 |
2010年 | 29篇 |
2009年 | 31篇 |
2008年 | 30篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 22篇 |
2001年 | 14篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 20篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1962年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有642条查询结果,搜索用时 15 毫秒
51.
Sludge accumulation, characteristics, and pathogen inactivation in four primary waste stabilization ponds in central Mexico 总被引:1,自引:0,他引:1
To support the development of safe and feasible sludge management strategies, the accumulation rates of sludge and its characteristics were studied in four primary wastewater stabilization ponds (WSPs) in central Mexico (three facultative and one anaerobic). The accumulation rates and distribution of sludge were determined by measuring the thickness of the sludge layer at 8-40 locations throughout each pond. The average, per capita sludge accumulation rates ranged from 0.021 to 0.036m(3)/person/yr. In the anaerobic pond the sludge distribution was uniform throughout the pond, whereas in the three facultative ponds most of the sludge accumulated directly in front of the inlet. To measure the horizontal and vertical variation in the sludge characteristics, sludge cores were collected from 3 to 7 locations in three of the ponds. Each core was divided into 4 sub-samples in which various physical, chemical, and microbiological parameters were measured. In addition, the inactivation of several pathogen indicator organisms was studied in a batch of sludge for 7 months. Based on the microbiological results, it is concluded that reasonable estimates of the inactivation of fecal coliform bacteria, fecal enterococci, F+ coliphage, somatic coliphage, and Ascaris eggs in WSP sludge in central Mexico can be made using first-order rate constants of 0.1, 0.1, 0.01, 0.001, and 0.001d(-1), respectively. From the observed changes in the concentrations of total solids and the volatile to fixed solids ratio, empirical equations were developed to describe anaerobic degradation and compression, which are the two most important processes affecting the volume of sludge after its deposition. 相似文献
52.
Vandenplas S Temsamani AB Lumori ML Cisneros Z Van Biesen L 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2001,48(4):985-997
A system identification technique is applied to estimate the intrinsic absorption and dispersion of two fine sands. The method is based on the parametric modeling of the wave propagation through a Plexiglas tank filled with the sediment under investigation. The applicability of various porous models is discussed. The viscoelastic constant Q model and viscoelastic rational form model are applied and compared. Closed form expressions describing the wave propagation are replaced by Debye series expansions with correction coefficients that consider the beamspread caused by the finite aperture of the emitter. A multiple input multiple output (MIMO) representation is used in conjunction with the maximum likelihood estimator (MLE) for the estimation of the sediment parameters. The estimated absorption and dispersion curves are depicted 相似文献
53.
The Programa para el Manejo del Agua y del Suelo (PROMAS) assists the local farming community in introducing new types of locally available irrigation equipment that are both inexpensive and water efficient. Field experiments enabled determining the maximum application rates that cause zero runoff for slopes above 16% for low-cost sprinkler systems. 相似文献
54.
Rodolfo Cuevas Juan-Carlos Ferrer Mathias Klapp Juan-Carlos Muñoz 《Journal of Scheduling》2016,19(1):91-106
The potential benefits of using human resources efficiently in the service sector constitute an incentive for decision makers in this industry to intelligently manage the work shifts of their employees, especially those dealing directly with customers. In the long term, they should attempt to find the right balance between employing as few labor resources as possible and keeping a high level of service. In the short run (e.g., 1 week), however, contracted staff levels cannot be adjusted, and management efforts thus focus on the efficient assignment of shifts and activities to each employee. This article proposes a mixed integer program model that solves the short-term multi-skilled workforce tour scheduling problem, enabling decision makers to simultaneously design workers’ shifts and days off, assign activities to shifts and assign those to employees so as to maximize and balance coverage of a firm’s demand for on-duty staff across multiple activities. Our model is simple enough to be solved with a commercial MIP solver calibrated by default without recurring to complex methodologies, such as extended reformulations and exact and/or heuristic column generation subroutines. A wide computational testing over 1000 randomly generated instances suggests that the model’s solution times are compatible with daily use and that multi-skilling is a significant source of labor flexibility to improve coverage of labor requirements, in particular when such requirements are negatively correlated and part-time workers are a scarce resource. 相似文献
55.
56.
We present in this paper an analysis of a semi-Lagrangian second order Backward Difference Formula combined with hp-finite
element method to calculate the numerical solution of convection diffusion equations in ℝ2. Using mesh dependent norms, we prove that the a priori error estimate has two components: one corresponds to the approximation
of the exact solution along the characteristic curves, which is
O(Dt2+hm+1(1+\frac\mathopen|logh|Dt))O(\Delta t^{2}+h^{m+1}(1+\frac{\mathopen{|}\log h|}{\Delta t})); and the second, which is O(Dtp+|| [(u)\vec]-[(u)\vec]h||L¥)O(\Delta t^{p}+\| \vec{u}-\vec{u}_{h}\|_{L^{\infty}}), represents the error committed in the calculation of the characteristic curves. Here, m is the degree of the polynomials in the finite element space, [(u)\vec]\vec{u} is the velocity vector, [(u)\vec]h\vec{u}_{h} is the finite element approximation of [(u)\vec]\vec{u} and p denotes the order of the method employed to calculate the characteristics curves. Numerical examples support the validity
of our estimates. 相似文献
57.
Roberto L. Pozzo Rodolfo J. Brandi Alberto E. Cassano Miguel A. Baltanás 《Chemical engineering science》2010,65(4):1345-1353
A comprehensive kinetic model for the photooxidation of oxalic acid (C2O4H4) in a fluidized bed (FB) of a TiO2/quartz sand composite, in a UV-fully illuminated photoreactor, was developed and correlated with experimental results. A proper solution for the mass balance of the reacting system was achieved by combining the complete radiation field profile and the most recent and updated pathway for the adsorption and photodecomposition of oxalic acid onto TiO2 (Mendive et al., 2007), which was employed to determine the kinetic expression and model parameters. 相似文献
58.
59.
Rodolfo Florence Teixeira Jr. Flavio Cesar Faria Fernandes Néocles Alves Pereira 《Computers & Industrial Engineering》2010
This paper describes the development and solution of binary integer formulations for production scheduling problems in market-driven foundries. This industrial sector is comprised of small and mid-sized companies with little or no automation, working with diversified production, involving several different metal alloy specifications in small tailor-made product lots. The characteristics and constraints involved in a typical production environment at these industries challenge the formulation of mathematical programming models that can be computationally solved when considering real applications. However, despite the interest on the part of these industries in counting on effective methods for production scheduling, there are few studies available on the subject. The computational tests prove the robustness and feasibility of proposed models in situations analogous to those found in production scheduling at the analyzed industrial sector. 相似文献
60.
Israel I. Zetina-Rios Gloria-L. Osorio-Gordillo Rodolfo A. Vargas-Méndez Guadalupe Madrigal-Espinosa Carlos-M. Astorga-Zaragoza 《International Journal of Adaptive Control and Signal Processing》2021,35(5):828-845
This article presents a generalized learning observer (GLO) design for the simultaneous estimation of states and actuator faults for polytopic quasi-linear parameter varying systems. The proposed approach is based on the use of a GLO, which generalized the existing results on the proportional-integral observers. Conditions of existence and stability of the observer are given through the stability analysis in the sense of Lyapunov. Its design is obtained in terms of a set of linear matrix inequalities. The performance of the proposed method is evaluated by simulation in a one-link-flexible joint robot system. 相似文献