全文获取类型
收费全文 | 895篇 |
免费 | 43篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 74篇 |
综合类 | 75篇 |
化学工业 | 82篇 |
金属工艺 | 26篇 |
机械仪表 | 57篇 |
建筑科学 | 117篇 |
矿业工程 | 20篇 |
能源动力 | 87篇 |
轻工业 | 72篇 |
水利工程 | 15篇 |
石油天然气 | 27篇 |
武器工业 | 7篇 |
无线电 | 31篇 |
一般工业技术 | 125篇 |
冶金工业 | 22篇 |
原子能技术 | 17篇 |
自动化技术 | 105篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 16篇 |
2020年 | 25篇 |
2019年 | 29篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 37篇 |
2015年 | 41篇 |
2014年 | 53篇 |
2013年 | 50篇 |
2012年 | 67篇 |
2011年 | 63篇 |
2010年 | 36篇 |
2009年 | 52篇 |
2008年 | 58篇 |
2007年 | 47篇 |
2006年 | 54篇 |
2005年 | 35篇 |
2004年 | 42篇 |
2003年 | 30篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 24篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有959条查询结果,搜索用时 15 毫秒
71.
Nan DingRajat Arora Michael NorconkSeong-Young Lee 《International Journal of Hydrogen Energy》2011,36(4):3222-3231
In recent years, research efforts have been channeled to explore the use of environmentally-friendly clean fuel in lean-premixed combustion so that it is vital to understand fundamental knowledge of combustion and emissions characteristics for an advanced gas turbine combustor design. The current study investigates the extinction limits and emission formations of dry syngas (50% H2-50% CO), moist syngas (40% H2-40% CO-20% H2O), and impure syngas containing 5% CH4. A counterflow flame configuration was numerically investigated to understand extinction and emission characteristics at the lean-premixed combustion condition by varying dilution levels (N2, CO2 and H2O) at different pressures and syngas compositions. By increasing dilution and varying syngas composition and maintaining a constant strain rate in the flame, numerical simulation showed among diluents considered: CO2 diluted flame has the same extinction limit in moist syngas as in dry syngas but a higher extinction temperature; H2O presence in the fuel mixture decreases the extinction limit of N2 diluted flame but still increases the flame extinction temperature; impure syngas with CH4 extends the flame extinction limit but has no effect on flame temperature in CO2 diluted flame; for diluted moist syngas, extinction limit is increased at higher pressure with the larger extinction temperature; for different compositions of syngas, higher CO concentration leads to higher NO emission. This study enables to provide insight into reaction mechanisms involved in flame extinction and emission through the addition of diluents at ambient and high pressure. 相似文献
72.
针对乐安油田草31断块的气顶稠油油气藏,在落实天然气储量规模和油气分布的基础上,运用油藏工程方法.借助数值模拟手段,对小气顶油藏的开采方式、布井方式、注水时机等开发技术界限进行了优化研究,确定出适宜该油气藏的开发方案。 相似文献
73.
74.
JERRY H. MELDON PIETER STROEVE CATHERINE E. GREGOIRE 《Chemical Engineering Communications》2013,200(1-6):263-300
The effect of reversible chemical reaction upon the diffusion of carbon dioxide in thin liquid film membranes is reviewed. Particular emphasis is placed upon the hydration reaction of CO2 and catalysis thereof. Theoretical analysis is developed for equilibrium, near-equilibrium and near-diffusion regimes. The important effects of weak acid buffers, proteins and amines upon CO2 transport are also discussed, as well as the significance of diffusion potentials, particularly in the case of protein systems. Results of experimental investigations of facilitated CO2 transport are reviewed, as well as general aspects of CO2 transport in biological systems and absorbers. 相似文献
75.
The influences of the exchange complex and pH of the solution used for cation saturation on Atterberg limits, compaction, and swelling potential of a compacted clay were investigated. The study involved transforming the exchange complex from a heterogeneous to a homogeneous one so that a frame of reference can be set for the clay behavior under such an ideal condition. The employed method for altering the exchange complex successfully yielded homo-ionic clay. The introduction of different species of cations gave rise to different particles associations. When introduced to the tested clay, potassium cations bond its particles with a rather strong bond (K-linkage), causing a drastic decrease in the specific area of the clay (about one-fourth of its untreated specific area), a decrease in the CEC, as well as a drastic decrease in the swell potential. For example, the swell pressure decreased from 1.87 kg/cm2 for the untreated samples to 0.4 kg/cm2 for the K-treated samples (under the same conditions). Also, the swell potential vs. time relationships can be modeled accurately using a rectangular hyperbola. 相似文献
76.
For many students, sustainability has become an obligatory add-on for any project. Here Ulysses Sengupta and Deljana Iossifova explain how they have sought to address this in their teaching at the University of Nottingham through a ‘systemic diagramming’ approach. This provides essential tools for understanding how resource flows and environmental concerns are embedded in physical urban transformation, socioeconomic fault lines and underlying power relations. 相似文献
77.
Position USBL/DVL sensor-based navigation filter in the presence of unknown ocean currents 总被引:2,自引:0,他引:2
Marco Morgado Pedro Batista Paulo Oliveira Carlos SilvestreAuthor vitae 《Automatica》2011,47(12):2604-2614
This paper presents a novel approach to the design of globally asymptotically stable (GAS) position and velocity filters for Autonomous Underwater Vehicles (AUVs) based directly on the sensor readings of an Ultra-short Baseline (USBL) acoustic array system and a Doppler Velocity Log (DVL). The proposed methodology is based on an equivalent linear time-varying (LTV) system that fully captures the dynamics of the nonlinear system, allowing for the use of powerful linear system analysis and filtering design tools that yield GAS filter error dynamics. Numerical results using Monte Carlo simulations and comparison to the Bayesian Cramér Rao Bound (BCRB) reveal that the performance of the proposed filter is tight to this theoretical estimation error lower bound. In comparison with other approaches, the present solution achieves the same level of performance of the Extended Kalman Filter (EKF), which does not offer GAS guarantees, and outperforms other classical filtering approaches designed in inertial coordinates instead of the body-fixed coordinate frame. 相似文献
78.
Stanislaw Sieniutycz 《Energy Conversion and Management》2000,41(18):2009-2039
We construct thermodynamic criteria for optimization of sequential work-assisted heating and drying operations which run jointly with ‘endoreversible’ thermal machines. The total power input is minimized with constraints which take into account the dynamics of heat and mass transport and rate of work consumption. Finite-rate, endoreversible models include the irreducible losses of classical exergy potential caused by the thermal resistances. Extremum performance functions for optimal work, which incorporate residual entropy production, are formulated in terms of end states, duration and (in discrete processes) number of stages. Formal analogies between entropy production expressions for work-assisted and conventional drying operations help formulate optimization models of the former. An optimization procedure for a two-stage drying operation with an endoreversible heat pump at each stage is outlined. 相似文献
79.
Stelios Arvanitis 《时间序列分析杂志》2014,35(6):536-557
Indirect estimators usually emerge from two‐step optimization procedures. Each step in such a procedure may induce complexities in the asymptotic theory of the estimator. In this note, we are occupied with a simple example in which the estimator defined by the inversion of the binding function has a ‘discontinuous’ limit theory even in cases where the auxiliary one does not. This example lives in the framework of estimation of the MA (1) parameter. The ‘discontinuities’ involve the dependence of the rate of convergence on the parameter, the non‐continuity of the limit distribution w.r.t. the parameter and the estimator's non‐regularity. We are also occupied with a more complex example where the discontinuities occur because of complexities induced in any step of the defining procedure. We present some Monte Carlo evidence on the quality of the approximations from the limit distributions. Copyright © 2014 Wiley Publishing Ltd 相似文献
80.
Quenching and blowoff limits of hydrogen diffusion flames on small burners were observed. Four burner types, with diameters as small as 8 μm, were considered: pinhole burners, curved-wall burners, tube burners, and leaky fittings. In terms of mass flow rate, hydrogen had a lower quenching limit and a higher blowoff limit than either methane or propane. Hydrogen flames at their quenching limits were the weakest flames recorded to date, with mass flow rates and heat release rates as low as 3.9 μg/s and 0.46 W. The quenching limit for a hydrogen flame at a 6 mm leaky compression fitting was found to be 28 μg/s. This limit was independent of supply pressure (up to 131 bar) and about an order of magnitude lower than the corresponding limits for methane and propane. 相似文献