全文获取类型
收费全文 | 32471篇 |
免费 | 3066篇 |
国内免费 | 1430篇 |
专业分类
电工技术 | 3869篇 |
技术理论 | 5篇 |
综合类 | 2372篇 |
化学工业 | 3639篇 |
金属工艺 | 2474篇 |
机械仪表 | 2128篇 |
建筑科学 | 5485篇 |
矿业工程 | 1688篇 |
能源动力 | 2547篇 |
轻工业 | 739篇 |
水利工程 | 1163篇 |
石油天然气 | 1239篇 |
武器工业 | 203篇 |
无线电 | 1478篇 |
一般工业技术 | 2814篇 |
冶金工业 | 3166篇 |
原子能技术 | 418篇 |
自动化技术 | 1540篇 |
出版年
2024年 | 61篇 |
2023年 | 354篇 |
2022年 | 767篇 |
2021年 | 868篇 |
2020年 | 1010篇 |
2019年 | 722篇 |
2018年 | 622篇 |
2017年 | 886篇 |
2016年 | 1070篇 |
2015年 | 1203篇 |
2014年 | 2443篇 |
2013年 | 1897篇 |
2012年 | 2800篇 |
2011年 | 2804篇 |
2010年 | 2198篇 |
2009年 | 2102篇 |
2008年 | 1656篇 |
2007年 | 2096篇 |
2006年 | 1934篇 |
2005年 | 1553篇 |
2004年 | 1368篇 |
2003年 | 1187篇 |
2002年 | 1016篇 |
2001年 | 894篇 |
2000年 | 749篇 |
1999年 | 602篇 |
1998年 | 433篇 |
1997年 | 368篇 |
1996年 | 264篇 |
1995年 | 253篇 |
1994年 | 194篇 |
1993年 | 127篇 |
1992年 | 87篇 |
1991年 | 74篇 |
1990年 | 74篇 |
1989年 | 41篇 |
1988年 | 25篇 |
1987年 | 28篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 6篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1966年 | 2篇 |
1959年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
1.
2.
Mehdi Hosseini Abadshapoori 《亚洲传热研究》2021,50(2):1056-1072
Increasing the heat capacity of heat exchangers is a crucial need for modern devices. The thermal conductivity of the usual fluids and the Nusselt (Nu) number of flows containing such fluids are two bottlenecks in the way of increasing heat delivery in the heat exchangers. For this reason, nanofluids have been introduced. The effect of utilizing a Cu-water nanofluid as a coolant of two hot pipes in a square cavity is investigated numerically with a two-component lattice Boltzmann method. The volume fraction of nanoparticles is assumed to be constant (0.03) while the Richardson (Ri) number varies from 0.02 to 20. Results show that the effectiveness of nanoparticles is better observed in the natural convection mode. However, sedimentation is also very probable at high Ri numbers, which significantly reduces the effectiveness of the nanoparticles. Configurations which produce a natural convection stream similar to the forced convection one as well as the configurations with high spacing and hence, low heat stream interactions, are the best choices for a uniform heat rate from the pipes. 相似文献
3.
The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO2 inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO2 inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO2-NaOH-H2O system, CO2 inleakage saturation was derived to quantify the amount of the dissolved CO2 in GICW. This parameter can be directly calculated with the measured conductivity and the [Na+] of GICW. The influence of CO2 inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO2 inleakage and the NaOH dosage. This study provides insights into the influence of CO2 inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO2 inleakage occurs. 相似文献
4.
5.
6.
7.
8.
随着互联网的高速发展,引发了网络流量、电信骨干网流量急速增长,使得网络容量的提升迫在眉睫。目前,100G 系统已经商用,超100G系统能够更有效地解决流量和网络带宽持续增长带来的压力,本文主要介绍新型单模光纤的特性以及探讨基于新型单模光纤的传输技术。 相似文献
9.
This paper presented the exergoeconomic evaluation of the developed desiccant-evaporative air-conditioning system. The developed system was evaluated based on the steady-state conditions at different regeneration and reference temperatures. The exergoeconomic evaluation method was implemented to the system components and the whole system to evaluate the exergy efficiency, exergy destruction ratios, cost rates, relative cost differences and exergoeconomic factors. The regeneration and reference temperatures affected the exergy efficiencies, exergy destruction ratios, cost rates, relative cost differences and exergoeconomic factors. The desiccant wheel, heating coil and evaporative cooler had a high cost rate (investment cost, operation and maintenance cost, and exergy destruction cost). The exit air fan, outdoor air fan and evaporative cooler had a high relative cost difference. The exit air fan, outdoor air fan and secondary heat exchanger had a high exergoeconomic factor. Replacement of the desiccant wheel with a higher dehumidification performance could decrease the high cost rate. A higher efficiency evaporative cooler and heating coil were needed. Cheaper air fans (outdoor air fans and exit air fans) were needed. 相似文献
10.
Matthias Siemon Olaf Riese Burkhard Forell Dominic Krnung Walter Klein‐Heßling 《火与材料》2019,43(5):497-513
In the context of industrial buildings and power plants, electrical installations and cable trays represent a main fuel load and a potential initial fire source due to possible short circuits or comparable malfunction. Furthermore, a fire can spread from one tray to additional trays mounted above and/or horizontally on one tray. Because of the high significance of cable fires, several research projects have been carried out, investigating the fire behaviour of cables from small‐scale tests, eg, the cone calorimeter, up to large‐scale tests, analysing complete cable tray constructions. The goal of the work presented in this paper is the extension of the knowledge regarding the influence of geometrical parameters like the packing density and tray distance on the burning behaviour and fire spread of cable tray installations. The results are considered, together with test results from the literature, to quantify the main physical parameters describing the burning behaviour. In a next step, the general applicability of these parameters as input data for the parametrization of the source term of numerical simulations is shown. The test results show that the burning behaviour and the fire spreading highly depend on the cable arrangement of the cables on the cable tray, in combination with other boundary conditions. By applying the results as input for a fire simulation, the mass loss rate is considered appropriately. 相似文献