全文获取类型
收费全文 | 987篇 |
免费 | 166篇 |
国内免费 | 8篇 |
学科分类
工业技术 | 1161篇 |
出版年
2023年 | 6篇 |
2022年 | 20篇 |
2021年 | 28篇 |
2020年 | 22篇 |
2019年 | 26篇 |
2018年 | 20篇 |
2017年 | 21篇 |
2016年 | 32篇 |
2015年 | 47篇 |
2014年 | 59篇 |
2013年 | 69篇 |
2012年 | 56篇 |
2011年 | 69篇 |
2010年 | 43篇 |
2009年 | 43篇 |
2008年 | 44篇 |
2007年 | 76篇 |
2006年 | 54篇 |
2005年 | 62篇 |
2004年 | 50篇 |
2003年 | 55篇 |
2002年 | 38篇 |
2001年 | 43篇 |
2000年 | 16篇 |
1999年 | 31篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 3篇 |
排序方式: 共有1161条查询结果,搜索用时 15 毫秒
41.
通过对CO2工质的特性进行分析和实验验证,探讨了CO2工质在热泵热水机中应用的可行性、优缺点、前景以及所面对的困难等,希望对CO2工质应用于热泵热水机起到促进作用。 相似文献
42.
王磊 《制冷与空调(北京)》2014,(8):67-70
基于制冷量为12 kW的风管送风式空调(热泵)机组进行试验研究,分析节流位置、工况等因素对长连接管制冷剂追加量的影响,得出9.52 mm液管和15.88 mm气管条件下R410A制冷剂追加量的参考值。研究发现,对于单冷型空调器,节流位置会对长连接管的制冷剂追加量产生较大影响,室内机节流时的追加量大于室外机节流;而对于热泵型空调器,节流位置对长连接管制冷剂追加量的影响较小。 相似文献
43.
王峰 《制冷与空调(四川)》2014,(2):170-173,177
针对水平管降膜蒸发器用筛板式制冷剂分布器的操作流量、开孔数目、开孔大小、孔口流出系数、分布均匀度等设计参数展开讨论,由此总结了制冷剂分布器各设计参数的确定方法,以及制冷剂分布器的理论设计思路;针对筛板式制冷剂分布器设计参数的讨论也适用于其他类型的分布器。 相似文献
44.
In this study, nucleate boiling heat transfer coefficients (HTCs) of HFO1234yf HFC134a are measured on a flat plain, Turbo-B, Turbo-C, and Thermoexcel-E surfaces. All data are taken at the liquid pool temperature of 7 °C on small flat horizontal square copper plates (9.53 mm × 9.53 mm) at heat fluxes from 10 kW m−2 to 200 kW m−2 with an interval of 10 kW m−2. Test results show that nucleate boiling HTCs of HFO1234yf on all four surfaces are similar to those of HFC134a at all heat fluxes tested in this study. At heat fluxes below 150 kW m−2, Thermoexcel-E surface shows the highest heat transfer performance and hence is the best surface for the manufacture of the evaporators in refrigeration and air-conditioning equipment. On the other hand, at high heat fluxes above 150 kW m−2, Turbo-B and Turbo-C show better heat transfer performance than Thermoexcel-E and hence are good for electronic cooling applications. Overall, HFO1234yf is a good long term candidate with excellent environmental properties to replace successfully HFC134a from the view point of pool boiling heat transfer. Hence HFO1234yf can be readily applied to the conventional evaporators designed for HFC134a. 相似文献
45.
46.
我国的地铁建设正处于高速发展期,但目前典型地铁列车空调制冷系统的能效比只有2.2~2.3,远低于同类工况下住宅空调制冷系统的能效水平。针对此问题,先建立了某地铁空调制冷系统模型,仿真与系统测试结果吻合良好。然后通过详细的仿真分析,改进蒸发器和冷凝器的制冷剂流路设计、采用小排量高能效比压缩机等方法,使得系统在冷量和成本基本不变的情况下能效比提升了21.7%。最后,研究了制冷剂R410A替代R407C的系统性能变化,系统能效比可进一步提升11.3%,达到3以上。该研究方法及结果对于设计高效节能的地铁列车空调制冷系统具有参考价值。 相似文献
47.
针对混合制冷剂等挥发性混合物粘度测量的需要,研制了一种新的适用于测量低沸点混合物粘度的旋转式毛细管粘度计。该新型粘度测量装置在压力容器内嵌入旋转式毛细管粘度计,将旋转法升液和压力容器承压结合起来,避免了传统密封型毛细管粘度计由于抽放气的升液方式而导致混合物成分的变化,可以实现在较高压力下循环测量挥发性混合物溶液的粘度。采用R22和R290对旋转式毛细管粘度计进行了标定,并用R410A对粘度计的测量精度和性能进行了评价,粘度测量值与文献值最大相对偏差为0.81%。 相似文献
48.
Performance of heat pumps charged with R170/R290 mixture 总被引:2,自引:0,他引:2
In this study, thermodynamic performance of R170/R290 mixture is measured on a heat pump bench tester in an attempt to substitute R22. The bench tester is equipped with a commercial hermetic rotary compressor providing a nominal capacity of 3.5 kW. All tests are conducted under the summer cooling and winter heating conditions of 7/45 °C and −7/41 °C in the evaporator and condenser, respectively. During the tests, the composition in R170/R290 mixture is varied from 0% to 10% with an interval of 2%. Test results show that the coefficient of performance (COP) and capacity of R290 are up to 15.4% higher and 7.5% lower, respectively than those of R22 for two conditions. For R170/R290 mixture, the COP decreases and the capacity increases with an increase in the composition of R170. The mixture of R170/R290 mixture at 4%/96% composition shows the similar capacity and COP as those of R22. For the mixture, the compressor discharge temperature is 17–28 °C lower than that of R22. For R170/R290 mixture, there is no problem with mineral oil since the mixture is composed of hydrocarbons. The amount of charge is reduced up to 58% as compared to R22. Overall, R170/R290 mixture is a good long term ‘drop-in’ candidate from the view point of energy efficiency and greenhouse warming to replace R22 in residential air-conditioners and heat pumps. 相似文献
49.
Modeling and energy simulation of the variable refrigerant flow air conditioning system with water-cooled condenser under cooling conditions 总被引:1,自引:0,他引:1
As a new system, variable refrigerant flow system with water-cooled condenser (water-cooled VRF) can offer several interesting characteristics for potential users. However, at present, its dynamic simulation simultaneously in association with building and other equipments is not yet included in the energy simulation programs. Based on the EnergyPlus's codes, and using manufacturer's performance parameters and data, the special simulation module for water-cooled VRF is developed and embedded in the software of EnergyPlus. After modeling and testing the new module, on the basis of a typical office building in Shanghai with water-cooled VRF system, the monthly and seasonal cooling energy consumption and the breakdown of the total power consumption are analyzed. The simulation results show that, during the whole cooling period, the fan-coil plus fresh air (FPFA) system consumes about 20% more power than the water-cooled VRF system does. The power comparison between the water-cooled VRF system and the air-cooled VRF system is performed too. All of these can provide designers some ideas to analyze the energy features of this new system and then to determine a better scheme of the air conditioning system. 相似文献
50.
In the present paper, an attempt has been made to review the performance of new refrigerant mixtures employed in vapour compression‐based refrigeration, air‐conditioning and heat pump units. The studies reported with refrigerant mixtures are categorized into six groups as follows: (i) hydrocarbon (HC), (ii) hydroflurocarbons (HFC), (iii) HFC/HC, (iv) hydrochloroflurocarbons (HCFC), (v) carbon dioxide (R744) and (vi) ammonia (R717). This paper explores the studies reported with new refrigerant mixtures in domestic refrigerators, commercial refrigeration systems, air conditioners, heat pumps, chillers and in automobile air conditioners. In addition, the technical difficulties faced with new refrigerant mixtures, further research needs in this field and future refrigerant options for new upcoming systems have been discussed in detail. This paper concludes that HC based refrigerant mixtures are identified as a long‐term alternative to phase out the existing halogenated refrigerants in the vapour compression‐based systems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献