全文获取类型
收费全文 | 36674篇 |
免费 | 2826篇 |
国内免费 | 1663篇 |
专业分类
电工技术 | 2922篇 |
技术理论 | 1篇 |
综合类 | 3081篇 |
化学工业 | 2160篇 |
金属工艺 | 2045篇 |
机械仪表 | 6198篇 |
建筑科学 | 4097篇 |
矿业工程 | 3899篇 |
能源动力 | 2549篇 |
轻工业 | 475篇 |
水利工程 | 3284篇 |
石油天然气 | 3115篇 |
武器工业 | 412篇 |
无线电 | 1326篇 |
一般工业技术 | 2505篇 |
冶金工业 | 1230篇 |
原子能技术 | 346篇 |
自动化技术 | 1518篇 |
出版年
2024年 | 143篇 |
2023年 | 333篇 |
2022年 | 741篇 |
2021年 | 918篇 |
2020年 | 1039篇 |
2019年 | 649篇 |
2018年 | 703篇 |
2017年 | 827篇 |
2016年 | 1105篇 |
2015年 | 1359篇 |
2014年 | 2461篇 |
2013年 | 2074篇 |
2012年 | 3185篇 |
2011年 | 3169篇 |
2010年 | 2259篇 |
2009年 | 2201篇 |
2008年 | 1840篇 |
2007年 | 2537篇 |
2006年 | 2342篇 |
2005年 | 1958篇 |
2004年 | 1686篇 |
2003年 | 1512篇 |
2002年 | 1316篇 |
2001年 | 1007篇 |
2000年 | 855篇 |
1999年 | 601篇 |
1998年 | 486篇 |
1997年 | 387篇 |
1996年 | 376篇 |
1995年 | 309篇 |
1994年 | 206篇 |
1993年 | 129篇 |
1992年 | 95篇 |
1991年 | 73篇 |
1990年 | 50篇 |
1989年 | 57篇 |
1988年 | 31篇 |
1987年 | 29篇 |
1986年 | 19篇 |
1985年 | 6篇 |
1984年 | 15篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1977年 | 3篇 |
1959年 | 3篇 |
1956年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
《Applied Thermal Engineering》2014,62(2):747-757
Untreated urban sewage contains large amounts of thermal energy; and its temperature is suitable as a heat source in heat pumps for the heating and cooling of buildings. However, it is not widely used in heat pump systems due to the problem of filth. This paper presents an untreated sewage source heat pump (USSHP) system in which auto-avoiding-clogging equipment is used to continuously capture suspended solids in the sewage. Thus, the block problems caused by filtration and fouling in the heat exchanger tubes can be efficiently resolved in this system. In an actual engineering application, the characteristic parameters of USSHP system are tested under typical operating conditions for heating status. Based on the test results, the performances of the USSHP system are examined. The results indicate that the thermal resistance of the convective heat transfer and fouling on the sewage side in the sewage exchanger is 80% of its total thermal resistance. The COP of the heat pump unit and the COP of the USSHP system are 4.3 and 3.6, respectively. 相似文献
992.
C. V. SUNDARAM A. K. TANEJA CH. SRIDHAR RAO 《Mineral Processing and Extractive Metallurgy Review》2013,34(1):239-265
The reactive and refractory metals zirconium, titanium, tantalum and niobium have been in commercial production and industrial application over the last 30 years and more. With growing experience, there has been progressive improvement in process and equipment designs in the industrial practice. There has also been a continuous drive to develop entirely new processes, and to diversify the applications of these metals. The paper reviews the present status and the emerging trends, and places the Indian work in the global perspective. 相似文献
993.
994.
峻德煤矿将半机械化水采工艺改为机械化采煤工艺,既适应煤矿地质条件要求,又提高了矿井机械化程度,促进了该矿向高产高效矿井发展。 相似文献
995.
根据无料钟炉顶布料器液压系统的布料工艺特点,结合钢铁厂实际存在的问题,提出了改造方案,设计了新型的液压系统。通过现有的炉顶试验平台进行实施方案改造,同时对涉及到电气及自动化程序控制系统进行了相关改造。经过模拟试验测得,改造后的液压系统在α角定位精度和解决机械导轮导轨磨损等方面有了很大提高。 相似文献
996.
Silvio Barbarelli Mario Amelio Teresa Castiglione Gaetano Florio Nino Michele Scornaienchi 《国际能源研究杂志》2021,45(1):661-690
The aim of this paper is to illustrate the design of a new wave energy converter, composed of a point absorber and a hydraulic system (power take off) and sized for recovering energy in calm seas from waves near the shore. The point absorber is consisting of a rectangular shaped buoy integrating a piston pump. The set buoy‐pump oscillates under the waves action and moves natural water in a closed circuit hydraulic system (power take off) composed of a piping connecting the piston pump itself, a pressurized reservoir, a hydraulic turbine and a discharge tank. The methodology adopted for designing the main constituents involves a 1D mathematical model, settled for understanding the motion of the buoy under the hypothesis of regular waves and fully developed sea, and a sizing procedure applied for the design of all the components of the hydraulic system. The project related to the Calabrian site of Cetraro (Mediterranean Sea—south Italy) led to designing a system with a 4 m large buoy, associated with a small 13 cm diameter micro Pelton turbine, so that more than 22 000 kWh could be recovered in a year. 相似文献
997.
叶片式液压摆动油缸正常运行的关键之一在于端面密封的密封可靠性。对叶片式液压摆动油缸端面密封在静密封条件下进行数学建模,通过对该模型求解得出端面密封与转子、定子之间的接触压力,同时运用有限元软件对端面密封与转子、定子的接触压力进行仿真求解。在预压缩量0~0.5 mm,油压0~20 MPa范围内,接触压力的解析解和有限元分析结果相近,同时样机实验结果也验证了在单侧预压缩量为0和0.1 mm,油压在0~20 MPa范围时模型的正确性,这表明所建立的端面密封模型可用于判断端面密封在静密封条件下的密封可靠性。 相似文献
998.
A novel heat pump and power generation integration system (HPPGIS) using solar energy as a low temperature heat source was presented in this study. This system could be operated in both an organic Rankine cycle power generation (ORC‐PG) mode and a reverse Carnot cycle heat pump (RCC‐HP) mode. Compared with a single heat pump and power generation system, this system improved the utilization efficiency of solar energy, thus showing potential for the generation of economic benefits. Contrastive analyses of different working fluids using ORC‐PG and RCC‐HP systems were conducted first, leading to the selection of R142b and R245fa as optimal fluids. Then, an experimental investigation of the system was carried out under different conditions. A heat pump and ORC system model was proposed and validated by comparing experimental and simulated values. The experimental results indicated that the HPPGIS had good feasibility and stability in both modes. In the ORC‐PG mode, HPPGIS had a power output of 1.29 kW and a thermal efficiency of 4.71% when the water inlet temperature of the evaporator was 90.03°C. In the RCC‐HP mode, HPPGIS had a COP of 3.16 and a heat capacity of 33.24 kW when the water outlet temperature of the condenser was 106.23°C. 相似文献
999.
To improve the defrosting accuracy and the energy efficiency of the air-source heat pump (ASHP) under frosting and defrosting conditions, a novel Temperature–Humidity–Time (T–H–T) defrosting control method, based on a frosting map for the ASHP unit, is proposed in this paper. A field test was conducted for two heating seasons, to verify the feasibility and applicability of the T–H–T method. The advantages of the T–H–T method, compared to the conventional Temperature–Time (T–T) defrosting control method, are presented. In total, eight cases are shown in this paper. Cases 1 to 4 were chosen to reveal the T–H–T performance under different frosting conditions. It was found that no matter what kind of frosting conditions, defrosting was always initiated in a similar situation: ∼90% of the outdoor coil surface was covered by frost; the temperature difference between the compressor suction and discharge increased by ∼20%; and the heating capacity decreased by ∼30%. These results indicate that the T–H–T method can make an accurate decision under different frosting conditions. Cases 5a, 5b and Cases 6a, 6b were two groups of cases to compare the advantages of the T–H–T method against the conventional T–T method. Cases 5a and 5b were chosen for the non-frosting condition. It was found that the T–T method initiated the defrosting operation 31 times within 24 h. However, none of the defrosting operations was conducted for the T–H–T method. Cases 6a and 6b were chosen to compare these two methods under consecutive and variable frosting conditions. For the T–T method, 63% of the defrosting processes were found to be executed under conditions where defrosting was not necessary. However, for the T–H–T method, all the defrosting controls were found to be accurate and reasonable. These results indicated that the novel T–H–T method is suitable for the defrosting control of the ASHP, and has a more competitive performance than the conventional T–T method. 相似文献
1000.
This study aims to develop a new type of peristaltic pump that transports high-viscosity and solid–liquid mixture fluids. Pumps capable of transporting such fluids are essential in various situations such as factory transportation, outdoors, and emergencies. These fluids are conventionally transported by positive-displacement and rotodynamic pumps. However, solid–liquid fluids could collide with the impeller of the rotodynamic pump and thereby damage the pump, whereas the positive-displacement pump must be sufficiently large to apply high pressure to the transported fluid. A small pump that can transport these fluids would save factory space and enable outdoor applications such as dredging operations. Thus, we adopted earthworm peristalsis as a model mechanism of fluid transport within a standard plumbing infrastructure. The insertion-type peristaltic pump developed in this study uses an artificial rubber muscle to achieve an earthworm-like mechanism. The capability and energy efficiency of the mechanism is evaluated in water transportation experiments. 相似文献