全文获取类型
收费全文 | 43125篇 |
免费 | 6598篇 |
国内免费 | 2577篇 |
专业分类
电工技术 | 3752篇 |
技术理论 | 1篇 |
综合类 | 4004篇 |
化学工业 | 2593篇 |
金属工艺 | 11596篇 |
机械仪表 | 4718篇 |
建筑科学 | 2548篇 |
矿业工程 | 1658篇 |
能源动力 | 1049篇 |
轻工业 | 1200篇 |
水利工程 | 1060篇 |
石油天然气 | 3304篇 |
武器工业 | 677篇 |
无线电 | 2961篇 |
一般工业技术 | 4416篇 |
冶金工业 | 1706篇 |
原子能技术 | 366篇 |
自动化技术 | 4691篇 |
出版年
2024年 | 81篇 |
2023年 | 460篇 |
2022年 | 1002篇 |
2021年 | 1050篇 |
2020年 | 1271篇 |
2019年 | 1147篇 |
2018年 | 1135篇 |
2017年 | 1652篇 |
2016年 | 1823篇 |
2015年 | 1739篇 |
2014年 | 2670篇 |
2013年 | 2955篇 |
2012年 | 3020篇 |
2011年 | 3190篇 |
2010年 | 2508篇 |
2009年 | 2520篇 |
2008年 | 2293篇 |
2007年 | 3121篇 |
2006年 | 2976篇 |
2005年 | 2435篇 |
2004年 | 2199篇 |
2003年 | 1849篇 |
2002年 | 1562篇 |
2001年 | 1317篇 |
2000年 | 1149篇 |
1999年 | 897篇 |
1998年 | 717篇 |
1997年 | 666篇 |
1996年 | 575篇 |
1995年 | 507篇 |
1994年 | 419篇 |
1993年 | 249篇 |
1992年 | 258篇 |
1991年 | 211篇 |
1990年 | 172篇 |
1989年 | 138篇 |
1988年 | 86篇 |
1987年 | 50篇 |
1986年 | 33篇 |
1985年 | 16篇 |
1984年 | 35篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 29篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1959年 | 5篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Yuelong Ma Le Zhang Tianyuan Zhou Bingheng Sun Chen Hou Shunshun Yang Jin Huang Rui Wang Farida A. Selim Zhongying Wang Ming Li Hao Chen Yun Wang 《Journal of the European Ceramic Society》2021,41(4):2834-2846
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs. 相似文献
2.
3.
Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-quality metal parts by WAAM,several problems about the heat build-up,the deposit-path optimization,and the stability of the process parameters need to be well addressed.To overcome these issues,a new WAAM method based on the double electrode micro plasma arc welding(DE-MPAW)was designed.The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically.The effects between the parameters,wire feed rate and torch stand-off distance,in the process of WAAM were investigated experimentally.In addition,a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance.Finally,a series of tests were performed to evaluate the con-trol system's performance.The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system.Further,the deposition paths about the metal part's layer heights in WAAM are simplified.Finally,the appearance of the WAAM-deposited metal layers is also improved with the use of the control system. 相似文献
4.
5.
Nicolas Larché Benoit Emo Audrey Allion Elisabeth Johansson Dominique Thierry 《工业材料与腐蚀》2021,72(8):1338-1349
With lower alloying cost and higher mechanical properties, lean duplex stainless steels can be an alternative to the more commonly used austenitic stainless steels. However, these alloys are still not the preferred choice, probably due to a lack of field experience. A study was thus initiated in view of defining the limits of use of selected (lean) duplexes for urban wastewater treatment units. The present paper shows the localized corrosion performance of selected lean duplexes in chloride contaminated solutions. The results are compared with austenitic S30403 and S31603 and with the more standard duplexes S82441 and S32205. The effect of welding was also investigated. Exposures in field municipal wastewater plants were conducted for 1 year in low and high chloride content units. The results show that lean duplexes S32101 and S32202 can be used as alternatives to S30403 and S31603 in low chloride electrolytes. At 500 ppm of chloride content, duplex stainless steel S32304 showed better corrosion resistance than S30403 and S31603. For higher chloride contents (1000 ppm and above) the standard duplexes S82441 and S32205 shall be preferred. 相似文献
6.
7.
8.
《Journal of dairy science》2022,105(4):3176-3191
Milk concentrates are used in the manufacturing of dairy products such as yogurt and cheese or are processed into milk powder. Processes for the nonthermal separation of water and valuable milk ingredients are becoming increasingly widespread at farm level. The technical barriers to using farm-manufactured milk concentrate in dairies are minimal, hence the suspicion that the practice of on-farm raw milk concentration is still fairly uncommon for economic reasons. This study, therefore, set out to investigate farmers' potential willingness to adopt a raw milk concentration plant. The empirical analysis was based on discrete choice experiments with 75 German dairy farmers to identify preferences and the possible adoption of on-farm raw milk concentration. The results showed that, in particular, farmers who deemed the current milk price to be insufficient viewed on-farm concentration using membrane technology as an option for diversifying their milk sales. We found no indication that adoption would be impeded by a lack of trustworthy information on milk processing technologies or capital. 相似文献
9.
《International Journal of Hydrogen Energy》2022,47(7):4814-4826
This paper develops a novel approach to the parameterisation of high temperature exchange membrane fuel cells (HTPEMFC) with limited and non-invasive measurements. The proposed method allows an effective identification of electrochemical parameters for three-dimensional fuel cell models by combining computational simulation tools and genetic algorithms. To avoid each evaluation undertaken by the optimisation method involving a complete computational simulation of the 3D model, a strategy has been designed that, thanks to an iterative process, makes it possible to decouple the fluid dynamic resolution from the electrochemistry one.Two electrochemical models have been incorporated into these tools to describe the behaviour of the catalyst layer, Butler-Volmer and spherical aggregate. For each one, a case study has been carried out to validate the results by comparing them with empirical data in the first model and with data generated by numerical simulation in the second. Results show that, from a set of measured operating conditions, it is possible to identify a unique set of electrochemical parameters that fits the 3D model to the target polarisation curve. The extension of this framework can be used to systematically estimate any model parameter in order to reduce the uncertainty in 3D simulation predictions. 相似文献
10.