全文获取类型
收费全文 | 272972篇 |
免费 | 4533篇 |
国内免费 | 1537篇 |
专业分类
电工技术 | 5776篇 |
技术理论 | 3篇 |
综合类 | 1429篇 |
化学工业 | 39802篇 |
金属工艺 | 10469篇 |
机械仪表 | 8782篇 |
建筑科学 | 7666篇 |
矿业工程 | 1311篇 |
能源动力 | 7772篇 |
轻工业 | 22521篇 |
水利工程 | 2530篇 |
石油天然气 | 4284篇 |
武器工业 | 168篇 |
无线电 | 36413篇 |
一般工业技术 | 52952篇 |
冶金工业 | 49636篇 |
原子能技术 | 5322篇 |
自动化技术 | 22206篇 |
出版年
2022年 | 1880篇 |
2021年 | 2742篇 |
2020年 | 2043篇 |
2019年 | 2356篇 |
2018年 | 3728篇 |
2017年 | 3893篇 |
2016年 | 3920篇 |
2015年 | 2910篇 |
2014年 | 4788篇 |
2013年 | 12556篇 |
2012年 | 7371篇 |
2011年 | 9793篇 |
2010年 | 7947篇 |
2009年 | 8895篇 |
2008年 | 9488篇 |
2007年 | 9328篇 |
2006年 | 8470篇 |
2005年 | 7586篇 |
2004年 | 6960篇 |
2003年 | 7200篇 |
2002年 | 6636篇 |
2001年 | 7027篇 |
2000年 | 6633篇 |
1999年 | 7105篇 |
1998年 | 17088篇 |
1997年 | 11948篇 |
1996年 | 9266篇 |
1995年 | 7053篇 |
1994年 | 6231篇 |
1993年 | 6087篇 |
1992年 | 4335篇 |
1991年 | 4186篇 |
1990年 | 3986篇 |
1989年 | 3757篇 |
1988年 | 3647篇 |
1987年 | 3060篇 |
1986年 | 2988篇 |
1985年 | 3248篇 |
1984年 | 2944篇 |
1983年 | 2833篇 |
1982年 | 2649篇 |
1981年 | 2555篇 |
1980年 | 2472篇 |
1979年 | 2311篇 |
1978年 | 2110篇 |
1977年 | 2606篇 |
1976年 | 3566篇 |
1975年 | 1766篇 |
1974年 | 1729篇 |
1973年 | 1665篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
J. Grune K. Sempert M. Kuznetsov T. Jordan 《International Journal of Hydrogen Energy》2021,46(23):12487-12496
This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m2 area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H2/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H2 was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames. 相似文献
86.
87.
88.
S.K. Vimala Bharathi M. Maria Leena J.A. Moses C. Anandharamakrishnan 《International Journal of Food Science & Technology》2020,55(3):1238-1245
The usage of cling wraps is emerging as an easy and cost-effective approach to protect fresh-cut fruits and vegetables from dust, whilst improving visual appeal on retail counters. This study focused on developing an alternate, protein-based packaging material as a food grade cling wrap for food packaging applications. Zein-based cling wraps were produced, and their physical and mechanical characteristics were evaluated and compared with conventionally used chitosan biopolymer films and commercial synthetic polymer films. Antioxidant potential of the prepared films was studied, and the effectiveness of the developed films as anti-browning cling wraps was evaluated using studies conducted on fresh-cut apple slices at ambient conditions. Anti-browning effects were in par with polymeric counterparts; however, zein cling wraps could better prevent weight loss in apple slices. Zein-based films can be adopted as biodegradable food grade cling wraps as an alternative to chitosan and synthetic polymeric materials. 相似文献
89.
Han Yan Gu Yi Chen Lei Li Bing Liu Xiang Ming Chen 《International Journal of Applied Ceramic Technology》2020,17(2):790-796
SrLa[Ga1−x(R0.5Ti0.5)x]O4 (R = Mg, Zn) ceramics were prepared by a standard solid state sintering method. The single-phase ceramics with K2NiF4-type layered perovskite structure and I4/mmm space group were obtained, indicating that SrLa(R0.5Ti0.5) and SrLaGaO4 can form the unlimited solid solutions. With increasing x for R = Mg and Zn, εr increases monotonously, the Qf value first increases and then decreases, while τf increases from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: εr = 23.3, Qf = 89 400 GHz, τf = −0.8 ppm/°C for SrLa[Ga0.6(Mg0.5Ti0.5)0.4]O4 and εr = 23.3, Qf = 76 200 GHz, τf = 0.2 ppm/°C for SrLa[Ga0.7(Zn0.5Ti0.5)0.3]O4, indicating that the present solid solution ceramics are the promising candidates as microwave resonator materials for the telecommunication applications. 相似文献
90.
Lokesh Kulhari Kanad Ray Ankit Paptan Nikhil Suri Pramod K Khanna 《International Journal of Applied Ceramic Technology》2020,17(3):1430-1439
Low temperature co-fired ceramic (LTCC) micro-hotplates show wide applications in gas sensors and micro-fluidic devices. It is easily structured in three-dimensional structures. This paper presents the low power consumption micro-hotplates which were developed with PTC (positive temperature coefficient) temperature sensor and inter-digitated electrodes. The paper presents two different structures for micro-hotplate with platinum as a heating element. The PTC temperature sensor using two different materials viz. PdAg and platinum paste are developed with micro-hotplates. The simulation has been achieved through COMSOL for LTCC and alumina micro-hotplates. The temperature variation with power consumption has been measured for the developed LTCC micro-hotplates. The change in resistance of PTC temperature sensors was measured with micro-hotplate temperature. The aim of this study was to place a temperature sensor with the gas sensor module to measure and control the temperature of micro-hotplate. A SnO2 sensing layer is coated on LTCC micro-hotplate using screen printing and characterized for the sensing of carbon monoxide gas (CO). This study will be beneficial for designing hotplates based on LTCC technology with low power consumption and better stability of temperature for gas-sensing applications. 相似文献