全文获取类型
收费全文 | 43737篇 |
免费 | 13037篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 788篇 |
综合类 | 11篇 |
化学工业 | 17767篇 |
金属工艺 | 452篇 |
机械仪表 | 903篇 |
建筑科学 | 1811篇 |
矿业工程 | 6篇 |
能源动力 | 1013篇 |
轻工业 | 7246篇 |
水利工程 | 307篇 |
石油天然气 | 60篇 |
无线电 | 7801篇 |
一般工业技术 | 12149篇 |
冶金工业 | 1151篇 |
原子能技术 | 33篇 |
自动化技术 | 5302篇 |
出版年
2023年 | 43篇 |
2022年 | 115篇 |
2021年 | 345篇 |
2020年 | 1457篇 |
2019年 | 3197篇 |
2018年 | 3139篇 |
2017年 | 3476篇 |
2016年 | 3950篇 |
2015年 | 4011篇 |
2014年 | 3978篇 |
2013年 | 5289篇 |
2012年 | 2910篇 |
2011年 | 2642篇 |
2010年 | 2885篇 |
2009年 | 2828篇 |
2008年 | 2304篇 |
2007年 | 2132篇 |
2006年 | 1846篇 |
2005年 | 1549篇 |
2004年 | 1487篇 |
2003年 | 1437篇 |
2002年 | 1356篇 |
2001年 | 1201篇 |
2000年 | 1134篇 |
1999年 | 546篇 |
1998年 | 278篇 |
1997年 | 199篇 |
1996年 | 166篇 |
1995年 | 98篇 |
1994年 | 113篇 |
1993年 | 111篇 |
1992年 | 69篇 |
1991年 | 58篇 |
1990年 | 49篇 |
1989年 | 42篇 |
1988年 | 47篇 |
1987年 | 31篇 |
1986年 | 32篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Since the end of the Cold War and due to the needs to produce titanium more cost‐efficient and thus more attractive for its civilian use, the electroslag remelting (ESR) process has become an increasingly important topic of international research programmes, because titanium and titanium aluminides can be chemically refined by ESR in some degree. Using ESR, titanium turnings from machining steps and scrap from foundries can be remelted, refined and provided as secondary titanium for the market at relatively favourable prices. This article investigates the removability of the main impurities out of titanium and titanium‐aluminium alloys by electroslag remelting using the active slag system CaF2‐Ca‐(CaO). Thermochemical and kinetic aspects of the ESR process are considered. 相似文献
83.
84.
85.
86.
The AlCoCrCuFeNi high-entropy alloy system was synthesized using a well-developed arc melting and casting method. Their elemental effect on microstructures and hardness was investigated with X-ray diffraction, scanning electron microscopy and Vickers hardness testing. The alloys exhibit quite simple FCC and BCC solid solution phases. Co, Cu and Ni elements enhance the formation of the FCC phase while Al and Cr enhance that of the BCC phase in the alloy system. BCC phases form a spinodal structure during cooling. Copper tends to segregate at the interdendrite region and forms a Cu-rich FCC phase. Low copper content renders the interdendrite as a thin film and the as-cast structure like recrystallized grain structure. The formation of BCC phases significantly increases the hardness level of the alloy system. The strengthening mechanism is discussed. 相似文献
87.
This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two‐dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two‐dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home‐based medical care and other situations in which safety, simplicity, and economy are important. 相似文献
88.
89.
90.
S. Danto P. Houizot C. Boussard‐Pledel X.‐H. Zhang F. Smektala J. Lucas 《Advanced functional materials》2006,16(14):1847-1852
Conditions of formation of bulk tellurium chalcogenide glasses, containing 70–80 at % Te associated to Ga and Ge are described. The characteristic temperatures are measured: the glass‐transition temperature, Tg, is situated in the range 140–185 °C and the difference Tx – Tg, where Tx is the onset crystallization temperature, is in the range 76–113 °C. Moreover, the optical transmission window is exceptional, ranging from 1.99 μm in the bandgap up to 28 μm in the phonon region. Developed within the framework of requirements for the Darwin mission (a search for and study of extrasolar planets), feasibility of infrared optical fibers formed from these glasses is studied. Drawing experiments are conducted with the glass Ga2‐Ge3Te15, which possesses the maximum Tx – Tg, and a first optical fiber is presented. 相似文献