全文获取类型
收费全文 | 62528篇 |
免费 | 7074篇 |
国内免费 | 3965篇 |
专业分类
电工技术 | 5247篇 |
技术理论 | 2篇 |
综合类 | 4578篇 |
化学工业 | 9470篇 |
金属工艺 | 3217篇 |
机械仪表 | 4067篇 |
建筑科学 | 4692篇 |
矿业工程 | 1896篇 |
能源动力 | 2039篇 |
轻工业 | 5829篇 |
水利工程 | 1596篇 |
石油天然气 | 2623篇 |
武器工业 | 777篇 |
无线电 | 7448篇 |
一般工业技术 | 6574篇 |
冶金工业 | 2658篇 |
原子能技术 | 897篇 |
自动化技术 | 9957篇 |
出版年
2024年 | 273篇 |
2023年 | 976篇 |
2022年 | 2132篇 |
2021年 | 3216篇 |
2020年 | 2219篇 |
2019年 | 1830篇 |
2018年 | 2063篇 |
2017年 | 2278篇 |
2016年 | 2187篇 |
2015年 | 2942篇 |
2014年 | 3695篇 |
2013年 | 4645篇 |
2012年 | 5252篇 |
2011年 | 5420篇 |
2010年 | 4799篇 |
2009年 | 4577篇 |
2008年 | 4270篇 |
2007年 | 4025篇 |
2006年 | 3610篇 |
2005年 | 2778篇 |
2004年 | 2006篇 |
2003年 | 1470篇 |
2002年 | 1421篇 |
2001年 | 1100篇 |
2000年 | 852篇 |
1999年 | 617篇 |
1998年 | 600篇 |
1997年 | 461篇 |
1996年 | 360篇 |
1995年 | 297篇 |
1994年 | 202篇 |
1993年 | 137篇 |
1992年 | 111篇 |
1991年 | 76篇 |
1990年 | 70篇 |
1989年 | 60篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 33篇 |
1985年 | 31篇 |
1984年 | 43篇 |
1983年 | 35篇 |
1982年 | 27篇 |
1981年 | 28篇 |
1980年 | 33篇 |
1979年 | 31篇 |
1978年 | 26篇 |
1977年 | 27篇 |
1976年 | 55篇 |
1975年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Lili Hou Axel Olesund Shameel Thurakkal Xiaoyan Zhang Bo Albinsson 《Advanced functional materials》2021,31(47):2106198
Developing high-performance visible-to-UV photon upconversion systems based on triplet–triplet annihilation photon upconversion (TTA-UC) is highly desired, as it provides a potential approach for UV light-induced photosynthesis and photocatalysis. However, the quantum yield and spectral range of visible-to-UV TTA-UC based on nanocrystals (NCs) are still far from satisfactory. Here, three different sized CdS NCs are systematically investigated with triplet energy transfer to four mediators and four annihilators, thus substantially expanding the available materials for visible-to-UV TTA-UC. By improving the quality of CdS NCs, introducing the mediator via a direct mixing fashion, and matching the energy levels, a high TTA-UC quantum yield of 10.4% (out of a 50% maximum) is achieved in one case, which represents a record performance in TTA-UC based on NCs without doping. In another case, TTA-UC photons approaching 4 eV are observed, which is on par with the highest energies observed in optimized organic systems. Importantly, the in-depth investigation reveals that the direct mixing approach to introduce the mediator is a key factor that leads to close to unity efficiencies of triplet energy transfer, which ultimately governs the performance of NC-based TTA-UC systems. These findings provide guidelines for the design of high-performance TTA-UC systems toward solar energy harvesting. 相似文献
12.
Juan José Burbano He/him Darío Marcelino Cabezas María Jimena Correa 《International Journal of Food Science & Technology》2022,57(8):4772-4781
Walnut flour (WF), a by-product of walnut oil production, is characterised by high polyunsaturated fatty acids, proteins, and fibre contents and presents suitability for bakery products. However, when using non-traditional ingredients, it is essential to evaluate the effect on the quality properties of the final product. So, this work aimed to assess the impact of WF on the technological, physicochemical, and sensory properties of gluten-free (GF) cakes. WF was added at a flour blend (cassava (CS) and maize (MS) starches and rice flour) at 0, 10%, 15%, and 20%. The results showed that WF modified starch gelatinisation, increased amylose–lipid complex (ALC) content, and made crumbs easier to chew. Besides, the total dietary fibre (TDF) and protein content significantly increased. Cakes with 15% WF presented the highest specific volume (SV) and no differences in overall acceptability with respect to control. Hence, WF is a suitable ingredient for gluten-free bakery products. 相似文献
13.
Tallison O. Abreu Roterdan F. Abreu Felipe F. do Carmo Wellington V. de Sousa Helenilson de O. Barros José E.V. de Morais João P.C. do Nascimento Marcelo A.S. da Silva Sergei Trukhanov Alex Trukhanov Larissa Panina Charanjeet Singh Antonio S.B. Sombra 《Ceramics International》2021,47(11):15424-15432
This work presents the dielectric properties of YNbO4 (YNO)–TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO2. Moreover, the addition of TiO2 results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO2 composites are interesting candidates for microwave operating devices. 相似文献
14.
Hongli Liu Peng Wang Bo Zhang Hongyan Li Jing Li Yajing Li Zhong Chen 《Ceramics International》2021,47(5):6487-6495
A novel carbon/m-HNTs composite aerogel was synthesized by introducing the modified halloysite nanotubes (m-HNTs) into phenolic (PR) aerogels through chemical grafting, followed with carbonization treatment. In order to explore the best proportion of HNTs to phenolic, the micromorphology of PR/m-HNTs were investigated by SEM before carbonization, confirming 10 wt% of m-HNTs is most beneficial to the porous network of aerogels. The interaction between PR and HNTs was studied by FTIR spectra, and microstructure evolution of the target product-carbon/m-HNTs composite aerogel were illustrated by SEM and TEM techniques. SEM patterns indicated that the carbon/m-HNTs aerogels maintain a stable porous structure at 1000 °C (carbonization temperature), while a ~20 nm carbon layer was formed around m-HNTs generating an integral unit through TEM analysis. Specific surface area and pore size distribution of composite aerogels were analyzed based on mercury intrusion porosimetry and N2 adsorption–desorption method, the obtained results stayed around 500 m2g?1 and 1.00 cm3g?1 (pore volume) without significant discrepancy, compared with pure aerogel, showing the uniformity of pore size. The weight loss rate (26.76%) decreased greatly compared with pure aerogel, at the same time, the best volumetric shrinkage rate was only 30.83%, contributed by the existence of HNTs supporting the neighbor structure to avoid over-shrinking. The highest compressive strength reached to 4.43 MPa, while the data of pure aerogel was only 1.52 MPa, demonstrating the excellent mechanical property of carbon/m-HNTs aerogels. 相似文献
15.
16.
17.
18.
Babilas R. Łoński W. Młynarek K. Bajorek A. Radoń A. 《Metallurgical and Materials Transactions A》2020,51(8):4215-4227
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y... 相似文献
19.
20.