全文获取类型
收费全文 | 384190篇 |
免费 | 4354篇 |
国内免费 | 603篇 |
专业分类
电工技术 | 6438篇 |
综合类 | 373篇 |
化学工业 | 62530篇 |
金属工艺 | 17033篇 |
机械仪表 | 12061篇 |
建筑科学 | 8188篇 |
矿业工程 | 2960篇 |
能源动力 | 7733篇 |
轻工业 | 32488篇 |
水利工程 | 4785篇 |
石油天然气 | 11962篇 |
武器工业 | 43篇 |
无线电 | 36796篇 |
一般工业技术 | 77306篇 |
冶金工业 | 69310篇 |
原子能技术 | 11328篇 |
自动化技术 | 27813篇 |
出版年
2021年 | 3460篇 |
2019年 | 3322篇 |
2018年 | 5916篇 |
2017年 | 5948篇 |
2016年 | 6396篇 |
2015年 | 3698篇 |
2014年 | 6482篇 |
2013年 | 15835篇 |
2012年 | 9752篇 |
2011年 | 12869篇 |
2010年 | 10331篇 |
2009年 | 11402篇 |
2008年 | 11773篇 |
2007年 | 11857篇 |
2006年 | 10331篇 |
2005年 | 9222篇 |
2004年 | 8791篇 |
2003年 | 8547篇 |
2002年 | 8600篇 |
2001年 | 8470篇 |
2000年 | 8203篇 |
1999年 | 8014篇 |
1998年 | 18722篇 |
1997年 | 13401篇 |
1996年 | 10242篇 |
1995年 | 7912篇 |
1994年 | 7049篇 |
1993年 | 7042篇 |
1992年 | 5554篇 |
1991年 | 5327篇 |
1990年 | 5628篇 |
1989年 | 5421篇 |
1988年 | 5240篇 |
1987年 | 4746篇 |
1986年 | 4851篇 |
1985年 | 5334篇 |
1984年 | 5081篇 |
1983年 | 4722篇 |
1982年 | 4451篇 |
1981年 | 4664篇 |
1980年 | 4447篇 |
1979年 | 4545篇 |
1978年 | 4692篇 |
1977年 | 5007篇 |
1976年 | 6513篇 |
1975年 | 4248篇 |
1974年 | 4182篇 |
1973年 | 4317篇 |
1972年 | 3784篇 |
1971年 | 3453篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Fabiana D'Isanto Federico Smeacetto Hans-Peter Martin Richard Sedlák Maksym Lisnichuk Andreas Chrysanthou Milena Salvo 《Ceramics International》2021,47(14):19774-19783
A silica-based glass-ceramic, with Y2Ti2O7 as the major crystalline phase, is designed, characterised and tested as an oxidation-protective coating for a titanium suboxide (TiOx) thermoelectric material at temperatures of up to 600 °C. The optimised sinter-crystallisation treatment temperatures are found to be 1300 °C and 855 °C for a duration of 30 min, and this treatment leads to a glass-ceramic with cubic Y2Ti2O7 and CaAl2Si2O8 as crystalline phases. An increase of ~270 °C in the dilatometric softening temperature is observed after devitrification of the parent glass, thus further extending its working temperature range.Excellent adhesion of the glass-ceramic coating to the thermoelectric material is maintained after exposure to a temperature of 600 °C for 120 h under oxidising conditions, thus confirming the effectiveness of the T1 glass-ceramic in protecting the TiOx material. 相似文献
22.
Matteo Di Giosia Alice Soldà Markus Seeger Andrea Cantelli Fabio Arnesano Maria I. Nardella Vincenzo Mangini Francesco Valle Marco Montalti Francesco Zerbetto Stefania Rapino Matteo Calvaresi Vasilis Ntziachristos 《Advanced functional materials》2021,31(20):2101527
Fullerenes are candidates for theranostic applications because of their high photodynamic activity and intrinsic multimodal imaging contrast. However, fullerenes suffer from low solubility in aqueous media, poor biocompatibility, cell toxicity, and a tendency to aggregate. C70@lysozyme is introduced herein as a novel bioconjugate that is harmless to a cellular environment, yet is also photoactive and has excellent optical and optoacoustic contrast for tracking cellular uptake and intracellular localization. The formation, water-solubility, photoactivity, and unperturbed structure of C70@lysozyme are confirmed using UV-visible and 2D 1H, 15N NMR spectroscopy. The excellent imaging contrast of C70@lysozyme in optoacoustic and third harmonic generation microscopy is exploited to monitor its uptake in HeLa cells and lysosomal trafficking. Last, the photoactivity of C70@lysozyme and its ability to initiate cell death by means of singlet oxygen (1O2) production upon exposure to low levels of white light irradiation is demonstrated. This study introduces C70@lysozyme and other fullerene-protein conjugates as potential candidates for theranostic applications. 相似文献
23.
Glass and Ceramics - An analysis of the specific mechanisms of the influence of the state of the grain structure on the thermoelectric properties (electrical resistivity and total thermal... 相似文献
24.
Bosyakova N. A. Pomortsev S. A. Gizatullin R. G. Klyosov Yu. L. Laptov S. V. Kashcheev I. D. Zemlyanoi K. G. 《Refractories and Industrial Ceramics》2021,62(4):381-383
Refractories and Industrial Ceramics - Technology for producing alumina-periclase-carbon refractories of the brands APUK-D and APU-D is developed and implemented. Use of complex antioxidant and... 相似文献
25.
Khammatova V. V. Gainutdinov R. F. Khammatova E. A. Titova L. V. 《Fibre Chemistry》2021,53(3):204-207
Fibre Chemistry - An analysis of the aramid fiber market including the range of industrial textile materials containing chemical fibers for specialized protective clothing of metallurgical workers,... 相似文献
26.
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
27.
N.A. Zhuk M.G. Krzhizhanovskaya N.A. Sekushin V.V. Kharton B.A. Makeev V.A. Belyy R.I. Korolev 《Ceramics International》2021,47(14):19424-19433
The solid solutions based on the pyrochlore-type system Bi2MgNb2-xTaxO9 were formed in the compositional range х = 0–2.0 (Bi1·6Mg0·8Nb1.6-tTatO7.2, t = 0–1.6). The Rietveld method was used to refine the structure for Bi2MgNb2-xTaxO9 (x = 0, 1.0, 2.0). The increasing tantalum content led to the slight decrease in the cubic unit cell parameters from 10.56934 (4) Å for x = 0 and 10.54607 (3) Å for x = 2 (sp.gr. Fd-3m:2). At the same time, tantalum additions suppressed grain growth in the pyrochlore ceramics during sintering and made it possible to obtain materials with an average grain size of 1–2 μm (Bi1·6Mg0·8Ta1·6O7.2). The increase in the Ta5+ concentration led to the decrease in the dielectric permeability from 104 (Bi1·6Mg0·8Nb1·6O7.2) to 20 (Bi1·6Mg0·8Ta1·6O7.2) at room temperature, while the dielectric loss tangent remained lower than 0.002, which is due to the small grain size and the high porosity of the samples. An increase in temperature has practically no effect on the values of the dielectric permittivity in the entire frequency range. The samples have weak through conductivity. The activation energies of electrical conductivity varied in the range of 0.84–1.00 eV, and the less tantalum, the lower the activation energy. The electrical properties of the samples at 200 Hz to 1 MHz are described by the simplest parallel scheme. 相似文献
28.
Zagidullin S. Kh. Dolganov V. L. Lozhkin I. G. 《Chemical and Petroleum Engineering》2022,57(9-10):765-769
Chemical and Petroleum Engineering - The hydrodynamics of oxidation towers used for bitumen production were studied using a model tower having transparent walls. Experiments were carried out in two... 相似文献
29.
Rudenko A. I. Nishchik A. P. Otrokh E. A. Terekh A. M. 《Journal of Engineering Physics and Thermophysics》2022,95(1):206-212
Journal of Engineering Physics and Thermophysics - Results of investigation into the influence of a corrosion process on thermotechnical characteristics of heat pipes of low-temperature range are... 相似文献
30.
Kamar M. S. Shalan A. S. Youssef W. M. Hussein A. E. M. Khawassek Y. M. Taha M. H. 《Radiochemistry》2022,64(2):244-256
Radiochemistry - Ferrugination, sericitization, desulfitization, chloritization, and kaolinitization of hydrothermal origin are the main wall rock alterations occurring within the NNW shear zones... 相似文献