全文获取类型
收费全文 | 35182篇 |
免费 | 1101篇 |
国内免费 | 69篇 |
专业分类
电工技术 | 447篇 |
综合类 | 35篇 |
化学工业 | 7797篇 |
金属工艺 | 675篇 |
机械仪表 | 688篇 |
建筑科学 | 1725篇 |
矿业工程 | 363篇 |
能源动力 | 819篇 |
轻工业 | 2479篇 |
水利工程 | 276篇 |
石油天然气 | 254篇 |
武器工业 | 1篇 |
无线电 | 2279篇 |
一般工业技术 | 5465篇 |
冶金工业 | 7563篇 |
原子能技术 | 334篇 |
自动化技术 | 5152篇 |
出版年
2022年 | 258篇 |
2021年 | 547篇 |
2020年 | 368篇 |
2019年 | 458篇 |
2018年 | 588篇 |
2017年 | 474篇 |
2016年 | 669篇 |
2015年 | 579篇 |
2014年 | 852篇 |
2013年 | 2198篇 |
2012年 | 1325篇 |
2011年 | 1731篇 |
2010年 | 1323篇 |
2009年 | 1350篇 |
2008年 | 1567篇 |
2007年 | 1473篇 |
2006年 | 1326篇 |
2005年 | 1181篇 |
2004年 | 1021篇 |
2003年 | 918篇 |
2002年 | 923篇 |
2001年 | 648篇 |
2000年 | 551篇 |
1999年 | 598篇 |
1998年 | 689篇 |
1997年 | 619篇 |
1996年 | 624篇 |
1995年 | 571篇 |
1994年 | 567篇 |
1993年 | 565篇 |
1992年 | 553篇 |
1991年 | 344篇 |
1990年 | 496篇 |
1989年 | 460篇 |
1988年 | 422篇 |
1987年 | 464篇 |
1986年 | 399篇 |
1985年 | 515篇 |
1984年 | 550篇 |
1983年 | 455篇 |
1982年 | 433篇 |
1981年 | 380篇 |
1980年 | 365篇 |
1979年 | 438篇 |
1978年 | 364篇 |
1977年 | 303篇 |
1976年 | 271篇 |
1975年 | 300篇 |
1974年 | 246篇 |
1973年 | 267篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Jincheng Yu Yabin Chang Ewa Jakubczyk Bing Wang Feridoon Azough Robert Dorey Robert Freer 《Journal of the European Ceramic Society》2021,41(9):4859-4869
Ca3Co4O9 is a promising p-type thermoelectric oxide material having intrinsically low thermal conductivity. With low cost and opportunities for automatic large scale production, thick film technologies offer considerable potential for a new generation of micro-sized thermoelectric coolers or generators. Here, based on the chemical composition optimized by traditional solid state reaction for bulk samples, we present a viable approach to modulating the electrical transport properties of screen-printed calcium cobaltite thick films through control of the microstructural evolution by optimized heat-treatment. XRD and TEM analysis confirmed the formation of high-quality calcium cobaltite grains. By creating 2.0 at% cobalt deficiency in Ca2.7Bi0.3Co4O9+δ, the pressureless sintered ceramics reached the highest power factor of 98.0 μWm?1 K-2 at 823 K, through enhancement of electrical conductivity by reduction of poorly conducting secondary phases. Subsequently, textured thick films of Ca2.7Bi0.3Co3.92O9+δ were efficiently tailored by controlling the sintering temperature and holding time. Optimized Ca2.7Bi0.3Co3.92O9+δ thick films sintered at 1203 K for 8 h exhibited the maximum power factor of 55.5 μWm?1 K-2 at 673 K through microstructure control. 相似文献
3.
Golam Haider Krishna Sampathkumar Tim Verhagen Lukáš Nádvorník Farjana J. Sonia Václav Valeš Jan Sýkora Peter Kapusta Petr Němec Martin Hof Otakar Frank Yang-Fang Chen Jana Vejpravová Martin Kalbáč 《Advanced functional materials》2021,31(29):2102196
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability. 相似文献
4.
Dr. Sandra Liebscher Dr. Sebastian Mathea Dr. Tobias Aumüller Dr. Andreas Pech Prof. Dr. Frank Bordusa 《Chembiochem : a European journal of chemical biology》2021,22(7):1201-1204
Fluorescent fusion proteins are powerful tools for studying biological processes in living cells, but universal application is limited due to the voluminous size of those tags, which might have an impact on the folding, localization or even the biological function of the target protein. The designed biocatalyst trypsiligase enables site-directed linkage of small-sized fluorescence dyes on the N terminus of integral target proteins located in the outer membrane of living cells through a stable native peptide bond. The function of the approach was tested by using the examples of covalent derivatization of the transmembrane proteins CD147 as well as the EGF receptor, both presented on human HeLa cells. Specific trypsiligase recognition of the site of linkage was mediated by the dipeptide sequence Arg-His added to the proteins’ native N termini, pointing outside the cell membrane. The labeling procedure takes only about 5 minutes, as demonstrated for couplings of the fluorescence dye tetramethyl rhodamine and the affinity label biotin as well. 相似文献
5.
Belcher Calvin H. Zheng Baolong MacDonald Benjamin E. Langlois Eric D. Lehman Benjamin Pearce Charles Delaney Robert Apelian Diran Lavernia Enrique J. Monson Todd C. 《Journal of Materials Science》2022,57(9):5518-5532
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic... 相似文献
6.
Puneet Parmar Nicolas Lopez-Villalobos John T. Tobin Eoin Murphy Frank Buckley Shane V. Crowley Alan L. Kelly Laurence Shalloo 《International Journal of Food Science & Technology》2021,56(5):2415-2422
The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T2 (R2 = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T2 (R2 = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm−3, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm−3 at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally. 相似文献
7.
A hybrid sorbent material for removal of hydrogen sulfide from air was developed. The material is based on activated carbon and iron compounds obtained from waste iron(II) sulfate(VI) heptahydrate. The iron salt is deposited on the carbonaceous support and subjected to oxidation (Fe2+ to Fe3+) using atmospheric oxygen under alkaline conditions. An effect of H2O2 addition to the process on the composition of the resultant material was also examined. X-ray diffraction (XRD) analyses confirmed easy conversion of waste FeSO4·7H2O to iron oxides Fe3O4 and FeOOH. The activated carbon supporting iron oxides revealed a higher efficiency in H2S elimination from air compared to the commercial activated carbon, without any modification. 相似文献
8.
Robert Bertuzzi 《岩石力学与岩土工程学报(英文版)》2019,11(3):494-510
This paper presents the results of ongoing research carried out by the author exploring methods to provide a more robust estimate of rock mass properties specifically for use in tunnel design. Data from various large-scale rock mass failures are introduced, including coal pillars. The damage-initiation,spalling-limit approach is compared to the coal pillar database. New comparisons of estimating the geological strength index(GSI) and relationships to estimate the Hoeke Brown failure criterion parameters, mb, s and a, are presented. 相似文献
9.
10.