全文获取类型
收费全文 | 55675篇 |
免费 | 1704篇 |
国内免费 | 793篇 |
专业分类
电工技术 | 839篇 |
综合类 | 60篇 |
化学工业 | 9578篇 |
金属工艺 | 3328篇 |
机械仪表 | 1676篇 |
建筑科学 | 1384篇 |
矿业工程 | 197篇 |
能源动力 | 1824篇 |
轻工业 | 5301篇 |
水利工程 | 493篇 |
石油天然气 | 1451篇 |
无线电 | 4619篇 |
一般工业技术 | 13194篇 |
冶金工业 | 8039篇 |
原子能技术 | 845篇 |
自动化技术 | 5344篇 |
出版年
2022年 | 483篇 |
2021年 | 858篇 |
2020年 | 694篇 |
2019年 | 800篇 |
2018年 | 1334篇 |
2017年 | 1318篇 |
2016年 | 1409篇 |
2015年 | 1033篇 |
2014年 | 1441篇 |
2013年 | 3674篇 |
2012年 | 2371篇 |
2011年 | 2862篇 |
2010年 | 2269篇 |
2009年 | 2508篇 |
2008年 | 2338篇 |
2007年 | 2448篇 |
2006年 | 1881篇 |
2005年 | 1579篇 |
2004年 | 1479篇 |
2003年 | 1377篇 |
2002年 | 1344篇 |
2001年 | 1302篇 |
2000年 | 1127篇 |
1999年 | 1141篇 |
1998年 | 2392篇 |
1997年 | 1841篇 |
1996年 | 1581篇 |
1995年 | 1123篇 |
1994年 | 855篇 |
1993年 | 847篇 |
1992年 | 641篇 |
1991年 | 619篇 |
1990年 | 555篇 |
1989年 | 523篇 |
1988年 | 402篇 |
1987年 | 422篇 |
1986年 | 386篇 |
1985年 | 413篇 |
1984年 | 345篇 |
1983年 | 331篇 |
1982年 | 321篇 |
1981年 | 311篇 |
1980年 | 367篇 |
1979年 | 356篇 |
1978年 | 303篇 |
1977年 | 429篇 |
1976年 | 648篇 |
1975年 | 321篇 |
1974年 | 298篇 |
1973年 | 318篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
V. M. Girshgorn P. P. Perepechkin G. A. Budnitskii V. G. Sobakin R. K. Kutnova Z. V. Baibakova 《Fibre Chemistry》1986,17(3):197-198
Conclusions The fundamental possibility of an action of a magnetic field on the service properties of a hollow, semipermeable acetate fibres has been demonstrated by treatment of the stream of precipitation bath.As a reason of the magnetic treatment the permeability of the hollow fibres increases by 40–130%; and the empirical quality criterion is increased by 82%.Translated from Khimicheskie Volokna, No. 3, pp. 37–38, May–June, 1985. 相似文献
992.
Z. Koczorowski E. Kucharska-Giziewicz Z. Figaszewski 《Journal of Applied Electrochemistry》1980,10(2):191-196
The characteristics of electrocapillary elements with their filling subjected to vibrations by mechanical and electrical harmonic input signals of frequencies in the range 0.003–30 Hz as well by voltage or pressure jump were studied. The idea of variable pressure or pressure jump measurement by means of an electrocapillary transducer and a model of such a manometer are presented. 相似文献
993.
S.A. Yashnik Z.R. Ismagilov V.V. Kuznetsov V.V. Ushakov V.A. Rogov I.A. Ovsyannikova 《Catalysis Today》2006,117(4):525-535
A synergetic effect in the catalytic activity has been found after palladium introduction in Mn–Al–O systems. The magnitude of the synergetic effect depends on the types of the oxidic manganese species: oxide Mn3O4, spinel (Mn, Mg)[Mn, Al]2O4 or hexaaluminate (Mn, Mg)LaAl11O19. The synergetic effect of Pd and manganese-containing compounds is observed only if palladium is introduced to the low-temperature precursor of the manganese alumina spinel or manganese hexaaluminate. The synergetic effect is not observed when high-temperature samples with formed spinel or hexaaluminate phases are modified with Pd. 相似文献
994.
995.
F. Pedro-García L.G. Betancourt-Cantera A.M. Bolarín-Miró C.A. Cortés-Escobedo A. Barba-Pingarrón F. Sánchez-De Jesús 《Ceramics International》2019,45(8):10114-10119
We report the effects of the Sr2+ and Ni2+ co-doping of BiFeO3 on the crystal structure and multiferroic properties of Bi1?xSrxFe1-yNiyO3 (x?=?0.05, 0.0?≤?y?≤?0.10, and Δy?=?0.05) that is synthesized using assisted high-energy ball milling. The mixtures of Bi2O3, Fe2O3, SrO and NiO were milled for 5?h, pressed at 900?MPa, and sintered at 800?°C in order to obtain cylindrical test pieces. X-ray diffraction and Rietveld refinement elucidated the effects of Sr2+ and Ni2+ on the crystal structure. Co-doping with SrNi in suitable proportions stabilizes rhombohedral BiFeO3. High contents of Ni2+ promote the precipitation of secondary phases in the forms of NiFe2O4 and Bi25FeO40. The magnetic behavior was examined by means of vibrating sample magnetometry. The results showed a change in the magnetic order from antiferromagnetic for the undoped sample to the ferromagnetic order for the co-doped samples. This change is attributed to the modulations in the magnetic moment due to crystal structure distortions. All samples show high relative permittivity values, which were enhanced by doping with Sr2+. Ni2+ cations increase the dielectric dissipation factor; this enhancement is related to their interactions with cations of a different oxidation state, such as Fe3+, Fe2+, Ni2+, Bi3+ and Sr2+ in the crystal structure of BiFeO3. The magnetoelectric coupling that was evaluated using magnetodielectric measurements was above 4% at 1?kHz for the higher applied magnetic field of 18?kOe. 相似文献
996.
Polyfunctional monomers (PFMs), namely, trimethylol propane trimethacrylate (TMPTMA), trimethylol propane triacrylate, ethylene glycol dimethacrylate, and diethylene glycol diacrylate were blended with low‐density polyethylene (LDPE) and exposed to different doses of EB irradiation. Fourier transform infrared and ultraviolet and UV–vis spectroscopy of the unirradiated, irradiated, unloaded, and PFMs‐loaded LDPE films were studied under various irradiation doses up to 300 kGy. The degree of crosslinking and oxidative degradation, as measured by the spectroscopic parameters, were dependent on both the irradiation dose and the type of loaded PFMs. For all of the loaded monomers, the extent of crosslinking increased at different rates as a function of irradiation dose. TMPTMA monomer was the most efficient in enhancing the crosslinking of LDPE films compared to the other loaded monomers. However, the unloaded LDPE film showed the least extent of crosslinking. In addition, the EB‐radiation‐induced changes, such as trans‐vinylene formation, a decrease in vinyl and vinylidene unsaturation; and carbonyl double‐bond formation and change in crystallinity were correlated. The importance of these results on the prediction of the role of polyfunctional monomers in the production of crosslinked polymers is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2025–2035, 2003 相似文献
997.
998.
999.
1000.
A novel process was developed for the bitumen emulsion upgrading, wherein emulsion breaking and upgrading occurred in the same reactor using H2 generated in situ from the water in the emulsion via the water gas shift reaction (WGSR). In this study, dibenzothiophene (DBT) was chosen as a model compound to investigate the effect of water and in situ H2 on hydrodesulfurization (HDS). All the experiments were performed in a 1-L autoclave reactor at temperatures between 300 and 380 °C using in situ H2 and ex situ H2 (externally supplied H2) over a dispersed Mo catalyst formed from phosphomolybdic acid (PMA). At very low water content, water was found to promote the HDS reaction in the ex situ H2 run probably because it facilitates the formation of more active dispersed MoSx species. At higher water content, however, water inhibits every individual reaction in the reaction network in the HDS of DBT, blocking the hydrogenation pathway more than the hydrogenolysis pathway. The relative reactivity of the in situ and ex situ H2 depends on the water content present in the reaction system. At an optimized mole ratio of H2O:CO (1.35), higher HDS activity was observed in the in situ H2 run compared to ex situ H2 run, and particularly, the hydrogenation pathway was promoted in the in situ H2 run. 相似文献