全文获取类型
收费全文 | 7020篇 |
免费 | 183篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 265篇 |
综合类 | 9篇 |
化学工业 | 1513篇 |
金属工艺 | 198篇 |
机械仪表 | 129篇 |
建筑科学 | 239篇 |
矿业工程 | 11篇 |
能源动力 | 285篇 |
轻工业 | 675篇 |
水利工程 | 34篇 |
石油天然气 | 13篇 |
无线电 | 533篇 |
一般工业技术 | 1083篇 |
冶金工业 | 1375篇 |
原子能技术 | 191篇 |
自动化技术 | 668篇 |
出版年
2022年 | 52篇 |
2021年 | 87篇 |
2020年 | 53篇 |
2019年 | 86篇 |
2018年 | 95篇 |
2017年 | 90篇 |
2016年 | 112篇 |
2015年 | 80篇 |
2014年 | 155篇 |
2013年 | 341篇 |
2012年 | 235篇 |
2011年 | 342篇 |
2010年 | 261篇 |
2009年 | 270篇 |
2008年 | 282篇 |
2007年 | 273篇 |
2006年 | 249篇 |
2005年 | 254篇 |
2004年 | 191篇 |
2003年 | 204篇 |
2002年 | 201篇 |
2001年 | 123篇 |
2000年 | 124篇 |
1999年 | 142篇 |
1998年 | 317篇 |
1997年 | 241篇 |
1996年 | 175篇 |
1995年 | 154篇 |
1994年 | 170篇 |
1993年 | 132篇 |
1992年 | 85篇 |
1991年 | 83篇 |
1990年 | 87篇 |
1989年 | 79篇 |
1988年 | 71篇 |
1987年 | 68篇 |
1986年 | 78篇 |
1985年 | 91篇 |
1984年 | 88篇 |
1983年 | 76篇 |
1982年 | 79篇 |
1981年 | 86篇 |
1980年 | 76篇 |
1979年 | 57篇 |
1978年 | 40篇 |
1977年 | 79篇 |
1976年 | 101篇 |
1975年 | 68篇 |
1973年 | 47篇 |
1972年 | 46篇 |
排序方式: 共有7221条查询结果,搜索用时 15 毫秒
91.
Gordon Chin 《Journal of Infrared, Millimeter and Terahertz Waves》1987,8(10):1219-1234
An optically pumped submillimeter laser operating in the 500 μm (600 GHz) to 100 μm (3 THz) spectral range is the primary and, at present, the only available local oscillator (LO) source for laboratory and astronomical heterodyne applications for this wavelength region. A short review of the state-of-the-art of submillimeter lasers as LO sources, with an emphasis given to receiver systems designed for airborne heterodyne observations, will be presented. The characteristics and prospects for constructing a spacequalifiable laser LO system will also be given. 相似文献
92.
93.
94.
Jesús F. Ontiveros Bing Hong Kenji Aramaki Christel Pierlot Jean-Marie Aubry Véronique Nardello-Rataj 《Journal of surfactants and detergents》2021,24(3):401-410
A series of symmetrical dialkyl methanesulfonate amphiphiles [DiC n CHSO 3 ] m M (n = 6, 7, 8) with different counter cations (Mm+ = H+, Li+, Na+, K+, Cu2+, Zn2+, Mg2+, Ca2+, Sc3+) were synthesized in five steps. Their solubility and critical micelle concentration (CMC) in water were determined highlighting a huge effect of the chain length and the nature of the cation. The hydrophilic–lipophilic balance of the surfactants were assessed with the phase inversion temperature (PIT)-slope method based on the deviation from the PIT of the reference C10E4/n-octane/0.01 M NaCl(aq) emulsion through addition of increasing amounts of the dialkyl methanesulfonates. The hydrophilicity of the surfactants was thus ranked in terms of dPIT/dxsulfonate. A “cation” scan with the [DiC 6 CHSO 3 ] m M /benzene/water systems at fw = 0.5 was finally performed confirming the hydrophilicity ranking obtained with the PIT-slope method. It revealed that the [DiC 6 CHSO 3 ] 2 Mg behaves as a “Balanced Surfactant” able to form spontaneously a three-phase microemulsion system (Winsor III) just in the presence of water and oil, in the same way as the catalytic surfactant dimethyldioctylammonium molybdate, which has the same PIT-slope. 相似文献
95.
Thronsen Elisabeth Mørkeseth Hanne Marioara Calin D. Minakuchi Kazuhiro Katsumi Tetsuya Marthinsen Knut Matsuda Kenji Holmestad Randi 《Metallurgical and Materials Transactions A》2022,53(9):3296-3310
Metallurgical and Materials Transactions A - The effect of 0.03 and 0.08 at. pct Fe additions on the formation of secondary phases in an Al–1.1Mg–0.5Cu–0.3Si at. pct alloy was... 相似文献
96.
Corrosion of iron-base alloys at 982°C (1800°F) by coal char is observed and the phase morphologies are discussed. No sulfidation was observed at 50 hr exposure. After 100 hr internal aluminum-rich sulfides were observed along with thick outer scales of iron oxide. The species causing the hightemperature-induced corrosion are probably sulfides and sulfates, present in most coal chars. Possible mechanisms for the corrosion are also discussed.Department of Materials Science and Mineral Engineering. 相似文献
97.
Laser-Sintered Barium Titanate 总被引:1,自引:0,他引:1
Toshihiro Kasai Yoshiharu Ozaki Hideki Noda Kenji Kawasaki Kei Tanemoto 《Journal of the American Ceramic Society》1989,72(9):1716-1718
Laser sintering of alkoxy-derived ultrafine BaTiO3 powders was investigated. The temperature increases of the sample with laser irradiation were measured with a thermocouple. It was found that laser irradiation could generate enough heat to sinter ceramics. A slurry was prepared by mixing an alkoxy-derived BaTiO3 powder, binder additives, solvent, and plasticizer. The slurry was tape cast and dried to give a green sheet. The green sheet was laser sintered and was then characterized by SEM, XRD, and density measurements. The effect of burnout before laser irradiation and the characteristic microstructure of laser-sintered BaTiO3 are described. 相似文献
98.
We examined the influence of polyaniline (PAn)'s unit sequence and doping with low molecular weight dopants or polymer dopants on permeation property. It was found that CO2 permeability was increased by the formation of a quinonediimine unit in PAn with the oxidation. CO2 sorption amount of PAn was decreased by oxidation. The increase of CO2 permeability with oxidation, therefore, resulted from the increase of diffusivity, which was attributable to morphological variation by the increase of a quinonediimine unit. The permselectivity of PAn films was found to be remarkably improved by doping. In particular, the selectivity value of the PAn film doped with polyvinyl sulphonic acid as a polymer dopant went up to over 2,000. This remarkable increase of selectivity was found to result in the increase of selectivity, depending on diffusivity. It was also found that the permselectivity of the PAn film doped by polymer dopants was surpassed, as compared with that doped by low molecular dopants. © 1995 John Wiley & Sons, Inc. 相似文献
99.
100.
Howard W. Starkweather Thomas F. Jordan Gordon B. Dunnington 《Polymer Engineering and Science》1974,14(10):678-681
The yield stress is a simple function of the deformation ratio in the direction of testing for specimens oriented by uniaxial or biaxial stretching or rolling. Unless the yield stress increases more rapidly than in proportion to the deformation ratio, there will be instability during tensile creep under high loads. The relative merit of various polymers differs for creep and stress relaxation. Fatigue and bend recovery are also related to the molecular structure. 相似文献