全文获取类型
收费全文 | 7900篇 |
免费 | 142篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 353篇 |
综合类 | 7篇 |
化学工业 | 1825篇 |
金属工艺 | 209篇 |
机械仪表 | 212篇 |
建筑科学 | 192篇 |
矿业工程 | 1篇 |
能源动力 | 240篇 |
轻工业 | 573篇 |
水利工程 | 32篇 |
石油天然气 | 10篇 |
无线电 | 662篇 |
一般工业技术 | 1525篇 |
冶金工业 | 1433篇 |
原子能技术 | 224篇 |
自动化技术 | 570篇 |
出版年
2023年 | 36篇 |
2022年 | 84篇 |
2021年 | 120篇 |
2020年 | 63篇 |
2019年 | 78篇 |
2018年 | 104篇 |
2017年 | 84篇 |
2016年 | 122篇 |
2015年 | 88篇 |
2014年 | 151篇 |
2013年 | 378篇 |
2012年 | 226篇 |
2011年 | 388篇 |
2010年 | 274篇 |
2009年 | 310篇 |
2008年 | 339篇 |
2007年 | 258篇 |
2006年 | 293篇 |
2005年 | 252篇 |
2004年 | 216篇 |
2003年 | 261篇 |
2002年 | 210篇 |
2001年 | 154篇 |
2000年 | 153篇 |
1999年 | 191篇 |
1998年 | 562篇 |
1997年 | 419篇 |
1996年 | 316篇 |
1995年 | 175篇 |
1994年 | 164篇 |
1993年 | 188篇 |
1992年 | 89篇 |
1991年 | 87篇 |
1990年 | 91篇 |
1989年 | 98篇 |
1988年 | 79篇 |
1987年 | 65篇 |
1986年 | 99篇 |
1985年 | 101篇 |
1984年 | 94篇 |
1983年 | 89篇 |
1982年 | 71篇 |
1981年 | 68篇 |
1980年 | 59篇 |
1979年 | 54篇 |
1978年 | 35篇 |
1977年 | 45篇 |
1976年 | 58篇 |
1974年 | 26篇 |
1973年 | 23篇 |
排序方式: 共有8068条查询结果,搜索用时 15 毫秒
41.
Tooru Tanaka Toshiyuki Yamaguchi Akihiro Wakahara Akira Yoshida Ryoichi Taniguchi Yatsuka Matsuda Masatoshi Fujishiro 《Solar Energy Materials & Solar Cells》2003,75(1-2):115-120
Radiation damages due to 8 MeV electron irradiation in electrical properties of CuInSe2 thin films have been investigated. The n-type CuInSe2 films in which the carrier concentration was about 3×1016 cm−3, were epitaxially grown on a GaAs(0 0 1) substrate by RF diode sputtering. No significant change in the electrical properties was observed under the electron fluence <3×1016 e cm−2. As the electron fluence exceeded 1017 e cm−2, both the carrier concentration and Hall mobility slightly decreased. The carrier removal rate was estimated to be about 0.8 cm−1, which is slightly lower than that of III–V compound materials. 相似文献
42.
Haruo Mimura Ryusei Sato Yu Sasaki Yuichi Furuyama Akira Taniike Kazutoshi Yoshida Akira Kitamura 《International journal of molecular sciences》2008,9(10):1989-2002
Tributyltin (TBT) released into seawater from ship hulls is a stable marine pollutant and obviously remains in marine environments. We isolated a TBT resistant marine Pseudoalteromonas sp. TBT1 from sediment of a ship’s ballast water. The isolate (109.3 ± 0.2 colony-forming units mL−1) adsorbed TBT in proportion to the concentrations of TBTCl externally added up to 3 mM, where the number of TBT adsorbed by a single cell was estimated to be 108.2. The value was reduced to about one-fifth when the lysozyme-treated cells were used. The surface of ethanol treated cells became rough, but the capacity of TBT adsorption was the same as that for native cells. These results indicate that the function of the cell surface, rather than that structure, plays an important role to the adsorption of TBT. The adsorption state of TBT seems to be multi-layer when the number of more than 106.8 TBT molecules is adsorbed by a single cell. 相似文献
43.
44.
The critical conditions in which the classical Flory-Stockmayer gelation theory (F-S theory) is applicable to monovinyl-divinyl copolymerizations were pursued in detail. The resulting prepolymers or precursors of ideal crosslinked-polymers were characterized as standard polymers for the discussion of network formation in free-radical monovinyl-divinyl copolymerizations. Methyl methacrylate was copolymerized with a small amount of ethylene dimethacrylate, butylene dimethacrylate or nonapropyleneglycol dimethacrylate in the presence of lauryl mercaptan, a chain transfer agent to reduce the occurrence of a thermodynamic excluded volume effect and intramolecular crosslinking as the primary and secondary factors, respectively, for the greatly delayed gelation in the free-radical monovinyl-divinyl copolymerizations and, moreover, to keep the primary chain length constant by inhibiting a gel effect. The ratio of the actual gel point to the theoretical one reached 1.1, supporting the validity of F-S theory. The resulting prepolymers were subjected to SEC-MALLS analysis to determine the molecular weights, the molecular-weight distributions and the radii of gyration; the correlations of molecular weight vs. elution volume and radius of gyration vs. molecular weight were useful for the characterization of the precursors of ideal network-polymers. 相似文献
45.
Akira Ishizaki Kazuhiko Takasaki Shoji Shimomura Kouichi Masaki Kanji Kitazawa 《Electrical Engineering in Japan》1996,116(5):128-137
Although brushless resolvers have been used widely as angular position transducers, they are expensive due to their intricate construction, involving a rotary transformer to supply the exciting coils wound on the rotor poles with the current. It is shown theoretically in this paper that the resolver without rotary transformer or brushes can be realized by simple construction, which consists of the stator core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has minimum gap at one side and a maximum gap at another side of the diameter. It is characterized by an outer surface form that makes the fluctuation part of gap permeance very in proportion to cos θ, where θ represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the aforementioned gap permeance variation is also shown. It has been confirmed not only by simulation but also experiment that the 2-phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy. 相似文献
46.
Jing-Feng Li Ryuzo Watanabe Bo-Ping Zhang Katsuhiko Asami Koji Hashimoto 《Journal of the American Ceramic Society》1996,79(12):3109-3112
2 mol% Y2 O3 -ZrO2 polycrystals were annealed in water and under vacuum to highlight the effect of the presence of H2 O on the low-temperature degradation transformation. The specimen surfaces with monoclinic phases transformed during annealing in the different environments were analyzed by X-ray photoelectron spectroscopy with special interest on the electron binding energy change of the constituent ions of the 2 mol% Y2 O3 -ZrO2 ceramics after the degradation transformation. It was found that no change occurred for the electron-bonding energies of core levels of zirconium ions after the transformation, whereas Y-OH bonds were formed during annealing in water. This result suggested a possibility that the preferred hydration of yttrium took place at the surface of Y2 O3 -partially-stabilized ZrO2 , which is likely to be the reason for the low-temperature degradation accelerated by the presence of H2 O. 相似文献
47.
F Suzuki S Miyamoto M Takita M Oshita Y Watanabe A Kakizuka S Narumiya T Taniguchi I Muramatsu 《Canadian Metallurgical Quarterly》1997,1323(1):6-11
We attempt to determine the utility of CERAD in detecting early Alzheimer's disease (AD). CERAD battery was administered to a group of 14 control subjects, 12 patients with possible dementia prodromes and to patients with Alzheimer's disease stratified according to severity (16 mild, 8 moderate). Other measures as some subtest of the Wechsler memory scale and the Rey Complex Figure Test were also applied. Delayed recall as well as logical memory of Wechsler memory scale were found to be the best discriminators for detecting very mild cases of AD (Prodromes) (p < 0.05). None of the memory test proved of value in staging the disorder. Visuospatial functions are better determinants of the progression of the illness. Fluency also distinguish between control subjects and very mild cases. These findings suggest that delayed recall memory and probably executive function are the most useful and sensitive indicators of Alzheimer's disease. 相似文献
48.
49.
When zinc oxide and graphite were placed into an alumina crucible, with a square hole (∼3 mm ×∼3 mm) near the top, and the crucible was covered by an alumina lid and heated at >1050°C, a hollow polycrystal composed of needlelike, ribbon(comb)-like, dendritic, and bulk zinc oxide crystals grew from the hole toward the outside of the crucible. The diameter and length of the polycrystal grown at 1050°C after 1 h were ∼2.2 mm and ∼20 cm, respectively. The diameter increased, while the length decreased, with increasing temperature. Most of the needlelike zinc oxide crystals in the hollow polycrystal were elongated along the c -axis. 相似文献
50.