全文获取类型
收费全文 | 2112篇 |
免费 | 55篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 102篇 |
综合类 | 5篇 |
化学工业 | 484篇 |
金属工艺 | 44篇 |
机械仪表 | 68篇 |
建筑科学 | 35篇 |
能源动力 | 109篇 |
轻工业 | 134篇 |
水利工程 | 3篇 |
无线电 | 227篇 |
一般工业技术 | 390篇 |
冶金工业 | 321篇 |
原子能技术 | 74篇 |
自动化技术 | 176篇 |
出版年
2023年 | 11篇 |
2022年 | 9篇 |
2021年 | 23篇 |
2020年 | 19篇 |
2019年 | 11篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 34篇 |
2015年 | 37篇 |
2014年 | 38篇 |
2013年 | 96篇 |
2012年 | 62篇 |
2011年 | 86篇 |
2010年 | 80篇 |
2009年 | 99篇 |
2008年 | 113篇 |
2007年 | 98篇 |
2006年 | 67篇 |
2005年 | 87篇 |
2004年 | 77篇 |
2003年 | 79篇 |
2002年 | 59篇 |
2001年 | 59篇 |
2000年 | 58篇 |
1999年 | 54篇 |
1998年 | 114篇 |
1997年 | 92篇 |
1996年 | 68篇 |
1995年 | 49篇 |
1994年 | 46篇 |
1993年 | 34篇 |
1992年 | 33篇 |
1991年 | 26篇 |
1990年 | 16篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 19篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 18篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1974年 | 8篇 |
1973年 | 3篇 |
排序方式: 共有2172条查询结果,搜索用时 31 毫秒
1.
2.
Eicosapentaenoic acid (EPA) production by an oleaginous fungus Mortierella alpina expressing heterologous the Δ17‐desaturase gene under ordinary temperature 下载免费PDF全文
3.
Shogo Mamada Naoyuki Yaguchi Masanori Hansaka Masafumi Yamato Hirohisa Yoshida 《应用聚合物科学杂志》2015,132(15)
This study was addressed to the influence of an electric field strength applied at fabrication process and matrix properties, such as the dielectric constant and the Young's modulus, on “pseudo‐1‐3 piezoelectric ceramic/polymer composite” in order to further enhance the piezoelectricity of that. The pseudo‐1‐3 piezoelectric ceramic/polymer composite consists of linearly ordered piezoelectric ceramic particles in polymer material. Silicone gel, silicone rubber, urethane rubber, and poly‐methyl‐methacrylate, which exhibit different dielectric constants and Young's modulus, were used as matrices to evaluate the matrix influence. The piezoelectricity of the pseudo‐1‐3 piezoelectric ceramic/polymer composite was evaluated using the piezoelectric strain constant d33. The d33 is one of the indices of the piezoelectric properties for piezoelectric materials. As a result, it was confirmed that d33 of the pseudo‐1‐3 piezoelectric ceramic/polymer composite increased with the increase of the electric filed strength applied at fabrication process, though, it reached a constant value at a certain strength value. Further it was confirmed that dielectric constant of the matrix had a small influence on d33 of the pseudo‐1‐3 piezoelectric ceramic/polymer composite, however, in case of matrix of lower Young's modulus, d33 was increase. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41817. 相似文献
4.
Hiromichi Ichinose Masanori Taira Sachiko Furuta Hiroaki Katsuki 《Journal of the American Ceramic Society》2003,86(9):1605-1608
Niobium- or vanadium-doped anatase sols were prepared by hydrothermal treatment of 0.1 mol/dm3 peroxotitanium complex aqueous solutions dissolving 0–10 mol% niobium or vanadium at 100°C for 8 h. Niobium-doping caused the increase of lattice constants of anatase and the shape change of anatase crystal from spindle-like to cubic-like structure, but no change of the optical absorbance. Vanadium-doping caused the decrease of lattice constant of c -axis, the miniaturization of anatase crystal and the increase of optical absorbance at the wavelength from 350–700 nm. 相似文献
5.
Deformation behavior of stoichiometric blends made from poly(styrene-co-styrenesulfonic acid) (SPS) and poly(styrene-co-4-vinylpyridine) (SVP) was investigated by TEM observation of strained thin films. An FTIR investigation revealed that ionic cross-links were formed between the component polymers upon blending due to intermolecular ion-ion interactions, which arose from proton transfer from sulfonic acid groups to pyridine groups. TEM observations indicate that the deformation mode of the blends changed from crazing only to crazing plus shear deformation, with the shear contribution becoming larger, as the ion content in the blends increased. Such changes in deformation mode can be understood as arising from an increase in the ‘effective’ strand density due to the formation of ionic cross-links upon blending. It was also found that the ionic cross-links via pyridinium cation/sulfonate anion ion pairs were more effective in inducing the transition of deformation mode than ionic cross-links via -SO3−/Na+ or -SO3−/Ca2+ ion pairs. 相似文献
6.
Suchapa Netpradit Suda Kiatkamjornwong Yujiro Ando Takeshi Ikeda 《Particulate Science and Technology》1998,16(4):311-327
We investigated the dependence of the toner charge-to-mass ratio (q/m) in a two-component electrophotographic developer on the shaking time, toner concentration (T/C), carrier sizes, and the carrier core and the coating materials, as well as the resulting print qualities in terms of print density, background density, tone reproduction, resolution, and dot gain. Four different sizes of spherical ferrite carriers, four different carrier coating materials, and an irregular iron carrier were used with two types of toner: 14 um red toner (NP-4080) and 8 um cyan toner (CLC-500). The q/m measurement by the blow-off method showed that the red toner charge was positive while the cyan toner charge was negative with these carriers. The toner q/m values, which depended on the shaking time and decreased with the increasing T/C were much more affected by the larger carrier and the smaller toner. The carriers which yielded charges in the proper range produced better print qualities than did the other carriers that yielded a toner q/m 相似文献
7.
Kotaro Take-uchi Takashi E-naka Norimitsu Kon-no Yozo Hosotani Takashi Orimoto Masanori Iwase 《国际钢铁研究》1997,68(12):516-519
By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO2 mixture as reference electrode, the equilibrium oxygen partial pressures for three-phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt were determined as: - log {PO2 (CS + C3S2 + L)/bar} = - 3.22 13000/(T/K) ± 0.05 - log {PO2 (C3S2 + C2S + L)/bar} = - 0.92 16400/ (T/K) ± 0.04. respectively, where CS, C3S2 and C2S indicate CaSiO3(s), Ca3Si2O7(s). and Ca2SiO4(s), respectively. 相似文献
8.
There are several damping phenomena in quantum optics. Such phenomena have been usually explained by open systems. In statistical physics, open system dynamics have been used to study the irreversibility and the approach to equilibrium. In this paper, the dynamical change of the mutual entropy for an open system, frequently studied in the quantum optics literature, is rigorously computed through a model of quantum Markov chain. In particular, the concrete formula of Stinespring expression for such a model is obtained and applied to the derivation of the mutual entropy, and some computational results are presented. 相似文献
9.
本文论述一种厚/薄铜复合PWB(及其可靠性),它允许PWB设计者在厚铜和薄铜之间以任何希望的图形进行随意选择,以使电源模块/分配电路可以和精细图形特征一起集成,从而适应离I/O数半导体封装的要求。 相似文献
10.
Wakejima A. Matsunaga K. Okamoto Y. Ando Y. Nakayama T. Miyamoto H. 《Electronics letters》2005,41(25):1371-1372
A single-ended amplifier using small packaged GaN-FETs exhibits a record 2.14 GHz W-CDMA output power. The amplifier, composed of paralleled 48 mm gate periphery FET die, delivers a peak saturated output power of 371 W with a linear gain of 11.2 dB at a drain voltage of 45 V under 2.14 GHz 3GPP W-CDMA signal input. The output power density (output power/package size) of 1.1 W/mm/sup 2/ is twice as high as that of the existing over 300 W GaAs-FET amplifiers. A low 5 MHz offset ACLR of -36 dBc with a drain efficiency of 24% is also obtained at 8 dB power back off from the saturated output power. 相似文献