全文获取类型
收费全文 | 82102篇 |
免费 | 7116篇 |
国内免费 | 4771篇 |
专业分类
电工技术 | 5075篇 |
技术理论 | 1篇 |
综合类 | 7838篇 |
化学工业 | 12524篇 |
金属工艺 | 4450篇 |
机械仪表 | 5196篇 |
建筑科学 | 5836篇 |
矿业工程 | 1944篇 |
能源动力 | 2239篇 |
轻工业 | 7078篇 |
水利工程 | 1707篇 |
石油天然气 | 3200篇 |
武器工业 | 720篇 |
无线电 | 9908篇 |
一般工业技术 | 8731篇 |
冶金工业 | 3521篇 |
原子能技术 | 1098篇 |
自动化技术 | 12923篇 |
出版年
2024年 | 254篇 |
2023年 | 929篇 |
2022年 | 1780篇 |
2021年 | 2522篇 |
2020年 | 1968篇 |
2019年 | 1740篇 |
2018年 | 1876篇 |
2017年 | 2160篇 |
2016年 | 2115篇 |
2015年 | 2994篇 |
2014年 | 3946篇 |
2013年 | 4684篇 |
2012年 | 5546篇 |
2011年 | 6039篇 |
2010年 | 5715篇 |
2009年 | 5604篇 |
2008年 | 5578篇 |
2007年 | 5367篇 |
2006年 | 5282篇 |
2005年 | 4410篇 |
2004年 | 3567篇 |
2003年 | 3137篇 |
2002年 | 3766篇 |
2001年 | 3339篇 |
2000年 | 2242篇 |
1999年 | 1612篇 |
1998年 | 1061篇 |
1997年 | 919篇 |
1996年 | 819篇 |
1995年 | 710篇 |
1994年 | 526篇 |
1993年 | 397篇 |
1992年 | 299篇 |
1991年 | 227篇 |
1990年 | 191篇 |
1989年 | 127篇 |
1988年 | 124篇 |
1987年 | 86篇 |
1986年 | 41篇 |
1985年 | 57篇 |
1984年 | 44篇 |
1983年 | 33篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
对甲苯甲烷氧化偶联制苯乙烯的工艺、催化剂、反应机理等方面的研究进展进行了评述,提出了今后研究的方向。 相似文献
102.
在一致Fb-凸函数,一致Fb-伪凸和一致Fb-拟凸等广义凸性函数的基础上,研究了一类分式半无限规划问题,得到了涉及这些广义凸性函数的一类非光滑分式半无限规划的一些最优条件。 相似文献
103.
The recently established spin-coating electrostatic self-assembly (SCESA) technique has been shown to facilitate not only the rapid fabrication of polyelectrolyte multilayer assemblies, but also allow each layer to be easily controlled on a monomolecular scale by minimizing the film thickness across a substrate surface. In this paper, the influence of polyelectrolyte concentration on the amount and thickness of spin-deposited polymer films has been examined for a multilayer system of poly(allyamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS), when the washing steps employed for removing weakly bound polyelectrolytes on a resultant film on a substrate are excluded from the standard fabrication procedure of the SCESA method. The thickness of the spin-deposited PAH/PSS bilayer increased linearly for the PSS concentrations in the range from 1 to 10 mM with PAH constant at 1 mM, which demonstrates the uniform deposition of each layer material onto the thin film. The thickness of PAH/PSS bilayers increased from 1.43 ± 0.06 to 3.37 ± 0.08 nm as the PSS concentration increased from 1 to 10 mM, while the PAH concentration was kept constant at 1 mM. The multilayer films were found to be stable in a good solvent (H2O) for at least 30 h, without any noticeable loss of the adsorbed layer component of the polyelectrolyte. This improvement to the SCESA method (exclusion of washing steps) provides a convenient way to create multilayer heterostructures with the thickness of each layer being easily adjusted. 相似文献
104.
105.
Seogil Oh Jungwoo Moon Taewook Kang Surin Hong Jongheop Yi 《Journal of Electroceramics》2006,17(2-4):999-1003
The use of surface plasmon resonance (SPR) spectroscopy has been applied to a wide variety of fields such as biosensors and
surface analysis instruments. In general, a SPR substrate is prepared using self-assembled monolayer (SAM) method of organic
molecules as receptor for the target on a layer of gold or silver. However, mesoporous inorganic materials such as SBA-15
have benefits as sensor substrate for SPR. Mesoporous silica has a large surface area which receptor molecule can be attached
and has a rigid body which has an excellent stability in the extreme condition compared to organic sensing layer. We prepared
an organic modified mesoporous silica and successfully immobilized it on a gold surface, in an attempt to use as a substrate
for SPR spectroscopy. For the comparison of sensitivity of prepared substrate, Pt2+ detection was selected as a model system. Substrate prepared in this study exhibited the capability of selective sensing
for Pt2+ ions. 相似文献
106.
Ki-Won Kim Pyeong-Seok Cho Jong-Heun Lee Seong-Hyeon Hong 《Journal of Electroceramics》2006,17(2-4):895-898
A new method for preparing SnO2 whiskers by the decomposition of SnC2O4 is suggested. A Whisker-like morphology of a SnC2O4 precipitate was attained via the gradual addition of an oxalic acid solution to a hot SnCl2 aqueous solution (T > 50∘C). In comparison, when the solution temperature was either lower than 50∘C or when ethanol was used as the solvent, the SnC2O4 precipitate showed an angular and relatively isotropic morphology. The morphology of the SnC2O4 precipitate remained even after its thermal decomposition into SnO2 at 400∘C indicating that SnC2O4 precipitation is a key step in preparing the whiskers. The formation mechanism of SnO2 whiskers was explained by the supersaturation during the precipitation of SnC2O4. 相似文献
107.
对现阶段我国民营二级学院数学课程的设置进行了介绍,讨论了民营二级学院数学课程的新定位、内涵以及应该予以重视的几个问题. 相似文献
108.
This paper simulates a kind of new sub-50 nm n-type double gate MOS nanotransistors by solving coupled Poisson-Schrödinger equations in a self-consistent manner with a finite element method, and presents a systematic simulation-based study on quantum-mechanical effects, gate leakage current of FinFETs. The simulation results indicate that the deviation from the classical model becomes more important as the gate oxide, gate length and Fin channel width becomes thinner and the Fin channel doping increases. Gate tunneling current density reduces with the body thickness decreasing. Excessive scaling increases the gate current below Fin thickness of 5 nm. The gate current can be dramatically reduced beyond 1017 cm−3 with the Fin body doping increasing. In order to understand the influence of electron confinement, quantum mechanical simulation results are also compared with the results from the classical approach. Our simulation results indicate that quantum mechanical simulation is essential for the realistic optimization of the FinFET structure. 相似文献
109.
首先着重分析了山西移动本地NGN的需求。阐述了山西移动NGN建设需要考虑的因素.最后就山西移动NGN的网络建设策略提出了具体的建议。 相似文献
110.
刘红 《广东输电与变电技术》2005,(1):20-21
变压器对抗短路强度的要求是很高的。文中介绍了变压器短路时的电动力的作用情况,结合单位实际情况介绍了提高变压器抗短路能力的措施。 相似文献