全文获取类型
收费全文 | 36934篇 |
免费 | 2492篇 |
国内免费 | 1694篇 |
专业分类
电工技术 | 637篇 |
技术理论 | 1篇 |
综合类 | 2477篇 |
化学工业 | 19569篇 |
金属工艺 | 1936篇 |
机械仪表 | 848篇 |
建筑科学 | 306篇 |
矿业工程 | 357篇 |
能源动力 | 765篇 |
轻工业 | 1432篇 |
水利工程 | 44篇 |
石油天然气 | 1986篇 |
武器工业 | 409篇 |
无线电 | 1875篇 |
一般工业技术 | 5409篇 |
冶金工业 | 818篇 |
原子能技术 | 255篇 |
自动化技术 | 1996篇 |
出版年
2024年 | 67篇 |
2023年 | 449篇 |
2022年 | 656篇 |
2021年 | 867篇 |
2020年 | 787篇 |
2019年 | 711篇 |
2018年 | 741篇 |
2017年 | 903篇 |
2016年 | 1082篇 |
2015年 | 1091篇 |
2014年 | 1777篇 |
2013年 | 1811篇 |
2012年 | 2319篇 |
2011年 | 2860篇 |
2010年 | 2158篇 |
2009年 | 2389篇 |
2008年 | 1997篇 |
2007年 | 2619篇 |
2006年 | 2406篇 |
2005年 | 2178篇 |
2004年 | 1780篇 |
2003年 | 1645篇 |
2002年 | 1474篇 |
2001年 | 1212篇 |
2000年 | 1051篇 |
1999年 | 826篇 |
1998年 | 683篇 |
1997年 | 487篇 |
1996年 | 429篇 |
1995年 | 364篇 |
1994年 | 316篇 |
1993年 | 243篇 |
1992年 | 189篇 |
1991年 | 124篇 |
1990年 | 115篇 |
1989年 | 61篇 |
1988年 | 49篇 |
1987年 | 36篇 |
1986年 | 25篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1975年 | 2篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
44.
45.
46.
This article, the first of three articles on the synthesis of rice processing plants, focuses on the development of simplified mathematical models necessary for use in optimizing rice processing plants. The second concentrates on the optimal synthesis of a rice plant and the third on the sensitivity of the optimization to uncertainty in model parameters. Existing models for rice processing unit operations are not suitable for flowsheet optimization and new models need to be developed to overcome numerical difficulties that occur in optimization applications, specifically in mixed integer nonlinear programming (MINLP) applications. Simplified models of the drying, cooling, and tempering units are developed. In addition head rice yield models, used as a quality indicator, energy consumption, and economic models were also developed. Naturally, the new models exhibit some mismatch with respect to the existing models from which they were developed. However, a sensitivity analysis, presented in Part III, has shown that the optimal flowsheet structure was not sensitive to a lack of fit between the simplified and complex models. The simplified models were found adequate to be appropriate for use at the synthesis stage. 相似文献
47.
48.
49.
50.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献