全文获取类型
收费全文 | 45146篇 |
免费 | 3473篇 |
国内免费 | 2705篇 |
专业分类
电工技术 | 1115篇 |
技术理论 | 1篇 |
综合类 | 2691篇 |
化学工业 | 9654篇 |
金属工艺 | 8860篇 |
机械仪表 | 1973篇 |
建筑科学 | 3263篇 |
矿业工程 | 1175篇 |
能源动力 | 2169篇 |
轻工业 | 2039篇 |
水利工程 | 710篇 |
石油天然气 | 2157篇 |
武器工业 | 353篇 |
无线电 | 4033篇 |
一般工业技术 | 7242篇 |
冶金工业 | 1768篇 |
原子能技术 | 314篇 |
自动化技术 | 1807篇 |
出版年
2024年 | 253篇 |
2023年 | 850篇 |
2022年 | 1251篇 |
2021年 | 1485篇 |
2020年 | 1496篇 |
2019年 | 1384篇 |
2018年 | 1304篇 |
2017年 | 1671篇 |
2016年 | 1521篇 |
2015年 | 1634篇 |
2014年 | 2412篇 |
2013年 | 2521篇 |
2012年 | 3083篇 |
2011年 | 3508篇 |
2010年 | 2653篇 |
2009年 | 2650篇 |
2008年 | 2324篇 |
2007年 | 2807篇 |
2006年 | 2821篇 |
2005年 | 2280篇 |
2004年 | 1931篇 |
2003年 | 1662篇 |
2002年 | 1421篇 |
2001年 | 1202篇 |
2000年 | 1073篇 |
1999年 | 809篇 |
1998年 | 662篇 |
1997年 | 531篇 |
1996年 | 456篇 |
1995年 | 389篇 |
1994年 | 287篇 |
1993年 | 270篇 |
1992年 | 237篇 |
1991年 | 129篇 |
1990年 | 99篇 |
1989年 | 89篇 |
1988年 | 46篇 |
1987年 | 23篇 |
1986年 | 24篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1959年 | 5篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Polyester‐based polyurethane/nano‐silica composites were obtained via in situ polymerization and investigated by Fourier‐transform infrared spectroscopy (FTIR), or FTIR coupled with attenuated total reflectance (FTIR‐ATR), Transmission electron microscopy (TEM), atomic force microscopy (AFM), an Instron testing machine, dynamic mechanical analysis (DMA) and ultraviolet‐visible spectrophotometry (UV‐vis). FTIR analysis showed that in situ polymerization provoked some chemical reactions between polyester molecules and nano‐silica particles. FTIR‐ATR, TEM and AFM analyses showed that both surface and interface contained nano‐silica particles. Instron testing and DMA data showed that introducing nano‐silica particles into polyurethane enhanced the hardness, glass temperature and adhesion strength of polyurethane to the substrate, but also increased the resin viscosity. UV‐vis spectrophotometry showed that nano‐silica obtained by the fumed method did not shield UV radiation in polyurethane films. Copyright © 2003 Society of Chemical Industry 相似文献
12.
论述了国内外金相测定球化退火钢脱碳层深度的标准方法和常用方法存在的不准确性和不适用性问题,提出了解决问题的途径——定量金相法。 相似文献
13.
P. T. Tsilingiris 《国际能源研究杂志》1991,15(9):723-730
The paper describes the calculation of the beam solar radiation transmission across the uniform salinity upper convecting zone (UCZ) and the salinity stratified gradient zone (GZ), when the extinction coefficient is not only wavelength but also salinity-concentration dependent, assuming that the effect of scattering to be negligible. The results are useful in determining the effects of dissolved salt ions on pure water transmission, at least according to the existing measured data in the literature. 相似文献
14.
Huseyin Selcuk Jeosadaque J Sene Marc A Anderson 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(9):979-984
This study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV254 removal and the degradation of color (Vis400) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10?1 min?1, 8.3 × 10?2 min?1 and 2.49 × 10?2 min?1 (R2 > 0.97) for UV254 degradation and 1.7 × 10?1 min?1, 6.5 × 10?2 min?1 and 2.0 × 10?2 min?1 for color removal from 5 mg dm?3, 10 mg dm?3 and 25 mg dm?3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm?3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV254 removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry 相似文献
15.
We have assessed the antimicrobial, vapor-phase activity of the following natural essential oils (EOs) when used in paraffin-based “active coatings” for paper packaging materials intended to come into contact with foods: clove (Sygzium aromaticum), cinnamon (Cinnamomum zeylanicum), and oregano (Origanum vulgare) EOs, and cinnamaldehyde-enriched cinnamon EO. To our knowledge, this is the first time that such an approach has been presented for consideration by the scientific community. 相似文献
16.
~~Growth of CeO_2, Y_2O_3 Buffer Layers for YBCO Coated Conductor 相似文献
17.
Cool 3D是一款特效图文制作软件,适用于动画片段、3D文字、图形等制作场合。Cool 3D中制作的特效素材应用于非线性编辑中,可以丰富素材的表现形式,提高节目编辑制作的整体质量。 相似文献
18.
In the research presented here, we explore the use of a low‐energy plasma to deposit thin silicone polymer films using tetramethyldisiloxane (TMDSO) (H(CH3)2? Si? O? Si? (CH3)2H) on the surface of an ethylene propylene diene elastomeric terpolymer (EPDM) in order to enhance the surface hydrophobicity, lower the surface energy and improve the degradation/wear characteristics. The processing conditions were varied over a wide range of treatment times and discharge powers to control the physical characteristics, thickness, morphology and chemical structure of the plasma polymer films. Scanning electron microscopy (SEM) shows that pore‐free homogeneous plasma polymer thin films of granular microstructure composed of small grains are formed and that the morphology of the granular structure depends on the plasma processing conditions, such as plasma power and time of deposition. The thicknesses of the coatings were determined using SEM, which confirmed that the thicknesses of the deposited plasma‐polymer films could be precisely controlled by the plasma parameters. The kinetics of plasma‐polymer film deposition were also evaluated. Contact angle measurements of different solvent droplets on the coatings were used to calculate the surface energies of the coatings. These coatings appeared to be hydrophobic and had low surface energies. X‐ray photoelectron spectroscopy (XPS) and photoacoustic Fourier‐transform infrared (PA‐FT‐IR) spectroscopy were used to investigate the detailed chemical structures of the deposited films. The optimum plasma processing conditions to achieve the desired thin plasma polymer coatings are discussed in the light of the chemistry that takes place at the interfaces. Copyright © 2004 Society of Chemical Industry 相似文献
19.
Asbestos fibres, of the chrysotile variety, and chopped carbon fibres were pretreated by an in-situ polycondensation technique eventually resulting in a polyamide coating on the fibre surface. Ionomer based composites containing either carbon or asbestos fibres in random in plane fibre orientation were prepared, and the influence of this coating process on the tensile properties was investigated. It was found that for the asbestos-filled composites the presence of the nylon 6,6 interlayer improves the tensile performance, especially at moderate polyamide depositions. This is not the case with the pretreated carbon-filled composites for which carbon fibres with higher polyamide contents are preferred. Combinations of the treated asbestos fibres with carbon and/or aramid fibres may be used to reduce the asbestos content in asbestos-only based engineering plastics. 相似文献
20.
硅外延片中的杂质控制 总被引:2,自引:0,他引:2
有5类掺杂源影响硅的外延片中的杂质分布。主掺杂质控制外延层的杂质浓度,决定外延层的电阻率。固态外扩散、气相自掺杂和系统自掺杂影响衬底界面附近的外延层杂质浓度的深度分布。该文介绍了此3类掺杂源的掺杂过程和抑制方法。金属杂质在外延层中对器件有害,防止沾污和使用吸杂技术能降低金属杂质在外延层中的浓度。 相似文献