全文获取类型
收费全文 | 46779篇 |
免费 | 4893篇 |
国内免费 | 2883篇 |
专业分类
电工技术 | 3221篇 |
技术理论 | 1篇 |
综合类 | 3899篇 |
化学工业 | 6915篇 |
金属工艺 | 3006篇 |
机械仪表 | 3161篇 |
建筑科学 | 3756篇 |
矿业工程 | 1569篇 |
能源动力 | 1321篇 |
轻工业 | 4133篇 |
水利工程 | 1246篇 |
石油天然气 | 1894篇 |
武器工业 | 521篇 |
无线电 | 5394篇 |
一般工业技术 | 5118篇 |
冶金工业 | 1918篇 |
原子能技术 | 724篇 |
自动化技术 | 6758篇 |
出版年
2024年 | 217篇 |
2023年 | 827篇 |
2022年 | 1637篇 |
2021年 | 2287篇 |
2020年 | 1701篇 |
2019年 | 1273篇 |
2018年 | 1342篇 |
2017年 | 1578篇 |
2016年 | 1416篇 |
2015年 | 1956篇 |
2014年 | 2509篇 |
2013年 | 2961篇 |
2012年 | 3370篇 |
2011年 | 3578篇 |
2010年 | 3221篇 |
2009年 | 3200篇 |
2008年 | 3077篇 |
2007年 | 2999篇 |
2006年 | 2779篇 |
2005年 | 2374篇 |
2004年 | 1584篇 |
2003年 | 1205篇 |
2002年 | 1154篇 |
2001年 | 984篇 |
2000年 | 879篇 |
1999年 | 734篇 |
1998年 | 610篇 |
1997年 | 487篇 |
1996年 | 527篇 |
1995年 | 419篇 |
1994年 | 351篇 |
1993年 | 277篇 |
1992年 | 216篇 |
1991年 | 182篇 |
1990年 | 131篇 |
1989年 | 109篇 |
1988年 | 105篇 |
1987年 | 70篇 |
1986年 | 45篇 |
1985年 | 37篇 |
1984年 | 34篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1959年 | 5篇 |
1958年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
Multimedia Tools and Applications - In geometry-based point cloud compression, the geometry information is typically compressed using octree coding. In octree coding, the size of the blocks in the... 相似文献
3.
Jiao Zhang Junjie Li Ayesha Murtaza Aamir Iqbal Lijuan Zhu Shinawar Waseem Ali Muhammad Usman Roshan Yameen Siyi Pan Wanfeng Hu 《International Journal of Food Science & Technology》2022,57(2):963-973
This work evaluated the synergistic effects of combined high-intensity ultrasound (HIU) with β-cyclodextrin (β-CD) treatments on inhibiting browning of apple juice and explored the mechanism through simulation system. The combined treatment of 300 W HIU with 0.006 g mL−1 β-CD had a synergistic impact on maintaining juice colour, resulting in a 39.06% reduction in browning degree, only a 36.64% decrease in total phenolic content, and a 17.82% reduction in PPO activity. The inhibition of enzymatic browning in simulated system revealed that HIU suppressed the enzyme (Polyphenol oxidase, PPO) and β-CD inhibited enzyme (PPO) and embedded substrate (polyphenol). The results of spectroscopic analysis showed that the particle-size distribution of PPO narrowed, the content of α-helix in the secondary structure increased, the fluorescence intensity increased, and the maximum wavelength was red-shifted after HIU and β-CD treatment. Changes in structure could further result in PPO activity loss. Hence, the combined treatment could synthetically alleviate the browning of apple juice. 相似文献
4.
5.
Yang Liu Liang-ming Pan Hong-bo Liu 《International Journal of Hydrogen Energy》2021,46(27):13923-13935
Relatively low efficiency is the biggest obstacle to the popularization of water electrolysis, which is a particularly feasible way to produce super-pure hydrogen. Imposing a magnetic field can increase the hydrogen production efficiency of water electrolysis. However, the enhancement's detailed mechanism still lacks an insightful understanding of the bubbles' micro vicinity. Our recent work aims to understand why the micro-magnetohydrodynamic (MHD) convection hinders single bubbles' detachment on the microelectrode. A water electrolysis experiment by microelectrode is performed under an electrode-normal magnetic field, and dynamic analysis of the single bubble growing on microelectrodes is performed. The variation of bubble diameter with time in the presence or absence of the magnetic field was measured, and the forces acting on the bubble were quantified. The result shows that the micro-MHD convection, induced by Lorentz force, can give rise to a downward hydrodynamic pressure force that will not appear in large-scale MHD convection. This force can be of the same magnitude as the surface tension, so it dramatically hinders bubbles' detachment. Besides, the Kelvin force provides a new potential way for further improving the efficiency of water electrolysis. 相似文献
6.
Chunyan Xu Ying Wang Daodong Pan Changyu Zhou Jun He Jinxuan Cao 《International Journal of Food Science & Technology》2021,56(4):1690-1702
To investigate the effect of cooking temperature (55, 65, 75, 85 and 95 °C) on texture and flavour binding of braised sauce porcine skin (BSPS), sensory acceptance, microstructure and flavour-binding capacity were investigated during the processing of BSPS. Samples cooked at 85 and 95 °C showed better texture and aroma scores. Hardness and chewiness of BSPS were obviously improved at 85 and 95 °C than control group. Collagen structure was significantly destroyed over 85 °C. The porcine skin collagen heated at 85 and 95 °C showed relatively higher flavour-binding capacity than other samples. The improvement of texture of BSPS was mainly attributed to the degradation of collagen. Higher aroma scores of BSPS were related to intense binding abilities with aroma compounds at 85 and 95 °C. Cooking at 85 or 95 °C could be an optimal cooking temperature for BSPS. 相似文献
7.
Jiangyou Long Qingfa Peng Gaopan Chen Yuliang Zhang Xiaozhu Xie Guoshun Pan Xiaofeng Wang 《Ceramics International》2021,47(16):23134-23143
Femtosecond (fs) lasers have been proved to be reliable tools for high-precision and high-quality micromachining of ceramic materials. Nevertheless, fs laser processing using a single-mode beam with a Gaussian intensity distribution is difficult to obtain large-area flat and uniform processed surfaces. In this study, we utilize a customized diffractive optical element (DOE) to redistribute the laser pulse energy from Gaussian to square-shaped Flat-Top profile to realize centimeter-scale low-damage micromachining on single-crystal 4H–SiC substrates. We systematically investigated the effects of processing parameters on the changes in surface morphology and composition, and an optimal processing strategy was provided. Mechanisms of the formation of surface nanoparticles and the removal of surface micro-burrs were discussed. We also examined the distribution of subsurface defects caused by fs laser processing by removing a thin surface layer with a certain depth through chemical mechanical polishing (CMP). Our results show that laser-induced periodic surface structures (LIPSSs) covered by fine SiO2 nanoparticles form on the fs laser-processed areas. Under optimal parameters, the redeposition of SiO2 nanoparticles can be minimized, and the surface roughness Sa of processed areas reaches 120 ± 8 nm after the removal of a 10 μm thick surface layer. After the laser processing, micro-burrs on original surfaces are effectively removed, and thus the average profile roughness Rz of 2 mm long surface profiles decreases from 920 ± 120 nm to 286 ± 90 nm. No visible micro-pits can be found after removing ~1 μm thick surface layer from the laser-processed substrates. 相似文献
8.
龚学进 《精细与专用化学品》2021,29(11):54-56
通过对煤焦油加氢装置能量进行梯级利用,优化能源的使用状态,保证温位的合理匹配,实现降本增效,同时消除装置运行瓶颈问题,提高装置加工负荷,优化设备运行,进而提高煤焦油加氢装置的市场竞争力. 相似文献
9.
10.
针对伊拉克米桑油田盐膏层巨厚、钻井液密度窗口窄、存在高压盐水层,储层段漏塌同层导致复杂时效高等问题,通过对比分析国内外盐膏层和窄压力窗口地层钻井技术,总结了米桑油田钻井面临的主要技术难点,从井身结构优化、钻井提速和复杂预防等方面入手,研究形成了适合米桑油田的钻井关键技术,并进行了现场试验应用,取得了显著的效果.伊拉克米桑油田钻井关键技术对该地区钻井技术方案设计和钻井提速提效具有较强的借鉴和指导作用. 相似文献