全文获取类型
收费全文 | 624篇 |
免费 | 22篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 14篇 |
综合类 | 10篇 |
化学工业 | 112篇 |
金属工艺 | 40篇 |
机械仪表 | 21篇 |
建筑科学 | 15篇 |
矿业工程 | 4篇 |
能源动力 | 69篇 |
轻工业 | 45篇 |
水利工程 | 10篇 |
无线电 | 162篇 |
一般工业技术 | 133篇 |
冶金工业 | 5篇 |
原子能技术 | 6篇 |
自动化技术 | 20篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 16篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 25篇 |
2016年 | 23篇 |
2015年 | 11篇 |
2014年 | 42篇 |
2013年 | 35篇 |
2012年 | 35篇 |
2011年 | 51篇 |
2010年 | 42篇 |
2009年 | 51篇 |
2008年 | 34篇 |
2007年 | 36篇 |
2006年 | 33篇 |
2005年 | 23篇 |
2004年 | 36篇 |
2003年 | 21篇 |
2002年 | 7篇 |
2001年 | 11篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有666条查询结果,搜索用时 15 毫秒
31.
Design of a high-speed sample-and-hold circuit using a substrate-biasing-effect attenuated T switch 总被引:1,自引:0,他引:1
A circuit technique for designing a high speed sample-and-hold circuit is proposed. A substrate-biasing-effect attenuated T switch is used during the hold mode of sample-and-hold circuit, the T type structure makes the input-dependent signal feed-through effect neglectable, and a high linearity performance can be assured. Based on SMIC 0.13 μm Standard CMOS process, a sample-and-hold circuit applicable to 12bit, 100 MHz Pipelined ADC is designed. Spectre simulation results show that the using this technique can improve the dynamic performance and the signal-to-noise and distortion ratio (SNADR) and spurs free dynamic range (SFDR) of the sample-and-hold circuit is 85.5 and 92.87 dB, respectively, under the Nyquist input frequency . 相似文献
32.
33.
Young Cheol Ryu Tae Gun Kim Guem-Seok Seo Jin Hwan Park Cha Soo Suh Seong-Soo Park Seong-Soo Hong Gun Dae Lee 《Journal of Industrial and Engineering Chemistry》2008,14(2):213-218
The TiO2/substrate pearlescent pigments were prepared by the hydrolysis of TiOCl2 on the substrate followed by a calcinations process. The natural mica (muscovite), synthetic mica (fluorophlogopite) and -alumina flake were selected as the substrates for pearlescent pigments. The effect of substrate on the anatase to rutile (A–R) phase transformation of TiO2 was studied. The A–R phase transformation of TiO2 during the preparation of pearlescent pigments and their proportion in the TiO2 layer have been analyzed by XRD measurements. The phase compositions of TiO2 layer in each pearlescent pigment are quite different depending on the substrates. The TiO2 layer deposited on -alumina has higher rutile fraction than those on the natural and synthetic mica. The XPS analysis showed that the cations originally present in the substrates diffused into the TiO2 layer. The TiO2 layer deposited on -alumina contains Al, while those on the natural and synthetic mica substrates contain Si and K in addition to Al. The metal cations diffusing from the substrate into TiO2 layer might retard the A–R phase transformation of TiO2. The suppressing effect on the A–R transformation of TiO2 by mixed cations seems to be much stronger than that of single cation, resulting in relatively higher rutile fraction in the case of TiO2 layer deposited on -alumina. 相似文献
34.
激光熔覆成形预热基板设计及试验研究 总被引:1,自引:0,他引:1
为了降低激光熔覆成形过程中熔覆层热应力和减少裂纹的产生,以热传导理论和激光快速成形理论为依据,进行了预热基板的结构和控制设计;并进行了不同预热温度下单道熔覆和平面熔覆的试验研究.结果表明,通过智能PID控制器可对预热温度进行良好控制,通过热电偶温度采集模块可以实现对基板预热温度的连续、实时检测;在基板预热条件下进行激光熔覆成形可以显著改善试样的成形质量,并有效降低成形过程的热应力,减少了熔覆层裂纹的产生. 相似文献
35.
36.
Xiaoqiang Zou Kakeza Nadege Irabogora Ninette Ye Wen Shibin Wu Xuan Jiang Hui Zhang Qingzhe Jin Xingguo Wang 《Journal of the American Oil Chemists' Society》2020,97(3):263-270
Docosahexaenoic acid (DHA)-rich diacylglycerol (DAG)-rich oil was prepared by lipase-catalyzed glycerolysis of microbial oil from Schizochytrium sp. in a solvent-free system. The reaction parameters including lipase type, substrate molar ratio, temperature, lipase concentration, and reaction time were screened. The selected conditions were determined as follows: Novozym® 435 (Novozymes A/S, Bagsvaerd, Denmark) as biocatalyst at 8 wt%, substrate ratio (DHA-rich microbial TAG/glycerol) of 1:1 mol/mol, temperature of 50 °C, and reaction time of 12 hours. Under these conditions, the triacylglycerol (TAG), DAG, and monoacylglycerol (MAG) contents in the product were 36.4%, 48.2%, and 15.4%, respectively. The lipase was reused successively for 18 cycles without significant loss of activity under the conditions given above. Fatty acid composition analysis of the final product showed that the contents of DHA in TAG, DAG, and MAG were 53.9%, 44.9%, and 34.8%, respectively. DHA-rich DAG has the potential to be used as an ingredient in infant formula to increase the bioavailability of DHA. 相似文献
37.
《化学,工程师,技术》2017,89(6):724-732
The impact of the substrate/inoculum ratio on the performance and process stability during batch digestion of grass silage, an important substrate in biogas plants, was investigated. The methane yield, degradability, and evolution of intermediary products were monitored in mesophilic reactors fed with increasing amounts of grass silage. A first‐order kinetics model was also applied. Signs of inhibition were observed for the highest loadings, but the system recovered and process failure was not observed. The methane yield decreased with increasing loading but the system was resilient to high loadings under batch conditions. 相似文献
38.
利用复合膜吸杂技术处理硅晶体材料改善硅衬底及外延片质量的吸杂原理.通过三探针测量、DLTS 检测、MOS 电容器弛预时间、器件结特性的改善和成品率的提高显示了复合膜吸杂的吸杂效果.实验结果表明,复合膜吸杂枝术是有效、简便、可控、稳定、成本低廉且与器件制造工艺是相容的.很有开发、推广价值. 相似文献
39.
Nylon-polystyrene microcapsules with immobilized ferroelectric liquid crystalline segments were prepared, and the permeability control of the encapsulated core material was investigated under an external electric field. A ferroelectric liquid crystal monomer possessing both mesogenicity and chirality effectively responded to an external electrical field. Permeation of the material (oxprenolol) contained in the inner aqueous core of the microcapsules was enhanced under a feeble electric field (2 V). Furthermore, it was found that the permeability of the microcapsules without the ferroelectric liquid crystal group did not depend on the external electrical field. In order to clarify the controlled release mechanism of the core material, the transmittance was quantitatively evaluated under an external electric field using a handmade polarized light transmittance apparatus. 相似文献
40.
D. Liu M. Seraffon P.E.J. Flewitt N.J. Simms J.R. Nicholls D.S. Rickerby 《Journal of the European Ceramic Society》2013,33(15-16):3345-3357
A set of aerofoil shaped air plasma sprayed thermal barrier coated (APS-TBC) specimens were adopted in this paper to investigate the stress distributions in the ceramic top coat (TC) and the thermally grown oxide (TGO), the mechanism of local crack generation and propagation at the TC/BC (bond coat) interface. The failure mode of the TBC system, the distribution of asperities at TC/BC interface, thickness of the TC and BC, and the TC microstructure were found to be influenced by substrate curvature. Residual stress was therefore measured across the thickness of the TC, along the undulating TGO and mapped at locations of asperities where failure tended to occur to interpret the initiation of local failure. The role of the TGO was investigated via its chemical bonding with the TC and the decohesion occurring at the TGO/BC interface. The crack propagation at the interface has been discussed with respect to the macro-failure of the TBC system. 相似文献