全文获取类型
收费全文 | 52166篇 |
免费 | 2912篇 |
国内免费 | 157篇 |
专业分类
电工技术 | 720篇 |
综合类 | 68篇 |
化学工业 | 11322篇 |
金属工艺 | 2167篇 |
机械仪表 | 3256篇 |
建筑科学 | 1229篇 |
矿业工程 | 29篇 |
能源动力 | 2157篇 |
轻工业 | 4360篇 |
水利工程 | 298篇 |
石油天然气 | 106篇 |
武器工业 | 3篇 |
无线电 | 7959篇 |
一般工业技术 | 11129篇 |
冶金工业 | 4381篇 |
原子能技术 | 675篇 |
自动化技术 | 5376篇 |
出版年
2024年 | 54篇 |
2023年 | 585篇 |
2022年 | 946篇 |
2021年 | 1600篇 |
2020年 | 1126篇 |
2019年 | 1223篇 |
2018年 | 1486篇 |
2017年 | 1497篇 |
2016年 | 1831篇 |
2015年 | 1379篇 |
2014年 | 2196篇 |
2013年 | 3162篇 |
2012年 | 3424篇 |
2011年 | 4082篇 |
2010年 | 2962篇 |
2009年 | 3048篇 |
2008年 | 2968篇 |
2007年 | 2340篇 |
2006年 | 2174篇 |
2005年 | 1824篇 |
2004年 | 1657篇 |
2003年 | 1598篇 |
2002年 | 1395篇 |
2001年 | 1187篇 |
2000年 | 1029篇 |
1999年 | 979篇 |
1998年 | 1604篇 |
1997年 | 1037篇 |
1996年 | 841篇 |
1995年 | 582篇 |
1994年 | 495篇 |
1993年 | 443篇 |
1992年 | 318篇 |
1991年 | 292篇 |
1990年 | 286篇 |
1989年 | 263篇 |
1988年 | 224篇 |
1987年 | 189篇 |
1986年 | 136篇 |
1985年 | 136篇 |
1984年 | 100篇 |
1983年 | 79篇 |
1982年 | 47篇 |
1981年 | 43篇 |
1980年 | 44篇 |
1979年 | 37篇 |
1978年 | 35篇 |
1977年 | 48篇 |
1976年 | 64篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Hyun Sun Choi Yun Kee Jo Gwang-Noh Ahn Kye Il Joo Dong-Pyo Kim Hyung Joon Cha 《Advanced functional materials》2021,31(46):2104602
The esophagus is a tubular-shaped muscular organ where swallowed fluids and muscular contractions constitute a highly dynamic environment. The turbulent, coordinated processes that occur through the oropharyngeal conduit can often compromise targeted administration of therapeutic drugs to a lesion, significantly reducing therapeutic efficacy. Here, magnetically guidable drug vehicles capable of strongly adhering to target sites using a bioengineered mussel adhesive protein (MAP) to achieve localized delivery of therapeutic drugs against the hydrodynamic physiological conditions are proposed. A suite of highly uniform microparticles embedded with iron oxide (IO) nanoparticles (MAP@IO MPs) is microfluidically fabricated using the genipin-mediated covalent cross-linking of bioengineered MAP. The MAP@IO MPs are successfully targeted to a specific region and prolongedly retained in the tubular-structured passageway. In particular, orally administered MAP@IO MPs are effectively captured in the esophagus in vivo in a magnetically guidable manner. Moreover, doxorubicin (DOX)-loaded MAP@IO MPs exhibit a sustainable DOX release profile, effective anticancer therapeutic activity, and excellent biocompatibility. Thus, the magnetically guidable locomotion and robust underwater adhesive properties of the proteinaceous soft microbots can provide an intelligent modular approach for targeted locoregional therapeutics delivery to a specific lesion site in dynamic fluid-associated tubular organs such as the esophagus. 相似文献
12.
13.
Lee Sangyul Kim Minjae Kim Hajin 《Journal of Mechanical Science and Technology》2018,32(12):5961-5972
Journal of Mechanical Science and Technology - The shape of the combustion chamber plays an important role in the formation of the air-fuel mixture in the chamber, which has a great influence on... 相似文献
14.
15.
Multimedia Systems - The preferences of Web information purchasers are changing. Cost-effectiveness (i.e., an emphasis on performance with respect to price) is becoming less regarded than... 相似文献
16.
17.
This study investigates the impact of lighting colors on subjective judgments of fabric: in particular, whether the influence of lighting varies depending on fabric types and color combinations. We conducted two visual assessments. In Study 1 (N = 44), eight illuminants and six types of fabric were presented as cloth stimuli. Derived from the literature review, four sets of adjectives (humble-luxurious, cool-warm, old-new, and not preferred-preferred) were used as metrics. In Study 2 (N = 41), five sets of fabric color combination swatches were assessed under lighting conditions that were identical to those of Study 1. Three bipolar scales (ordinary-characterful, classic-modern, and soft-rigid), were employed from factor analysis along with three unipolar scales (luxurious, preferred, harmonious with lighting). The results showed that hue characteristics of lighting and cloth types influenced participants' perceptions of the fabric. Overall, white lighting with 4000 K was the most preferred and luxurious lighting across various types of clothes, while a pinkish white with 4700 K (duv = −0.0127) was the best matched in every color combination. In addition, there were interaction effects between lighting colors, clothes types, and fabric color combinations with regard to each of the perceptual qualities. This study provides empirical evidence for optimally match lighting colors with fabric in the presentation of fabric goods. 相似文献
18.
Eui Dae Jung Amit Kumar Harit Do Hui Kim Chung Hyeon Jang Jong Hyun Park Shinuk Cho Myoung Hoon Song Han Young Woo 《Advanced materials (Deerfield Beach, Fla.)》2020,32(30):2002333
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s. 相似文献
19.
20.
Su-Il Ri Song-Il Hong Jong-Chol Kim Ju-Hyok Wi 《International Journal of Hydrogen Energy》2021,46(5):3319-3328
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance. 相似文献