全文获取类型
收费全文 | 8452篇 |
免费 | 736篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 93篇 |
综合类 | 11篇 |
化学工业 | 1890篇 |
金属工艺 | 328篇 |
机械仪表 | 532篇 |
建筑科学 | 131篇 |
矿业工程 | 1篇 |
能源动力 | 340篇 |
轻工业 | 657篇 |
水利工程 | 20篇 |
石油天然气 | 7篇 |
武器工业 | 2篇 |
无线电 | 1580篇 |
一般工业技术 | 1951篇 |
冶金工业 | 595篇 |
原子能技术 | 118篇 |
自动化技术 | 949篇 |
出版年
2023年 | 101篇 |
2022年 | 101篇 |
2021年 | 211篇 |
2020年 | 191篇 |
2019年 | 239篇 |
2018年 | 311篇 |
2017年 | 275篇 |
2016年 | 342篇 |
2015年 | 275篇 |
2014年 | 431篇 |
2013年 | 586篇 |
2012年 | 546篇 |
2011年 | 698篇 |
2010年 | 499篇 |
2009年 | 538篇 |
2008年 | 468篇 |
2007年 | 372篇 |
2006年 | 347篇 |
2005年 | 296篇 |
2004年 | 264篇 |
2003年 | 255篇 |
2002年 | 222篇 |
2001年 | 189篇 |
2000年 | 155篇 |
1999年 | 161篇 |
1998年 | 251篇 |
1997年 | 173篇 |
1996年 | 143篇 |
1995年 | 97篇 |
1994年 | 65篇 |
1993年 | 74篇 |
1992年 | 44篇 |
1991年 | 35篇 |
1990年 | 42篇 |
1989年 | 29篇 |
1988年 | 22篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 11篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 8篇 |
1973年 | 6篇 |
1967年 | 5篇 |
排序方式: 共有9205条查询结果,搜索用时 15 毫秒
1.
Shin Hansub Sim Sungyong Kwon Hyukyoon Hwang Sangheum Lee Younho 《International Journal of Information Security》2022,21(1):25-36
International Journal of Information Security - This paper deals with a well-known problem in the area of the smudge attacks: when a user draws a pattern to unlock the pattern lock on a smartphone... 相似文献
2.
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
3.
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
4.
5.
6.
Machine Learning - We consider the problem of learning a binary classifier from only positive and unlabeled observations (called PU learning). Recent studies in PU learning have shown superior... 相似文献
7.
Bioactive compounds and antioxidant activities of the Korean lotus leaf (Nelumbo nucifera) condiment: volatile and nonvolatile metabolite profiling during fermentation 下载免费PDF全文
Recent studies have shown that lotus (Nelumbo nucifera) leaf has various pharmacological effects. However, there have been no scientific investigations into these leaves as a fermented crude liquid. This study compared the in vitro antioxidant capacity of lotus leaf‐fermented broth (LLFB) with that of 57° Brix sugar broth (SB) as a control over a period of 6 months based on 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity, ferric ion reducing power, superoxide dismutase‐like activity, tyrosinase inhibition and nitrite scavenging activity. The dominant species during fermentation process were Leuconostoc lactis and Saccharomyces cerevisiae for LLFB. A total of thirty‐six metabolites such as alkaloids, fatty acids, organic acids, phenolics, sugar and sugar derivatives, ethyl esters and monoterpenoids differed between SB and LLFB using gas chromatography–mass spectrometry. Meanwhile, nine volatile compounds in LLFB contributed pleasant, slightly sweetish and fruity odour of condiment and sensory evaluation score of 4.06 ± 1.52 in the proportion of 1:9 LLFB/water. 相似文献
8.
A device able to electrokinetically concentrate cationic samples has many potential medical and industrial applications, but until now has remained undeveloped due to the lack of a commercial anion-permselective material leading to a prohibitively complex fabrication procedure. Herein, a novel multiscale-porous anion exchange membrane (MP-AEM) that enables the convenient and scalable electrokinetic concentration of cationic species is proposed. A mechanically enhanced multiscale-porous structure with a solid framework is realized by adopting polyester resin as an additive to overcome the intrinsic limitations of the AEM material. The scalable MP-AEM-embedded electrokinetic concentrator is devised based on the peculiar properties of the MP-AEM that for allow both ion and fluid transport. With the MP-AEM, the concentrator is fabricated in a highly streamlined manner consisting only of a simple insertion and assembly. The concentration performance of the MP-AEM-embedded electrokinetic concentrator is demonstrated with a positively charged fluorescent dye and a fluorescein-labeled protein, and the results show enrichment factors of 250 and 500, respectively. The MP-AEM makes cationic electrokinetic concentration more accessible and scalable, thereby enabling further progress in a wide range of fields. 相似文献
9.
Seung Han Ryu Seil Kim Young-Tae Kwon Young Ki Park Sung-Oong Kang Hong-Baek Cho Yong-Ho Choa 《应用聚合物科学杂志》2020,137(8):48390
Here, we report a facile approach to electrostatically couple the surface charges of graphite nanoplate (GNP) fillers and poly(methyl methacrylate) (PMMA) polymer particles using ethylene maleic anhydride (EMA) copolymer as an electrostatic coupling agent. Our strategy involved switching the intrinsic repulsive electrostatic interactions between the directly exfoliated GNPs fillers and the PMMA particles to attractive electrostatic surface interactions for preparing core(PMMA)-shell (GNP) precursor in order to optimizing 3-dimensionally dispersed polymer nanocomposite. As a result, the electrical conductivity of the composites dramatically increased by a factor of 16.7 in the EMA-coupled GNP/PMMA composites compared with that of the EMA-free GNP/PMMA composites. In addition, the percolation threshold was also notably reduced from 0.32 to 0.159 vol% after electrostatic coupling of the GNPs fillers and PMMA particles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48390. 相似文献
10.
Characterisation of two biomass fuels (pelletised Miscanthus Giganteus and wood) was performed using thermogravimetric analysis with measurement of products by means of Fourier transform infrared spectroscopy (TG-FTIR). Three heating rate profiles were applied (10, 30 and 100 °C/min), with a final temperature of 900 °C. HCN and HNCO were found to be the major N-products, while the NH3 fraction was detected to a minor extent. Kinetic parameters were obtained from the TG-FTIR results using a model based on parallel first-order reactions with a Gaussian distribution of activation energies. On the basis of the above kinetic analysis and product yields, input files for the functional group-devolatilisation, vaporisation, cross-linking biomass-pyrolysis model were prepared. The fit of model parameters to TG-FTIR product-evolution data was found to be generally good, but the model-predicted yields for some species did not fit experimental data at all heating rates. Further improvements in the model are needed to resolve above difficulty. 相似文献