全文获取类型
收费全文 | 104240篇 |
免费 | 10457篇 |
国内免费 | 5848篇 |
专业分类
电工技术 | 8130篇 |
技术理论 | 3篇 |
综合类 | 7899篇 |
化学工业 | 15559篇 |
金属工艺 | 6465篇 |
机械仪表 | 6798篇 |
建筑科学 | 7823篇 |
矿业工程 | 3021篇 |
能源动力 | 3408篇 |
轻工业 | 7005篇 |
水利工程 | 2430篇 |
石油天然气 | 5053篇 |
武器工业 | 1227篇 |
无线电 | 12618篇 |
一般工业技术 | 11490篇 |
冶金工业 | 5098篇 |
原子能技术 | 1326篇 |
自动化技术 | 15192篇 |
出版年
2024年 | 385篇 |
2023年 | 1395篇 |
2022年 | 2805篇 |
2021年 | 4049篇 |
2020年 | 3048篇 |
2019年 | 2481篇 |
2018年 | 2696篇 |
2017年 | 3271篇 |
2016年 | 3124篇 |
2015年 | 4227篇 |
2014年 | 5515篇 |
2013年 | 6557篇 |
2012年 | 7769篇 |
2011年 | 8166篇 |
2010年 | 7511篇 |
2009年 | 7301篇 |
2008年 | 7065篇 |
2007年 | 6646篇 |
2006年 | 6275篇 |
2005年 | 5228篇 |
2004年 | 3960篇 |
2003年 | 3645篇 |
2002年 | 3829篇 |
2001年 | 3221篇 |
2000年 | 2153篇 |
1999年 | 1780篇 |
1998年 | 1252篇 |
1997年 | 1043篇 |
1996年 | 929篇 |
1995年 | 711篇 |
1994年 | 566篇 |
1993年 | 389篇 |
1992年 | 317篇 |
1991年 | 239篇 |
1990年 | 191篇 |
1989年 | 152篇 |
1988年 | 133篇 |
1987年 | 91篇 |
1986年 | 81篇 |
1985年 | 41篇 |
1984年 | 56篇 |
1983年 | 41篇 |
1982年 | 48篇 |
1981年 | 29篇 |
1980年 | 24篇 |
1979年 | 29篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 14篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
32.
33.
34.
Anxiang Su Gaoxing Ma Minhao Xie Yang Ji Xiangfei Li Liyan Zhao Qiuhui Hu 《International Journal of Food Science & Technology》2019,54(6):2277-2287
In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota. 相似文献
35.
36.
The effect of charge on the dihydrogen storage capacity of Sc2–C6H6 has been investigated at B3LYP-D3/6-311G(d,p) level. The neutral system Sc2–C6H6 can store 8H2 with gravimetric density of 8.76 wt %, and one H2 dissociates and bonds atomically on the scandium atom. The adsorption of 8H2 on Sc2–C6H6 is energetically favorable below 155 K. The atom-centered density matrix propagation (ADMP) molecular dynamics simulations show that Sc2–C6H6 can adsorb 3H2 within 1000 fs at 300K. Compared with Sc2–C6H6, the charged systems can adsorb more hydrogen molecules with higher gravimetric density, and all the H2 are adsorbed in the molecular form. The gravimetric densities of Sc2–C6H6+ and Sc2–C6H62+ are 9.75 and 10.71 wt%. Moreover, the maximum adsorption of charged systems are favorable in wider temperature range. Most importantly, the ADMP-MD simulations indicate that Sc2–C6H62+ can adsorb 6 hydrogen molecules within 1000 fs at 300K. It can be found that the gravimetric density (6.72 wt%) of Sc2–C6H62+ still exceeds the target of US Department of Energy (DOE) under ambient conditions. 相似文献
37.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
38.
39.
Bin Zhang Xuesong Jiang Fei Shen Xueming He Yong Fang Qiuhui Hu 《International Journal of Food Science & Technology》2021,56(6):2588-2595
This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s−1 on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg−1 as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing. 相似文献
40.
Muhammad Sheeraz Mamoon Ur Rashid Asad Ali Fazli Akram Ho Jeong Lee Jin San Choi Jong-Seong Bae Yong Soo Kim Young-Han Shin Chang Won Ahn Tae Heon Kim 《Journal of the European Ceramic Society》2021,41(10):5155-5162
We demonstrate the structural evolution of polymorphic phases in Al2O3-inserted SrMnO3 ceramics synthesized by solid state reaction. While the 4H-hexagonal phase is predominant in pure SrMnO3 ceramics, a small amount of 6H-hexagonal polymorph is identified in addition to the primary 4H-hexagonal SrMnO3 and the secondary hexagonal SrAl2O4 phases in the as-sintered ceramics, evidenced by x-ray diffraction and subsequent Rietveld refinement analyses. The existence of the 6H-hexagonal SrMnO3 phase is corroborated using Raman spectroscopy. The chemical compositions and electronic structures of the Al2O3-inserted SrMnO3 compounds are also examined using energy dispersive spectroscopy and x-ray photoelectron spectroscopy, respectively. The first-principles calculations reveal that there is no clear difference between the total energies of 4H- and 6H-hexagonal polymorphs regardless of the presence/absence of Sr and oxygen vacancies. Possible origins are discussed with the estimation of actual strain based on the refined lattice parameter of 6H SrMnO3. 相似文献