全文获取类型
收费全文 | 88730篇 |
免费 | 9091篇 |
国内免费 | 5355篇 |
专业分类
电工技术 | 5929篇 |
技术理论 | 8篇 |
综合类 | 7721篇 |
化学工业 | 13786篇 |
金属工艺 | 4901篇 |
机械仪表 | 5333篇 |
建筑科学 | 6784篇 |
矿业工程 | 2526篇 |
能源动力 | 2297篇 |
轻工业 | 9906篇 |
水利工程 | 2229篇 |
石油天然气 | 4206篇 |
武器工业 | 851篇 |
无线电 | 10082篇 |
一般工业技术 | 9174篇 |
冶金工业 | 3363篇 |
原子能技术 | 1004篇 |
自动化技术 | 13076篇 |
出版年
2024年 | 541篇 |
2023年 | 1649篇 |
2022年 | 3202篇 |
2021年 | 4135篇 |
2020年 | 3309篇 |
2019年 | 2482篇 |
2018年 | 2728篇 |
2017年 | 3114篇 |
2016年 | 2778篇 |
2015年 | 4093篇 |
2014年 | 5223篇 |
2013年 | 6042篇 |
2012年 | 6872篇 |
2011年 | 7382篇 |
2010年 | 6579篇 |
2009年 | 6052篇 |
2008年 | 6072篇 |
2007年 | 5523篇 |
2006年 | 5011篇 |
2005年 | 3995篇 |
2004年 | 2887篇 |
2003年 | 2391篇 |
2002年 | 2417篇 |
2001年 | 2046篇 |
2000年 | 1440篇 |
1999年 | 1270篇 |
1998年 | 758篇 |
1997年 | 650篇 |
1996年 | 587篇 |
1995年 | 439篇 |
1994年 | 350篇 |
1993年 | 258篇 |
1992年 | 236篇 |
1991年 | 151篇 |
1990年 | 121篇 |
1989年 | 95篇 |
1988年 | 58篇 |
1987年 | 49篇 |
1986年 | 36篇 |
1985年 | 18篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 17篇 |
1980年 | 23篇 |
1979年 | 14篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1959年 | 7篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
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
33.
Baofeng Hou Hong He Ruixiu Jia Meilong Fu Yanbin Cao Shaoqun He Liwen Luo Youqing Huang 《应用聚合物科学杂志》2019,136(10):47161
The synthesis and performance of a novel temperature-tolerant foamed resin for enhanced oil recovery were investigated using various methods, including infrared, NMR, scanning electron microscopy (SEM), and displacement experiments. Polycondensation of furfuryl alcohol prepolymers was confirmed by the infrared and NMR results. The poor temperature tolerance of furfuryl alcohol prepolymers after gelation at high temperatures is mainly due to the fracture of furan rings. The addition of ester additives is an effective method of increasing the temperature tolerance of the prepared foamed resins and can effectively reduce the weight-loss rate of the polycondensation products. The SEM results show that the skeleton structure of the foamed resin remains intact after high-temperature treatment. Thus, the novel plugging agent system has excellent thermal stability and still has a high strength (>0.8 MPa) after high-temperature aging treatment for 40 days, giving the prepared foamed resin a good plugging performance (plugging rate > 91%) at 250 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47161. 相似文献
34.
35.
36.
Wenjia Jing Baoqiang Hou Jinxiao Wang Qiang Zhi Jianfeng Yang Bo Wang 《Journal of the American Ceramic Society》2022,105(5):3141-3146
Photocatalysts often show excellent performances on the basis of their surface state of exposed faces with high reactivity, but unfortunately surfaces of this type are usually concealed into the interior of crystals for their high surface energy. We report here a possibility that for fluorine-terminated surfaces of monoclinic ZrO2, these higher-energy surfaces could be retained and exposed. Urchin-like ZrO2 hollow microspheres (UZHS) composed of nanoribbons with exposed (010) facets are obtained through a fluoride mediately solvothermal method. We prove the stabilization effect of fluorine adsorption on (010) facets by density functional theory calculations. More interestingly, UZHS exhibit tunable photocatalytic selectivity in dye degradation. The fluorinated UZHS exhibit good performances both on decomposing Congo red (CR) and methylene blue, while the surface-modified UZHS by calcination only favor decomposition of CR. 相似文献
37.
Replacement of precious single metal catalysts with cost-effective, highly-dispersed composite catalysts for catalytic hydrothermal conversion of residue holds tremendous promise for the residue upgrading technologies. Organic metals were added to the feed as the oil-soluble precursors, and transformed into the catalytic active phases in this work. Physical properties and structures of the composite catalysts had been investigated by X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope and transmission electron microscopy. The composite catalysts were found to be highly efficient in the catalytic hydrothermal conversion of both model compound and residue. Increased metal dispersion and synergistic effects of two metals played indispensable roles in such catalytic system. Results showed that under the test conditions in the article, the catalyst had the best catalytic performance when the mass ratio of molybdenum to iron was 1.5. 相似文献
38.
针对工业控制系统传统单一检测算法模型对不同攻击类型检测率和检测速度不佳的问题,提出一种优化支持向量机和K-means++算法结合的入侵检测模型。首先利用主成分分析法(PCA)对原始数据集进行预处理,消除其相关性;其次在粒子群优化(PSO)算法的基础上加入自适应变异过程避免在训练的过程中陷入局部最优解;然后利用自适应变异粒子群优化(AMPSO)算法优化支持向量机的核函数和惩罚参数;最后利用密度中心法改进K-means算法与优化后的支持向量机组合成入侵检测模型,从而实现工业控制系统的异常检测。实验结果表明,所提方法在检测速度和对各类攻击的检测率上得到明显提升。 相似文献
39.
40.