全文获取类型
收费全文 | 73427篇 |
免费 | 5673篇 |
国内免费 | 2778篇 |
专业分类
电工技术 | 3881篇 |
技术理论 | 6篇 |
综合类 | 4443篇 |
化学工业 | 12715篇 |
金属工艺 | 3956篇 |
机械仪表 | 4820篇 |
建筑科学 | 5210篇 |
矿业工程 | 2404篇 |
能源动力 | 2234篇 |
轻工业 | 4777篇 |
水利工程 | 1001篇 |
石油天然气 | 5328篇 |
武器工业 | 461篇 |
无线电 | 7671篇 |
一般工业技术 | 9463篇 |
冶金工业 | 3934篇 |
原子能技术 | 750篇 |
自动化技术 | 8824篇 |
出版年
2024年 | 304篇 |
2023年 | 1267篇 |
2022年 | 2119篇 |
2021年 | 2901篇 |
2020年 | 2200篇 |
2019年 | 1968篇 |
2018年 | 2309篇 |
2017年 | 2511篇 |
2016年 | 2086篇 |
2015年 | 2697篇 |
2014年 | 3449篇 |
2013年 | 4226篇 |
2012年 | 4356篇 |
2011年 | 4868篇 |
2010年 | 4179篇 |
2009年 | 3963篇 |
2008年 | 3865篇 |
2007年 | 3723篇 |
2006年 | 3811篇 |
2005年 | 3437篇 |
2004年 | 2290篇 |
2003年 | 2092篇 |
2002年 | 1873篇 |
2001年 | 1642篇 |
2000年 | 1801篇 |
1999年 | 2051篇 |
1998年 | 1769篇 |
1997年 | 1426篇 |
1996年 | 1408篇 |
1995年 | 1187篇 |
1994年 | 958篇 |
1993年 | 722篇 |
1992年 | 549篇 |
1991年 | 430篇 |
1990年 | 328篇 |
1989年 | 258篇 |
1988年 | 226篇 |
1987年 | 142篇 |
1986年 | 120篇 |
1985年 | 96篇 |
1984年 | 66篇 |
1983年 | 40篇 |
1982年 | 42篇 |
1981年 | 30篇 |
1980年 | 25篇 |
1979年 | 13篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1945年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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
42.
Wei Mengnan Ban Boyuan Li Jingwei Sun Jifei Li Feifei Jiang Xuesong Chen Jian 《SILICON》2020,12(2):327-338
Silicon - A novel green cationic surfactant Poly (propylene glycol) bis (2-aminopropyl ether) (PEA) with multiple amine groups was utilized as a collector for flotation separation of quartz from... 相似文献
43.
44.
45.
Anti-washout and tissue adhesion properties are essential for the clinical application of injectable bone materials. In this study, we prepared calcium phosphate cement (CPC) with anti-washout and tissue adhesion properties and attempted to build covalent bonds between CPC and the amino groups in bone tissue under a self-regulating pH system in the CPC (acidic to basic). The results of push-out tests demonstrated that a significant enhancement (from 6.42 ± 0.76 N to 61.5 ± 4.09 N) in tissue adhesion was obtained with the addition of 6% (w/w) oxidized sodium alginate (OSA) in CPC. The FTIR, XRD, anti-washout test, XPS, pH test, and SEM results suggested that the synergistic effect of OSA-citric acid (CA) led to the formation of a three-dimensional gel network structure in the CPC, and the Schiff base reaction between aldehyde and amino groups induced adhesion between CPC and the bone tissue. Further, the addition of less OSA had no significant negative effect on the hydration properties of CPC. Our work aims to promote the development of injectable bone material in clinical applications. 相似文献
46.
Zhang Xi Wang Xianhai Zhao Hongke Ordóñez de Pablos Patricia Sun Yongqiang Xiong Hui 《Scientometrics》2019,119(3):1311-1344
Scientometrics - Altmetrics indices are increasingly applied to measure scholarly influence in recent years because they can reflect the influence of research outputs more timely comparing with... 相似文献
47.
This paper presents a spatio-temporal fusion method for remote sensing images by using a linear injection model and local neighbourhood information. In this method, the linear injection model is first introduced to generate an initial fused image, the spatial details are extracted from the fine-resolution image at the base date, and are weighted by a proper injection gains. Then, the spatial details and the relative spectral information from the coarse-resolution images are blended to generate the fusion result. To further enhance its robustness to the noise, the local neighbourhood information, derived from the fine-resolution image and the fused result simultaneously, is introduced to refine the initial fused image to obtain a more accurate prediction result. The algorithm can effectively capture phenology change or land-cover-type change with minimum input data. Simulated data and two types of real satellite images with seasonal changes and land-cover-type changes are employed to test the performance of the proposed method. Compared with a spatial and temporal adaptive reflectance fusion model (STARFM) and a flexible spatio-temporal fusion algorithm (FSDAF), results show that the proposed approach improves the accuracy of fused images in phenology change area and effectively captures land-cover-type reflectance changes. 相似文献
48.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
49.
Zhao Chao-Yue Jia Rui-Sheng Liu Qing-Ming Liu Xiao-Ying Sun Hong-Mei Zhang Xing-Li 《Multimedia Tools and Applications》2021,80(1):263-277
Multimedia Tools and Applications - To address the problems of insufficient detail extraction and long training time in the super-resolution reconstruction of chest X-ray images, a method of chest... 相似文献
50.
Jialin Sun Jun Zhao Xiuying Ni Feng Gong Zuoli Li 《Journal of the European Ceramic Society》2018,38(9):3096-3103
This work investigates the critical roles of two-step sintering (TSS) and laminated structure on the sintering behavior and mechanical properties of functionally graded WC-TiC-Al2O3 nanostructured composite materials doped with Cr3C2/VC. Results show that excellent mechanical properties are achieved for tailored TSS conditions with a hardness of 27.91?±?2.3?GPa and a flexural strength of 1423.3?±?23.5?MPa. The desirable mechanical properties are attributed to the suppressed grain growth without densification deterioration. TSS is more effective in facilitating the favorable dispersion of secondary phase toughening nano-particulates in a WC matrix than conventional sintering (CS). Cr3C2/VC dopant plays an important role in maximizing and shifting the temperature range of the kinetic window for WC-Al2O3 composites. Al2O3 crack deflection, transgranular Al2O3, microcracking, WC crack bridging and plate-like WC crack deflection are the major toughening mechanisms. Residual surface compressive stress induced by the graded structure is also an appreciated contribution to the improvement of mechanical properties. 相似文献