首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   72521篇
  免费   5549篇
  国内免费   2727篇
电工技术   3838篇
技术理论   6篇
综合类   4418篇
化学工业   12347篇
金属工艺   3929篇
机械仪表   4903篇
建筑科学   5164篇
矿业工程   2379篇
能源动力   2227篇
轻工业   4755篇
水利工程   984篇
石油天然气   5241篇
武器工业   465篇
无线电   7593篇
一般工业技术   9343篇
冶金工业   3789篇
原子能技术   745篇
自动化技术   8671篇
  2024年   199篇
  2023年   1198篇
  2022年   1746篇
  2021年   2791篇
  2020年   2150篇
  2019年   1907篇
  2018年   2247篇
  2017年   2475篇
  2016年   2059篇
  2015年   2684篇
  2014年   3427篇
  2013年   4200篇
  2012年   4353篇
  2011年   4867篇
  2010年   4176篇
  2009年   3965篇
  2008年   3856篇
  2007年   3729篇
  2006年   3806篇
  2005年   3441篇
  2004年   2291篇
  2003年   2086篇
  2002年   1875篇
  2001年   1649篇
  2000年   1809篇
  1999年   2049篇
  1998年   1764篇
  1997年   1418篇
  1996年   1402篇
  1995年   1179篇
  1994年   939篇
  1993年   711篇
  1992年   546篇
  1991年   423篇
  1990年   325篇
  1989年   251篇
  1988年   220篇
  1987年   138篇
  1986年   101篇
  1985年   90篇
  1984年   60篇
  1983年   34篇
  1982年   43篇
  1981年   28篇
  1980年   22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 109 毫秒
41.
42.
43.
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   
44.
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   
45.
46.
47.
48.
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   
49.
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   
50.
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   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号