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   113086篇
  免费   8552篇
  国内免费   4257篇
电工技术   6110篇
技术理论   11篇
综合类   6732篇
化学工业   19291篇
金属工艺   5928篇
机械仪表   6807篇
建筑科学   8716篇
矿业工程   3109篇
能源动力   3152篇
轻工业   6829篇
水利工程   1760篇
石油天然气   6313篇
武器工业   719篇
无线电   14074篇
一般工业技术   14353篇
冶金工业   5830篇
原子能技术   1266篇
自动化技术   14895篇
  2024年   379篇
  2023年   1701篇
  2022年   2916篇
  2021年   4008篇
  2020年   3053篇
  2019年   2578篇
  2018年   2984篇
  2017年   3390篇
  2016年   2966篇
  2015年   3934篇
  2014年   4983篇
  2013年   6382篇
  2012年   6697篇
  2011年   7326篇
  2010年   6378篇
  2009年   6294篇
  2008年   6297篇
  2007年   5884篇
  2006年   6179篇
  2005年   5513篇
  2004年   3766篇
  2003年   3279篇
  2002年   2898篇
  2001年   2801篇
  2000年   2935篇
  1999年   3438篇
  1998年   2934篇
  1997年   2568篇
  1996年   2306篇
  1995年   1947篇
  1994年   1553篇
  1993年   1223篇
  1992年   972篇
  1991年   738篇
  1990年   598篇
  1989年   496篇
  1988年   385篇
  1987年   288篇
  1986年   198篇
  1985年   170篇
  1984年   94篇
  1983年   77篇
  1982年   86篇
  1981年   56篇
  1980年   44篇
  1979年   32篇
  1978年   25篇
  1977年   25篇
  1976年   40篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Wu  Zheng  Meng  Xuan  Shi  Li  Liu  Naiwang 《Journal of Porous Materials》2022,29(2):493-500
Journal of Porous Materials - In this work, a trifluoromethanesulfonic acid (TFOH) modified clay (TFOH-Clay) was developed for the removal of trace olefins in heavy naphtha. 5%TFOH-Clay can...  相似文献   
52.
Tsay  Ming-yueh  Tseng  Yu-wei  Wu  Tai-luan 《Scientometrics》2019,121(3):1323-1338
Scientometrics - In this study, scholarly communication systems provided by commercial services and open access systems are examined on the basis of the comprehensiveness and uniqueness of their...  相似文献   
53.
Wu  Xiaolan  Zhang  Chengzhi 《Scientometrics》2019,119(2):1017-1035
Scientometrics - Specialized academic social networking sites are gaining popularity in scientific communication. A huge volume of interdisciplinary information is generated when researchers from...  相似文献   
54.
Waxy, normal and high-amylose maize starches were subjected to heat-moisture treatment (HMT) and then added to wheat flour (WF) in different ratios (1%, 5% and 10%). The properties of blends and their cooked noodles were studied to investigate the effects of HMT starches. The incorporation of HMT starch in WF led to an increase in swelling power, peak viscosity and breakdown and to a decrease in setback, thus inhibiting retrogradation, hence enhancing resultant noodle softness. Compared to the same addition ratio of native starch to WF, HMT starch led to higher tensile strength and extensibility in resultant noodles. WF with added HMT starch had higher resistant starch than with native starch. This study showed that addition of HMT maize starch has potential to bring nutritional benefits. However, it is necessary to select the proper blending ratio and amylose content of starch to add, in consideration of its effect on noodle quality.  相似文献   
55.
王钦  吴云昌  金意 《城市燃气》2021,561(11):37-41
大力发展天然气对于促进能源结构优化调整和大气污染防治具有重要意义,是实现"碳达峰""碳中和"的重要路径.借力胶东一体化发展战略的提出,引领胶东五市天然气基础设施协同发展,促进胶东一体化战略在能源领域的实施.  相似文献   
56.
Chen  Yaqi  Wu  Xiaoren  Liu  Qing  He  Maoshuai  Bai  Hongcun 《Catalysis Letters》2022,152(9):2738-2744

This work proposed a new path to synthesize Ni-phyllosilicate through the reaction of nickel hydroxide and silica sol on the surface of Ni-foam to form the monolithic Ni-phyllosilicate/Ni-foam catalyst. Ni-phyllosilicate could reprint the morphology of nickel hydroxid and firmly anchor on the framework of Ni-foam, which obtained fine Ni particles of 2.8 nm after reduction in H2 at 650 °C, resulting in high catalytic activity for CO2 methanation. In addition, the Ni-phyllosilicate/Ni-foam catalyst showed high long-term stability in a 100 h-lifetime test owing to the combined effects of surface confinement of Ni-phyllosilicate, firm anchoring between Ni-phyllosilicate and Ni-foam, as well as the high heat transfer property of Ni-foam.

Graphical Abstract
  相似文献   
57.
Liu  Song  Cui  Yuan-Zhen  Zou  Nian-Jun  Zhu  Wen-Hao  Zhang  Dong  Wu  Wei-Guo 《计算机科学技术学报》2019,34(2):456-475
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front...  相似文献   
58.
Electromagnetic signal emitted by satellite communication (satcom) transmitters are used to identify specific individual uplink satcom terminals sharing the common transponder in real environment, which is known as specific emitter identification (SEI) that allows for early indications and warning (I&W) of the targets carrying satcom furnishment and furthermore the real time electromagnetic situation awareness in military operations. In this paper, the authors are the first to propose the identification of specific transmitters of satcom by using probabilistic neural networks (PNN) to reach the goal of target recognition. We have been devoted to the examination by exploring the feasibility of utilizing the Hilbert transform to signal preprocessing, applying the discrete wavelet transform to feature extraction, and employing the PNN to perform the classification of stationary signals. There are a total of 1000 sampling time series with binary phase shift keying (BPSK) modulation originated by five types of satcom transmitters in the test. The established PNNs classifier implements the data testing and finally yields satisfactory accuracy at 8 dB(±1 dB) carrier to noise ratio, which indicates the feasibility of our method, and even the keen insight of its application in military.  相似文献   
59.
International Journal of Computer Vision - Expressive representations for characterizing face appearances are essential for accurate face detection. Due to different poses, scales, illumination,...  相似文献   
60.
Thermosetting materials are widely used as encapsulation in the electrical packaging to protect the core electronic components from external force, moisture, dust, and other factors. However, the spreading and curing behaviors of such kind of fluid on a heated surface have been rarely explored. In this study, we experimentally and numerically investigated the spreading and curing behaviors of the silicone(OE6550 A/B, which is widely used in the light-emitting diode packaging) droplet with diameter of ~2.2 mm on a heated surface with temperature ranging from 25 ℃ to 250 ℃. For the experiments, we established a setup with high-speed camera and heating unit to capture the fast spreading process of the silicone droplet on the heated surface. For the numerical simulation, we built a viscosity model of the silicone by using the Kiuna's model and combined the viscosity model with the Volume of Fluid(VOF) model by the User Defined Function(UDF) method. The results show that the surface temperature significantly affected the spreading behaviors of the silicone droplet since it determines the temperature and viscosity distribution inside the droplet. For surface temperature varied from 25 ℃ to 250 ℃, the final contact radius changed from ~2.95 mm to ~1.78 mm and the total spreading time changed from ~511 s to ~0.15 s. By further analyzing the viscosity evolution of the droplet, we found that the decreasing of the total spreading time was caused by the decrease of the viscosity under high surface temperature at initial spreading stage, while the reduction of the final contact radius was caused by the curing of the precursor film. This study supplies a strategy to tuning the spreading and curing behavior of silicone by imposing high surface temperature, which is of great importance to the electronic packaging.  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