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   87123篇
  免费   1277篇
  国内免费   436篇
电工技术   862篇
综合类   2329篇
化学工业   12203篇
金属工艺   4838篇
机械仪表   3172篇
建筑科学   2338篇
矿业工程   565篇
能源动力   1393篇
轻工业   3842篇
水利工程   1304篇
石油天然气   381篇
无线电   9551篇
一般工业技术   16876篇
冶金工业   2850篇
原子能技术   286篇
自动化技术   26046篇
  2023年   75篇
  2022年   110篇
  2021年   242篇
  2020年   221篇
  2019年   267篇
  2018年   14654篇
  2017年   13584篇
  2016年   10151篇
  2015年   774篇
  2014年   501篇
  2013年   606篇
  2012年   3388篇
  2011年   9683篇
  2010年   8451篇
  2009年   5727篇
  2008年   6883篇
  2007年   7827篇
  2006年   183篇
  2005年   1259篇
  2004年   1158篇
  2003年   1203篇
  2002年   566篇
  2001年   117篇
  2000年   191篇
  1999年   70篇
  1998年   77篇
  1997年   44篇
  1996年   59篇
  1995年   24篇
  1994年   21篇
  1993年   20篇
  1992年   14篇
  1991年   32篇
  1988年   12篇
  1969年   25篇
  1968年   43篇
  1967年   33篇
  1966年   42篇
  1965年   45篇
  1964年   11篇
  1963年   28篇
  1962年   22篇
  1961年   18篇
  1960年   30篇
  1959年   35篇
  1958年   37篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
In this work, we designed a magnetically-separable Fe3O4-rGO-ZnO ternary catalyst, ZnO anchored on the surface of reduced graphene oxide (rGO)-wrapped Fe3O4 magnetic nanoparticles, where rGO, as an effective interlayer, can enhance the synergistic effect between ZnO and Fe3O4. The effects of three operational parameters, namely irradiation time, hydrogen peroxide dosage, and the catalyst dosage, on the photo-Fenton degradation of methylene blue and methyl orange were investigated. The results showed that the Fe3O4-rGO-ZnO had great potential for the destruction of organic compounds from wastewater using the Fenton chemical oxidation method at neutral pH. Repeatability of the photocatalytic activity after 5 cycles showed only a tiny drop in the catalytic efficiency.  相似文献   
2.
Wireless Networks - Orthogonal frequency-division multiplexing with random multiple access (OFDRMA) is discussed for down-link communications, whereby a single base-station transmits information...  相似文献   
3.
Wireless Personal Communications - Network coding (NC) significantly increases communication opportunities and improves network performance. The focus of most research is on performance analysis...  相似文献   
4.
Journal of Materials Science: Materials in Electronics - The main weakness of polymer gas sensors is its stability. Here, we report stability enhancement of a 100 nm polypyrrole (PPy) thin...  相似文献   
5.
Wireless Personal Communications - The importance of environmental pollution has motivated the researchers to investigate the electrical power consumption of any emerging technology. Edge Computing...  相似文献   
6.
Multimedia Tools and Applications - In this paper, blind image quality assessment (IQA) of Gaussian blurred images based on Discrete Fourier Transform (DFT) is proposed. The proposed work is based...  相似文献   
7.
Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations.  相似文献   
8.
This paper presents an energy-efficient switching scheme for successive approximation register (SAR) analogue-to-digital converter (ADC). The proposed scheme employs charge recycling method to keep the capacitor arrays free of transitional energy between bit generations except reset phase. In comparison with the conventional switching scheme, the proposed one achieves 100% transitional energy saving without considering reset phase. In addition, configuration of a 10-bit SAR ADC shows that the proposed switching scheme reduces the capacitor area by 25% compared with the conventional switching scheme.  相似文献   
9.
Analog Integrated Circuits and Signal Processing - Modern time microwave stages require low power consumption, low size, low-noise amplifier (LNA) designs with high-performance measures. These...  相似文献   
10.
Journal of Porous Materials - In the present work, the adsorption performance of powdered activated carbon magnetized by iron(III) oxide magnetic nanoparticles (PAC@Fe3O4-MN) for the removal of...  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