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   279777篇
  免费   3840篇
  国内免费   600篇
电工技术   4791篇
综合类   885篇
化学工业   43499篇
金属工艺   9936篇
机械仪表   8245篇
建筑科学   6249篇
矿业工程   1776篇
能源动力   5542篇
轻工业   26650篇
水利工程   3016篇
石油天然气   5139篇
武器工业   36篇
无线电   26810篇
一般工业技术   47968篇
冶金工业   63962篇
原子能技术   6123篇
自动化技术   23590篇
  2021年   2207篇
  2019年   2074篇
  2018年   3943篇
  2017年   4097篇
  2016年   4706篇
  2015年   3002篇
  2014年   4311篇
  2013年   10586篇
  2012年   8183篇
  2011年   10614篇
  2010年   7186篇
  2009年   7966篇
  2008年   8176篇
  2007年   8302篇
  2006年   7419篇
  2005年   9230篇
  2004年   8291篇
  2003年   7576篇
  2002年   6498篇
  2001年   6271篇
  2000年   5653篇
  1999年   5840篇
  1998年   17796篇
  1997年   12170篇
  1996年   9008篇
  1995年   6597篇
  1994年   5650篇
  1993年   5578篇
  1992年   3881篇
  1991年   3641篇
  1990年   3843篇
  1989年   3705篇
  1988年   3559篇
  1987年   3078篇
  1986年   3097篇
  1985年   3518篇
  1984年   3273篇
  1983年   2958篇
  1982年   2846篇
  1981年   2981篇
  1980年   2880篇
  1979年   2675篇
  1978年   2773篇
  1977年   3507篇
  1976年   4995篇
  1975年   2459篇
  1974年   2277篇
  1973年   2413篇
  1972年   2003篇
  1971年   1901篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
1.
2.
3.
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some.  相似文献   
4.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
5.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  相似文献   
6.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the...  相似文献   
7.
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized...  相似文献   
8.
Abnormal levels of glutathione, a cellular antioxidant, can lead to a variety of diseases. We have constructed a near-infrared ratiometric fluorescent probe to detect glutathione concentrations in biological samples. The probe consists of a coumarin donor, which is connected through a disulfide-tethered linker to a rhodamine acceptor. Under the excitation of the coumarin donor at 405 nm, the probe shows weak visible fluorescence of the coumarin donor at 470 nm and strong near-infrared fluorescence of the rhodamine acceptor at 652 nm due to efficient Forster resonance energy transfer (FRET) from the donor to the acceptor. Glutathione breaks the disulfide bond through reduction, which results in a dramatic increase in coumarin fluorescence and a corresponding decrease in rhodamine fluorescence. The probe possesses excellent cell permeability, biocompatibility, and good ratiometric fluorescence responses to glutathione and cysteine with a self-calibration capability. The probe was utilized to ratiometrically visualize glutathione concentration alterations in HeLa cells and Drosophila melanogaster larvae.  相似文献   
9.
Glass and Ceramics - An analysis of the specific mechanisms of the influence of the state of the grain structure on the thermoelectric properties (electrical resistivity and total thermal...  相似文献   
10.
Fibre Chemistry - An analysis of the aramid fiber market including the range of industrial textile materials containing chemical fibers for specialized protective clothing of metallurgical workers,...  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