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   241323篇
  免费   2935篇
  国内免费   427篇
电工技术   4285篇
综合类   257篇
化学工业   39421篇
金属工艺   9395篇
机械仪表   7419篇
建筑科学   5452篇
矿业工程   1396篇
能源动力   5159篇
轻工业   24808篇
水利工程   2476篇
石油天然气   5124篇
武器工业   32篇
无线电   25065篇
一般工业技术   44914篇
冶金工业   45384篇
原子能技术   5986篇
自动化技术   18112篇
  2021年   2103篇
  2019年   2027篇
  2018年   3500篇
  2017年   3431篇
  2016年   3697篇
  2015年   2238篇
  2014年   3907篇
  2013年   10192篇
  2012年   6152篇
  2011年   8303篇
  2010年   6555篇
  2009年   7244篇
  2008年   7592篇
  2007年   7721篇
  2006年   6896篇
  2005年   6056篇
  2004年   5827篇
  2003年   5606篇
  2002年   5681篇
  2001年   5569篇
  2000年   5391篇
  1999年   5306篇
  1998年   12576篇
  1997年   8901篇
  1996年   6863篇
  1995年   5335篇
  1994年   4737篇
  1993年   4627篇
  1992年   3674篇
  1991年   3392篇
  1990年   3603篇
  1989年   3478篇
  1988年   3313篇
  1987年   2907篇
  1986年   2938篇
  1985年   3381篇
  1984年   3228篇
  1983年   2896篇
  1982年   2744篇
  1981年   2823篇
  1980年   2724篇
  1979年   2628篇
  1978年   2689篇
  1977年   2954篇
  1976年   3816篇
  1975年   2371篇
  1974年   2249篇
  1973年   2384篇
  1972年   1977篇
  1971年   1865篇
排序方式: 共有10000条查询结果,搜索用时 15 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