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   1691502篇
  免费   43866篇
  国内免费   15959篇
电工技术   46634篇
技术理论   18篇
综合类   18837篇
化学工业   300930篇
金属工艺   74259篇
机械仪表   54163篇
建筑科学   60546篇
矿业工程   17247篇
能源动力   55200篇
轻工业   128839篇
水利工程   18592篇
石油天然气   48411篇
武器工业   1758篇
无线电   217082篇
一般工业技术   304956篇
冶金工业   174647篇
原子能技术   35890篇
自动化技术   193318篇
  2022年   16709篇
  2021年   24206篇
  2020年   18241篇
  2019年   19598篇
  2018年   21334篇
  2017年   21380篇
  2016年   26964篇
  2015年   25121篇
  2014年   38173篇
  2013年   99049篇
  2012年   48552篇
  2011年   61888篇
  2010年   54227篇
  2009年   61699篇
  2008年   55653篇
  2007年   52381篇
  2006年   54842篇
  2005年   48030篇
  2004年   46829篇
  2003年   45760篇
  2002年   44517篇
  2001年   40830篇
  2000年   39347篇
  1999年   38890篇
  1998年   48663篇
  1997年   42389篇
  1996年   38127篇
  1995年   32861篇
  1994年   30576篇
  1993年   29878篇
  1992年   27187篇
  1991年   24067篇
  1990年   24190篇
  1989年   23176篇
  1988年   21646篇
  1987年   19805篇
  1986年   19082篇
  1985年   22332篇
  1984年   22521篇
  1983年   20426篇
  1982年   19361篇
  1981年   19483篇
  1980年   18092篇
  1979年   18648篇
  1978年   17851篇
  1977年   17639篇
  1976年   18793篇
  1975年   16084篇
  1974年   15598篇
  1973年   15676篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field.  相似文献   
22.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
23.
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...  相似文献   
24.
25.
Multimedia Tools and Applications - Recently, many concepts in technology has been changed. According to the digital transformation trends, Internet of Things (IoT) represents an interested...  相似文献   
26.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  相似文献   
27.
This study investigated the inhibitory effects of curcumin and piperine on fluorescent advanced glycation end products (fAGEs) formation in a bovine serum albumin (BSA)–fructose model. Model systems of BSA and fructose were prepared, and curcumin or piperine was added. fAGEs and BSA oxidation product (dityrosine, kynurenine and N'-formylkynurenine) contents were determined. The results showed that fAGEs content decreased with increasing concentration of curcumin and piperine (P < 0.05). Addition of curcumin and piperine at 160 µg mL−1 could inhibit fluorescent AGEs by 100% and 93% respectively. Dityrosine and N'-formylkynurenine contents decreased as curcumin and piperine concentration increased (P < 0.05). Furthermore, the result of principal component analysis indicated that curcumin and piperine markedly impeded BSA oxidation, resulting in a lower level of fAGEs in model systems. Therefore, adding curcumin and piperine may facilitate reduced fAGEs levels in BSA–fructose model.  相似文献   
28.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
29.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
30.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  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