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   174960篇
  免费   18527篇
  国内免费   11078篇
电工技术   14943篇
技术理论   4篇
综合类   14964篇
化学工业   24285篇
金属工艺   10845篇
机械仪表   11900篇
建筑科学   14585篇
矿业工程   5781篇
能源动力   5288篇
轻工业   13544篇
水利工程   4430篇
石油天然气   8523篇
武器工业   2200篇
无线电   21181篇
一般工业技术   17252篇
冶金工业   7173篇
原子能技术   2043篇
自动化技术   25624篇
  2024年   704篇
  2023年   2704篇
  2022年   5568篇
  2021年   7882篇
  2020年   5870篇
  2019年   4490篇
  2018年   5029篇
  2017年   5874篇
  2016年   5136篇
  2015年   7864篇
  2014年   9945篇
  2013年   11781篇
  2012年   13854篇
  2011年   14392篇
  2010年   13373篇
  2009年   12616篇
  2008年   12514篇
  2007年   11787篇
  2006年   10639篇
  2005年   8335篇
  2004年   5828篇
  2003年   4878篇
  2002年   4654篇
  2001年   4133篇
  2000年   3295篇
  1999年   2554篇
  1998年   1687篇
  1997年   1367篇
  1996年   1257篇
  1995年   1078篇
  1994年   878篇
  1993年   557篇
  1992年   432篇
  1991年   318篇
  1990年   265篇
  1989年   222篇
  1988年   156篇
  1987年   105篇
  1986年   95篇
  1985年   37篇
  1984年   37篇
  1983年   26篇
  1982年   32篇
  1981年   41篇
  1980年   53篇
  1979年   25篇
  1977年   35篇
  1976年   44篇
  1959年   11篇
  1951年   15篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
The in-situ fabrication of an electron-blocking layer between the Ba-containing anode and the ceria-based electrolyte is an effective approach in suppressing the internal electronic leakage in ceria-based solid oxide fuel cell (SOFC). To improve the thickness of the electron-blocking layer and to research the effect of the layer thickness on the improvement of SOFC, a Ba-containing compound (0.6NiO-0.4BaZr0.1Ce0.7Y0.2O3-δ) modified by Y stabilized zirconia (YSZ) was employed as a composite anode in this research. SEM analyses demonstrated that the thickness of the interlayer can be simply controlled by regulating the proportion of YSZ at anode. The in-situ formed interlayer in the cell with the anode modified by 20?mol% YSZ possesses a thickness of 0.9?µm which is more suitable for the cell achieving an enhanced performance.  相似文献   
113.
Frontiers of Information Technology & Electronic Engineering - Reconstruction of a 12-lead electrocardiogram (ECG) from a serial 3-lead ECG has been researched in the past to satisfy the need...  相似文献   
114.
A facile and effective method was proposed to prepare the molecularly imprinted fluorescence sensor with carbon quantum dots, which were modified vinyl groups by acrylic acid on the surface. The obtained fluorescence composite material was investigated by transmission electron microscope and Fourier transform infrared spectra. After the experimental conditions were optimized, a linear range of 1.0–60 μmol L−1 was obtained and the detection limit was 0.17 μmol L−1. The novel fluorescence sensor can be successfully used to detect tetracycline in real samples. This study provides a convenient strategy for selective recognition and rapid detection of tetracycline in the complex environment.  相似文献   
115.
116.
117.
The molecular design of short peptides to achieve a tailor-made functional architecture has attracted attention during the past decade but remains challenging as a result of insufficient understanding of the relationship between peptide sequence and assembled supramolecular structures. We report a hybrid-resolution model to computationally explore the sequence–structure relationship of self-assembly for tripeptides containing only phenylalanine and isoleucine. We found that all these tripeptides have a tendency to assemble into nanofibers composed of laterally associated filaments. Molecular arrangements within the assemblies are diverse and vary depending on the sequences. This structural diversity originates from (1) distinct conformations of peptide building blocks that lead to different surface geometries of the filaments and (2) unique sidechain arrangements at the filament interfaces for each sequence. Many conformations are available for tripeptides in solution, but only an extended β-strand and another resembling a right-handed turn are observed in assemblies. It was found that the sequence dependence of these conformations and the packing of resulting filaments are determined by multiple competing noncovalent forces, with hydrophobic interactions involving Phe being particularly important. The sequence pattern for each type of assembly conformation and packing has been identified. These results highlight the importance of the interplay between conformation, molecular packing, and sequences for determining detailed nanostructures of peptides and provide a detailed insight to support a more precise design of peptide-based nanomaterials.  相似文献   
118.
The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe (3DAP) and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni (Co-Ti) interactions than Co-Ti (Fe-Ti) interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition.  相似文献   
119.
120.
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