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   194215篇
  免费   20090篇
  国内免费   11813篇
电工技术   15872篇
技术理论   5篇
综合类   16332篇
化学工业   27882篇
金属工艺   12008篇
机械仪表   13222篇
建筑科学   16421篇
矿业工程   6278篇
能源动力   5804篇
轻工业   14436篇
水利工程   4774篇
石油天然气   9516篇
武器工业   2271篇
无线电   23283篇
一般工业技术   19802篇
冶金工业   7641篇
原子能技术   2165篇
自动化技术   28406篇
  2024年   813篇
  2023年   2930篇
  2022年   5898篇
  2021年   8437篇
  2020年   6242篇
  2019年   4932篇
  2018年   5489篇
  2017年   6362篇
  2016年   5564篇
  2015年   8481篇
  2014年   10638篇
  2013年   12667篇
  2012年   14827篇
  2011年   15465篇
  2010年   14383篇
  2009年   13692篇
  2008年   13428篇
  2007年   12742篇
  2006年   11868篇
  2005年   9331篇
  2004年   6593篇
  2003年   5825篇
  2002年   5865篇
  2001年   5139篇
  2000年   3920篇
  1999年   3278篇
  1998年   2145篇
  1997年   1740篇
  1996年   1637篇
  1995年   1413篇
  1994年   1117篇
  1993年   752篇
  1992年   596篇
  1991年   411篇
  1990年   336篇
  1989年   286篇
  1988年   209篇
  1987年   132篇
  1986年   98篇
  1985年   53篇
  1984年   49篇
  1983年   31篇
  1982年   41篇
  1981年   46篇
  1980年   53篇
  1979年   27篇
  1978年   10篇
  1976年   10篇
  1959年   10篇
  1951年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
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   
122.
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   
123.
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   
124.
本文旨在改善某选厂硫精矿浓密机溢流跑浑问题,对生产现场进行勘察和分析,分析浓密机溢流跑浑的原因,并开展原矿配比和沉降试验研究。对采场原矿矿样和硫精矿矿浆进行系统的试验研究,分别采用不同沉降方案进行条件试验,考察絮凝剂种类、絮凝剂用量、pH调整剂用量、不同药剂之间的配比等条件对沉降的影响,确定合适的原矿配比及合理药剂制度,有效地控制金属在溢流中的损失,充分获取现有产品的蕴含价值。  相似文献   
125.
126.
127.
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   
128.
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   
129.
130.
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