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   168750篇
  免费   17687篇
  国内免费   10513篇
电工技术   14224篇
技术理论   4篇
综合类   14190篇
化学工业   23414篇
金属工艺   10370篇
机械仪表   11486篇
建筑科学   14200篇
矿业工程   5531篇
能源动力   5087篇
轻工业   12620篇
水利工程   4225篇
石油天然气   8221篇
武器工业   2008篇
无线电   20416篇
一般工业技术   16724篇
冶金工业   7641篇
原子能技术   1931篇
自动化技术   24658篇
  2024年   729篇
  2023年   2594篇
  2022年   5354篇
  2021年   7541篇
  2020年   5596篇
  2019年   4323篇
  2018年   4830篇
  2017年   5672篇
  2016年   4940篇
  2015年   7519篇
  2014年   9511篇
  2013年   11296篇
  2012年   13253篇
  2011年   13763篇
  2010年   12791篇
  2009年   12037篇
  2008年   11890篇
  2007年   11228篇
  2006年   10175篇
  2005年   7953篇
  2004年   5545篇
  2003年   4697篇
  2002年   4507篇
  2001年   3977篇
  2000年   3173篇
  1999年   2541篇
  1998年   1907篇
  1997年   1474篇
  1996年   1340篇
  1995年   1100篇
  1994年   916篇
  1993年   591篇
  1992年   438篇
  1991年   331篇
  1990年   262篇
  1989年   232篇
  1988年   166篇
  1987年   120篇
  1986年   102篇
  1985年   59篇
  1984年   37篇
  1983年   26篇
  1982年   37篇
  1981年   46篇
  1980年   49篇
  1979年   25篇
  1977年   34篇
  1976年   98篇
  1975年   14篇
  1951年   14篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
蔚然 《地热能》2020,(1):28-28
根据科技部“十三五”科技战略部署,于2018、2019两年时间顺利完成“干热岩能量获取及利用关键科学问题研究”、“深部碳酸盐岩热储层强化增产与利用综合评价技术”及“砂岩热储采灌增效技术与装备”三项重点研发计划项目从申报、函审、视频答辩到立项的工作。  相似文献   
102.
103.
104.
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   
105.
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   
106.
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   
107.
108.
109.
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   
110.
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   
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