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   185531篇
  免费   17409篇
  国内免费   8947篇
电工技术   12127篇
技术理论   13篇
综合类   12315篇
化学工业   30248篇
金属工艺   10379篇
机械仪表   11966篇
建筑科学   14131篇
矿业工程   5888篇
能源动力   5574篇
轻工业   13049篇
水利工程   3496篇
石油天然气   10861篇
武器工业   1524篇
无线电   22409篇
一般工业技术   22143篇
冶金工业   8773篇
原子能技术   2038篇
自动化技术   24953篇
  2024年   819篇
  2023年   3551篇
  2022年   6639篇
  2021年   9323篇
  2020年   6954篇
  2019年   5469篇
  2018年   6110篇
  2017年   6780篇
  2016年   6013篇
  2015年   8112篇
  2014年   10041篇
  2013年   11893篇
  2012年   13025篇
  2011年   13625篇
  2010年   11565篇
  2009年   10840篇
  2008年   10280篇
  2007年   9385篇
  2006年   9475篇
  2005年   8077篇
  2004年   5376篇
  2003年   4507篇
  2002年   4027篇
  2001年   3628篇
  2000年   3552篇
  1999年   4150篇
  1998年   3453篇
  1997年   2937篇
  1996年   2733篇
  1995年   2209篇
  1994年   1770篇
  1993年   1279篇
  1992年   1034篇
  1991年   766篇
  1990年   556篇
  1989年   455篇
  1988年   359篇
  1987年   237篇
  1986年   198篇
  1985年   122篇
  1984年   108篇
  1983年   77篇
  1982年   80篇
  1981年   66篇
  1980年   65篇
  1979年   32篇
  1978年   25篇
  1977年   24篇
  1976年   26篇
  1975年   16篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
31.
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM.  相似文献   
32.
For the purpose of developing biodegradable magnesium alloys with suitable properties for biomedical applications, Mg–Zn–Ca–Cu metallic glasses were prepared by copper mold injection methods. In the present work, the effect of Cu doping on mechanical properties, corrosion behavior, and glass-forming ability of Mg66Zn30Ca4 alloy was studied. The experimental findings demonstrated that the incorporation of Cu decreases the corrosion resistance of alloys, but increases the microhardness and degradation rate slightly. However, the addition of a trace amount of Cu can make the samples have antibacterial properties. Therefore, Mg–Zn–Ca–Cu has great advantages in clinical implantation and is the potential implant material.  相似文献   
33.
34.
35.
In this study, a kind of Ni-based superalloy specially designed for additive manufacturing (AM) was investigated. Thermo-Calc simulation and differential scanning calorimetry (DSC) analysis were used to determine phases and their transformation temperature. Experimental specimens were prepared by laser metal deposition (LMD) and traditional casting method. Microstructure, phase constitution and mechanical properties of the alloy were characterized by scanning electron microscopy (SEM), transmission scanning electron microscopy (TEM), X-ray diffraction (XRD) and tensile tests. The results show that this alloy contains two basic phases, γ/γ', in addition to these phases, at least two secondary phases may be present, such as MC carbides and Laves phases. Furthermore, the as-deposited alloy has finer dendrite, its mean primary dendrite arm space (PDAS) is about 30-45 μm, and the average size of γ' particles is 100-150 nm. However, the dendrite size of the as-cast alloy is much larger and its PDAS is 300-500 μm with secondary and even third dendrite arms. Correspondingly, the alloy displays different tensile behavior with different processing methods, and the as-deposited specimen shows better ultimate tensile stress (1,085.7±51.7 MPa), yield stress (697±19.5 MPa) and elongation (25.8%±2.2%) than that of the as-cast specimen. The differences in mechanical properties of the alloy are due to the different morphology and size of dendrites, γ', and Laves phase, and the segregation of elements, etc. Such important information would be helpful for alloy application as well as new alloy development.  相似文献   
36.
Sheng  Mingming  Yang  Rongkun  Gong  Hongyu  Zhang  Yujun  Lin  Xiao  Jing  Jie 《Journal of Materials Science》2022,57(10):5805-5824
Journal of Materials Science - With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of...  相似文献   
37.
At present, the development and implementation of digital transformation are the keys to promoting high-quality industry development. The new digital fabrication method of robotic 3D printing is a research area being studied by many to tackle the issue of the declining productivity of traditional construction methods. Although many studies have been done, most of the current 3D printing projects are facing limitations in terms of scale. In order to bridge the gap, this article proposed a mass customization 3D printing framework system for large-scale projects. This article discusses how mass customization is made possible through the joint operation of the FUROBOT software and 3D printing hardware. By taking the east gate of Nanjing Happy Valley Plaza as a case study, the article demonstrates and studies the feasibility of the large-scale mass customization 3D printing framework system.  相似文献   
38.
Gao  Zehai  Liu  Yang  Li  Nan  Ma  Kangjie 《Water Resources Management》2022,36(8):2685-2702
Water Resources Management - Urban river not only has the important function in urban hydrological environment, but also is an area for entertainment. Water quality assessment is the core technique...  相似文献   
39.
40.
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