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   222287篇
  免费   19701篇
  国内免费   10210篇
电工技术   13955篇
技术理论   20篇
综合类   14603篇
化学工业   36446篇
金属工艺   12436篇
机械仪表   14226篇
建筑科学   16823篇
矿业工程   6811篇
能源动力   6681篇
轻工业   15021篇
水利工程   3976篇
石油天然气   13351篇
武器工业   1834篇
无线电   26544篇
一般工业技术   26836篇
冶金工业   10673篇
原子能技术   2552篇
自动化技术   29410篇
  2024年   900篇
  2023年   3964篇
  2022年   7120篇
  2021年   10182篇
  2020年   7595篇
  2019年   6048篇
  2018年   6912篇
  2017年   7746篇
  2016年   6914篇
  2015年   9284篇
  2014年   11696篇
  2013年   14069篇
  2012年   15274篇
  2011年   16108篇
  2010年   13787篇
  2009年   13034篇
  2008年   12536篇
  2007年   11614篇
  2006年   11700篇
  2005年   10040篇
  2004年   6766篇
  2003年   5728篇
  2002年   5264篇
  2001年   4701篇
  2000年   4622篇
  1999年   5207篇
  1998年   4339篇
  1997年   3689篇
  1996年   3432篇
  1995年   2745篇
  1994年   2236篇
  1993年   1589篇
  1992年   1278篇
  1991年   953篇
  1990年   714篇
  1989年   582篇
  1988年   466篇
  1987年   293篇
  1986年   249篇
  1985年   154篇
  1984年   135篇
  1983年   99篇
  1982年   103篇
  1981年   79篇
  1980年   68篇
  1979年   35篇
  1978年   26篇
  1977年   26篇
  1976年   32篇
  1975年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 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