全文获取类型
收费全文 | 333527篇 |
免费 | 32009篇 |
国内免费 | 18144篇 |
专业分类
电工技术 | 24760篇 |
技术理论 | 16篇 |
综合类 | 25249篇 |
化学工业 | 49798篇 |
金属工艺 | 19570篇 |
机械仪表 | 22170篇 |
建筑科学 | 27124篇 |
矿业工程 | 10586篇 |
能源动力 | 10036篇 |
轻工业 | 24031篇 |
水利工程 | 7312篇 |
石油天然气 | 18033篇 |
武器工业 | 3337篇 |
无线电 | 40234篇 |
一般工业技术 | 36206篇 |
冶金工业 | 14494篇 |
原子能技术 | 3715篇 |
自动化技术 | 47009篇 |
出版年
2024年 | 860篇 |
2023年 | 5511篇 |
2022年 | 10121篇 |
2021年 | 14889篇 |
2020年 | 11285篇 |
2019年 | 8751篇 |
2018年 | 9968篇 |
2017年 | 11363篇 |
2016年 | 10069篇 |
2015年 | 14451篇 |
2014年 | 18211篇 |
2013年 | 21790篇 |
2012年 | 24704篇 |
2011年 | 25908篇 |
2010年 | 23193篇 |
2009年 | 21825篇 |
2008年 | 21285篇 |
2007年 | 19891篇 |
2006年 | 19045篇 |
2005年 | 15608篇 |
2004年 | 10634篇 |
2003年 | 9005篇 |
2002年 | 8379篇 |
2001年 | 7450篇 |
2000年 | 6582篇 |
1999年 | 6493篇 |
1998年 | 4943篇 |
1997年 | 4125篇 |
1996年 | 3805篇 |
1995年 | 3164篇 |
1994年 | 2558篇 |
1993年 | 1769篇 |
1992年 | 1426篇 |
1991年 | 1053篇 |
1990年 | 788篇 |
1989年 | 656篇 |
1988年 | 497篇 |
1987年 | 329篇 |
1986年 | 277篇 |
1985年 | 157篇 |
1984年 | 144篇 |
1983年 | 98篇 |
1982年 | 108篇 |
1981年 | 101篇 |
1980年 | 101篇 |
1979年 | 53篇 |
1978年 | 31篇 |
1977年 | 31篇 |
1976年 | 35篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
磁声发射(MAE)是铁磁性材料磁化过程中产生的声发射信号,在构件应力检测和微观损伤检测中有着广泛的应用。针对MAE信号非稳态、复杂性、衰减性等特点,提出海鸥算法结合变分模态分解(SOA-VMD)的去噪方法,为克服海鸥算法求解过程中易陷入局部最优解问题,利用柯西变异算子产生随机迭代过程,使改进算法即柯西变异海欧算法(CVSOA)跳出早熟收敛。采用以幅值谱熵为适应度函数,优化VMD算法中分解模态个数K和二次惩戒因子α ![]()
![]()
两个参数,将含噪声的MAE信号进行VMD分解重构。经仿真信号和实际检测信号分析表明,改进后的CVSOA-VMD算法全局寻优能力和去噪性能优于传统的SOA-VMD算法,降噪后的MAE信号特征值对于不同应力下均方根、偏斜度特征值的重复性更好,可靠性更高。 相似文献
52.
Because of its ability to change optical absorption dynamically by applied electric field, nickel oxide (NiO) is a promising anodic material in smart windows, which can improve energy conversion efficiency in construction buildings. Although many works have achieved high electrochromic performance with different method. The underlying mechanism is still not fully investigated. In this article, we prepared the NiO films with large specific surface area and high stability by electron beam evaporation. X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to figure out the surface morphology and composition of as-deposited films. Afterwards, the electrochemical properties and optical performance of the prepared NiO films were investigated. On this basis, the origin of surface charge was fully analyzed by cyclic voltammetry and diffusion coefficient test. These experimental and theoretical results firmly confirm that both the surface reaction and capacitive effect bring about the excellent EC performance in NiO films. These results not only provide clear evidence about electrochemical kinetics in NiO films, but also offer some useful guidelines for the design of EC materials with higher performance and longer stability. 相似文献
53.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
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
54.
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
55.
58.
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
59.
60.
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