全文获取类型
收费全文 | 7368篇 |
免费 | 1081篇 |
国内免费 | 625篇 |
专业分类
电工技术 | 314篇 |
技术理论 | 1篇 |
综合类 | 1091篇 |
化学工业 | 505篇 |
金属工艺 | 303篇 |
机械仪表 | 826篇 |
建筑科学 | 637篇 |
矿业工程 | 203篇 |
能源动力 | 128篇 |
轻工业 | 134篇 |
水利工程 | 185篇 |
石油天然气 | 233篇 |
武器工业 | 149篇 |
无线电 | 1049篇 |
一般工业技术 | 845篇 |
冶金工业 | 367篇 |
原子能技术 | 94篇 |
自动化技术 | 2010篇 |
出版年
2024年 | 20篇 |
2023年 | 113篇 |
2022年 | 146篇 |
2021年 | 217篇 |
2020年 | 269篇 |
2019年 | 222篇 |
2018年 | 204篇 |
2017年 | 265篇 |
2016年 | 291篇 |
2015年 | 333篇 |
2014年 | 489篇 |
2013年 | 474篇 |
2012年 | 602篇 |
2011年 | 630篇 |
2010年 | 444篇 |
2009年 | 515篇 |
2008年 | 414篇 |
2007年 | 507篇 |
2006年 | 484篇 |
2005年 | 392篇 |
2004年 | 300篇 |
2003年 | 282篇 |
2002年 | 264篇 |
2001年 | 214篇 |
2000年 | 142篇 |
1999年 | 140篇 |
1998年 | 118篇 |
1997年 | 84篇 |
1996年 | 72篇 |
1995年 | 74篇 |
1994年 | 70篇 |
1993年 | 54篇 |
1992年 | 40篇 |
1991年 | 34篇 |
1990年 | 27篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1980年 | 4篇 |
1965年 | 3篇 |
1964年 | 5篇 |
1963年 | 2篇 |
1962年 | 3篇 |
1956年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有9074条查询结果,搜索用时 31 毫秒
1.
2.
《Advanced Powder Technology》2022,33(12):103879
Heat transfer within ceramic feedstock powders is still unclear, which impedes optimization of the thermal and mechanical properties of the thermal sprayed coatings. The microspheres (yttria-stabilized zirconia YSZ and lanthanum zirconate LZO) were prepared via the electro-spraying assisted phase inversion method (ESP). The thermal properties of the two ESP microspheres and a commercial hollow spherical powder (HOSP) were investigated by using theoretical, experimental, and simulation methods. Thermal conductivity of the single microsphere was estimated via a novel nest model that was derived from the Maxwell-Eucken 1 and the EMT model. Thermal conductivity of a single YSZ/LZO-ESP microsphere prepared at 1100–1200 °C was within 0.36–0.75 W/m K, which was ~ 20 % lower than that of a single YSZ-HOSP microsphere with a similar porosity. Heat flux simulation showed that high tortuosity around the multi-scaled voids of the ESP microsphere led to a more efficient decrease in thermal conductivity compared with total porosity. 相似文献
3.
针对流程工业生产系统监测数据存在强噪声和混沌性的特点,提出了一种局部投影方法(Local Projection Method)与小波包方法相结合的信号降噪方法。该方法先利用局部投影方法从动力学系统嵌入流形的角度进行多次迭代降噪,并根据关联维数来判定迭代终止;再利用小波包方法从频率的角度进行降噪,抑制高频噪声的干扰,取得了较好的降噪效果。用Lorenz时间序列进行仿真验证,对仿真时间序列加入不同程度的噪声,对比分析小波包、局部投影与该方法降噪后的相空间、SNR值和最大Lyapunov指数,证明了该方法对于中高强度噪声具有更好的降噪效果。并将该方法用于某压缩机组的实际监测数据降噪,评估三种方法的降噪效果,进一步验证了该方法的优越性。 相似文献
5.
基于双应力加速寿命试验的关节轴承寿命预测与可靠性分析 总被引:1,自引:0,他引:1
自润滑关节轴承寿命主要是由衬垫的磨损性能决定的,但衬垫的磨损一般是非线性的,使得寿命难以预测。采用同时改变载荷和摆频2种应力的方法进行加速寿命试验,建立以pv值、磨损量退化数据为输入参数,寿命值为输出参数的灰色神经网络预测模型。经验证该预测模型对关节轴承寿命预测的最大误差仅为7.33%,平均误差仅为3.892%。对不同加速应力下自润滑关节轴承可靠性进行评估,结果表明,关节轴承的可靠性在L_(10)(可靠度为90%时的寿命)之前下降趋势缓慢,然后迅速下降,pv值越大可靠性下降越迅速;随着pv值的增大,关节轴承寿命近似呈指数下降,经验证可用逆幂率加速模型反映二者关系。 相似文献
6.
Significant emergency measures should be taken until an emergency event occurs. It is understood that the emergency is characterized by limited time and information, harmfulness and uncertainty, and decision-makers are always critically bound by uncertainty and risk. This paper introduces many novel approaches to addressing the emergency situation of COVID-19 under spherical fuzzy environment. Fundamentally, the paper includes six main sections to achieve appropriate and accurate measures to address the situation of emergency decision-making. As the spherical fuzzy set (FS) is a generalized framework of fuzzy structure to handle more uncertainty and ambiguity in decision-making problems (DMPs). First, we discuss basic algebraic operational laws (AOLs) under spherical FS. In addition, elaborate on the deficiency of existing AOLs and present three cases to address the validity of the proposed novel AOLs under spherical fuzzy settings. Second, we present a list of Einstein aggregation operators (AgOp) based on the Einstein norm to aggregate uncertain information in DMPs. Thirdly, we are introducing two techniques to demonstrate the unknown weight of the criteria. Fourthly, we develop extended TOPSIS and Gray relational analysis approaches based on AgOp with unknown weight information of the criteria. In fifth, we design three algorithms to address the uncertainty and ambiguity information in emergency DMPs. Finally, the numerical case study of the novel carnivorous (COVID-19) situation is provided as an application for emergency decision-making based on the proposed three algorithms. Results explore the effectiveness of our proposed methodologies and provide accurate emergency measures to address the global uncertainty of COVID-19. 相似文献
7.
8.
9.
As a novel type of polynomial chaos expansion (PCE), the data-driven PCE (DD-PCE) approach has been developed to have a wide range of potential applications for uncertainty propagation. While the research on DD-PCE is still ongoing, its merits compared with the existing PCE approaches have yet to be understood and explored, and its limitations also need to be addressed. In this article, the Galerkin projection technique in conjunction with the moment-matching equations is employed in DD-PCE for higher-dimensional uncertainty propagation. The enhanced DD-PCE method is then compared with current PCE methods to fully investigate its relative merits through four numerical examples considering different cases of information for random inputs. It is found that the proposed method could improve the accuracy, or in some cases leads to comparable results, demonstrating its effectiveness and advantages. Its application in dealing with a Mars entry trajectory optimization problem further verifies its effectiveness. 相似文献
10.
Bharti M. Shinde 《热应力杂志》2020,43(10):1234-1257
Abstract In the present study, thermoelastic analysis of laminated composite and sandwich shells (cylindrical/spherical) is presented using fifth-order shear and normal deformation theory. The significant characteristic of the present theory is that it includes the effects of both transverse shear and normal deformations. The mathematical formulation uses the principle of virtual work to derive the variationally consistent governing equations and traction free boundary conditions. To obtain the static solution, these governing equations are solved by employing Navier’s solution technique. The shell is subjected to a mechanical/thermal load sinusoidally distributed over the top surface of the shell. The thermal load linearly varies across the thickness of the shell. The present results are compared with other higher-order models and 3D elasticity solution wherever possible. Thermal stresses presented in this study will act as a benchmark for the future work. 相似文献