全文获取类型
收费全文 | 181381篇 |
免费 | 15624篇 |
国内免费 | 8780篇 |
专业分类
电工技术 | 10802篇 |
技术理论 | 17篇 |
综合类 | 13297篇 |
化学工业 | 29296篇 |
金属工艺 | 9643篇 |
机械仪表 | 10953篇 |
建筑科学 | 14005篇 |
矿业工程 | 4979篇 |
能源动力 | 4900篇 |
轻工业 | 15059篇 |
水利工程 | 3678篇 |
石油天然气 | 8976篇 |
武器工业 | 1431篇 |
无线电 | 21951篇 |
一般工业技术 | 21000篇 |
冶金工业 | 8052篇 |
原子能技术 | 2064篇 |
自动化技术 | 25682篇 |
出版年
2024年 | 730篇 |
2023年 | 2868篇 |
2022年 | 5137篇 |
2021年 | 7236篇 |
2020年 | 5584篇 |
2019年 | 4414篇 |
2018年 | 5010篇 |
2017年 | 5677篇 |
2016年 | 4986篇 |
2015年 | 7119篇 |
2014年 | 9123篇 |
2013年 | 11229篇 |
2012年 | 12365篇 |
2011年 | 13419篇 |
2010年 | 11816篇 |
2009年 | 11254篇 |
2008年 | 11250篇 |
2007年 | 10429篇 |
2006年 | 10183篇 |
2005年 | 8682篇 |
2004年 | 6015篇 |
2003年 | 5103篇 |
2002年 | 4797篇 |
2001年 | 4427篇 |
2000年 | 3952篇 |
1999年 | 4201篇 |
1998年 | 3337篇 |
1997年 | 2879篇 |
1996年 | 2599篇 |
1995年 | 2112篇 |
1994年 | 1694篇 |
1993年 | 1337篇 |
1992年 | 1077篇 |
1991年 | 808篇 |
1990年 | 645篇 |
1989年 | 535篇 |
1988年 | 409篇 |
1987年 | 307篇 |
1986年 | 215篇 |
1985年 | 174篇 |
1984年 | 101篇 |
1983年 | 84篇 |
1982年 | 99篇 |
1981年 | 66篇 |
1980年 | 63篇 |
1979年 | 42篇 |
1978年 | 26篇 |
1977年 | 27篇 |
1976年 | 40篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Yuzhu Su Junpu Wang Xin Li Qiqi Tang Jing Yang Li Lei Yi Tian Zhiwei Wang Duanwei He 《Ceramics International》2021,47(15):21077-21082
The in situ axial X-ray diffraction patterns of four ceramic powder samples (MgO, Al2O3, AlN, and cBN) that were compressed in a diamond anvil cell under uniaxial non-hydrostatic conditions were recorded. The microscopic deviatoric stress as a function of the pressure was determined from the X-ray diffraction peak broadening analysis: the curves increased approximately linearly with the pressure at the initial compression stage and then levelled off under further compression. Pressure-induced transparency was observed in all of the samples under compression, and the pressure at the turning point on the curves of the microscopic deviatoric stress versus pressure corresponded to the pressure at which the samples became transparent. Analysis of the microstructural features of the pressure-induced transparent samples indicated that the compression caused the grains to fracture, and the broken grains bonded with each other. We demonstrated that the ceramics’ pressure-induced transparency was a process during which the grains were squeezed and broken, the pores were close between the grains, and the broken grains were re-bonded under compression. 相似文献
12.
Developing the thermal stability of metal-based ceramic composites or their films has always been challenging and bottlenecks for the utilization of energy. In this paper, the novel mesh-like functional Al doped-MoO3 nanocomposite film with even distribution and high purity was firstly fabricated by the high-efficiency electrophoretic deposition and surface modification. The optimal suspension turned out to be the mixture of isopropanol and the additives of polyethyleneimine and benzoic acid. The microtopography, crystalline structure, environmental resistance and thermal stability were analyzed by field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), exposure and droplet-impacting test, DSC analysis and ignition test, respectively. The water contact angle and sliding angle of product can reach ~170° and <1°, indicating the excellent anti-wetting property. In addition, the high heat-release (~3180 J/g) of product all kept almost unchangeable after six months exposure experiments, demonstrating the outstanding thermostability. The exquisite design idea here can perfectly match microelectromechanical system (MEMS), providing the valuable reference for fabricating other metal-based high-energy composites with long lifespan for real industrial applications. 相似文献
13.
14.
氢脆具有很强的微观组织敏感性,威胁着各类高强结构材料的安全服役.采用激光-电弧复合焊工艺对BS960E型高强钢进行焊接,并对接头在原位电化学充氢的条件下进行慢应变速率(10-5s-1)拉伸试验,结合微观组织和断裂特征进行分析并对接头的氢脆行为进行研究.结果 表明,焊接热循环所形成的富马氏体中的细晶区可以使接头表现出一定的氢脆敏感性,马氏体较大的氢扩散系数和较低的氢溶解度以及氢在晶界上的快速扩散是引起接头对氢脆敏感的主要原因,通过控制焊接工艺参数可抑制焊接热循环所引起的马氏体转变量,能够降低BS960E型高强钢激光-电弧复合焊接头的氢脆敏感性. 相似文献
16.
Electric nanogenerators that directly convert the energy of moving drops into electrical signals require hydrophobic substrates with a high density of static electric charge that is stable in “harsh environments” created by continued exposure to potentially saline water. The recently proposed charge-trapping electric generators (CTEGs) that rely on stacked inorganic oxide–fluoropolymer (FP) composite electrets charged by homogeneous electrowetting-assisted charge injection (h-EWCI) seem to solve both problems, yet the reasons for this success have remained elusive. Here, systematic measurements at variable oxide and FP thickness, charging voltage, and charging time and thermal annealing up to 230 °C are reported, leading to a consistent model of the charging process. It is found to be controlled by an energy barrier at the water-FP interface, followed by trapping at the FP-oxide interface. Protection by the FP layer prevents charge densities up to −1.7 mC m−2 from degrading and the dielectric strength of SiO2 enables charge decay times up to 48 h at 230 °C, suggesting lifetimes against thermally activated discharging of thousands of years at room temperature. Combining high dielectric strength oxides and weaker FP top coatings with electrically controlled charging provides a new paradigm for developing ultrastable electrets for applications in energy harvesting and beyond. 相似文献
17.
18.
Reliable joints of Ti3SiC2 ceramic and TC11 alloy were diffusion bonded with a 50 μm thick Cu interlayer. The typical interfacial structure of the diffusion boned joint, which was dependent on the interdiffusion and chemical reactions between Al, Si and Ti atoms from the base materials and Cu interlayer, was TC11/α-Ti + β-Ti + Ti2Cu + TiCu/Ti5Si4 + TiSiCu/Cu(s, s)/Ti3SiC2. The influence of bonding temperature and time on the interfacial structure and mechanical properties of Ti3SiC2/Cu/TC11 joint was analyzed. With the increase of bonding temperature and time, the joint shear strength was gradually increased due to enhanced atomic diffusion. However, the thickness of Ti5Si4 and TiSiCu layers with high microhardness increased for a long holding time, resulting in the reduction of bonding strength. The maximum shear strength of 251 ± 6 MPa was obtained for the joint diffusion bonded at 850 °C for 60 min, and fracture primarily occurred at the diffusion layer adjacent to the Ti3SiC2 substrate. This work provided an economical and convenient solution for broadening the engineering application of Ti3SiC2 ceramic. 相似文献
19.
Zhang Qi Wang Yujing Zhang Xueling Song Jun Li Yinlei Wu Xuehong Yuan Kunjie 《Journal of Materials Science》2022,57(14):7208-7224
Journal of Materials Science - Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after... 相似文献
20.