全文获取类型
收费全文 | 58012篇 |
免费 | 5112篇 |
国内免费 | 2614篇 |
专业分类
电工技术 | 3410篇 |
综合类 | 4258篇 |
化学工业 | 9472篇 |
金属工艺 | 2947篇 |
机械仪表 | 3573篇 |
建筑科学 | 4327篇 |
矿业工程 | 1677篇 |
能源动力 | 1639篇 |
轻工业 | 4856篇 |
水利工程 | 1216篇 |
石油天然气 | 3317篇 |
武器工业 | 468篇 |
无线电 | 6650篇 |
一般工业技术 | 6834篇 |
冶金工业 | 2459篇 |
原子能技术 | 708篇 |
自动化技术 | 7927篇 |
出版年
2024年 | 248篇 |
2023年 | 1064篇 |
2022年 | 1934篇 |
2021年 | 2747篇 |
2020年 | 2123篇 |
2019年 | 1758篇 |
2018年 | 1857篇 |
2017年 | 2074篇 |
2016年 | 1856篇 |
2015年 | 2652篇 |
2014年 | 3200篇 |
2013年 | 3787篇 |
2012年 | 4071篇 |
2011年 | 4222篇 |
2010年 | 3757篇 |
2009年 | 3587篇 |
2008年 | 3525篇 |
2007年 | 3267篇 |
2006年 | 3162篇 |
2005年 | 2674篇 |
2004年 | 1877篇 |
2003年 | 1395篇 |
2002年 | 1307篇 |
2001年 | 1036篇 |
2000年 | 1044篇 |
1999年 | 1061篇 |
1998年 | 835篇 |
1997年 | 703篇 |
1996年 | 659篇 |
1995年 | 530篇 |
1994年 | 436篇 |
1993年 | 298篇 |
1992年 | 242篇 |
1991年 | 190篇 |
1990年 | 118篇 |
1989年 | 114篇 |
1988年 | 95篇 |
1987年 | 57篇 |
1986年 | 53篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1959年 | 4篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Liang Xu Xuhai Li Yihang Cui Zhiguo Li Qingyun Chen Chuanmin Meng Haibing Zhang Jianbo Hu Qiang Wu 《Ceramics International》2021,47(15):21008-21012
Ti3SiC2 is of interest due to its unique dual nature reminiscent of both brittle ceramics and ductile metals at ambient conditions. In this work, plate-impact experiments have been performed to study the dynamic behavior of Ti3SiC2 under shock compression up to 112 GPa by using laser velocity interferometer and electric pin techniques. Hugoniot elastic limits (HEL), spall strength, and Hugoniot equations of state have been obtained based on measured particle velocity profiles and shock wave velocities. The ratio of spall strength to HEL for Ti3SiC2 is larger than brittle ceramics but smaller than metals. This result indicates that the dual nature of Ti3SiC2 remains at least up to 10 GPa. On the other hand, the linearity of the Hugoniot equation of state, , suggests that the initial structure of Ti3SiC2 should be stable up to 112 GPa, in contrast to the result reported by Jordan et al. [J. Appl. Phys., 93 (2003) 9639]. 相似文献
44.
45.
Quantifying and understanding quantum correlations may give a direct reply for many issues regarding the interesting behaviors of quantum system. To explore the quantum correlations in quantum teleportation, we have used a two-qubit Heisenberg XYZ system with spin–orbit interaction as a quantum channel to teleport an unknown state. By using different measures and standard teleportation protocols, we have derived the analytical expressions for quantum discord, entanglement of formation, purity, and maximal teleportation fidelity of the system. We compare their different characteristics and analyze the relationships between these quantities. 相似文献
46.
研究了硫调型氯丁橡胶乳液聚合中转化率对产晶结构与性能的影响.结果表明,随单体转化率的提高,聚合物的凝胶量及其交联密度增大,致使断链速度减慢,所得断链胶的门尼粘度上升,残存凝胶量增加,分子支化程度增大,分子量分布变宽,焦烧时间缩短。而相应硫化胶的拉伸强度、撕裂强度、冲击弹性和硬度等提高,扯断伸长率和永久变形下降。这些变化一般在转化率为80——85%时有明显转折.综合考虑产量与质量,聚合转化率控制在82±2%较为适宜。 相似文献
47.
48.
49.
高霞 《网络安全技术与应用》2014,(11):172-173
在教学中,创设问题情境是一种科学有效的教学手段。通过对一堂计算机基础课《PPT动画路径》的分析,探究如何在中职计算机课程中创设问题情境,提高课堂教学实效性,并对容易出现的问题进行简单的阐述。 相似文献
50.
Shape‐memory polyurethane/multiwalled carbon nanotube (SMP–MWNT) composites with various multiwalled carbon nanotube (MWNT) contents were synthesized, and the corresponding SMP–MWNT fibers were prepared by melt spinning. The influence of the MWNT content on the spinnability, fracture morphology, thermal and mechanical properties, and shape‐memory behavior of the shape‐memory polymer was studied. The spinning ability of SMP–MWNTs decreased significantly with increasing MWNT content. When the MWNT content reached 8.0 wt %, the fibers could not be produced because of the poor rheological properties of the composites. The melt‐blending, extrusion, and melt‐spinning processes for the shape‐memory fiber (SMF), particularly at low MWNT contents, caused the nanotubes to distribute homogeneously and preferentially align along the drawing direction of the SMF. The crystallization in the SMF was promoted at low MWNT contents because it acted as a nucleation agent. At high MWNT contents, however, the crystallization was hindered because the movement of the polyurethane chains was restricted. The homogeneously distributed and aligned MWNTs preserved the SMF with high tenacity and initial modulus. The recovery ratio and recovery force were also improved because the MWNTs helped to store the internal elastic energy during stretching and fixing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献