全文获取类型
收费全文 | 36844篇 |
免费 | 3239篇 |
国内免费 | 1645篇 |
专业分类
电工技术 | 2242篇 |
技术理论 | 3篇 |
综合类 | 2715篇 |
化学工业 | 6247篇 |
金属工艺 | 1973篇 |
机械仪表 | 2142篇 |
建筑科学 | 2674篇 |
矿业工程 | 971篇 |
能源动力 | 971篇 |
轻工业 | 3124篇 |
水利工程 | 831篇 |
石油天然气 | 2321篇 |
武器工业 | 302篇 |
无线电 | 4086篇 |
一般工业技术 | 4152篇 |
冶金工业 | 1663篇 |
原子能技术 | 436篇 |
自动化技术 | 4875篇 |
出版年
2024年 | 150篇 |
2023年 | 598篇 |
2022年 | 1090篇 |
2021年 | 1563篇 |
2020年 | 1212篇 |
2019年 | 936篇 |
2018年 | 1039篇 |
2017年 | 1235篇 |
2016年 | 1055篇 |
2015年 | 1477篇 |
2014年 | 1951篇 |
2013年 | 2288篇 |
2012年 | 2535篇 |
2011年 | 2789篇 |
2010年 | 2477篇 |
2009年 | 2378篇 |
2008年 | 2320篇 |
2007年 | 2253篇 |
2006年 | 2135篇 |
2005年 | 1854篇 |
2004年 | 1308篇 |
2003年 | 999篇 |
2002年 | 925篇 |
2001年 | 738篇 |
2000年 | 715篇 |
1999年 | 745篇 |
1998年 | 558篇 |
1997年 | 482篇 |
1996年 | 436篇 |
1995年 | 366篇 |
1994年 | 267篇 |
1993年 | 211篇 |
1992年 | 177篇 |
1991年 | 133篇 |
1990年 | 71篇 |
1989年 | 74篇 |
1988年 | 67篇 |
1987年 | 27篇 |
1986年 | 26篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1959年 | 3篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Objective To study on the role of thymus transplantation for heart allograft in rats. Methods Vascularized heart-thymus combined transplantation was performed with microsurgical technique. Graft survival, histopathology,
level of IL-2, IL-4 and its mRNA expression in serum and cardiac grafts were investigated. Results Heart-thymus combined transplantation achieved effect in the prolongation of cardiac graft survival with short-term administration
of cyclosporine. Conclusions Vascularized thymus transplantation induced immune tolerance in thymectomized rats. 相似文献
82.
奥氏体锰钢是一种非常坚硬的无磁性合金钢,它的性能和大多数普遍使用的抗磨损结构钢不同。对许多轨道工程部件来说,它是一种更可取的材料。铁路辙岔和交叉处是重要的,但其它重要部件还包括开关的防护装置、铸造镶嵌件和桥式轨道部件。奥氏体锰钢承载力高,耐久性好。在冲击和负重下不会断裂。它的淬火硬化能力是最主要的一个优势。零部件表面在冲击下硬化,有些变形,但下面的母材仍保留原来的硬度。裂缝的蔓延速度非常慢。 相似文献
83.
84.
Two kinds of SiC whiskers were annealed at temperatures similar to those for the processing of ceramic matrix composites. The morphology and structure of the as-received and postannealed whiskers were investigated by SEM, TEM, and XRD, and the influence of processing temperature on the mechanical properties of ceramic matrix composites was discussed. 相似文献
85.
Arghavani R. Xia L. M'Saad H. Balseanu M. Karunasiri G. Mascarenhas A. Thompson S.E. 《Electron Device Letters, IEEE》2006,27(2):114-116
This letter discusses a reliable and manufacturable integration technique to induce greater than 1 GPa of stress into a p-channel MOSFET, which will be required to increase the drive current beyond 1 mA//spl mu/m at the sub-90-nm process generation. Uniaxial compressive stress is introduced into the p-channel by both a selective deposition of SiGe in the source/drain and an engineered 2.5-GPa compressively stressed nitride. The highest to date compressively stressed SiN film is obtained by heavy ion bombardment during the deposition of the film. 相似文献
86.
L. X. Che R. Q. Yang Y. Gu T. K. Xia 《The International Journal of Advanced Manufacturing Technology》2006,31(5-6):614-620
This paper presents a method of calculating the insulating safety distances for hot-line working robots at high voltage when dielectric is adulterated with conducts. Also, finite element method is adopted to calculate the electric field strength to find whether it is beyond the critical. The above methods have been applied to analyze the insulating safety of the robot for hot-line sweeping post insulators in a 220 KV substation. They have also been testified by experimentations. 相似文献
87.
Kemppi公司的新型MinarcMig^TM自适应逆变器是重量很轻、功能强大、使用方便的焊机。 相似文献
88.
在保证机组运行安全、可靠的前提下,对热力系统进行了优化,合理地减少了备用设备和备用容量,降低系统阻力及工质损失。从而达到了降低能耗和初投资,减少运行成本的目的。 相似文献
89.
Meng Yan Minyu Yao Hongming Zhang Li Xia Ye Zhang 《Photonics Technology Letters, IEEE》2008,20(10):788-790
A novel en/decoder for spectral phase-coded optical code-division multiple-access system based on amplitude sampled fiber Bragg grating (FBG) is proposed. Both equivalent chirp and equivalent phase shift are achieved by amplitude sampling. Compared with previous en/decoder based on step chirped FBG, it is easier to fabricate. The performance of the proposed en/decoder is verified by both numerical simulation and experimental demonstration. 相似文献
90.
Peichun Li Amar Zerroukhi Jianding Chen Yvan Chalamet Thomas Jeanmaire Zhean Xia 《应用聚合物科学杂志》2008,110(6):3990-3998
Chemical shrinkage was used for the in situ measurement of the progressing chemical stabilization reactions and the influence of ozone during the stabilization of polyacrylonitrile. A method for evaluating the activation energy through the sensitivity temperature is presented. The calculated results show that the activation energies were 161.57 kJ/mol in air and 181.23 kJ/mol in ozone-enriched air. Therefore, the chemical reactions were postponed during stabilization in ozone-enriched air. Ozone seemed to act in three ways: first, ozone promoted the formation of the serious skin–core structure. Second, ozone accelerated the chemical reactions and shortened the stabilization time at lower heating rates. Third, ozone postponed the chemical reactions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献