全文获取类型
收费全文 | 21787篇 |
免费 | 2355篇 |
国内免费 | 1126篇 |
专业分类
电工技术 | 1338篇 |
技术理论 | 1篇 |
综合类 | 1416篇 |
化学工业 | 3402篇 |
金属工艺 | 1406篇 |
机械仪表 | 1538篇 |
建筑科学 | 1665篇 |
矿业工程 | 658篇 |
能源动力 | 596篇 |
轻工业 | 1540篇 |
水利工程 | 500篇 |
石油天然气 | 1189篇 |
武器工业 | 238篇 |
无线电 | 2568篇 |
一般工业技术 | 2647篇 |
冶金工业 | 1160篇 |
原子能技术 | 362篇 |
自动化技术 | 3044篇 |
出版年
2024年 | 156篇 |
2023年 | 460篇 |
2022年 | 825篇 |
2021年 | 1097篇 |
2020年 | 887篇 |
2019年 | 746篇 |
2018年 | 767篇 |
2017年 | 874篇 |
2016年 | 788篇 |
2015年 | 1148篇 |
2014年 | 1403篇 |
2013年 | 1564篇 |
2012年 | 1673篇 |
2011年 | 1524篇 |
2010年 | 1360篇 |
2009年 | 1237篇 |
2008年 | 1166篇 |
2007年 | 1143篇 |
2006年 | 1085篇 |
2005年 | 867篇 |
2004年 | 560篇 |
2003年 | 497篇 |
2002年 | 488篇 |
2001年 | 429篇 |
2000年 | 365篇 |
1999年 | 327篇 |
1998年 | 278篇 |
1997年 | 216篇 |
1996年 | 223篇 |
1995年 | 178篇 |
1994年 | 146篇 |
1993年 | 106篇 |
1992年 | 99篇 |
1991年 | 72篇 |
1990年 | 61篇 |
1989年 | 45篇 |
1988年 | 48篇 |
1987年 | 31篇 |
1986年 | 40篇 |
1985年 | 21篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1977年 | 12篇 |
1976年 | 23篇 |
1975年 | 11篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Yi Liang Long Zhang Mengdao Xing Zheng Bao 《Frontiers of Electrical and Electronic Engineering in China》2009,4(2):127-133
The frequency modulated continuous wave (FMCW) radar has the characteristics of low probability of interception, good hidden
property and the ability to counter anti-radiation missiles. This paper proposes a new method for high-speed ground moving
target detection (GMTD) using triangular modulation FMCW. According to the characteristic of the opposite range shift induced
by the upslope and downslope modulation FMCW, the upslope and downslope are imaged, respectively. After compensation of continuous
motion of the platform and time difference between upslope and downslope signals for imaging, the moving target can be detected
through displaced phase center antenna (DPCA) technology. When the moving target is detected, the moving target image is extracted,
and correlation processing is used to obtain the range shift, which can be used to estimate the target radial velocity, and
further to find the real position of the target. The effectiveness of this method is verified by the result of computer simulation.
__________
Translated from Journal of Xidian University, 2008, 35(4): 586–591 [译自: 西安电子科技大学学报(自然科学版)] 相似文献
52.
53.
为了解决光学材料多功能耦合与集成的光谱诉求及其材料设计冲突难题,本文提出一种基于[TiAlN/Ag]2/TiAlN序构复合薄膜开展可见光透射诱导与红外辐射抑制的协同设计方法,诠释序构薄膜材料多功能耦合的新原理与新机制,并对其光学兼容性能测试表征。研究表明,构筑的[TiAlN(厚度30 nm)/Ag(厚度15 nm)]2/TiAlN(厚度30 nm)序构复合薄膜具备带通状选择性透射与中远红外低辐射的光学特性,可较好实现透视、遮阳、低辐射控温与红外隐身多功能兼容效果,在军用车辆、绿色建筑等特种玻璃的辐射控温与红外隐身领域有应用潜力。 相似文献
54.
采用原位乳液聚合方法制备了基于共价键结合的P(MMA-AN)/TiO2复合粒子,红外光谱和热失重分析结果表明P(MMA-AN)在TiO2表面接枝率为15.9%。以甲基橙溶液为目标污染物,研究了P(MMA-AN)/TiO2复合粒子和TiO2对甲基橙的吸附和光催化降解甲基橙溶液的性能,结果表明:两种粒子对甲基橙的吸附都很少;在相同时间内,P(MMA-AN)/TiO2复合粒子对甲基橙溶液的降解性能优于TiO2,紫外光照180 min后,P(MMA-AN)/TiO2复合粒子对甲基橙溶液的降解率达到了88%,而TiO2仅为74%。 相似文献
55.
Hao Long Yang Wei Tongjun Yu Zhe Wang Chuanyu Jia Zhijian Yang Guoyi Zhang Shoushan Fan 《Nano Research》2012,5(9):646-653
A novel carbon nanotube-patterned sapphire substrate (CPSS) has been utilized for the growth of GaN material and fabrication of a InGaN/GaN light emitting diode (LED) by metal-organic vapor phase epitaxy. Different lateral strain distributions and stress reductions were observed in a GaN thin film on CPSS compared with those on a conventional sapphire substrate. Nanoheteroepitaxy induced by small size nucleation islands of about 50 nm is ascribed to this significant strain modulation. The crystalline quality of the GaN thin film was also improved, as illustrated by X-ray diffraction. Performances of 1 mm × 1 mm LEDs on CPSS were also enhanced, with an operational power increase of 37.5% and higher saturation current. 相似文献
56.
APS单反相机在1997年问世,APS表现出优良的画面质量,使得消费者在对它冷落一段时间之后不得不进行重新评价。另外,提出了APS在中国所遇到问题,如缺少冲扩店,胶卷价格贵等。 相似文献
57.
He N Wang T Jiang L Wang D Hu Y Zhang L 《Journal of nanoscience and nanotechnology》2010,10(8):5320-5323
In this study we prepared nanocarrier of erythropoietin (EPO) and the curative effect of the EPO-containing nanoparticles for periventricular leukomalacia (PVL) model was validated. It was demonstrated that EPO-containing nanoparticles can ameliorate drug-induced liquefaction caused by hypoxia. EPO-containing nanomedicine may open new therapeutic strategies in hypoxia cure. 相似文献
58.
Background The accelerator-driven subcritical transmuta-tion system(ADS)is an advanced technology for the harmless disposal of nuclear waste.A theoretical analy... 相似文献
59.
Based on the simplified planar quadruped model with a passive spine joint, this paper focuses on studying the effect of the spine joint on the dynamic performance and the stability of the rotary galloping gait. The stable, periodic, and symmetric rotary galloping gait is achieved by the particle swarm optimization method without any parameter symmetry for leg motion and without any limitation for spine motion. By analyzing the symmetric pattern of the rotary galloping gait, the stability criterion is derived: the closer to zero is the pitching angle at peak time of the center of mass, the better is the stability of the galloping gait. Then, we study the effect of rear leg touchdown angle and spine stiffness on the stability. Moreover, the unstable rotary galloping gait can be stabilized by adjusting one or more of the touchdown angle, spine stiffness, and leg stiffness. Furthermore, the effect of the spine stiffness on the key kinematic and kinetic properties is also studied for different initial values and mechanical parameters. The presented stability criterion and the achieved dynamic performance analysis results will be instructive for the design and control of the quadruped robot. 相似文献
60.
Zedong Zhao Minqiang Sun Tianqi Wu Jiajia Zhang Peng Wang Long Zhang Chongyang Yang Chengxin Peng Hongbin Lu 《纳微快报(英文)》2021,(8):40-55
Lithium- and manganese-rich (LMR) layered cath-ode materials hold the great promise in designing the next-genera-tion high energy density lithium ion batteries.... 相似文献