全文获取类型
收费全文 | 133678篇 |
免费 | 13279篇 |
国内免费 | 6584篇 |
专业分类
电工技术 | 9444篇 |
技术理论 | 18篇 |
综合类 | 9586篇 |
化学工业 | 21064篇 |
金属工艺 | 7597篇 |
机械仪表 | 8079篇 |
建筑科学 | 10798篇 |
矿业工程 | 4127篇 |
能源动力 | 3901篇 |
轻工业 | 9472篇 |
水利工程 | 2876篇 |
石油天然气 | 6942篇 |
武器工业 | 1314篇 |
无线电 | 15929篇 |
一般工业技术 | 15709篇 |
冶金工业 | 6190篇 |
原子能技术 | 1606篇 |
自动化技术 | 18889篇 |
出版年
2024年 | 670篇 |
2023年 | 2441篇 |
2022年 | 4750篇 |
2021年 | 6378篇 |
2020年 | 4876篇 |
2019年 | 3784篇 |
2018年 | 4355篇 |
2017年 | 4652篇 |
2016年 | 4379篇 |
2015年 | 5923篇 |
2014年 | 7222篇 |
2013年 | 8474篇 |
2012年 | 9414篇 |
2011年 | 10140篇 |
2010年 | 8520篇 |
2009年 | 8019篇 |
2008年 | 7863篇 |
2007年 | 7213篇 |
2006年 | 6839篇 |
2005年 | 5768篇 |
2004年 | 4097篇 |
2003年 | 3312篇 |
2002年 | 3027篇 |
2001年 | 2574篇 |
2000年 | 2667篇 |
1999年 | 2900篇 |
1998年 | 2380篇 |
1997年 | 1937篇 |
1996年 | 1931篇 |
1995年 | 1531篇 |
1994年 | 1330篇 |
1993年 | 930篇 |
1992年 | 744篇 |
1991年 | 513篇 |
1990年 | 440篇 |
1989年 | 387篇 |
1988年 | 292篇 |
1987年 | 196篇 |
1986年 | 141篇 |
1985年 | 108篇 |
1984年 | 75篇 |
1983年 | 52篇 |
1982年 | 66篇 |
1981年 | 43篇 |
1980年 | 44篇 |
1979年 | 20篇 |
1977年 | 12篇 |
1976年 | 22篇 |
1974年 | 12篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Jianmou Lu Yanli Huang Shunyan Ren 《International Journal of Control, Automation and Systems》2020,18(5):1250-1263
This paper investigates the general decay synchronization and general decay H∞ synchronization problems of multi-weighted coupled reaction-diffusion 相似文献
92.
为了给海面溢油污染识别检测提供理论基础,根据菲涅尔反射公式的偏振反射系数,结合偏振双向反射率因子和粗糙海面的概率密度分布函数,建立了完善的pBRDF模型,仿真在不同太阳入射角度、不同探测器观测角度以及不同海面风速风向等条件下海水和油膜的偏振反射分布函数。结果表明:海水和油膜太阳天顶角为53°和56°时P偏振反射率分别为1.0×10^-5和2.5×10^-5,S偏振反射率随着太阳天顶角的增加而增加;海面风速越大偏振反射率峰值越小;海面风向只改变pBRDF的空间位置;海水和油膜线偏振度空间分布有明显差异。搭建实验平台相机以40°拍摄时,得出海水和油膜的线偏振度分别在0.2~0.4, 0.5~0.7之间,同时表明利用偏振探测获取目标场景的偏振度和偏振角图可提高图像质量。 相似文献
93.
Yong Liu Kangzhuang Chen Fengbo Dong Shuai Peng Yongjie Cui Chenyu Zhang Keqing Han Muhuo Yu Hui Zhang 《Ceramics International》2018,44(9):10199-10203
In this paper, polyborosilazane precursor was synthesied from HMDZ, HSiCl3, BCl3 and CH3NH2 using a multistep method. By controlling the storage conditions, parts of the polyborosilazane fibers were hydrolyzed. FT-IR, NMR, XRD, TEM and monofilament tensile strength test were employed to study the effects of hydrolysis of precursor on the structures and properties of polymer-derived SiBN ceramic fibers. FT-IR and NMR results indicate that Si-N group in PBSZ reacts with H2O to form Si-O-Si group. After pyrolysis reaction at 1400℃, Si-O-Si group will finally transformed into highly ordered cristobalite and β-quartz, resulting in formation of the wrinkled surface of the obtained SiBN ceramic fiber. The strip-like defects on fiber surface, according to monofilament tensile strength test, had a significant effect on mechanical property of the obtained SiBN ceramic fiber and caused no increase in fiber tensile strength of hydrolytic polyborosilazane fiber before and after pyrolytic process. 相似文献
94.
Hechun Cao Hui Zheng Lining Fan Zifeng Cheng Jianwei Zhou Qiong Wu Peng Zheng Liang Zheng Yang Zhang 《International Journal of Applied Ceramic Technology》2020,17(2):813-822
In this study, yttrium iron garnet co-doped with Zn and Zr atoms with a chemical formula Y3ZnxZrxFe(5−2x)O12 (x = 0.0-0.3) has been successfully prepared by the solid-state reaction method. The effects of doping concentration on the microstructure, crystal structure, magnetic properties, and dielectric properties of Y3ZnxZrxFe(5−2x)O12 were investigated. The microstructure analysis indicates that co-doping of YIG with Zn and Zr can effectively reduce the grain size of the ceramic. The crystal structure results reveal that the doping concentration of Zn–Zr has substantial influence on the lattice parameters of YIG, such as, increases the lattice constant, crystal cell size, and interplanar spacing. However, the second phase of ZrO2 appears once x ≥ 0.15. Additionally, the dielectric properties of YIG ferrite can be regulated using this Zn–Zr co-doping method. Zn–Zr co-doping can improve the dielectric stability and reduce the dielectric loss at high temperature. The magnetization measurement shows that the saturation magnetization is stabilized at x < 0.15, and the magnetic loss is decreased with the increase in the doping concentration. Overall, the findings show that the ceramic with x = 0.1 exhibits better properties included high saturation magnetization (24.607 emu/g), low magnetic loss (0.0025 @ 1 MHz), and relatively low dielectric loss (496 @ 400°C). 相似文献
95.
96.
Neural Computing and Applications - In this paper, an adaptive neural network (NN) output feedback control is investigated for incommensurate fractional-order permanent magnet synchronous motors... 相似文献
97.
98.
激光脉冲编码是激光制导武器的抗干扰措施之一。角度欺骗式干扰和高重频干扰是目前半主动激光制导武器的主要有源干扰来源。为研究不同激光脉冲编码方式对激光半主动制导武器抗这两种干扰性能的影响,本文针对敌方激光告警机的识别算法与我方导引头的解码过程,提出自相关函数与归一化互相关函数评价方法,并对目前主要编码方式进行仿真,仿真结果表明:激光脉冲编码的抗角度欺骗式干扰能力受编码序列周期性与脉冲间隔随机性的影响;抗高重频激光干扰能力受编码序列脉冲间隔随机性的影响;LFSR状态码的抗角度欺骗式干扰与抗高重频干扰效果均优于其他编码方式。 相似文献
99.
Zhao Hongliang Lu Tingting Liu Fengqin Yin Pan Wang Sen 《JOM Journal of the Minerals, Metals and Materials Society》2019,71(5):1643-1649
JOM - The Isa/Ausmelt smelting technology with a top submerged lance (TSL) has been extensively used in copper smelting processes. However, the TSL is extremely vulnerable to damage and failure... 相似文献
100.
Identification of vivianite,an unusual blue pigment,in a sixteenth century painting and its implications 下载免费PDF全文
António João Cruz Erica Eires Luís Dias Teresa Desterro Carla Rego 《Color research and application》2018,43(2):177-183
Vivianite, a blue pigment employed in the past practically only in Northern and Central Europe, but with very limited use, was identified in an early sixteenth century painting, stylistically with Flemish features, from a church in Portugal. The identification of this iron phosphate mineral was made by SEM‐EDS based on the atomic ratio between phosphorus and iron in layers of blue paint (area analysis) and in particles of these same layers (spot analysis). This painting, about which there is no document to prove its authorship, becomes the first case, known in detail, of a sixteenth century painting containing vivianite. Moreover, this find and the presence of a chalk ground, also identified, strongly support the hypothesis of being a Flemish painting. 相似文献