全文获取类型
收费全文 | 95364篇 |
免费 | 10035篇 |
国内免费 | 5072篇 |
专业分类
电工技术 | 7572篇 |
技术理论 | 10篇 |
综合类 | 7127篇 |
化学工业 | 14424篇 |
金属工艺 | 5527篇 |
机械仪表 | 6224篇 |
建筑科学 | 8395篇 |
矿业工程 | 3109篇 |
能源动力 | 2835篇 |
轻工业 | 6521篇 |
水利工程 | 2124篇 |
石油天然气 | 4606篇 |
武器工业 | 1027篇 |
无线电 | 11389篇 |
一般工业技术 | 10659篇 |
冶金工业 | 3845篇 |
原子能技术 | 1299篇 |
自动化技术 | 13778篇 |
出版年
2024年 | 408篇 |
2023年 | 1750篇 |
2022年 | 3568篇 |
2021年 | 4919篇 |
2020年 | 3612篇 |
2019年 | 2824篇 |
2018年 | 3187篇 |
2017年 | 3450篇 |
2016年 | 3201篇 |
2015年 | 4400篇 |
2014年 | 5420篇 |
2013年 | 6361篇 |
2012年 | 7186篇 |
2011年 | 7613篇 |
2010年 | 6645篇 |
2009年 | 6242篇 |
2008年 | 5929篇 |
2007年 | 5446篇 |
2006年 | 5145篇 |
2005年 | 4288篇 |
2004年 | 2870篇 |
2003年 | 2267篇 |
2002年 | 2120篇 |
2001年 | 1778篇 |
2000年 | 1663篇 |
1999年 | 1595篇 |
1998年 | 1173篇 |
1997年 | 1022篇 |
1996年 | 1028篇 |
1995年 | 763篇 |
1994年 | 638篇 |
1993年 | 442篇 |
1992年 | 361篇 |
1991年 | 227篇 |
1990年 | 181篇 |
1989年 | 157篇 |
1988年 | 136篇 |
1987年 | 83篇 |
1986年 | 55篇 |
1985年 | 48篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1962年 | 43篇 |
1961年 | 39篇 |
1960年 | 16篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
52.
53.
54.
正项目地址_中国北京项目面积_8000m~2设计单位_ArkA北京亦庄半岛幼儿园项目是设计团队与半岛教育集团的第二次合作,目标是将蒙特梭利教育理念和建筑设计融为一体,创造出一个更合理的空间和安全的环境,让孩子们能够自由快乐地学习和成长。原有的建筑物是一个开放的空间,整个大空间分作4层。设计团队的首要任务是根据孩子的比例改造空间。在设计时,设计团队加入了许多小房屋的设计,以此让孩子更具有主人感和安全感。对教室的设计是简约的房屋;图书馆则是一个开放空间,在其中央种下一棵树,好似一个乡村小镇的广场;走廊设计成多功能的开放空间,孩子 相似文献
55.
Bing Yang Yu Zhou Wenjie Yu Song Zhang Hongxiang Chen Ju Ye 《Polymer International》2019,68(4):675-683
In order to improve the dispersity and stability of the nano‐SiO2 aqueous system with high solid content, a kind of polyacrylic acid dispersant with methoxysilicon end groups (KH590‐PAA) was synthesized by photopolymerization of acrylic acid (AA) initiated with (3‐mercaptopropyl)trimethoxysilane (KH590). After adding KH590‐PAA into the nano‐SiO2 aqueous dispersion system (20 wt% solid content), the viscosity and the curing time of the system were measured with a rotational viscometer and the inverted bottle method. Moreover, the dispersion mechanism of KH590‐PAA for the nano‐SiO2 aqueous system was researched by measuring the adsorption capacity, the particle size and the zeta potential of the nanoparticles with a conductivity meter, dynamic light scattering, SEM and TEM, respectively. The results showed that the methoxysilicon groups in KH590‐PAA could react with hydroxyl groups on the surface of nano‐SiO2 in the process of stirring, which enhanced the adsorption capacity of the dispersant and then increased the surface charge of the particles. Therefore, electrostatic repulsion and steric hindrance effects between the SiO2 nanoparticles could be further enhanced by adding the KH590‐PAA dispersant, and then the nano‐SiO2 aqueous system exhibited better dispersity and stability. Besides, the dispersion properties of SiO2 nanoparticles in water were closely related to the addition amount and the molecular weight of the KH590‐PAA dispersant. © 2018 Society of Chemical Industry 相似文献
56.
57.
58.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
59.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency. 相似文献
60.
Jiajia Ye Xuting Li Guang Xia Guanghao Gong Zhiqiang Zheng Chuanzhong Chen Cheng Hu 《材料科学技术学报》2021,77(18):100-107
We report for the first time a Na-ion battery anode material composed of P-doped CoSe2 nanoparticles(P-CoSe2)with the size of 5-20 nm that are uniformly embed in a 3D porous honeycomb-like carbon network.High rate capability and cycling stability are achieved simultaneously.The honeycomb-like carbon network is rationally designed to support high electrical conductivity,rapid Na-ion diffusion as well as the accommodation of the volume expansion from the active P-CoSe2 nanoparticles.In particular,heteroatom P-doping within CoSe2 introduces stronger P-Co bonds and additional P-Se bonds that signif-icantly improve the structure stability of P-CoSe2 for highly stable sodiation/desodiation over long-term cycling.P-doping also improves the electrical conductivity of the CoSe2 nanoparticles,leading to highly elevated electrochemical kinetics to deliver high specific capacities at high current densities.Benefiting from the unique nanostructure and atomic-level P-doping,the P-CoSe2(2∶1)/C anode delivers an excel-lent cycle stability with a specific capacity of 206.9 mA h g-1 achieved at 2000 mA g-1 after 1000 cycles.In addition,this material can be synthesized using a facile pyrolysis and selenization/phosphorization approach.This study provides new opportunities of heteroatom doping as an effective method to improve the cycling stability of Na-ion anode materials. 相似文献