全文获取类型
收费全文 | 33657篇 |
免费 | 4168篇 |
国内免费 | 2585篇 |
专业分类
电工技术 | 3047篇 |
技术理论 | 1篇 |
综合类 | 3324篇 |
化学工业 | 4262篇 |
金属工艺 | 1915篇 |
机械仪表 | 2181篇 |
建筑科学 | 2594篇 |
矿业工程 | 942篇 |
能源动力 | 948篇 |
轻工业 | 3174篇 |
水利工程 | 840篇 |
石油天然气 | 1209篇 |
武器工业 | 483篇 |
无线电 | 4005篇 |
一般工业技术 | 3612篇 |
冶金工业 | 2269篇 |
原子能技术 | 514篇 |
自动化技术 | 5090篇 |
出版年
2024年 | 205篇 |
2023年 | 670篇 |
2022年 | 1314篇 |
2021年 | 1629篇 |
2020年 | 1235篇 |
2019年 | 992篇 |
2018年 | 1021篇 |
2017年 | 1107篇 |
2016年 | 1032篇 |
2015年 | 1480篇 |
2014年 | 1767篇 |
2013年 | 2144篇 |
2012年 | 2543篇 |
2011年 | 2598篇 |
2010年 | 2476篇 |
2009年 | 2276篇 |
2008年 | 2223篇 |
2007年 | 2191篇 |
2006年 | 1971篇 |
2005年 | 1589篇 |
2004年 | 1148篇 |
2003年 | 963篇 |
2002年 | 1102篇 |
2001年 | 984篇 |
2000年 | 680篇 |
1999年 | 479篇 |
1998年 | 610篇 |
1997年 | 405篇 |
1996年 | 323篇 |
1995年 | 233篇 |
1994年 | 185篇 |
1993年 | 193篇 |
1992年 | 120篇 |
1991年 | 73篇 |
1990年 | 65篇 |
1989年 | 58篇 |
1988年 | 46篇 |
1987年 | 33篇 |
1986年 | 20篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 17篇 |
1978年 | 4篇 |
1977年 | 36篇 |
1976年 | 90篇 |
1959年 | 6篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Zhang Xi Wang Xianhai Zhao Hongke Ordóñez de Pablos Patricia Sun Yongqiang Xiong Hui 《Scientometrics》2019,119(3):1311-1344
Scientometrics - Altmetrics indices are increasingly applied to measure scholarly influence in recent years because they can reflect the influence of research outputs more timely comparing with... 相似文献
12.
Xi Chen Zhengkun Yu Chen Yang Yao Chen Chao Jin Yuejiao Ding Wenbin Li Zhongmin Wan 《International Journal of Hydrogen Energy》2021,46(19):11127-11139
Flow field structure can largely determine the output performance of Polymer electrolyte membrane fuel cell. Excellent channel configuration accelerates electrochemical reactions in the catalytic layer, effectively avoiding flooding on the cathode side. In present study, a three-dimensional, multi-phase model of PEMFC with a 3D wave flow channel is established. CFD method is applied to optimize the geometry constructions of three-dimensional wave flow channels. The results reveal that 3D wave flow channel is overall better than straight channel in promoting reactant gases transport, removing liquid water accumulated in microporous layer and avoiding thermal stress concentration in the membrane. Moreover, results show the optimal flow channel minimum depth and wave length of the 3D wave flow channel are 0.45 mm and 2 mm, respectively. Due to the periodic geometric characteristics of the wave channel, the convective mass transfer is introduced, improving gas flow rate in through-plane direction. Furthermore, when the cell output voltage is 0.4 V, the current density in the novel channel is 23.8% higher than that of conventional channel. 相似文献
13.
在"一带一路"倡议深入实施的背景下,中国境外产业园区得到沿线国家的普遍认同,正在成为支撑"一带一路"倡议落地开花的重要手段,这也为中国开发区规划技术"走出去"提供了机会和提出了需求.本文系统梳理了相关领域的学术研究状况,在分析相关法定规划体系架构基础上,结合实地调研,对中国境外产业园区的规划实践进行了系统梳理和分析,对既有境外园区规划类型与内容、规划技术标准、规划编制组织和管理体系等进行了总结,结合园区就业者对规划建设的评价和需求等,分析了境外园区规划建设存在的主要问题,提出了境外产业园区规划体系创新的策略性建议,为构建全球化的境外产业园区规划技术体系提供支撑,也为中国城乡规划技术"走出去"探路. 相似文献
14.
Scientometrics - Due to the development of academic, more and more attentions are paid to citation recommendation. To solve the citation recommendation problem, researchers begin to focus on the... 相似文献
15.
16.
17.
18.
四川盆地作为国内页岩气开发的重点区域,通过近几年的不断攻关和实践,机械钻速得到了提高,但由于受地层复杂、可钻性差、非均质性强等地质因素的影响,导致井下钻柱系统不良振动剧烈,容易出现钻头损坏严重、钻速较低等问题,严重影响了钻井时效。为了解决上述难题,以该盆地涪陵工区上二叠统龙潭组—中二叠统茅口组为例,采用井下振动高频测量工具的实测手段,测量了钻头—钻柱系统的动态振动加速度参数,结合地层的岩性和矿物组分分析,研究钻头失效原因与对策,并开展了现场试验。研究结果表明:①在非均质地层中钻进的钻头—钻柱系统产生了大于40 m/s~2的高幅值瞬时冲击振动,高幅值的瞬时冲击是导致钻头先期失效的主要原因;②提出了抑制高幅值的瞬时冲击振动采用"减振+增压"工具组合和避免井下工具共振的钻井参数;③采用钻井新参数的试验井比邻井的高幅值瞬时振动降低了17%,单只钻头进尺增加24%,钻头工作环境得到了较大的改善,钻头使用数量减少。结论认为,该研究成果能够有效地改善钻头—钻柱系统的振动状态,有利于达成延长钻头使用寿命的目标。 相似文献
19.
Changwei Dun Guoxi Xi Ye Zhang Tingting Zhao Yumin Liu Xiaoying Heng Lu Yao 《Ceramics International》2018,44(17):20984-20991
In this study, we investigated the effects of substituting Li+ for Co2+ at the B sites of the spinel lattice on the structural, magnetic and magnetostrictive properties of cobalt ferrites. The Li+ substituted cobalt ferrites, Co1-xLixFe2O4, with x varying from 0 to 0.7 in 0.1 increments, were synthesized with a sol-gel auto-combustion method using the cathode materials of spent Li-ion batteries. X-ray diffraction analysis revealed that all the Co1-xLixFe2O4 nanopowders had a single-phase spinel structure and the lattice parameters decreased with increasing Li+ content, which can be proved by slight shifts towards higher diffraction angle values of the (311) peak. Field emission scanning electron microscopy was used to observe the fractured inner surface of the sintered cylindrical rods and the increased porosity resulted in a decreased magnetostriction. The oxidation states of Co and Fe in the cobalt ferrite samples were examined by X-ray photoelectron spectroscopy. High resolution transmission electron microscopy micrographs showed that most particles were roughly spherical and with sizes of 25–35?nm. Li+ substitution had a strong effect on the saturation magnetization and coercivity, which were characterized with a vibrating sample magnetometer. The Curie temperature was reduced due to the decrease in magnetic cations and the weakening of the exchange interactions. The magnetostrictive properties were influenced by the incorporation of Li+ at the B sites of the spinel structure and correlated with the changes in porosity, magnetocrystalline anisotropy and the cation distribution. 相似文献
20.
Linlin Zhu Liyuan Zhang Xi Li Xiaoqi Jin Tiejun Shi 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(7):551-560
AbstractGraphene oxide (GO) was functionalized by polyether amine (PEA) via two methods which were one-pot modification in acetone (GON) and two steps with the intermediate product of GOCO-Cl generated (GONS). There were more PEA successfully grafted onto GO for GONS than GON. The onset polymerization temperatures of the benzoxazine (Bz) composites decreased by the inclusion of 1?wt% of GO, GON or GONS. Thermal stability of the polybenzoxazine (PBz) composites was significantly improved indicated from the increase of weight loss temperature. T10, T20 and T50 values of the composites with GONS were higher than that of the others. Toughness of PBzs may be enhanced by the incorporation of nanofillers, and GONS had stronger interfacial interaction with PBz matrix than GON. 相似文献