全文获取类型
收费全文 | 8606篇 |
免费 | 1452篇 |
国内免费 | 1014篇 |
专业分类
电工技术 | 374篇 |
技术理论 | 1篇 |
综合类 | 334篇 |
化学工业 | 1115篇 |
金属工艺 | 331篇 |
机械仪表 | 179篇 |
建筑科学 | 141篇 |
矿业工程 | 52篇 |
能源动力 | 374篇 |
轻工业 | 127篇 |
水利工程 | 39篇 |
石油天然气 | 80篇 |
武器工业 | 44篇 |
无线电 | 2087篇 |
一般工业技术 | 1375篇 |
冶金工业 | 148篇 |
原子能技术 | 79篇 |
自动化技术 | 4192篇 |
出版年
2024年 | 9篇 |
2023年 | 38篇 |
2022年 | 89篇 |
2021年 | 78篇 |
2020年 | 83篇 |
2019年 | 56篇 |
2018年 | 33篇 |
2017年 | 38篇 |
2016年 | 59篇 |
2015年 | 71篇 |
2014年 | 149篇 |
2013年 | 311篇 |
2012年 | 370篇 |
2011年 | 388篇 |
2010年 | 422篇 |
2009年 | 607篇 |
2008年 | 1097篇 |
2007年 | 1995篇 |
2006年 | 1779篇 |
2005年 | 909篇 |
2004年 | 425篇 |
2003年 | 322篇 |
2002年 | 305篇 |
2001年 | 202篇 |
2000年 | 233篇 |
1999年 | 158篇 |
1998年 | 165篇 |
1997年 | 135篇 |
1996年 | 130篇 |
1995年 | 93篇 |
1994年 | 67篇 |
1993年 | 108篇 |
1992年 | 108篇 |
1991年 | 17篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
91.
92.
93.
提出的门户环境下的缓存模型和算法的基本思想是把门户页面分解为I序列、布局块和内容块.用户请求页面时,门户系统只生成和传递发生改变的块,再由客户端根据这些块和I序列组装成完整的页面.实验结果表明,该算法可以提高网络带宽的利用率,缩短响应时间. 相似文献
94.
95.
Linux下互斥机制及其分析 总被引:6,自引:0,他引:6
详细介绍了在Linux环境下,特别是内核态下可能遇到的各种互斥场景,依据代码执行路径对其进行了分类。在此基础上,比较了各种互斥问题的解决方案的使用环境、优缺点以及使用时要注意的问题。 相似文献
96.
Aiming at the complex and restrictive characteristics of human resource allocation in multiple scientific university research projects, an improved pigeon-inspired optimization(IPIO) algorithm is proposed wherein loss minimization and the shortest project delay time are considered as optimization goals. Firstly, mathematical modelling of the problem is carried out, and the multi-objective optimization problem is transformed into a single-objective optimization problem by means of a weighted solution. In the second step, the traditional pigeon-inspired optimization(PIO) algorithm is discretized, and an adaptive parameter strategy is adopted to improve the shortcomings of the algorithm itself. Finally, by comparing the simulation results with the original algorithm and the genetic algorithm in the optimization of human resource allocation in multiple projects, the feasibility and superiority of the proposed algorithm in the optimization of human resource allocation in multi-scientific research projects is verified. 相似文献
97.
Preparation of ceramic coatings on inner surface of steel tubes using a combined technique of hot-dipping and plasma electrolytic oxidation 总被引:2,自引:0,他引:2
Wei-Chao Gu Guo-Hua Lv Huan Chen Guang-Liang Chen Wen-Ran Feng Gu-Ling Zhang Si-Ze Yang 《Journal of Alloys and Compounds》2007,430(1-2):308-312
A new method for inner surface modification of steel tubes, named a combined technique of hot-dipping and plasma electrolytic oxidation (PEO) was proposed and demonstrated in this paper. In this work, metallurgically bonded ceramic coatings on inner surface of steel tubes were obtained using this method. In the combined process, aluminum coatings on steel were firstly prepared by the hot-dip process and then metallurgically bonded ceramic coatings were obtained on the aluminum coatings by PEO. The element distribution, phase composition and morphology of the aluminide layer and the ceramic coatings were characterized by SEM/EDX and XRD. The corrosion resistance of the ceramic coatings were also studied. The results show that, after hot-dip treatment, the coating layers consist of two layers, where Al, FexAl (1−x) were detected from external topcoat to the aluminide/steel substrate. Then after PEO process, uniform Al2O3 ceramic coatings have been deposited on inner surface of steel tubes. The ceramic coatings are mainly composed of -Al2O3 and γ-Al2O3 phase. The compound coatings show favorable corrosion resistance property. The investigations indicate that the combination of hot-dipping and plasma electrolytic oxidation proves a promising technique for inner surface modification of steel tubes for protective purposes. 相似文献
98.
The characterization of La
x
Sr1−x
MnO3 powders produced by spray pyrolysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation,
specific surface area (Brunauer-Emett-Teller), and particle size distribution measurements shows that the resultant large
particles are loose agglomerates consisting of many small particles. However, the sintered tiny particles can form hard agglomerates,
and the particle size increases remarkably. The structures of the powders before and after sintering were identified by x-ray
diffraction (XRD). The study of the electrical property of the powder shows that the powder is a metallic conductor. In a
reducing atmosphere, the powder can be decomposed. When the powder is cofired with yttria-stabilized zirconia 5% (YSZ) powder
at 1200 °C for 5 h, no new phase is produced, and the powder remains a single provskite hexagonal-rhombohedral structure. 相似文献
99.
100.
X.G.Cao J.L.Huang E.Sukedai Y.G.Wang W.Z.Chen S.X.Zhou Henan University of Science Technology Luoyang China Okayama University of Science Okayama Japan Beijing Laboratory of Electron Microscope The Chinese Academy of Sciences Beij 《金属学报(英文版)》2002,15(4):363-368
Rapidly quenching embrittlement (RQE) sometimes appears in Fe73.5Cu1Nb3Si13.5B9 nanocrystalline soft magnetic alloy (FINEMET) during production process. As a re-sult of RQE the ductility of the as-quenched ribbon drops seriously. The mechanism of RQE has been elucidated in the recent works of current authors. It was believed that RQE is due to the structural relaxation but not related to a-Fe(Si) crystallization. In this paper, the high resolution TEM (HRTEM) method and image digital processing were applied to analyze the HRTEM images of two FINEMET rapidly quenched ribbons with different thicknesses in detail. In the thinner ductile sample, the ordering domains with the size of about 3nm are observed. In the thicker RQE sample, the metastable nanocrystalline domains with the size of 18nm are observed along with the structural relaxation. These domains seem to have Fe3B-like metastable phase struc-ture on nanometer scale. The result indicates that the local atomic ordering regions extend when RQE induced 相似文献