全文获取类型
收费全文 | 60226篇 |
免费 | 6657篇 |
国内免费 | 4404篇 |
专业分类
电工技术 | 5010篇 |
综合类 | 5089篇 |
化学工业 | 8008篇 |
金属工艺 | 4149篇 |
机械仪表 | 4115篇 |
建筑科学 | 4132篇 |
矿业工程 | 2200篇 |
能源动力 | 1803篇 |
轻工业 | 5955篇 |
水利工程 | 1655篇 |
石油天然气 | 2356篇 |
武器工业 | 694篇 |
无线电 | 6790篇 |
一般工业技术 | 6704篇 |
冶金工业 | 2906篇 |
原子能技术 | 1132篇 |
自动化技术 | 8589篇 |
出版年
2024年 | 375篇 |
2023年 | 1133篇 |
2022年 | 2279篇 |
2021年 | 3073篇 |
2020年 | 2253篇 |
2019年 | 1662篇 |
2018年 | 1908篇 |
2017年 | 1998篇 |
2016年 | 1863篇 |
2015年 | 2628篇 |
2014年 | 3166篇 |
2013年 | 3970篇 |
2012年 | 4665篇 |
2011年 | 4881篇 |
2010年 | 4507篇 |
2009年 | 4423篇 |
2008年 | 4319篇 |
2007年 | 4143篇 |
2006年 | 3674篇 |
2005年 | 3085篇 |
2004年 | 2330篇 |
2003年 | 1649篇 |
2002年 | 1465篇 |
2001年 | 1322篇 |
2000年 | 1115篇 |
1999年 | 703篇 |
1998年 | 511篇 |
1997年 | 391篇 |
1996年 | 360篇 |
1995年 | 301篇 |
1994年 | 242篇 |
1993年 | 157篇 |
1992年 | 134篇 |
1991年 | 98篇 |
1990年 | 91篇 |
1989年 | 78篇 |
1988年 | 46篇 |
1987年 | 53篇 |
1986年 | 50篇 |
1985年 | 27篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 10篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 11篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1959年 | 9篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
LiFePO4 is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO4 because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe2+ in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO4 is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO4 fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property. 相似文献
14.
A practical resource management method that can significantly reduce cochannel interference (CCI) and improve spectrum utilisation in FH-OFDMA packet-based cellular networks is presented. The proposed method seeks an effective combination of dynamic resource allocation with fractional coding and bit loading to respectively minimise CCI and maximise system throughput for a desired performance. 相似文献
15.
Preparation of Plate Fe_(60)Co_8Zr_(10)Mo_5W_2B_(15) Bulk Amorphous Alloy and Its Fracture Toughness
肖华星 《武汉理工大学学报(材料科学英文版)》2005,20(2)
1Introduction Duwez[1]synthesizedthefoilAu Siamorphousalloyforthefirsttimewithrapidsolidification,whichinitiatedthepreparationofamorphousalloysintheprocessofalloysolidification,andthereaftertheresearchonamorphousal loysdevelopedrapidly.Since1980s,withthec… 相似文献
16.
Injun Lee Taeseong Jung Junggi Kim Suho Ro Chulsu Kim Yeji Lee Youngmi Kim Juhyun Lee Misook Kang 《Journal of Industrial and Engineering Chemistry》2008,14(6):869-873
This study focuses on the relationship between photo-catalytic performance and optical property over Si-incorporated TiO2. The Si-incorporated TiO2 particles exhibited a pure structure of anatase having a particle size of less than 20 nm and surface area of more than 190 m2/g. The absorbance did not shift to a higher wavelength in spite of the incorporation of the Si ions, but the intensity of the photoluminescence (PL) curve was the smallest in the case of the 2.0 mol% Si-TiO2, which was related to the recombination between the excited electrons and holes. Based on these results, the photodecomposition of methyl orange in the liquid reaction was enhanced over the 2.0 mol% Si-incorporated TiO2 compared with that over pure TiO2: Methyl orange at 10.0 ppm was completely decomposed after 100 min when 1.0 g of the 2.0 mol% Si-incorporated TiO2 was used. 相似文献
17.
肖起清 《机械工业高教研究》2008,(2):34-37
大学在办学资源、办学过程、办学质量、办学形象的竞争中出现大量的不良倾向。大学的不良竞争是由于政府主导资源配置、资源和制度供给不足、大学系统重构等因素导致。必须通过控制主体、控制手段的转变和控制对象的发展形成新的控制机制,以保证大学竞争的秩序化和规范化。 相似文献
18.
自国务院<关于进一步深化城镇住房制度改革加快住房建设的通知>(国发[1998]23号)文发布以来,我国城镇住房制度改革不断向纵深推进,居民住房需求的不断提高促使居民住房观念发生重要转变,居民住房消费有效启动,住房商品化的新体制基本确立,房地产市场体系逐步建立,房地产投资持续快速增长,以住宅为主的房地产业已经成为国民经济的支柱产业.2003年,国务院就进一步推动和促进我国房地产业的持续健康发展下发了<关于促进房地产市场持续健康发展的通知>(以下简称国务院l 8号令),明确提出房地产业是关联度高、带动力强、涉及面广的国民经济支柱产业.这一重要判断对于我们认识房地产市场的现状,确定正确的方针政策,促进房地产业持续健康发展具有重要意义.国务院18号令是指导房改和房地产工作的重要文件,对于促进房地产市场持续健康发展必将产生积极作用,我国房地产将迎来新的春天. 相似文献
19.
Y.M. Wong W.P. Kang J.L. Davidson J.H. Huang D.V. Kerns 《Diamond and Related Materials》2008,17(4-5):552-555
A novel integrated vacuum field emission (VFE) differential amplifier (diff-amp) utilizing carbon nanotube (CNT) emitters has been developed. A dual-mask microfabrication process was employed to achieve a VFE diff-amp by integrating identical CNT VFE transistors with built-in split gates and integrated anodes. The identical pair of triode amplifiers was well-matched in their device characteristics. The measured ac small-signal characteristics of the diff-amp showed a common-mode-rejection ratio (CMRR) of ~ 320 (~ 50 dB). The proposed analytical model of the CMRR was verified to be in good agreement with the experimental data. The successful implementation of the CNT diff-amp demonstrates a new way to achieve temperature and radiation tolerant VFE integrated microelectronics. 相似文献
20.
The instability of solid–liquid interface (ISLI) during the liquid-phase sintering was studied using carbide–Ni composites. Of the various transitional metal carbides TiC of 4th period is the only carbide that exhibits a strong ISLI with negative curvatures in molten Ni. No ISLI was observed for other carbides in the 5th and 6th periods. The origin of ISLI is strain developed at the interface between the carbides and the newly formed solid solutions. The difference in the size of the atoms involved can be used to predict the formation of a carbide–Ni solid solution when the Hume-Rothery rules are applied. Aside from the size factor, other factors in the rules are not effective in predicting this phenomenon. 相似文献