全文获取类型
收费全文 | 8133篇 |
免费 | 403篇 |
国内免费 | 205篇 |
专业分类
电工技术 | 835篇 |
综合类 | 428篇 |
化学工业 | 555篇 |
金属工艺 | 423篇 |
机械仪表 | 779篇 |
建筑科学 | 216篇 |
矿业工程 | 151篇 |
能源动力 | 147篇 |
轻工业 | 254篇 |
水利工程 | 22篇 |
石油天然气 | 82篇 |
武器工业 | 87篇 |
无线电 | 1518篇 |
一般工业技术 | 672篇 |
冶金工业 | 238篇 |
原子能技术 | 276篇 |
自动化技术 | 2058篇 |
出版年
2024年 | 11篇 |
2023年 | 32篇 |
2022年 | 90篇 |
2021年 | 105篇 |
2020年 | 102篇 |
2019年 | 79篇 |
2018年 | 74篇 |
2017年 | 166篇 |
2016年 | 198篇 |
2015年 | 302篇 |
2014年 | 533篇 |
2013年 | 455篇 |
2012年 | 600篇 |
2011年 | 859篇 |
2010年 | 722篇 |
2009年 | 853篇 |
2008年 | 653篇 |
2007年 | 596篇 |
2006年 | 579篇 |
2005年 | 409篇 |
2004年 | 262篇 |
2003年 | 238篇 |
2002年 | 172篇 |
2001年 | 129篇 |
2000年 | 88篇 |
1999年 | 85篇 |
1998年 | 59篇 |
1997年 | 43篇 |
1996年 | 47篇 |
1995年 | 34篇 |
1994年 | 27篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1974年 | 3篇 |
1968年 | 2篇 |
1960年 | 2篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有8741条查询结果,搜索用时 31 毫秒
1.
In the first critical assessment of knowledge economy dynamic paths in Africa and the Middle East, but for a few exceptions, we find overwhelming support for diminishing cross-country disparities in knowledge-based economy dimensions. The paper employs all the four components of the World Bank's Knowledge Economy Index (KEI): economic incentives, innovation, education, and information infrastructure. The main finding suggests that sub-Saharan African (SSA) and the Middle East and North African (MENA) countries with low levels of KE dynamics and catching-up their counterparts of higher KE levels. We provide the speeds of integration and time necessary to achieve full (100%) integration. Policy implications are also discussed. 相似文献
2.
《Intermetallics》2015
An equiatomic CoCrFeNiMn high-entropy alloy was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). During MA, a solid solution with refined microstructure of 10 nm which consists of a FCC phase and a BCC phase was formed. After SPS consolidation, only one FCC phase can be detected in the HEA bulks. The as-sintered bulks exhibit high compressive strength of 1987 MPa. An interesting magnetic transition associated with the structure coarsening and phase transformation was observed during SPS process. 相似文献
3.
Mitsuo Miyazawa Hideki Kawazoe Mitsuro Hyakumachi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(6):620-625
The microbial transformation of l‐menthol ( 1 ) was investigated by using 12 isolates of soil‐borne plant pathogenic fungi, Rhizoctonia solani (AG‐1‐IA Rs24, Joichi‐2, RRG97‐1; AG‐1‐IB TR22, R147, 110.4; AG‐1‐IC F‐1, F‐4, P‐1; AG‐1‐ID RCP‐1, RCP‐3, and RCP‐7) as a biocatalyst. Rhizoctonia solani F‐1, F‐4 and P‐1 showed 89.7–99.9% yields of converted product from 1 , RCP‐1, RCP‐3, and RCP‐7 26.0–26.9% and the other isolates 0.1–12.0%. In the cases of F‐1, F‐4 and P‐1, substrate 1 was converted to (?)‐(1S,3R,4S,6S)‐6‐hydroxymenthol ( 2 ), (?)‐(1S,3R,4S)‐1‐hydroxymenthol ( 3 ) and (+)‐(1S,3R,4R,6S)‐6,8‐dihydroxymenthol ( 4 ), which was a new compound. Substrate 1 was converted to 2 and/or 3 by RRG97‐1, 110.4, RCP‐1, RCP‐3 and RCP‐7. The structures of the metabolic products were elucidated on the basis of their spectral data. In addition, metabolic pathways of the biotransformation of 1 by Rhizoctonia solani are discussed. Finally, from the main component analysis and the differences in the yields of converted product from 1 , the 12 isolates of Rhizoctonia solani were divided into three groups based on an analysis of the metabolites. Copyright © 2003 Society of Chemical Industry 相似文献
4.
The present paper includes experimental and analytical data on the fracture properties of a nickel-iron superalloy, a ferromagnetic austenite, at 4 K in magnetic fields of 0 and 6 T. The tensile, notch tensile and small punch tests are employed. A finite element analysis is also performed to convert the experimentally measured load-displacement data into useful engineering information. To interpret the results we review the available theory of the influence of magnetic field on the stress intensity factor for a crack in ferromagnetic materials. 相似文献
5.
6.
7.
泥化软化性F_5断层是故县大坝坝基范围内最大的一条断层,位于左岸,对左坝肩的稳定极为不利,采用水泥灌浆处理无效,故改用化学灌浆处理。选用EAA化学浆材,采用“优选组合配方综合施灌”的创新施工工艺,效果良好,为今后低渗透性复杂的泥化软化性断层的防渗加固处理,提供了新的依据和途径。 相似文献
8.
9.
10.