全文获取类型
收费全文 | 6898篇 |
免费 | 340篇 |
国内免费 | 169篇 |
专业分类
电工技术 | 692篇 |
综合类 | 357篇 |
化学工业 | 527篇 |
金属工艺 | 380篇 |
机械仪表 | 626篇 |
建筑科学 | 205篇 |
矿业工程 | 120篇 |
能源动力 | 134篇 |
轻工业 | 236篇 |
水利工程 | 21篇 |
石油天然气 | 77篇 |
武器工业 | 75篇 |
无线电 | 1195篇 |
一般工业技术 | 620篇 |
冶金工业 | 198篇 |
原子能技术 | 258篇 |
自动化技术 | 1686篇 |
出版年
2024年 | 9篇 |
2023年 | 32篇 |
2022年 | 79篇 |
2021年 | 96篇 |
2020年 | 91篇 |
2019年 | 65篇 |
2018年 | 64篇 |
2017年 | 145篇 |
2016年 | 172篇 |
2015年 | 243篇 |
2014年 | 441篇 |
2013年 | 378篇 |
2012年 | 484篇 |
2011年 | 731篇 |
2010年 | 609篇 |
2009年 | 701篇 |
2008年 | 538篇 |
2007年 | 495篇 |
2006年 | 479篇 |
2005年 | 364篇 |
2004年 | 226篇 |
2003年 | 202篇 |
2002年 | 153篇 |
2001年 | 124篇 |
2000年 | 86篇 |
1999年 | 82篇 |
1998年 | 52篇 |
1997年 | 41篇 |
1996年 | 43篇 |
1995年 | 32篇 |
1994年 | 25篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5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7407条查询结果,搜索用时 15 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.
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
7.
8.
针对温室内的温湿度过程控制中参数人工设定的困难和参数自设定的必要性,提出了一种新颖的基于经验数据的适用于温室内的温湿度过程控制系统.该系统硬件采用新型的数字式温湿度一体化传感器LTM8901.温湿度过程控制系统采用具有大容量Flash存储器的C8051F023微控制器,它可在1年时间内以小时为单位设定经验温湿度值,用于控制并记录实测值,实现在1年时间内完全自动控制,无须操作人员干预.具有数据可靠、安装简单、使用和维修方便的特点. 相似文献
9.
Suzana Corte Real Maria de Nazareth Leal de Meirelles 《Microscopy research and technique》1991,18(2):192-196
Immunocytochemistry was used to investigate the localization of F1 ATPase in mitochondria of cryosections of adult mouse heart muscle cells. The initial aldehyde fixation was the only denaturation step for antigens. The fine structure was preserved with contrast enhancement as the sections were maintained hydrated, with the advantage that the entire procedure is completed in one working day. The reaction was highly specific, and entire mitochondria were labeled with the Protein A-gold complex. A new analytical technique, electron spectroscopic imaging (ESI), contributed to a better visualization of the localization of the F1 factor. 相似文献
10.
SD2300是兴威帆电子公司生产的一种新型高精度实时时钟芯片。TMS320F2812是TI公司最新推出的DSP芯片,该芯片广泛地运用于测控和控制场合。文中给出了基于SD2300和TMS320F2812的时钟输入、低功耗“软件时间锁”的硬件和软件设计方法。 相似文献