全文获取类型
收费全文 | 84871篇 |
免费 | 9625篇 |
国内免费 | 5357篇 |
专业分类
电工技术 | 6407篇 |
技术理论 | 5篇 |
综合类 | 7089篇 |
化学工业 | 13117篇 |
金属工艺 | 4948篇 |
机械仪表 | 5436篇 |
建筑科学 | 6688篇 |
矿业工程 | 2539篇 |
能源动力 | 2690篇 |
轻工业 | 8296篇 |
水利工程 | 1985篇 |
石油天然气 | 3921篇 |
武器工业 | 898篇 |
无线电 | 10049篇 |
一般工业技术 | 8942篇 |
冶金工业 | 3110篇 |
原子能技术 | 888篇 |
自动化技术 | 12845篇 |
出版年
2024年 | 611篇 |
2023年 | 1979篇 |
2022年 | 3734篇 |
2021年 | 4772篇 |
2020年 | 3371篇 |
2019年 | 2780篇 |
2018年 | 2975篇 |
2017年 | 3095篇 |
2016年 | 2878篇 |
2015年 | 4017篇 |
2014年 | 4794篇 |
2013年 | 5247篇 |
2012年 | 6219篇 |
2011年 | 6532篇 |
2010年 | 5607篇 |
2009年 | 5395篇 |
2008年 | 5147篇 |
2007年 | 4788篇 |
2006年 | 4303篇 |
2005年 | 3590篇 |
2004年 | 2694篇 |
2003年 | 2599篇 |
2002年 | 2950篇 |
2001年 | 2506篇 |
2000年 | 1655篇 |
1999年 | 1291篇 |
1998年 | 776篇 |
1997年 | 701篇 |
1996年 | 607篇 |
1995年 | 516篇 |
1994年 | 376篇 |
1993年 | 301篇 |
1992年 | 245篇 |
1991年 | 170篇 |
1990年 | 124篇 |
1989年 | 92篇 |
1988年 | 88篇 |
1987年 | 69篇 |
1986年 | 59篇 |
1985年 | 27篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 31篇 |
1981年 | 17篇 |
1980年 | 33篇 |
1979年 | 18篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1959年 | 4篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
3.
在役超高压水晶釜主要检测方法 总被引:1,自引:0,他引:1
介绍了在役超高压水晶釜的常见缺陷以及应用超声波探伤、磁粉探伤、金相分析等无损检测方法对其进行在役检验的要点. 相似文献
4.
Yu‐Qing Cao Zhan Zhang Yan‐Xin Guo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1441-1444
A new efficient method for synthesising nitriles, important organic reagents, is reported in this paper. In an environmentally benign solvent‐free system, aryl carboxylic acids were converted into the corresponding nitriles via one‐pot reactions, by amidation with ethyl carbamate followed by dehydration with thionyl chloride, in excellent yields. The results showed that the method has the advantages of lower cost, higher yield, less pollution and greater ease of work‐up. Copyright © 2008 Society of Chemical Industry 相似文献
5.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
6.
憎水性栀子蓝色素制备的研究 总被引:1,自引:0,他引:1
以浓盐酸为催化剂,采用乙酸酐酯化处理水溶性栀子蓝色素,制备了憎水性栀子蓝色素.探讨了栀子蓝色素与乙酸酐料液比、反应时间和反应温度等因素对憎水性栀子蓝色素色价的影响.结果表明:采用料液比1:20,在常温下反应4 h,为制备憎水性栀子蓝色素的最优条件.同时,通过红外光谱、可见吸收光谱及溶解性对栀子蓝色素的酯化改性进行了初步的探讨. 相似文献
7.
Xin Sun Qiang Lu Moroz V. Takeuchi H. Gebara G. Wetzel J. Shuji Ikeda Changhwan Shin Tsu-Jae King Liu 《Electron Device Letters, IEEE》2008,29(5):491-493
A tri-gate bulk MOSFET design utilizing a low-aspect-ratio channel is proposed to provide an evolutionary pathway for CMOS scaling to the end of the roadmap. 3-D device simulations indicate that this design offers the advantages of a multi-gate FET (reduced variability in performance and improved scalability) together with the advantages of a conventional planar MOSFET (low substrate cost and capability for dynamic threshold-voltage control). 相似文献
8.
9.
Evolving artificial neural network ensembles 总被引:3,自引:0,他引:3
Using a coordinated group of simple solvers to tackle a complex problem is not an entirely new idea. Its root could be traced back hundreds of years ago when ancient Chinese suggested a team approach to problem solving. For a long time, engineers have used the divide-and-conquer strategy to decompose a complex problem into simpler sub-problems and then solve them by a group of solvers. However, knowing the best way to divide a complex problem into simpler ones relies heavily on the available domain knowledge. It is often a manual process by an experienced engineer. There have been few automatic divide-and-conquer methods reported in the literature. Fortunately, evolutionary computation provides some of the interesting avenues to automatic divide-and-conquer methods. An in-depth study of such methods reveals that there is a deep underlying connection between evolutionary computation and ANN ensembles. Ideas in one area can be usefully transferred into another in producing effective algorithms. For example, using speciation to create and maintain diversity had inspired the development of negative correlation learning for ANN ensembles, and an in-depth study of diversity in ensembles. This paper will review some of the recent work in evolutionary approaches to designing ANN ensembles. 相似文献
10.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献