全文获取类型
收费全文 | 3594篇 |
免费 | 188篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 57篇 |
综合类 | 7篇 |
化学工业 | 839篇 |
金属工艺 | 56篇 |
机械仪表 | 66篇 |
建筑科学 | 102篇 |
矿业工程 | 21篇 |
能源动力 | 111篇 |
轻工业 | 295篇 |
水利工程 | 26篇 |
石油天然气 | 20篇 |
无线电 | 376篇 |
一般工业技术 | 704篇 |
冶金工业 | 369篇 |
原子能技术 | 37篇 |
自动化技术 | 703篇 |
出版年
2023年 | 32篇 |
2022年 | 91篇 |
2021年 | 139篇 |
2020年 | 82篇 |
2019年 | 98篇 |
2018年 | 106篇 |
2017年 | 95篇 |
2016年 | 131篇 |
2015年 | 90篇 |
2014年 | 143篇 |
2013年 | 237篇 |
2012年 | 193篇 |
2011年 | 241篇 |
2010年 | 169篇 |
2009年 | 150篇 |
2008年 | 149篇 |
2007年 | 156篇 |
2006年 | 143篇 |
2005年 | 117篇 |
2004年 | 108篇 |
2003年 | 103篇 |
2002年 | 93篇 |
2001年 | 54篇 |
2000年 | 54篇 |
1999年 | 60篇 |
1998年 | 69篇 |
1997年 | 58篇 |
1996年 | 51篇 |
1995年 | 42篇 |
1994年 | 29篇 |
1993年 | 38篇 |
1992年 | 27篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 23篇 |
1986年 | 16篇 |
1985年 | 25篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 23篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1973年 | 13篇 |
排序方式: 共有3789条查询结果,搜索用时 15 毫秒
31.
BACKGROUND: The matrix metalloproteinases (MMPs) MMP2 and MMP9 play a significant role in epidermal detachment, inflammation and re-epithelialization. We have evaluated their activity in toxic epidermal necrolysis (TEN). DESIGN: The level and pattern of activity of MMP2 and MMP9 were investigated by measuring the degradation of 3H-labelled gelatin and by zymography in blister fluid from six TEN patients and compared the results with three other blistering conditions: bullous pemphigoid (n = 6), second-degree burn (n = 13) or suction blister (n = 3). RESULTS: A higher amount of MMP2 was found in TEN blister fluid with the constant presence of a significantly larger proportion of the activated forms of MMP2, a particular feature of TEN, than the other blistering diseases studied. CONCLUSION: This study emphasizes the potential role of MMP2 in the specific inflammatory reaction and reparation process in TEN skin. 相似文献
32.
33.
Matthew N. Ashby Patrick R. Errada Victor L. Boyartchuk Jasper Rine 《Yeast (Chichester, England)》1993,9(8):907-913
We isolated a mutant defective in C-terminal farnesyl cysteine:carboxyl methyltransferase activity from a screen for mutations causing a -specific sterility. A genomic fragment was cloned from a yeast multi-copy library that restored mating. Both the cloned gene and the sterile mutation were allelic to the STE14 gene. A ste14-complementing 2·17 kb BamHI fragment subclone was sequenced and found to encode a 239 amino acid protein with a molecular weight of 27,887 Daltons. The hydrophobicity profile of the methyltransferase reveals the presence of at least five potential transmembrane domains. In comparisons of the C-terminal methyltransferase amino acid sequence with those in the PIR and Swiss protein databases, no significantly similar sequences were found nor were conserved regions from other methyltransferases present. 相似文献
34.
This paper describes the development of a conceptual model of an interaction system for future human-computer interaction. It is suggested that an integrated system is the most promising solution for diverse users and tasks. A ' hybrid interaction system' is considered, which tries to efficiently direct manipulation, menu selection, and natural language. The mechanism of the natural language interface module is described in more detail. Finally, the allocation of functionalities for generalized tasks on the conceptual model is considered from the taxonomic approach. 相似文献
35.
Woodward William R.; Benassi Victor A.; Knoth Russell 《Canadian Metallurgical Quarterly》1993,48(1):53
Commemorates G. M. Haslerud, who died suddenly on April 10, 1990. In his doctoral dissertation (1934) he addressed free and prescribed maze patterns in rats, pointing to a lifetime interest in creative transfer. In 1972 he completed his magnum opus, Transfer, Memory, and Creativity: After-Learning as Perceptual Process, which reflects continuing conversations with his mentor, Robert Yerkes. Haslerud is remembered as a co-founder of the New Hampshire Psychological Association. (0 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
Dynamic Reservation Multiple Access (DRMA): A new multiple access scheme for Personal Communication System (PCS) 总被引:2,自引:0,他引:2
To improve the spectrum efficiency of integrated voice and data services in Personal Communication System (PCS), several reservation-type multiple access schemes, such as Packet Reservation Multiple Access (PRMA), Dynamic Time Division Multiple Access (D-TDMA), Resource Auction Multiple Access (RAMA), etc., have been proposed. PRMA uses the data packet itself to make a channel reservation, and is inefficient in that each unsuccessful reservation wastes one slot. However, it does not have a fixed reservation overhead and offers shorter access delay. On the other hand, fixed reservation overhead is unavoidable in both RAMA and D-TDMA. Compared to D-TDMA and PRMA, RAMA is superior in the sense that its slot assignment is independent of the traffic load. But its implementation is difficult. With these observations, a new reservation protocol, called Dynamic Reservation Multiple Access (DRMA), is proposed in this paper. With this new protocol, the success probability of channel access is greatly improved at the expense of slightly increased system complexity. It solves the problem of inefficiency in PRMA, but without introducing the fixed reservation overhead as in D-TDMA and RAMA. In addition, it is more suited to the dynamic behavior of the integrated traffic because there is no fixed boundary between voice and data slots (which is mandatory in D-TDMA and RAMA). Our numerical results indicate that its performance is superior to the existing reservation protocols, especially in the integrated traffic scenario. Moreover, the soft capacity feature is exhibited when the traffic load increases. 相似文献
37.
An integrated approach of the design and optimization problem of reinforced concrete frames, based on the use of interactive computer graphics is presented. The formulation of the optimization problem in terms of all the design variables and constraints is given. The size of the problem is greatly reduced if reinforcement areas are considered as dependent variables. A fully stressed design method is employed to optimize an automatically generated initial design. Analysis and design results plots, including complete reinforcement drawings, are available to designers, helping them to evaluate the current status of the design and allowing them to direct the entire computation process. 相似文献
38.
39.
This paper surveys recent research in deliberative real-time artificial intelligence (AI). Major areas of study have beenanytime algorithms, approximate processing, and large system architectures. We describe several systems in each of these areas, focusing both on progress within the field, and the costs, benefits and interactions among different problem and algorithm complexity limitations used in the surveyed work. 相似文献
40.
Paulo Victor Rodrigues de Carvalho Tahar‐Hakim Benchekroun Jose Orlando Gomes 《人机工程学与制造业中的人性因素》2012,22(2):130-144
Shift work situations occur in almost all safety‐critical organizations, and the investigations of some catastrophes like Chernobyl, Exxon Valdez, and the Gol/Legacy mid‐air collision indicated that shift work information exchange played an important role during the evolution of the situation before the accidents. Inadequate communications during shift changeovers challenged operators' work in the moments that preceded these accidents, because they got inadequate information about the current situation. Our research focuses on the information exchange activities (verbal, written, and nonverbal) of nuclear power plant control operators during shift changeovers. Our aim is to investigate how verbal exchanges and other representations enable operator crews to share information regarding the events that occurred in the previous shift to achieve adequate situation awareness. Our findings indicated the importance and richness of the information exchange during the shift changeover process to update and validate individual and collective situation awareness, showing that information adequately shared enables the ad hoc configurations of regulation loops and a safer use of simplified strategies that can be understood and be validated by other operators, reducing the occurrence of cognitive overloads and contributing to the construction of a common cognitive ground that enhances system resilience. © 2010 Wiley Periodicals, Inc. 相似文献