全文获取类型
收费全文 | 2838篇 |
免费 | 256篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 51篇 |
综合类 | 2篇 |
化学工业 | 611篇 |
金属工艺 | 59篇 |
机械仪表 | 189篇 |
建筑科学 | 100篇 |
能源动力 | 130篇 |
轻工业 | 138篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 550篇 |
一般工业技术 | 597篇 |
冶金工业 | 260篇 |
原子能技术 | 25篇 |
自动化技术 | 378篇 |
出版年
2023年 | 27篇 |
2022年 | 50篇 |
2021年 | 84篇 |
2020年 | 57篇 |
2019年 | 84篇 |
2018年 | 83篇 |
2017年 | 94篇 |
2016年 | 135篇 |
2015年 | 98篇 |
2014年 | 125篇 |
2013年 | 185篇 |
2012年 | 185篇 |
2011年 | 231篇 |
2010年 | 171篇 |
2009年 | 131篇 |
2008年 | 139篇 |
2007年 | 146篇 |
2006年 | 103篇 |
2005年 | 94篇 |
2004年 | 85篇 |
2003年 | 94篇 |
2002年 | 82篇 |
2001年 | 62篇 |
2000年 | 72篇 |
1999年 | 45篇 |
1998年 | 99篇 |
1997年 | 53篇 |
1996年 | 46篇 |
1995年 | 38篇 |
1994年 | 21篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有3098条查询结果,搜索用时 31 毫秒
991.
Cell level analysis of ATM networks by means of simulation requires an accurate model for traffic sources. We present a simple model for TCP over ATM traffic sources in an ATM LAN, which captures the fundamental characteristics of the behaviour of tcp in this environment. The model was developed by extensive statistical analysis of numerous traffic traces recorded in an atm testbed. Simulated traffic generated by our model has roughly the same properties as observed in real traffic, even on the time scale of milliseconds. This makes it suitable for use by the analysis of various scheduling and congestion management algorithms. 相似文献
992.
Tam S. Rusu S. Nagarji Desai U. Kim R. Ji Zhang Young I. 《Solid-State Circuits, IEEE Journal of》2000,35(11):1545-1552
The clock design for the first implementation of the IA-64 microprocessor is presented. A clock distribution with an active distributed deskewing technique is used to achieve a low skew of 28 ps. This technique is capable of compensating skews caused by within-die process variations that are becoming a significant factor of the clock design. The global, regional and local clock distributions are described. A multilevel skew budget and local clock timing methodology are used to enable a high-performance design by providing support for intentional clock skew injection and time borrowing. By providing a test access port interface to the deskew architecture and the incorporation of the on-die-clock-shrink, this design is equipped with two very powerful post-silicon timing debug tools that are critical to high-performance microprocessor design and enabled quick time-to-market 相似文献
993.
Zhongding Lei Teng Joon Lim 《Communications, IEEE Transactions on》2000,48(6):1022-1028
An algorithm is proposed for estimating the directions of arrival (DOAs) of multipath signals received from multiple users on the uplink of a code-division multiple-access system. The correlation matrices of the received signal before and after code-matched filtering are used to provide unique estimates even when the number of required DOAs exceeds the number of antenna array elements. This scenario is well known to cause conventional direction-finding algorithms (such as MUSIC) to fail. Both intersymbol interference (ISI) and multiple-access interference (MAI) are modeled exactly, and so the algorithm performs much better than those which model ISI and MAI as Gaussian noise 相似文献
994.
Sang Bin Jeong Ki Joon Heo Hyun Sik Ko Jae Pyoung Ahn Seung-Bok Lee Jae Hee Jung 《Indoor air》2021,31(4):1134-1143
After the WHO designated COVID-19 a global pandemic, face masks have become a precious commodity worldwide. However, uncertainty remains around several details regarding face masks, including the potential for transmission of bioaerosols depending on the type of mask and secondary spread by face masks. Thus, understanding the interplay between face mask structure and harmful bioaerosols is essential for protecting public health. Here, we evaluated the microbial survival rate at each layer of commercial of filtering facepiece respirators (FFRs) and surgical masks (SMs) using bacterial bioaerosols. The penetration efficiency of bacterial particles for FFRs was lower than that for SMs; however, the microbial survival rate for all tested masks was >13%, regardless of filtration performance. Most bacterial particles survived in the filter layer (44%–77%) (e.g., the core filtering layer); the outer layer also exhibited significant survival rates (18%–29%). Most notably, survival rates were determined for the inner layers (<1% for FFRs, 3%–16% for SMs), which are in contact with the respiratory tract. Our comparisons of the permeability and survival rate of bioaerosols in each layer will contribute to bioaerosol-face mask research, while also providing information to facilitate the establishment of a mask-reuse protocol. 相似文献
995.
In recent years, mobile devices and social network games (SNGs) have gained wide popularity among the mainstream users. The present study aims to investigate the psychological elements that may contribute to user behaviors regarding mobile-social network games (M-SNGs). This study introduces an integrated model for M-SNGs. Statistical results from an online survey of players of M-SNGs indicate that the proposed research model effectively demonstrates and examines player acceptance of and attitudes toward M-SNGs. This research model is valid, and illustrates not only perceived enjoyment and usefulness as determinant variables of intention to use among players, but also perceived mobility together with perceived control and skill as motivational factors for players. The results also describe that satisfaction has a moderate role, which in turn has significant effects on multiple connections in the research model. Both theoretical and practical implications are provided based on the findings. 相似文献
996.
997.
998.
999.
1000.
Byung Joon Lim Bryce E. Ackermann Dr. Galia T. Debelouchina 《Chembiochem : a European journal of chemical biology》2020,21(9):1315-1319
Dynamic nuclear polarization (DNP) has shown great promise as a tool to enhance the nuclear magnetic resonance signals of proteins in the cellular environment. As sensitivity increases, the ability to select and efficiently polarize a specific macromolecule over the cellular background has become desirable. Herein, we address this need and present a tetrazine-based DNP agent that can be targeted selectively to proteins containing the unnatural amino acid (UAA) norbornene-lysine. This UAA can be introduced efficiently into the cellular milieu by genetic means. Our approach is bio-orthogonal and easily adaptable to any protein of interest. We illustrate the scope of our methodology and investigate the DNP transfer mechanisms in several biological systems. Our results shed light on the complex polarization-transfer pathways in targeted DNP and ultimately pave the way to selective DNP-enhanced NMR spectroscopy in both bacterial and mammalian cells. 相似文献