全文获取类型
收费全文 | 15158篇 |
免费 | 1046篇 |
国内免费 | 498篇 |
专业分类
电工技术 | 670篇 |
综合类 | 687篇 |
化学工业 | 2313篇 |
金属工艺 | 696篇 |
机械仪表 | 822篇 |
建筑科学 | 907篇 |
矿业工程 | 336篇 |
能源动力 | 415篇 |
轻工业 | 756篇 |
水利工程 | 202篇 |
石油天然气 | 856篇 |
武器工业 | 72篇 |
无线电 | 1845篇 |
一般工业技术 | 1718篇 |
冶金工业 | 2536篇 |
原子能技术 | 91篇 |
自动化技术 | 1780篇 |
出版年
2024年 | 43篇 |
2023年 | 223篇 |
2022年 | 357篇 |
2021年 | 516篇 |
2020年 | 349篇 |
2019年 | 310篇 |
2018年 | 354篇 |
2017年 | 383篇 |
2016年 | 366篇 |
2015年 | 494篇 |
2014年 | 672篇 |
2013年 | 819篇 |
2012年 | 774篇 |
2011年 | 930篇 |
2010年 | 783篇 |
2009年 | 717篇 |
2008年 | 760篇 |
2007年 | 692篇 |
2006年 | 750篇 |
2005年 | 682篇 |
2004年 | 429篇 |
2003年 | 368篇 |
2002年 | 312篇 |
2001年 | 286篇 |
2000年 | 277篇 |
1999年 | 453篇 |
1998年 | 966篇 |
1997年 | 643篇 |
1996年 | 476篇 |
1995年 | 291篇 |
1994年 | 265篇 |
1993年 | 214篇 |
1992年 | 114篇 |
1991年 | 90篇 |
1990年 | 74篇 |
1989年 | 62篇 |
1988年 | 58篇 |
1987年 | 28篇 |
1986年 | 39篇 |
1985年 | 20篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 24篇 |
1981年 | 17篇 |
1980年 | 23篇 |
1979年 | 5篇 |
1977年 | 47篇 |
1976年 | 104篇 |
1975年 | 6篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation 下载免费PDF全文
2.
3.
4.
Jui-Ting Weng Jiunn Ru Lai Wanjiun Liao 《Wireless Communications, IEEE Transactions on》2006,5(7):1676-1684
In this paper, we analyze node mobility for reliable packet delivery in mobile IP networks. In mobile IP, packets destined to roaming nodes are intercepted by their home agents and delivered via tunneling to their care of addresses (CoA). A mobile node may roam across multiple subnets. At each boundary crossing, a handoff is initiated such that the CoA is updated and a new tunnel is established. We consider both basic mobile IP handoff and smooth handoff. We find that reliable packet delivery in mobile IP networks can be modeled as a renewal process, because the retransmission over a new tunnel after each boundary crossing is independent of the previous history. We then derive the probability distribution of boundary crossings for each successful packet, based on which the packet reliable delivery time can be obtained. Our analytical model is derived based on a general distribution of residence time in a subnet and a general distribution of successful retransmission attempts in each subnet. The results can be readily applied to any distributions for both items. We also provide numerical examples to calculate the probability distribution of boundary crossings, and conduct simulations to validate our analytical results 相似文献
5.
Ray-Guang Cheng Cun-Yi Wang Li-Hung Liao Jen-Shun Yang 《Communications Letters, IEEE》2006,10(2):123-125
This work presents a wireless token-passing protocol, named Ripple, for wireless mesh networks (WMNs). In contrast to existing random-access approaches, Ripple uses a decentralized controlled-access approach to protect nodes from unintentional packet collisions and maximize the spatial reuse. The performance of Ripple under an error-free wireless channel was investigated and the accuracy of the analysis was verified by simulation. Simulation results also indicated that Ripple achieved throughput, stability, and QoS enhancement than that of 802.11 DCF under a highly loaded situation. 相似文献
6.
7.
8.
BACKGROUND: The enterococci have become important nosocomial pathogens. They can cause multiple site infections and enterococcal bacteremia becomes more frequently associated with a high mortality rate. Previous studies of enterococcal bacteremia showed a variety of results. To establish the significance and importance of enterococci as nosocomial pathogens in this hospital, to characterize their clinical pictures and to search for the risk factors for mortality, this retrospective study was performed. METHODS: There were 208 cases of enterococcal bacteremia which occurred from 1988 to 1992. Twenty-seven cases had no medical charts, dismissing possibility of evaluation. Finally, 181 cases of enterococcal bacteremia were analysed. RESULTS: One hundred and eighteen episodes were nosocomial infections. Polymicrobial bacteremia occurred in 68.5% of the patients and the most common co-isolate was Pseudomonas aeruginosa. Those patients (78.5%) with underlying diseases and malignancies were the most common underlying problems. The portal of entry could be found in 69.6 percent of patients, with the gastrointestinal tract the most common sources. Antimicrobial susceptibility testing showed high gentamicin resistance rate (89.5%), and ampicillin still had about 80 percent sensitivity rate. The group who received specific antibiotic therapy for enterococcus showed lower mortality (36.4% versus 47.6%). Only one case had infective endocarditis. Forty-nine patients suffered from septic shock, the cause of 30 deaths. Totally 75 patients died during hospitalization. Besides sepsis, another major cause of death was their underlying diseases itself. CONCLUSIONS: Enterococci have no doubt become important nosocomial pathogens and enterococcal bacteremia were associated with high mortality, especially in elderly patients with underlying diseases such as malignancy or diabetes. When clinically dealing with sepsis from the gastrointestinal or biliary tract, especially when previous cephalosporins therapy showed no response, the possibility of enterococcal bacteremia should always be considered. 相似文献
9.
10.
1960-1970年那段时间被称为立体声的黄金岁月 ,那时要调试并建立一套立体声系统是非常简单的,整个系统只包括一对音箱,一个功放(纯A/V功放或附带收音功能)或纯粹的无线电接收器以及诸如唱片机这类型的音源即可,而设置过程更是简单,只需要连接很少的几根线,再将扬声器放到一个合适的位置就可以了。[编者按] 相似文献