全文获取类型
收费全文 | 632133篇 |
免费 | 25609篇 |
国内免费 | 12530篇 |
专业分类
电工技术 | 22086篇 |
技术理论 | 31篇 |
综合类 | 17826篇 |
化学工业 | 95661篇 |
金属工艺 | 30666篇 |
机械仪表 | 29316篇 |
建筑科学 | 30662篇 |
矿业工程 | 10732篇 |
能源动力 | 16675篇 |
轻工业 | 44257篇 |
水利工程 | 7893篇 |
石油天然气 | 24614篇 |
武器工业 | 2317篇 |
无线电 | 78712篇 |
一般工业技术 | 100696篇 |
冶金工业 | 84310篇 |
原子能技术 | 9298篇 |
自动化技术 | 64520篇 |
出版年
2023年 | 5277篇 |
2022年 | 9499篇 |
2021年 | 13976篇 |
2020年 | 10396篇 |
2019年 | 9779篇 |
2018年 | 12395篇 |
2017年 | 13513篇 |
2016年 | 12541篇 |
2015年 | 14126篇 |
2014年 | 18842篇 |
2013年 | 31253篇 |
2012年 | 26107篇 |
2011年 | 30946篇 |
2010年 | 25896篇 |
2009年 | 26447篇 |
2008年 | 26989篇 |
2007年 | 26663篇 |
2006年 | 26464篇 |
2005年 | 23772篇 |
2004年 | 18307篇 |
2003年 | 16916篇 |
2002年 | 15716篇 |
2001年 | 15281篇 |
2000年 | 15360篇 |
1999年 | 17219篇 |
1998年 | 29415篇 |
1997年 | 21505篇 |
1996年 | 17685篇 |
1995年 | 13639篇 |
1994年 | 11822篇 |
1993年 | 10588篇 |
1992年 | 8030篇 |
1991年 | 7151篇 |
1990年 | 6542篇 |
1989年 | 5857篇 |
1988年 | 5397篇 |
1987年 | 4472篇 |
1986年 | 4271篇 |
1985年 | 4707篇 |
1984年 | 4278篇 |
1983年 | 3784篇 |
1982年 | 3611篇 |
1981年 | 3646篇 |
1980年 | 3339篇 |
1979年 | 3107篇 |
1978年 | 2880篇 |
1977年 | 3444篇 |
1976年 | 4475篇 |
1975年 | 2588篇 |
1974年 | 2573篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
On the capacities of bipartite Hamiltonians and unitary gates 总被引:2,自引:0,他引:2
Bennett C.H. Harrow A.W. Leung D.W. Smolin J.A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(8):1895-1911
We consider interactions as bidirectional channels. We investigate the capacities for interaction Hamiltonians and nonlocal unitary gates to generate entanglement and transmit classical information. We give analytic expressions for the entanglement generating capacity and entanglement-assisted one-way classical communication capacity of interactions, and show that these quantities are additive, so that the asymptotic capacities equal the corresponding 1-shot capacities. We give general bounds on other capacities, discuss some examples, and conclude with some open questions. 相似文献
112.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献
113.
Membrane separation technology represents an alternative way to achieve biomass retention in anaerobic bioreactors for wastewater treatment. Due to high biomass concentrations of anaerobic reactors, cake formation is likely to represent a major cause of flux decline. In the presented research, experiments are performed on the effect of biomass concentration and level of gas sparging on the hydraulic capacity of a submerged anaerobic membrane bioreactor. Both parameters significantly affected the hydraulic capacity, with biomass exerting the most pronounced effect. After 50 days of continuous operation the critical flux remained virtually unchanged, despite an increase in membrane resistance, suggesting that biomass characteristics and hydraulic conditions determine the bio-layer formation rather than the membrane's fouling level. The concept of bio-layer management is introduced to describe the programmed combination of actions performed in order to control the formation of biomass layer over membranes. 相似文献
114.
钻井参数仪的模块化设计方法研究 总被引:1,自引:0,他引:1
文章以模块化设计原理为基础,讨论了钻井参数仪的模块划分,模块化设计准则和主要设计内容。采用模块化设计方法、现场设备网络的开放网络和现场总线解决方案设计的钻井参数仪,具有传输信号稳定、可靠性高、抑制噪声能力强、组建现场网络成本低等特点。 相似文献
115.
可控震源在施工中,常常出现各种电台干扰,导致震源数据传输不正常或震源收不到仪器发出的遥控启动信号,影响正常施工.本文介绍了各种电台干扰引起的故障现象,分析了故障产生的原因,给出了故障的排除方法. 相似文献
116.
Use of citric acid for heavy metals extraction from contaminated sewage sludge for land application.
Recent studies revealed that organic acids such as citric and oxalic acids seemed to be more promising as chemical extracting agents for removal of heavy metals from contaminated sludge, since they are biodegradable and can attain a higher metal extraction efficiency at mildly acidic pH compared to other extracting agents. Results of a lab-scale study on the efficiency of citric acid in the extraction of chromium (Cr), copper (Cu), lead (Pb), nickel (Ni) and zinc (Zn) from anaerobically digested sludge, revealed that citric acid seemed to be highly effective in extracting Cr (at 100%), Cu (at 88%), Ni (at 98%) and Zn (at 100%) at pH 2.33, mostly at 5 days leaching time except for Cu and Zn, which are at 1 day and 2 h contact times respectively. Lead removal at the same pH was also high at 95% but at a longer leaching time of 11 days. At pH 3, citric acid seemed to be highly effective in extracting Pb (at 100%) at 1 day leaching time, although higher removals were also attained for Ni (70%) and Zn (80%) at only 2 h leaching time. Chemical speciation studies showed that Cr, Cu and Ni in the sludge sample seem to predominate in residual fractions, while Pb and Zn were found mostly bound to organic and inorganic matter forms, hence the potential of the sludge for land application. 相似文献
117.
118.
Robust programming aims to prevent abnormal termination or unexpected actions and requires code to handle bad (invalid or absurd) inputs in a way that is consistent with the developer's intent. For example, if an internal error occurs, the program might terminate gracefully rather than simply failing, providing enough information for the programmer to debug the program and avoiding giving the user additional access or information. This article focuses on teaching these principles. 相似文献
119.
In this letter, the concept of pseudorandom active reflector, based on the ultra-wideband (UWB) technology, is introduced. It consists of a simple device that repeats a slightly delayed version of the received UWB signal only in certain time intervals according to a suitable pseudorandom time-hopping sequence. An example of application of this device for accurate ranging in precise location systems is given. The advantages of this solution are in the hardware simplicity (only the analog section is present), in the low power consumption of the reflector and in the low timing constraint regarding the relative transmitter and reflector clock rates. 相似文献
120.
D. Vignolles D. Smirnov G. Rikken B. Raquet H. Rakoto C. Proust M. Nardone J. Léotin F. Lecouturier M. Goiran O. Drachenko J. M. Broto L. Brossard A. Audouard 《Journal of Low Temperature Physics》2003,133(1-2):97-120
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned. 相似文献