全文获取类型
收费全文 | 342839篇 |
免费 | 6443篇 |
国内免费 | 753篇 |
专业分类
电工技术 | 6440篇 |
综合类 | 575篇 |
化学工业 | 54296篇 |
金属工艺 | 10785篇 |
机械仪表 | 9624篇 |
建筑科学 | 9117篇 |
矿业工程 | 924篇 |
能源动力 | 9343篇 |
轻工业 | 37702篇 |
水利工程 | 2916篇 |
石油天然气 | 3796篇 |
武器工业 | 9篇 |
无线电 | 41449篇 |
一般工业技术 | 64022篇 |
冶金工业 | 61358篇 |
原子能技术 | 5557篇 |
自动化技术 | 32122篇 |
出版年
2021年 | 3290篇 |
2020年 | 2496篇 |
2019年 | 3047篇 |
2018年 | 5117篇 |
2017年 | 4926篇 |
2016年 | 5173篇 |
2015年 | 3764篇 |
2014年 | 5929篇 |
2013年 | 17279篇 |
2012年 | 9775篇 |
2011年 | 12294篇 |
2010年 | 9552篇 |
2009年 | 10656篇 |
2008年 | 11195篇 |
2007年 | 10982篇 |
2006年 | 9538篇 |
2005年 | 8731篇 |
2004年 | 8520篇 |
2003年 | 8181篇 |
2002年 | 7959篇 |
2001年 | 7935篇 |
2000年 | 7556篇 |
1999年 | 7879篇 |
1998年 | 19206篇 |
1997年 | 13855篇 |
1996年 | 10765篇 |
1995年 | 8233篇 |
1994年 | 7534篇 |
1993年 | 7216篇 |
1992年 | 5399篇 |
1991年 | 5171篇 |
1990年 | 5021篇 |
1989年 | 4861篇 |
1988年 | 4770篇 |
1987年 | 3964篇 |
1986年 | 4076篇 |
1985年 | 4799篇 |
1984年 | 4364篇 |
1983年 | 4072篇 |
1982年 | 3658篇 |
1981年 | 3837篇 |
1980年 | 3530篇 |
1979年 | 3463篇 |
1978年 | 3260篇 |
1977年 | 3909篇 |
1976年 | 5044篇 |
1975年 | 2824篇 |
1974年 | 2699篇 |
1973年 | 2717篇 |
1972年 | 2219篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A. M. Mirzabaev V. P. Kanonerov T. A. Makhkamov O. R. Sytdykov Sh. M. Mirzabekov 《Applied Solar Energy》2018,54(3):224-226
The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered. 相似文献
62.
Carbon supported bimetallic Ru‐Co catalysts for H2 production through NaBH4 and NH3BH3 hydrolysis
下载免费PDF全文
![点击此处可从《国际能源研究杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This work investigates the effect of the addition of small amounts of Ru (0.5‐1 wt%) to carbon supported Co (10 wt%) catalysts towards both NaBH4 and NH3BH3 hydrolysis for H2 production. In the sodium borohydride hydrolysis, the activity of Ru‐Co/carbon catalysts was sensibly higher than the sum of the activities of corresponding monometallic samples, whereas for the ammonia borane hydrolysis, the positive effect of Ru‐Co systems with regard to catalytic activity was less evident. The performances of Ru‐Co bimetallic catalysts correlated with the occurrence of an interaction between Ru and Co species resulting in the formation of smaller ruthenium and cobalt oxide particles with a more homogeneous dispersion on the carbon support. It was proposed that Ru°, formed during the reduction step of the Ru‐Co catalysts, favors the H2 activation, thus enhancing the reduction degree of the cobalt precursor and the number of Co nucleation centers. A subsequent reduction of cobalt and ruthenium species also occurs in the hydride reaction medium, and therefore the state of the catalyst before the catalytic experiment determines the state of the active phase formed in situ. The different relative reactivity of the Ru and Co active species towards the two investigated reactions accounted for the different behavior towards NaBH4 and NH3BH3 hydrolysis. 相似文献
63.
Buryakov A. M. Khusyainov D. I. Mishina E. D. Khabibullin R. A. Yachmenev A. E. Ponomarev D. S. 《Technical Physics Letters》2018,44(12):1115-1119
Technical Physics Letters - The influence of excitation photons energy on the relaxation times of photoexcited carriers is studied. The involved relaxation mechanisms are evaluated and the... 相似文献
64.
Technical Physics Letters - Specific features of monitoring the state of a flowing medium by method of nuclear magnetic resonance (NMR) are considered. An approach to studying the state of a... 相似文献
65.
Fominski V. Yu. Nevolin V. N. Fominski D. V. Romanov R. I. Gritskevich M. D. 《Technical Physics Letters》2020,46(1):83-86
Technical Physics Letters - We present the results of a comparative investigation of the friction and wear characteristics of MoSx and MoSex coatings in an oxidizing medium (argon–air... 相似文献
66.
67.
Verbovitskii Yu. V. Denis R. V. Shtender V. V. Zavalii I. Yu. 《Powder Metallurgy and Metal Ceramics》2015,54(3-4):220-226
Powder Metallurgy and Metal Ceramics - Multiphase La 2 MgNi 9 alloys are synthesized by induction melting. The crystalline structures of all phases in the alloys are determined with X-ray... 相似文献
68.
69.
Nathan M. Wilbur Antin M. O'Sullivan Kerry T. B. MacQuarrie Tommi Linnansaari R. Allen Curry 《河流研究与利用》2020,36(5):769-783
Anthropogenic influences, including climate change, are increasing river temperatures in northern and temperate regions and threatening the thermal habitats of native salmonids. When river temperatures exceed the tolerance levels of brook trout and Atlantic salmon, individuals exhibit behavioural thermoregulation by seeking out cold‐water refugia – often created by tributaries and groundwater discharge. Thermal infrared (TIR) imagery was used to map cold‐water anomalies along a 53 km reach of the Cains River, New Brunswick. Trout and salmon parr did not use all identified thermal anomalies as refugia during higher river temperature periods (>21°C). Most small‐bodied trout (8–30 cm) were observed in 80% of the thermal anomalies sampled. Large‐bodied trout (>35 cm) required a more specific set of physical habitat conditions for suitable refugia, that is, 100% of observed large trout used 30% of the anomalies sampled and required water depths >65 cm within or adjacent to the anomaly. Densities of trout were significantly higher within anomalies compared with areas of ambient river temperature. Salmon parr were less aligned with thermal anomalies at the observed temperatures, that is, 59% were found in 65% of the sampled anomalies; and densities were not significantly different within/ outside anomalies. Salmon parr appeared to aggregate at 27°C, and after several events over 27°C variability in aggregation behaviour was observed – some fish aggregated at 25°C, others did not. We stipulate this is due to variances of thermal fatigue. Habitat suitability curves were developed for velocity, temperature, depth, substrate, and deep water availability to characterize conditions preferred by fish during high‐temperature events. These findings are useful for managers as our climate warms, and can potentially be used as a tool to help conserve and enhance thermal refugia for brook trout and Atlantic salmon in similar systems. 相似文献
70.