首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   61729篇
  免费   6479篇
  国内免费   3314篇
电工技术   4196篇
技术理论   1篇
综合类   4620篇
化学工业   10093篇
金属工艺   3373篇
机械仪表   3917篇
建筑科学   4903篇
矿业工程   1893篇
能源动力   1735篇
轻工业   5197篇
水利工程   1283篇
石油天然气   3197篇
武器工业   673篇
无线电   7233篇
一般工业技术   7134篇
冶金工业   2477篇
原子能技术   886篇
自动化技术   8711篇
  2024年   396篇
  2023年   1286篇
  2022年   2393篇
  2021年   3290篇
  2020年   2355篇
  2019年   1962篇
  2018年   2064篇
  2017年   2221篇
  2016年   1905篇
  2015年   2795篇
  2014年   3367篇
  2013年   3876篇
  2012年   4300篇
  2011年   4519篇
  2010年   3999篇
  2009年   3831篇
  2008年   3549篇
  2007年   3300篇
  2006年   3204篇
  2005年   2817篇
  2004年   1873篇
  2003年   1623篇
  2002年   1634篇
  2001年   1428篇
  2000年   1267篇
  1999年   1195篇
  1998年   913篇
  1997年   793篇
  1996年   753篇
  1995年   593篇
  1994年   491篇
  1993年   364篇
  1992年   274篇
  1991年   228篇
  1990年   164篇
  1989年   133篇
  1988年   104篇
  1987年   60篇
  1986年   49篇
  1985年   31篇
  1984年   20篇
  1983年   19篇
  1982年   24篇
  1981年   16篇
  1980年   15篇
  1979年   8篇
  1974年   1篇
  1972年   1篇
  1959年   9篇
  1951年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
基于“IPv6+”的智能IP网络方案   总被引:1,自引:1,他引:0       下载免费PDF全文
随着第4次工业革命的到来,人类社会正逐步迈向万物互联的智能时代。智能时代需要更加自动化、智能化的IP网络,基于“IPv6+”的SRv6、BIERv6等技术是使能新一代IP网络的关键基础。全面阐述了“IPv6+”的技术内涵,结合华为在智能 IP 网络解决方案上的创新和思考,介绍了“IPv6+”在极简连接、SLA 保障、专网体验、质量感知和云网一体等多个解决方案场景的关键技术与典型应用,助力5G与云业务发展。  相似文献   
22.
23.
24.
In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota.  相似文献   
25.
26.
27.
Bromine-based flow batteries (Br-FBs) are considered one of the most promising energy storage systems due to their features of high energy density and low cost. However, they generally suffer from uncontrolled diffusion of corrosive bromine particularly at high temperatures. That is because the interaction between polybromide anions and the commonly used complexing agent (N–methyl–N–ethyl–pyrrolidinium bromide [MEP]) decreases with increasing temperatures, which causes serious self-discharge and capacity fade. Herein, a novel bromine complexing agent, 1–ethyl–2–methyl–pyridinium bromide (BCA), is introduced in Br-FBs to solve the above problems. It is proven that BCA can combine with polybromide anions very well even at a high temperature of 60 °C. Moreover, the BCA contributes to decreasing the electrochemical polarization of Br/Br2 couple, which in turn improves their power density. As a result, a zinc–bromine flow battery with BCA as the complexing agent can achieve a high energy efficiency of 84% at 40 mA cm−2, even at high temperature of 60 °C and it can stably run for more than 400 cycles without obvious performance decay. This paper provides an effective complexing agent to enable a wide temperature range Br-FB.  相似文献   
28.
Enriching the micronutrients, selenium (Se) and lithium (Li), in grapes to improve their nutraceutical properties were implemented by foliar application of organic fertiliser rich in Se and Li onto five grape cultivars. The effects of this biofortification on vine vigour, fruit quality, overall micronutrients and phenolic compounds also were investigated. Agronomic biofortification was found greatly increased the Se and Li content in the whole grape by multiple times, meanwhile it did not significantly affect the vine vigour and fruit quality of grapes. However, the biofortification did impact the Ionome (including all the mineral nutrients and trace elements) and phenolic compounds in grapes and this varied among cultivars. This study demonstrated foliar spray of organic Se/Li fertiliser was a very effective strategy to biofortify these micronutrients in grape berries, particularly in the skin, and therefore might be a promising strategy to increase the consumption and awareness of these grapes.  相似文献   
29.
This work demonstrates a facile Nb2O5-decorated electrocatalyst to prepare cost-effective Ni–Fe–P–Nb2O5/NF and compared HER & OER performance in alkaline media. The prepared electrocatalyst presented an outstanding electrocatalytic performance towards hydrogen evolution reaction, which required a quite low overpotential of 39.05 mV at the current density of ?10 mA cm?2 in 1 M KOH electrolyte. Moreover, the Ni–Fe–P–Nb2O5/NF catalyst also has excellent oxygen evolution efficiency, which needs only 322 mV to reach the current density of 50 mA cm?2. Furthermore, its electrocatalytic performance towards overall water splitting worked as both cathode and anode achieved a quite low potential of 1.56 V (10 mA cm?2).  相似文献   
30.
SiC nano wires were fabricated on the silicon substrate dipped with a layer of Ni catalyst at 900 ℃ by gas pressure annealing processing. The morphologies and crystal structures were determined by scanning electron microscopy(SEM), transmission electron microscopy(TEM)and X-ray diffraction(XRD). The results show that the assynthesized nanowires are β-SiC single crystalline with diameter range of 50-100 nm, and length of tens of micron by directly annealing at 900 ℃. The SiC nano wires grow along the [111] direction with highly uniform morphology. And the possible growth mechanism of SiC nano wires is proposed.The present work provides an efficient strategy for the production of high-quality SiC nano wires.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号