全文获取类型
收费全文 | 60484篇 |
免费 | 5759篇 |
国内免费 | 2917篇 |
专业分类
电工技术 | 3606篇 |
技术理论 | 5篇 |
综合类 | 3794篇 |
化学工业 | 10021篇 |
金属工艺 | 3552篇 |
机械仪表 | 4095篇 |
建筑科学 | 4507篇 |
矿业工程 | 1730篇 |
能源动力 | 1732篇 |
轻工业 | 3979篇 |
水利工程 | 944篇 |
石油天然气 | 3277篇 |
武器工业 | 506篇 |
无线电 | 7398篇 |
一般工业技术 | 7874篇 |
冶金工业 | 3272篇 |
原子能技术 | 665篇 |
自动化技术 | 8203篇 |
出版年
2024年 | 256篇 |
2023年 | 1147篇 |
2022年 | 1837篇 |
2021年 | 2968篇 |
2020年 | 2157篇 |
2019年 | 1902篇 |
2018年 | 1979篇 |
2017年 | 2046篇 |
2016年 | 1941篇 |
2015年 | 2603篇 |
2014年 | 3111篇 |
2013年 | 3634篇 |
2012年 | 3832篇 |
2011年 | 4225篇 |
2010年 | 3469篇 |
2009年 | 3343篇 |
2008年 | 3441篇 |
2007年 | 3090篇 |
2006年 | 3164篇 |
2005年 | 2653篇 |
2004年 | 1996篇 |
2003年 | 1697篇 |
2002年 | 1639篇 |
2001年 | 1426篇 |
2000年 | 1380篇 |
1999年 | 1399篇 |
1998年 | 1173篇 |
1997年 | 1029篇 |
1996年 | 916篇 |
1995年 | 753篇 |
1994年 | 604篇 |
1993年 | 448篇 |
1992年 | 347篇 |
1991年 | 286篇 |
1990年 | 253篇 |
1989年 | 226篇 |
1988年 | 144篇 |
1987年 | 117篇 |
1986年 | 86篇 |
1985年 | 60篇 |
1984年 | 50篇 |
1983年 | 51篇 |
1982年 | 46篇 |
1981年 | 30篇 |
1980年 | 46篇 |
1979年 | 23篇 |
1978年 | 20篇 |
1977年 | 21篇 |
1976年 | 21篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Mohammad Reza Gaeeni Morteza Sasani Ghamsari Abbas Majd Abadi Mohammad Hossein Majles Ara Wooje Han Hyung‐Ho Park 《Journal of the American Ceramic Society》2015,98(6):1818-1822
A facile sol–gel procedure has been developed for the synthesis of colloidal alumina nanocrystals. For the first time, optical characterization procedures were employed to study the quantum confinement effects in optical properties of the prepared Al2O3 sol. Accordingly, the hyperbolic band model was used to determine the optical band gap of colloidal alumina nanocrystals. X‐Ray diffraction pattern was used to study the crystallographic phase of the dried gel. Morphological characterization was performed using scanning electron microscopy (SEM). Inductively Coupled Plasma (ICP) emission spectroscopy was used to determination purity of the Al2O3 powder. High‐resolution TEM showed that the diameter of colloidal nanocrystals is about 10 nm. Photoluminescence spectroscopy demonstrated that quantum yields for colloidal nanocrystals are 68% with 300 nm excitation wavelength. The experimental observations confirm that highly stable alumina sol with strong UV emission was synthesized. The mentioned optical properties have not been reported before. 相似文献
62.
Yingchao Hu Wenqiang Liu Yuandong Yang Xianliang Tong Qianjun Chen Zijian Zhou 《Ceramics International》2018,44(14):16668-16677
Li4SiO4 sorbents for high-temperature CO2 removal have drawn extensive attention owing to their potential application in carbon capture and storage (CCS). The major challenge in the application lies in the poor CO2 capture performance under realistic conditions of low CO2 concentrations, owing to the dense structure and poor porosity. In this work, Li4SiO4 sorbents were prepared with porous micromorphologies and large contact areas using a variety of organometallic Li-precursors, achieving fast CO2 sorption kinetics, high capacity and excellent cyclic stability at a low CO2 concentration (15?vol%). It was found that a high conversion of ~?74% was maintained for pure Li4SiO4 even after 100 sorption/desorption cycles. Moreover, by doping with Na2CO3 to reduce the CO2 diffusion resistance, the conversion of the sorbent was further enhanced to 93.2%. The enhancement mechanism of alkali carbonate have been proven here to be ascribed to the formation of the eutectic melt of Li/Na carbonates, the existence and function of which has been confirmed in this study. 相似文献
63.
64.
通过HPT250轧机在技术改造中遇到的一个问题,即滑移系数对冷轧元缝钢管在轧制过程中所起的作用。在实际生产中经过不断的技术研究和改进。使闲置多年的HPT250轧机为钢管公司的生产迭拉起到很大的作用。 相似文献
65.
介绍了如何配置与优化水电厂的自动化元件,其配置选型应以可靠实用、结构简单、便于维护为原则,同时还应结合电厂的各种介质特点、设备运行方式、控制方式等因素综合考虑. 相似文献
66.
67.
炼油达标污水回用处理试验研究 总被引:1,自引:0,他引:1
采用曝气生物滤池、多介质过滤、超滤、反渗透工艺,对炼油达标外排污水进行回用处理中试试验。结果表明,曝气生物滤池对油、COD和浊度去除效果良好,超滤、反渗透膜化学清洗周期达到 2个月以上,脱盐率稳定在98%以上,产水品质达到回用要求。 相似文献
68.
Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3+ as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar. 相似文献
69.
汽油烃类族组成测试方法对比 总被引:1,自引:0,他引:1
介绍了使用荧光指示剂吸附色谱法、多维气相色谱法的测定影响因素和近红外光谱快速法的分析特点以及三种方法在汽油族组成测定中的应用,并就三种方法对同一试样的测定结果进行了对比,找出各种测定方法容易产生误差的原因及分析对策。 相似文献
70.
介绍了一种基于FPGA(Field Programmable Gates Array)技术的可重构的软测量系统。该系统由一个单片机控制着一片FPGA芯片,芯片上配置的软测量模型在一个BP人工神经网络模型及其训练模型之间切换(即重构)。该系统在实际中有广泛的用途,如测量工业生产中的过程变量、生物体内部状态、海洋探测、空间设备等。 相似文献