全文获取类型
收费全文 | 6775篇 |
免费 | 646篇 |
国内免费 | 230篇 |
专业分类
电工技术 | 212篇 |
综合类 | 251篇 |
化学工业 | 1542篇 |
金属工艺 | 367篇 |
机械仪表 | 252篇 |
建筑科学 | 329篇 |
矿业工程 | 148篇 |
能源动力 | 216篇 |
轻工业 | 786篇 |
水利工程 | 98篇 |
石油天然气 | 220篇 |
武器工业 | 13篇 |
无线电 | 504篇 |
一般工业技术 | 1241篇 |
冶金工业 | 271篇 |
原子能技术 | 71篇 |
自动化技术 | 1130篇 |
出版年
2023年 | 96篇 |
2022年 | 158篇 |
2021年 | 229篇 |
2020年 | 227篇 |
2019年 | 203篇 |
2018年 | 279篇 |
2017年 | 361篇 |
2016年 | 357篇 |
2015年 | 289篇 |
2014年 | 392篇 |
2013年 | 700篇 |
2012年 | 453篇 |
2011年 | 441篇 |
2010年 | 366篇 |
2009年 | 303篇 |
2008年 | 219篇 |
2007年 | 166篇 |
2006年 | 113篇 |
2005年 | 90篇 |
2004年 | 152篇 |
2003年 | 243篇 |
2002年 | 349篇 |
2001年 | 313篇 |
2000年 | 140篇 |
1999年 | 93篇 |
1998年 | 99篇 |
1997年 | 63篇 |
1996年 | 57篇 |
1995年 | 50篇 |
1994年 | 42篇 |
1993年 | 44篇 |
1992年 | 30篇 |
1991年 | 34篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 29篇 |
1984年 | 32篇 |
1983年 | 30篇 |
1982年 | 26篇 |
1981年 | 26篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1976年 | 22篇 |
1975年 | 20篇 |
1974年 | 21篇 |
1973年 | 21篇 |
排序方式: 共有7651条查询结果,搜索用时 0 毫秒
971.
972.
973.
针对我国水资源紧缺、水生态损害、水环境污染等相关水问题,以提升全民爱水惜水节水护水的意识和能力为目标,从水素养概念出发,通过扎根理论质性研究方法对公民水素养评价的表征因素进行筛选和提炼,最终得出包含水知识、水态度、水行为为主范畴的10个表征因素并运用解释结构模型(ISM)深入剖析各因素之间的内在联系。在此基础上建立了3级多层次递阶结构模型,进一步精确描述系统各要素两两之间的直接关系。结果表明:公民水素养评价的表征因素自上而下形成了表象层、中间层和根源层等3个层级,可直观、清晰地反映表征因素之间的递阶、层级关系;水态度在各表征因素中具有调节作用以及各表征因素之间存在内在逻辑关系。研究成果为提高公民水素养水平提供一定的科学依据和政策参考。 相似文献
974.
Ondřej Jankovský Filip Antončík Tomáš Hlásek Vladimír Plecháček David Sedmidubský Štěpán Huber Michal Lojka Vilém Bartůněk 《Journal of the European Ceramic Society》2018,38(6):2541-2546
YBa2Cu3O7-δ (YBCO) is a well-known high-temperature superconductor. However, its critical current density and thus maximum trapped magnetic field can be improved significantly by introducing the secondary phases (artificial pinning centers). In this contribution, we successfully prepared YBCO single-grain bulks with Y2Ba4CuWO10.8 phase serving as a source of pinning centers. This phase was prepared by solid-state reaction and further refined by milling. In the next step single-grain YBCO bulks with homogeneously distributed Y2Ba4CuWO10.8 were prepared by top-seeded melt growth. Precursors as well as the final product were characterized by XRD, SEM and EDS. The phase composition of YBCO bulks containing Y2Ba4CuWO10.8 was analyzed using Rietveld analysis. Thermal stability of YBCO bulk was studied by STA. Furthermore, PPMS was used to study electrical resistivity and critical current density. Bulk superconducting properties such as levitation force and trapped field ability were also measured. 相似文献
975.
R. Peter Richards Mirjan Žorž John Rakovan Quintin Wight Jim Houran 《Rocks & Minerals》2018,93(6):495-497
976.
Marija Prekajski Đorđević Jelena Maletaškić Nadežda Stanković Biljana Babić Katsumi Yoshida Toyohiko Yano Branko Matović 《Ceramics International》2018,44(2):1771-1777
Hydroxyapatite was used as the inert matrix for in-situ immobilization of strontium (Sr) radioactive isotopes at room temperature. A nano-emulsification method was applied to synthesize Sr-substituted calcium hydroxyapatite (Ca1?xSrx)10(PO4)6(OH)2. The concentration of incorporated Sr was in the range of 0 ≤ x ≤ 1. Immobilization of Sr was evaluated using a stable isotope instead of radioactive isotope. The effect of strontium concentration on the crystal structure was studied and the results have showed that in the whole concentration range, Sr forms solid solutions with the host hydroxyapatite crystal structure. Powders comprised of nanometre sized particles were obtained and their properties, such as crystallite and particle size, changes in lattice parameters as function of dopant content and thermal stability, were further examined. It was found that the crystal structure of obtained powders is thermally stable at high temperatures. No secondary phases were formed in as-prepared powders or during calcination. The results in this study showed that nano-emulsion strategy provides a simple pathway for synthesis of a single-phase Sr-substituted hydroxyapatite, which can be used for immobilization of Sr radioactive isotopes. 相似文献
977.
Prediction of Power Consumption in a Mechanically Agitated Gassed Reactor in Viscous Batches
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Volumetric mass transfer coefficient, power input, and gas holdup are key parameters in the design of mechanically agitated gas‐liquid contactors. Although the majority of industrial batches are of higher viscosity, reliable transport characteristics correlations for viscous batches are lacking in literature. These correlations are often based on the power input as the scale of energy dissipation. In order to develop reliable power input correlations, its measurements were carried out in a pilot‐plant vessel using multiple impellers of various types and diameters. Power input correlation shapes providing the best match with the comprehensive database are also expected to predict most precisely the impeller power in industrial‐scale vessels. 相似文献
978.
979.
This paper offers an overall picture of the importance of Strategic Environmental Assessment (SEA) in Romania and its opportunities and constraints. The role, scope and effectiveness of SEA in Romania are presented in two good practice examples and examined in order to highlight the strengths and weaknesses of the procedure at national and local scale. In practice, the number of SEA procedures is very high due to the legislation in force, and it is increasingly effective in decision-making about programmes and plans. SEA can be viewed as a great opportunity for the implementation of sustainable development in practice. It also continues to be an important procedural and decisional instrument for management and monitoring of socioeconomic development, spatial planning and environmental protection in Romania. 相似文献
980.
Arsić Miodrag Arsić Dušan Flajs Željko Grbović Aleksandar Todić Aleksandar 《Russian Journal of Nondestructive Testing》2021,57(10):918-931
Russian Journal of Nondestructive Testing - Loads at vital steel structures occur during their production and assembly (residual stresses), during the execution of functional tasks in exploitation... 相似文献