全文获取类型
收费全文 | 306193篇 |
免费 | 25106篇 |
国内免费 | 15303篇 |
专业分类
电工技术 | 18016篇 |
技术理论 | 57篇 |
综合类 | 38753篇 |
化学工业 | 46100篇 |
金属工艺 | 12637篇 |
机械仪表 | 14958篇 |
建筑科学 | 39848篇 |
矿业工程 | 15753篇 |
能源动力 | 10815篇 |
轻工业 | 17215篇 |
水利工程 | 14172篇 |
石油天然气 | 13428篇 |
武器工业 | 2651篇 |
无线电 | 18869篇 |
一般工业技术 | 27509篇 |
冶金工业 | 18385篇 |
原子能技术 | 3100篇 |
自动化技术 | 34336篇 |
出版年
2024年 | 1052篇 |
2023年 | 3536篇 |
2022年 | 6261篇 |
2021年 | 7316篇 |
2020年 | 7789篇 |
2019年 | 6720篇 |
2018年 | 6303篇 |
2017年 | 7566篇 |
2016年 | 8716篇 |
2015年 | 9454篇 |
2014年 | 17039篇 |
2013年 | 15900篇 |
2012年 | 20360篇 |
2011年 | 21905篇 |
2010年 | 17223篇 |
2009年 | 17960篇 |
2008年 | 16387篇 |
2007年 | 21426篇 |
2006年 | 20424篇 |
2005年 | 17761篇 |
2004年 | 15151篇 |
2003年 | 13642篇 |
2002年 | 11207篇 |
2001年 | 9341篇 |
2000年 | 7930篇 |
1999年 | 6451篇 |
1998年 | 4952篇 |
1997年 | 4245篇 |
1996年 | 3929篇 |
1995年 | 3306篇 |
1994年 | 2949篇 |
1993年 | 2203篇 |
1992年 | 1933篇 |
1991年 | 1448篇 |
1990年 | 1271篇 |
1989年 | 1081篇 |
1988年 | 865篇 |
1987年 | 613篇 |
1986年 | 456篇 |
1985年 | 413篇 |
1984年 | 384篇 |
1983年 | 286篇 |
1982年 | 239篇 |
1981年 | 177篇 |
1980年 | 146篇 |
1979年 | 110篇 |
1978年 | 63篇 |
1977年 | 74篇 |
1976年 | 59篇 |
1975年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Asbestos fibres, of the chrysotile variety, and chopped carbon fibres were pretreated by an in-situ polycondensation technique eventually resulting in a polyamide coating on the fibre surface. Ionomer based composites containing either carbon or asbestos fibres in random in plane fibre orientation were prepared, and the influence of this coating process on the tensile properties was investigated. It was found that for the asbestos-filled composites the presence of the nylon 6,6 interlayer improves the tensile performance, especially at moderate polyamide depositions. This is not the case with the pretreated carbon-filled composites for which carbon fibres with higher polyamide contents are preferred. Combinations of the treated asbestos fibres with carbon and/or aramid fibres may be used to reduce the asbestos content in asbestos-only based engineering plastics. 相似文献
92.
D. P. Dreoni D. Pinelli F. Trifirò Z. Tvaruzkova H. Habersberger P. Jiru 《Catalysis Letters》1991,11(3-6):285-294
The catalyst behaviour of titanium silicalite, which was found the most active and selective catalyst for liquid-phase ammoximation of cyclohexanone to the corresponding oxime with hydrogen peroxide, was investigated in the gas-phase ammoximation with molecular oxygen in and compared with those of pure silicalite and samples of vanadium and chromium silicalites. The results showed that Ti-silicalite is a selective catalyst not only in the reaction with hydrogen peroxide but also in the reaction with molecular oxygen. However, a big limitation was found in the poor activity of the silicalites which do not allow to reach high oxime yields. 相似文献
93.
Safe and Economic Operation of Power Plants – Research Results in the Field of Materials, Design and Maintenance Components of power plants which undergo high temperatures are subjected to complex loading situations. The requirements on the used materials result from the special operation conditions of the plants and have to be adjusted to the steadily growing requirements on higher efficiency of the complete power plant as well as to those of safe and economic operation. The expenses for control and downtimes are directly connected with economic efficiency and availability. However, in case of new procedures or components it is not possible to revert to the existing know‐how. Different failure mechanisms than known before can occur. The same goes for the load situation. Therefore the knowledge base has to be extended to in‐advance or even parallely running scientific examinations that life assessment and maintenance strategies can be applied which guarantee the operational reliability and the efficiency of the plant. The main emphasis of these F&E works has to be put on condition monitoring based on actual operational data, the standard materials’ and component’s behaviour (deformation, damage and failure behaviour) in connection with design of components and the related material laws. In the framework of applied AVIF projects, following problems are handled:. – qualification of materials by determinating parameters related to practise. – optimal design of components by making available material laws and numerical tools. – economic manufacturing of components by qualifying processing methods such as welding. – The results can be transferred to concepts for safe and economic operation of power plants, especially for newly introduced materials for which there is no operational experience available. 相似文献
94.
总结了实际工作中防突管理的经验和问题 ,探讨了科学理论与具体实际的有机结合与统一 ,采取针对性强的有效措施 ,确保突出矿井的安全生产 相似文献
95.
The present work has concentrated on the structure of CO2 hydrate in the NPT ensemble using SPC (simple point charge) intermolecular potential model of water by the Monte Carlo (MC) molecular simulation. A mixture of water and CO2 placed arbitrarily in a cubic cell has been used as a model system to simulate the CO2 clathrate hydrate at temperatures ranging from 150–280 K and pressure up to 10 MPa. The result shows that the obtained MC simulation agrees well with the results obtained by molecular dynamic (MD) simulation. The present work is also directed to the study of structure with TIP4P potential model of water. 相似文献
96.
In a series of experiments, participants were required to keep track of 1 or 2 working memory (WM) objects, having to update their values in 80% of the trials. Updating cost, defined as the difference between update and non-update trials, was larger when 2 objects were involved compared with when there was only 1 object was involved. This finding was interpreted as evidence that the updating process encompasses both objects in WM, even though only 1 of them is actually updated. This feature of WM updating is limited to objects defined as "updateable," throughout the trial sequence. The results are explained by the need to reprogram the phonological loop when updating or the need for desynchronization followed by resynchronization of WM contents. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
The kinetics of the chlorination reaction of molybdenum trioxide with gaseous carbon tetrachloride has been studied at temperatures between 713 and 753 K. The effects of temperature, reaction time, residence time and gaseous reactant concentration on conversion were studied throughout the reaction. In all cases, there was an increase in conversion when the above operating variables were increased. The kinetic model proposed is consistent with and correlates the experimental data. In the range studied for the different variables, the step that controls the rate of reaction is the surface chemical reaction. Values of the rate constant and the activation energy were estimated. 相似文献
98.
99.
The solubilities of ethyl palmitate, ethyl oleate, ethyl eicosapentaenoate (EPA) and ethyl docosahexaenoate (DHA) in supercritical
carbon dioxide were determined by a continuous flow method. The solubilities of fatty acid ethyl esters increased with pressure
and decreased as the temperature was increased. An empirical equation, similar to Chrastil's equation, was used to describe
the relationship between solute solubility and the density of carbon dioxide. The empirical equation was further used to qualitatively
estimate the separation efficiency of isolating EPA and DHA ethyl esters from fatty acid esters. The operating conditions
yielding high solubility gave fast extraction rate but resulted in low separation efficiency. Experiments were conducted to
separate ethyl EPA and ethyl DHA from a model mixture containing four fatty acid ethyl esters and from esterified squid visceral
oil. The experimental data compared closely with the calculated values. 相似文献
100.
全文围绕树立和落实科学发展观这一主题 ,研究和探索如何在新时期、新阶段进一步做好国土资源管理工作的新思路、新途径和新方法。提出要进一步加强国土资源宏观管理 ,更好地为甘肃省经济社会的协调、可持续发展提供保障服务。 相似文献