全文获取类型
收费全文 | 51471篇 |
免费 | 4488篇 |
国内免费 | 2128篇 |
专业分类
电工技术 | 5773篇 |
技术理论 | 1篇 |
综合类 | 4220篇 |
化学工业 | 3994篇 |
金属工艺 | 1611篇 |
机械仪表 | 4139篇 |
建筑科学 | 6456篇 |
矿业工程 | 6138篇 |
能源动力 | 1421篇 |
轻工业 | 1480篇 |
水利工程 | 1450篇 |
石油天然气 | 1989篇 |
武器工业 | 1287篇 |
无线电 | 3743篇 |
一般工业技术 | 2728篇 |
冶金工业 | 2879篇 |
原子能技术 | 311篇 |
自动化技术 | 8467篇 |
出版年
2024年 | 174篇 |
2023年 | 470篇 |
2022年 | 1119篇 |
2021年 | 1535篇 |
2020年 | 1585篇 |
2019年 | 1010篇 |
2018年 | 912篇 |
2017年 | 1263篇 |
2016年 | 1635篇 |
2015年 | 1755篇 |
2014年 | 4054篇 |
2013年 | 3013篇 |
2012年 | 4565篇 |
2011年 | 4500篇 |
2010年 | 3446篇 |
2009年 | 3324篇 |
2008年 | 3027篇 |
2007年 | 3675篇 |
2006年 | 3086篇 |
2005年 | 2592篇 |
2004年 | 2119篇 |
2003年 | 2010篇 |
2002年 | 1553篇 |
2001年 | 1267篇 |
2000年 | 1015篇 |
1999年 | 769篇 |
1998年 | 533篇 |
1997年 | 480篇 |
1996年 | 379篇 |
1995年 | 290篇 |
1994年 | 255篇 |
1993年 | 154篇 |
1992年 | 107篇 |
1991年 | 83篇 |
1990年 | 66篇 |
1989年 | 47篇 |
1988年 | 39篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1979年 | 10篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1960年 | 3篇 |
1957年 | 3篇 |
1955年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
连续蒸煮器内洗涤结合器外扩散洗涤,具有洗涤时间长、洗涤效率高、提取黑液浓度高、浆层厚度均匀、浆层结构组织和浓度一致等特点,运行可靠,易于自动化控制,实现了洗涤用水的封闭循环。 相似文献
33.
S. Suppan J. Trawczyski J. Kaczmarczyk G. Djga-Mariadassou A. Hynaux C. Sayag 《Applied Catalysis A: General》2005,280(2):209-214
Carbon black composites (CBCs) have been prepared by pyrolyzing mixture of a carbon black with polyfurfuryl alcohol and then pretreated by oxidation with nitric acid, gasification with water steam or ammoxidation. The effects of the chemical character of the carrier surface, nature of the active metal phase and pH value of the impregnation solution on the catalytic activity towards the hydrodesulfurization (HDS) of thiophene of the CBC supported Mo (Co) catalysts were determined. It was stated that the catalytic properties of the CBC supported sulfides of Mo or Co and of Mo carbides are affected by the chemical character of the carrier surface. Generally, catalysts supported over basic surface CBC exhibit higher activity than those ones supported over CBC possessing acidic surface character. Co catalysts supported on acidic surface show lower activity (per mol of active metal) than Mo based ones supported on the same carrier. In the case of catalysts supported on basic CBC, Co exhibits distinctly higher activity than Mo. At the experimental conditions adopted for this study, CBC surface properties, active phase nature, and catalyst impregnation pH were found to exert a relatively small influence on both HDS and hydrogenation activities. 相似文献
34.
Predictive Maintenance can provide an increase in safety, quality and availability in industrial plants. However, the setting up of a Predictive Maintenance Programme is a strategic decision that until now has lacked analysis of questions related to its setting up, management and control. In this paper, an evaluation system is proposed that carries out the decision making in relation to the feasibility of the setting up. The evaluation system uses a combination of tools belonging to operational research such as: Analytic Hierarchy Process, decision rules and Bayesian tools. This system is a help tool available to the managers of Predictive Maintenance Programmes which can both increase the number of Predictive Maintenance Programmes set up and avoid the failure of these programmes. The Evaluation System has been tested in a petrochemical plant and in a food industry. 相似文献
35.
In an industrial plant, the level of maintenance provided to individual equipment is directly related to the availability that is expected from it. Thus, it is hoped that the most critical equipments will not fail or, at least, that any failure will be rapidly detected and corrected in the minimum time possible. Since resources are limited, it is necessary to determine how they should be distributed, so that no important equipment remains neglected while more resources are concentrated on the most critical items. Therefore, it is necessary to classify equipment in an objective way according to its importance. The method of multicriterion classification of critical equipments (MCCE)2, which is described in the present work, allows systematic and detailed quantification of the criticality of all equipment, that is to say, it provides an evaluation of the importance that its correct operation has for the plant. To provide this information, the consequences for a company of any failure in the equipment concerned are analysed. Finally, a real case example of an urban wastewater treatment plant is described, in which the MCCE method is applied. 相似文献
36.
混凝土喷锚支护可提高边坡岩土的结构强度和抗变形刚度,增强边坡的整体稳定性和承载能力.本文根据宝珠寺水电站左右岸边坡主要采用混凝土喷锚支护的工程实践,介绍了施工方案设计、材料要求、施工方法、技术措施,以及现场质量管理和检测等问题. 相似文献
37.
Comments on the article by K. T. Herbst-Damm and J. A. Kulik (see record 2005-02260-012) entitled Volunteer support, marital status, and the survival times of terminally ill patients. Can a simple and low-cost intervention, such as a visit by a volunteer, extend the life of terminally ill patients? The answer, according to a study by Herbst-Damm and Kulik (2005), is yes. When it comes to quality of life, however, the effects of volunteer visits remain murky. Thus, it is critical that we look beyond effects on longevity and assess how such a program would influence quality of life. Extending the life of terminally ill patients might not always a blessing. Prolonging their life might even cause harm, as it can extend unwanted physical and mental suffering. It may also go against some patients' desire to hasten their death. Despite Herbst-Damm and Kulik's important findings, the current author remains unconvinced as to the merits of implementing volunteer visits as an intervention policy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
介绍了利用ASP技术对图书馆主页上的光盘数据库进行远程维护,给出整个实施过程的步骤及部分程序的源程序。 相似文献
39.
本文介绍了南钢中板厂将系统工程最优化技术中的随机服务系统理论和可靠性设计方法引入到电气设备的维护和管理工作中,并结合现场实际情况摸索出一套电气设备可靠性保障方法。 相似文献
40.
地下连续墙在太钢老厂改造工程中的应用 总被引:1,自引:1,他引:0
结合某深基坑支护施工实例 ,介绍了采用多头潜水钻成槽机进行地下连续墙施工的基本原理、工艺流程及注意事项。指出该方案对于在老厂区改造工程狭窄场地条件下 ,解决深基坑施工保护附近建 (构 )筑物安全具有独特的优势 相似文献