全文获取类型
收费全文 | 34974篇 |
免费 | 4347篇 |
国内免费 | 2406篇 |
专业分类
电工技术 | 4819篇 |
综合类 | 3725篇 |
化学工业 | 1842篇 |
金属工艺 | 655篇 |
机械仪表 | 2278篇 |
建筑科学 | 3653篇 |
矿业工程 | 4480篇 |
能源动力 | 925篇 |
轻工业 | 571篇 |
水利工程 | 818篇 |
石油天然气 | 677篇 |
武器工业 | 618篇 |
无线电 | 3021篇 |
一般工业技术 | 1963篇 |
冶金工业 | 1095篇 |
原子能技术 | 131篇 |
自动化技术 | 10456篇 |
出版年
2024年 | 126篇 |
2023年 | 358篇 |
2022年 | 847篇 |
2021年 | 1109篇 |
2020年 | 1150篇 |
2019年 | 896篇 |
2018年 | 874篇 |
2017年 | 1082篇 |
2016年 | 1360篇 |
2015年 | 1500篇 |
2014年 | 2531篇 |
2013年 | 2152篇 |
2012年 | 3039篇 |
2011年 | 3165篇 |
2010年 | 2528篇 |
2009年 | 2486篇 |
2008年 | 2487篇 |
2007年 | 2765篇 |
2006年 | 2284篇 |
2005年 | 1832篇 |
2004年 | 1378篇 |
2003年 | 1172篇 |
2002年 | 894篇 |
2001年 | 701篇 |
2000年 | 578篇 |
1999年 | 397篇 |
1998年 | 325篇 |
1997年 | 292篇 |
1996年 | 256篇 |
1995年 | 205篇 |
1994年 | 221篇 |
1993年 | 119篇 |
1992年 | 109篇 |
1991年 | 80篇 |
1990年 | 82篇 |
1989年 | 76篇 |
1988年 | 53篇 |
1987年 | 29篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
This paper presents an efficient method which provides the optimal generation mix and the optimal generation construction process. The approximation method in which the dynamic programming technique and gradient method are combined is applied to determine the optimal generation mix with hydropower generation technologies. The successive approximations dynamic programming (SADP) technique, which is very suitable for high-dimensional multistage decision process problems, is used for obtaining the optimal generation construction process. The effectiveness and feasibility of the developed technique are demonstrated on a practical power system model which has five types of generation technologies including a hydropower generation technology. 相似文献
62.
从力学角度分析了钢带捆扎对木箱强度的影响,指出木箱经钢带捆扎后,可减小箱底的最大弯矩,提高木箱的承载能力和减少板厚。同时还在无支撑间隔的基础上,详细介绍了钢带捆扎的设计方法。 相似文献
63.
Melt index is considered an important quality variable determining product specifications. Reliable prediction of melt index (MI) is crucial in quality control of practical propylene polymerization processes. In this paper a least squares support vector machines (LS‐SVM) soft‐sensor model of propylene polymerization process is developed to infer the MI of polypropylene from other process variables. Considering the use of a SSE cost function without regularization might lead to less robust estimates; the weighted least squares support vector machines (weighted LS‐SVM) approach of propylene polymerization process is further proposed to obtain a robust estimation of melt index. The performance of standard SVM model is taken as a basis of comparison. A detailed comparison research among the standard SVM, LS‐SVM, and weighted LS‐SVM models is carried out. The research results confirm the effectiveness of the presented methods. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 285–289, 2006 相似文献
64.
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
65.
Support vector clustering involves three steps—solving an optimization problem, identification of clusters and tuning of hyper-parameters. In this paper, we introduce a pre-processing step that eliminates data points from the training data that are not crucial for clustering. Pre-processing is efficiently implemented using the R*-tree data structure. Experiments on real-world and synthetic datasets show that pre-processing drastically decreases the run-time of the clustering algorithm. Also, in many cases reduction in the number of support vectors is achieved. Further, we suggest an improvement for the step of identification of clusters. 相似文献
66.
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
67.
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
68.
69.
70.
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