全文获取类型
收费全文 | 12593篇 |
免费 | 1285篇 |
国内免费 | 994篇 |
专业分类
电工技术 | 270篇 |
综合类 | 1092篇 |
化学工业 | 646篇 |
金属工艺 | 2757篇 |
机械仪表 | 2031篇 |
建筑科学 | 948篇 |
矿业工程 | 180篇 |
能源动力 | 345篇 |
轻工业 | 232篇 |
水利工程 | 52篇 |
石油天然气 | 417篇 |
武器工业 | 147篇 |
无线电 | 309篇 |
一般工业技术 | 4295篇 |
冶金工业 | 586篇 |
原子能技术 | 98篇 |
自动化技术 | 467篇 |
出版年
2024年 | 23篇 |
2023年 | 208篇 |
2022年 | 268篇 |
2021年 | 350篇 |
2020年 | 478篇 |
2019年 | 431篇 |
2018年 | 375篇 |
2017年 | 471篇 |
2016年 | 552篇 |
2015年 | 620篇 |
2014年 | 716篇 |
2013年 | 742篇 |
2012年 | 764篇 |
2011年 | 819篇 |
2010年 | 616篇 |
2009年 | 683篇 |
2008年 | 571篇 |
2007年 | 694篇 |
2006年 | 647篇 |
2005年 | 570篇 |
2004年 | 533篇 |
2003年 | 445篇 |
2002年 | 387篇 |
2001年 | 362篇 |
2000年 | 358篇 |
1999年 | 313篇 |
1998年 | 244篇 |
1997年 | 267篇 |
1996年 | 258篇 |
1995年 | 176篇 |
1994年 | 160篇 |
1993年 | 136篇 |
1992年 | 121篇 |
1991年 | 91篇 |
1990年 | 91篇 |
1989年 | 68篇 |
1988年 | 62篇 |
1987年 | 27篇 |
1986年 | 17篇 |
1985年 | 34篇 |
1984年 | 38篇 |
1983年 | 35篇 |
1982年 | 35篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
51.
疲劳/蠕变复合作用下聚苯乙烯的交互损伤研究 总被引:3,自引:0,他引:3
探讨了在疲劳/蠕变复合作用下聚苯乙烯的损伤交互作用,结果表明,在疲劳/蠕变复合作用下聚苯乙烯存在疲劳和蠕变的交互损伤,其断裂寿命比纯疲劳或纯蠕变的断裂寿命低;断裂机制是疲劳循环载荷松动和活化了分子链或链段,从而促进蠕变运动和断裂,并且,疲劳/蠕变的交互损伤程度与温度密切相关。 相似文献
52.
G. G. Martin 《Journal of Failure Analysis and Prevention》2004,4(1):37-39
Piston failures are not a common occurrence, but they do occur, and failure is usually associated with fatigue crack growth.
Most failures initiate at the gudgeon pin hole or in the skirt of the piston. Occasionally they fail elsewhere. In the example
covered in this paper, failure initiated in the crown and progressed down to the gudgeon pin before final failure occurred.
This paper outlines the cause and mode of failure and shows that small metallurgical discontinuities can contribute to these
failures under the right circumstances. 相似文献
53.
M. R. JOYCE K. K. LEE S. SYNGELLAKIS P. A. S. REED 《Fatigue & Fracture of Engineering Materials & Structures》2004,27(11):1025-1036
Complex multi‐phase Al–Sn–Si alloys are commonly employed in the manufacture of small automotive plain bearings. The fundamental fatigue initiation behaviour of this class of alloys is currently not well understood. A range of analytical techniques were applied to investigate preferential initiation site location and to attempt to identify critical microstructural features. It was apparent from experimental studies that points of fatigue crack initiation are associated with the Si secondary phase. Using tessellation approaches and subsequently both adaptive numerical modelling and micro‐scale finite element modelling allowed the identification of features affecting the probability that a given Si phase would initiate a fatigue crack. 相似文献
54.
R. A. SMITH 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(10):901-907
The importance of the wheel–rail interface to the safe operation of railways is discussed. Some aspects of the history of rails and wheels are introduced. Several recent accidents involving the wheel–rail interface are described. The great importance of operating both vehicles and track as a system is emphasized, together with the necessity of maintaining both in good condition. 相似文献
55.
本文考虑了焊接结构的几何形状、受载形式、应力比、残余应力、尺寸效应以及材料等因素对疲劳寿命的影响,利用Peterson公式和极值疲劳切口系数概念,建立了一般应力比时焊接结构S-N曲线的预估模型.文中对几类典型的焊接结构的S-N曲线进行了预测,预测值与实验结果符合较好.本文方法可以大量减少疲劳实验,具有一定的工程实用价值. 相似文献
56.
PZT铁电薄膜的制备及电学性能研究 总被引:6,自引:1,他引:5
使用硝酸锆作锆源的溶胶-凝胶方法制备PZT铁电薄膜。他们的电学性能被测试包括电滞回线,电流I(t)特性,漏电流,矫顽场疲劳和老化。测到的PZT薄膜剩余极化8.2μC/cm~2,矫顽场68kV/cm.簿膜的寿命可超过10~(11)周期。 相似文献
57.
This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and ‘metadelaminations’ between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a ‘meta-CDS’) was observed. It was found that woven composites have a unit area of damage accumulation (called a ‘unit cell’) and the damage of each unit cell and its distribution control the total fatigue damage of the material. 相似文献
58.
59.
Abstract— In response to the increasing structural applications in duplex steels for welded structures, fatigue behaviour of a SAF 2304 grade duplex stainless steel was investigated, considering both the base metal and GTAW welded joints. Fatigue curves and fatigue limits under rotary bending fatigue were obtained. The study focused attention on the microstructural features of fatigue crack propagation of the two series of experiments, thereby permitting an evaluation of the tortuous crack path of welded joints and the mechanisms related to threshold microstructural barriers. 相似文献
60.
C. M. Branco J. M. Ferreira M. O. W. Richardson P. Fael 《International Journal of Fatigue》1992,14(6):367-376
This paper presents results of a fatigue life investigations carried out in plate specimens of a fibre-glass-reinforced phenolic matrix composite. Tensile and Young's modulus data were obtained at four different testing temperatures (room temperature, 100, 150 and 200 °C). The fatigue S−N data were obtained at room temperature only and for two stress ratio values (R=0 and 0.4). Fatigue and tensile behaviour was assesesed in the composite with the fibres aligned in the longitudinal loading direction. The results were obtained for two values of volume fraction (0.28 and 0.42) and three different glass surface treatments. A detailed comparison of fatigue results is given taking into account several fatigue parameters and also the testing variables. Results of observations of SEM fracture surfaces are also presented. 相似文献