全文获取类型
收费全文 | 12760篇 |
免费 | 1359篇 |
国内免费 | 985篇 |
专业分类
电工技术 | 257篇 |
综合类 | 1082篇 |
化学工业 | 653篇 |
金属工艺 | 2748篇 |
机械仪表 | 2082篇 |
建筑科学 | 956篇 |
矿业工程 | 177篇 |
能源动力 | 351篇 |
轻工业 | 238篇 |
水利工程 | 52篇 |
石油天然气 | 414篇 |
武器工业 | 147篇 |
无线电 | 310篇 |
一般工业技术 | 4394篇 |
冶金工业 | 671篇 |
原子能技术 | 103篇 |
自动化技术 | 469篇 |
出版年
2024年 | 53篇 |
2023年 | 219篇 |
2022年 | 272篇 |
2021年 | 349篇 |
2020年 | 483篇 |
2019年 | 433篇 |
2018年 | 393篇 |
2017年 | 494篇 |
2016年 | 570篇 |
2015年 | 627篇 |
2014年 | 725篇 |
2013年 | 777篇 |
2012年 | 764篇 |
2011年 | 844篇 |
2010年 | 608篇 |
2009年 | 692篇 |
2008年 | 583篇 |
2007年 | 691篇 |
2006年 | 652篇 |
2005年 | 569篇 |
2004年 | 526篇 |
2003年 | 436篇 |
2002年 | 382篇 |
2001年 | 365篇 |
2000年 | 358篇 |
1999年 | 316篇 |
1998年 | 249篇 |
1997年 | 273篇 |
1996年 | 258篇 |
1995年 | 181篇 |
1994年 | 163篇 |
1993年 | 140篇 |
1992年 | 122篇 |
1991年 | 92篇 |
1990年 | 96篇 |
1989年 | 72篇 |
1988年 | 68篇 |
1987年 | 30篇 |
1986年 | 22篇 |
1985年 | 33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 15 毫秒
21.
L. T. MO M. HUURMAN S. P. WU A. A. A. MOLENAAR 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(9):823-831
Tensile fatigue behaviours of bitumen–stone adhesion were investigated using a dynamic mechanics analyser under stress‐controlled mode at two temperatures of 5 and 25°C and various controlled‐stress levels. Failure characteristics including interfacial failure and cohesive failure were examined using image analysis of fracture surfaces. Finite‐element analysis on stress distributions was conducted under different temperatures, film thickness and interfacial bonding conditions. A Coulomb–Mohr like criterion in combination with shear and normal stresses is proposed to deal with the extreme thin adhesive layer, which can be further simplified into an adhesive zone without significant loss of accuracy for stress analysis. 相似文献
22.
The influence of an aggressive environment (0.6 M, aerated NaCl solution) on short fatigue crack initiation and growth behaviour has been studied. The study involved three major test series, namely: air fatigue, corrosion fatigue, and intermittent air fatigue/corrosion fatigue. The above tests carried out under fully reversed torsional loading conditions at a frequency of 5 Hz, showed that it was the non-metallic inclusions which took part in crack initiation resulting from debonding at metal matrix/inclusion interface and pitting of inclusions in both air and corrosove environments, respectively. Short fatigue crack growth results in these two environments obtained by using plastic replication technique, indicated a large effect of microstructure i.e. prior austenite grain boundaries. The stage/stages at which the environmental contribution was dominant has been discussed by considering the results achieved from intermittent tests. However, the mechanisms involved in corrosion fatigue short crack growth have also been described in the light of results obtained from futher investigations carried out by conducting corrosion fatigue tests under applied cathodic potential conditions and tests on hydrogen pre-charged specimens under air fatigue and uniaxial tension conditions. 相似文献
23.
K. P. Balan 《Journal of Failure Analysis and Prevention》2002,2(3):71-74
Wire ropes, pulleys, counterweights, and connecting systems are used for auto tensioning of contact wires of electric railways.
A wire rope in one such auto tensioning system suffered premature failure. Failure investigation revealed fatigue cracks initiating
at nonmetallic inclusions near the surface of individual wire strands in the rope. The inclusions were identified as Al-Ca-Ti
silicates in a large number of stringers, and some oxide and nitride inclusions were also found. The wire used in the rope
did not conform to the composition specified for AISI 316 grade steel, nor did it satisfy the minimum tensile strength requirements.
Failure of the wire rope was found to be due to fatigue; however, the ultimate fracture of the rope was the result of overload
that occurred after fatigue failure had reduced the number of wire strands supporting the load. 相似文献
24.
25.
本文研究在13SiMnNiCrMoV 结构钢中用尖裂纹的应力强度因子来反映三点弯曲缺口试样的疲劳裂纹萌生规律。当 R=0.1,f=100Hz,试样尺寸 B×W×L=12.5×25×117mm 时,缺口名义应力幅的门槛值为Δσ_(th)=3315ρ~(0.352) MPa,0.5mm≤ρ≤5mmΔK_(th)=250ρ~(0.352) MPam~(1/2)门槛值与ρ有关。同时得到缺口裂纹萌生的循环次数 N_i 与名义应力幅Δσ、缺口曲率半径ρ的定量关系是N_i=3.98×10~(22)ρ~(1.62)/Δσ~(4.85),N_i≤10~(5.5)并讨论了(ΔK_1/ρ~(1/2))_(th)与ρ无关的结论。 相似文献
26.
K.W. Allen S.M. Smith W.C. Wake A.O. van Raalte 《International Journal of Adhesion and Adhesives》1985,5(1):23-32
The effect of cyclic stressing on the strength of single lap adhesive joints has been studied and a considerable reduction in strength observed when the maximum stress exceeds about 40% of the ultimate tensile strength, but whether or not a true endurance limit exists is not proven. Fallacies are shown in some of the techniques which have been proposed for studying the fatigue behaviour of adhesive joints. 相似文献
27.
G. Biallas Dr.‐Ing. C. Sick J. Schneider K.‐H. Trautmann 《Materialwissenschaft und Werkstofftechnik》2007,38(9):705-711
Biaxial fatigue of friction stir welded stiffened panels Within the framework of the European WelAir project, cruciform specimens made from stiffening FSW overlap joints were fatigued in the DLR biaxial test rig. To resemble the loading situation of pressurized fuselage structures, proportional loading without any phase shift, but with different load ratios λ between the loading components in both directions was applied.Natural crack initiation and subsequent crack growth were governed by the stiffness gradient caused by introducing the stringer. Cracks initiated and propagated at run‐in and run‐out locations in a direction perpendicular to the weld seam. The shortest fatigue life was observed for uniaxial loading in welding direction (λ = 0). An additional stress component perpendicular to the joint line (λ > 0) resulted in a higher number of cycles to failure. Similar to single stringer panels, increasing the load ratio also increased the number of cycles to failure for FSW clip‐stringer structural members, but additionally gives a different location of the fatal crack. 相似文献
28.
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
29.
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
30.
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