全文获取类型
收费全文 | 29080篇 |
免费 | 3434篇 |
国内免费 | 2760篇 |
专业分类
电工技术 | 1130篇 |
技术理论 | 1篇 |
综合类 | 3061篇 |
化学工业 | 1338篇 |
金属工艺 | 2740篇 |
机械仪表 | 1718篇 |
建筑科学 | 5359篇 |
矿业工程 | 819篇 |
能源动力 | 667篇 |
轻工业 | 428篇 |
水利工程 | 1209篇 |
石油天然气 | 917篇 |
武器工业 | 275篇 |
无线电 | 3724篇 |
一般工业技术 | 5720篇 |
冶金工业 | 1354篇 |
原子能技术 | 254篇 |
自动化技术 | 4560篇 |
出版年
2024年 | 124篇 |
2023年 | 326篇 |
2022年 | 725篇 |
2021年 | 740篇 |
2020年 | 946篇 |
2019年 | 828篇 |
2018年 | 746篇 |
2017年 | 1035篇 |
2016年 | 1074篇 |
2015年 | 1151篇 |
2014年 | 1688篇 |
2013年 | 1788篇 |
2012年 | 1909篇 |
2011年 | 2185篇 |
2010年 | 1777篇 |
2009年 | 1977篇 |
2008年 | 1960篇 |
2007年 | 2365篇 |
2006年 | 1937篇 |
2005年 | 1703篇 |
2004年 | 1227篇 |
2003年 | 1167篇 |
2002年 | 1016篇 |
2001年 | 880篇 |
2000年 | 709篇 |
1999年 | 541篇 |
1998年 | 504篇 |
1997年 | 434篇 |
1996年 | 328篇 |
1995年 | 278篇 |
1994年 | 231篇 |
1993年 | 180篇 |
1992年 | 162篇 |
1991年 | 126篇 |
1990年 | 127篇 |
1989年 | 92篇 |
1988年 | 66篇 |
1987年 | 26篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 36篇 |
1983年 | 30篇 |
1982年 | 30篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 3篇 |
1963年 | 2篇 |
1959年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
P.-Y. CHANG J.-M. YANG H. SEO H. T. HAHN 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(12):1158-1171
The off‐axis fatigue cracking behaviour of notched fibre metal laminates under constant amplitude loading conditions was investigated experimentally and numerically. It was found that the off‐axis fatigue crack initiation life decreased as the off‐axis angles increased. This indicated that the off‐axis laminates raised the applied stress level in the aluminium (Al) layer and subsequently resulted in earlier cracking in the Al layer. The off‐axis fatigue crack initiation lives of notched fibre metal laminates were predicted using lamination theory and an energy‐based critical plane fatigue damage analysis from the literature. After a crack initiated in the Al layer, it was observed that the crack path angles of the off‐axis specimens were neither perpendicular to the fibre nor to the loading direction. A finite‐element model was established for predicting the crack path angles. 相似文献
32.
Crack closure in fibre metal laminates 总被引:1,自引:0,他引:1
H.M. PLOKKER R.C. ALDERLIESTEN R. BENEDICTUS 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(7):608-620
GLARE is a fibre metal laminate (FML) built up of alternating layers of S2-glass/FM94 prepreg and aluminium 2024-T3. The excellent fatigue behaviour of GLARE can be described with a recently published analytical prediction model. This model is based on linear elastic fracture mechanics and the assumption that a similar stress state in the aluminium layers of GLARE and monolithic aluminium result in the same crack growth behaviour. It therefore describes the crack growth with an effective stress intensity factor (SIF) range at the crack tip in the aluminium layers, including the effect of internal residual stress as result of curing and the stiffness differences between the individual layers. In that model, an empirical relation is used to calculate the effective SIF range, which had been determined without sufficiently investigating the effect of crack closure. This paper presents the research performed on crack closure in GLARE. It is assumed that crack closure in FMLs is determined by the actual stress cycles in the metal layers and that it can be described with the available relations for monolithic aluminium published in the literature. Fatigue crack growth experiments have been performed on GLARE specimens in which crack growth rates and crack opening stresses have been recorded. The prediction model incorporating the crack closure relation for aluminium 2024-T3 obtained from the literature has been validated with the test results. It is concluded that crack growth in GLARE can be correlated with the effective SIF range at the crack tip in the aluminium layers, if it is determined with the crack closure relation for aluminium 2024-T3 based on actual stresses in the aluminium layers. 相似文献
33.
V. P. Efimov 《Journal of Mining Science》2003,39(4):384-386
The procedure is proposed for estimating the crack resistance and tensile strength of rocks by the results of experiments on disk samples with holes. The gradient approach to the strength problem is employed in processing the experimental data. 相似文献
34.
35.
StudyonHotDeformationCracksofSteelD2UsingProcesingMapGaoShan,LiuXianghua,WangGuodongABSTRACTThehotdeformationbehaviorsofsteel... 相似文献
36.
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
37.
38.
V. P. Naumenko 《Strength of Materials》1996,28(1):10-18
The adoption of unified fracture mechanics terminology (UFMT) will promote efficient communication between specialists in different fields of fracture research, harmonization of national and international standards relating to fracture mechanics, and last but not least improvement of the existing methodology for teaching and education in fatigue and fracture. In this paper the definitions of some basic and related terms included in different standards on fracture mechanics terminology are confronted with one another. Alternative definitions of the same terms are offered. By this strategy the author tries to show that the definitions of basic and related terms appropriate for the UFMT should emerge as a consequence of harmonizing a crack model with an actual crack and then both taken together with a fracture model, laboratory test methods, and failure assessment codes.Published in Problemy Prochonsti, No. 1, pp. 17–29, January, 1996.This paper is published as a matter of discussion. 相似文献
39.
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
40.
Shou-ren Wang Hao-ran Geng Lin-hai Hui Ying-zi Wang 《Journal of Materials Engineering and Performance》2007,16(1):113-118
A multiphase reticulated porous ceramic (RPC) as Si3N4–Al2O3–SiO2 was fabricated by replication techniques. Proper volumes of additives and twice sinter- twice immerse process endow the RPC
an excellent crack healing and submerging property. The compressive strength and fracture toughness improved owing to the
crack bridging behavior. The existence of pores in struts in RPC blunt the crack tip and increased the external force needed
to propagate the crack. The mechanisms play a beneficial role in enhancing the compressive strength and fracture strength.
Si3N4 RPC with additives of 5%Al and 5% Al2O3 yielded the compressive strength of 9.8 MPa and fracture toughness of 0.3 MPa m1/2. 相似文献