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71.
THEINFLUENCEOFENVIRONMENTONFATIGUEANDFRACTUREOFIRONALUMINIDESSTOLOFF,N.S.andALVEN,D.A.(DepartmentofMaterialsEngineeringRensse... 相似文献
72.
Local-strain and linear-elastic fracture-mechanics (LEFM) methodologies have been investigated for prediction of the corrosion-fatigue
life of notched components of specially developed Al-2.5Mg alloys exposed to Arabian Gulf seawater environment. Corrosion-fatigue
crack initiation life estimates were obtained using strain-life relationships; corrosion-fatigue crack propagation life estimates
were obtained using LEFM relationships. The total corrosion-fatigue life was considered to be the sum of the crack initiation
and crack propagation lives. Estimated corrosion-fatigue lives were compared with experimentally obtained corrosion-fatigue
life data using center-notched specimens of three types of Al-2.5Mg alloys (containing different amounts of chromium) exposed
to Arabian Gulf seawater environment. Two notch geometries, a circular notch (K
t= 2.42) and an elliptical notch (K
t= 4.2), were investigated. Good corrosion-fatigue life predictions can be obtained using local-strain and LEFM methodologies
by determining the relevant material constants via a few simple fatigue tests on smooth specimens and a few crack-growth-rate
tests in the environment at the frequency of interest. 相似文献
73.
表面微观屈服强度与疲劳极限的关系SCIEI 总被引:8,自引:0,他引:8
本文利用X射线对不同碳含量钢的表面微观屈服强度进行了研究。试验结果表明,表面微观屈服强度σ_(ms)远低于整体材料的屈服限,是一个反映表面抵抗塑性变形能力大小的参量。材料光滑疲劳极限往往是由裂纹荫生所控制的,与表面抵抗塑性变形的能力有关。本试验表明不同材料的σ_(ms)与存活率为50%疲劳极限的关系为:σ_(ms)=(0.81—1.02)σ_(-1);40Cr不同热处理状态的σ_(ms)与存活率为99.9%疲劳极限的关系为:σ_(ms)=(0.98—1.10)σ_(-1)。σ_(ms)的测定要比疲劳极限σ_(-1)的测定省时得多,有可能在工程上获得应用。 相似文献
74.
弹簧表层优化喷丸残余应力场的工程计算方法 总被引:2,自引:0,他引:2
以往多是依靠疲劳试验或经验来选择弹簧的喷丸强化工艺参数,这种传统作法不仅人力和物力耗费大,而且所确定的工艺参数也不一定具有最佳的强化效果。依据作者提出的并已获得试验验证的“内部疲劳极限理论”,提出一种通过工程计算获得达到预先规定疲劳强度应具备的“优化残余应力场”。这样便有可能把喷丸强化工艺技术在制造业中的应用由以往单纯依靠试验和经验而步入到以工程计算为基础与少量典型试验相结合的更科学的途径。 相似文献
75.
对45钢经盐浴硫氮碳共渗处理的大批试样,进行了滚子接触疲劳性能试验,绘出了P-S-N曲线,分析了接触疲劳断口形貌及破坏机理。 相似文献
76.
高纯钛的反复弯曲疲劳 总被引:1,自引:0,他引:1
通过对不同应力幅度下高纯钛的反复弯曲疲劳的研究,发现在较低应力幅度下(~±100MPa),材料表现出循环软化,伴随表面滑移带数量的增加、发达的滑移带挤出片的出现。疲劳裂纹萌生主要与滑移带相关,在挤出物内存在两类疲劳损伤形式:沿滑移带的孔洞和与滑移带垂直的微裂纹。在较高应力幅度下(~±200MPa),则表现为硬化,次滑移及晶界附近多个滑移系同时起动,有大的形变孪晶出现。裂纹于滑移带、李晶界和晶界结点萌生。断口特征复杂,但与表面变形特征有对应关系。TEM亚结构分析表明,随应力幅度的提高,位错组态分别为散乱分布于滑移面的偶极子、位错束带和位错胞。李晶内存在复杂的精细结构,而且有堆垛层错出现。 相似文献
77.
用化学成分分析、金相组织检验、硬度测试以及对刹车鼓的宏观和微观分析等方法,对刹车鼓刹车失灵进行分析,并探讨了刹车鼓失效的原因、失效形式以及对刹车鼓铸件质量控制。 相似文献
78.
The main aim of this work was to study the effects of particle size, particle volume fraction, and matrix strength on the
long fatigue crack growth resistance of two different grades of Al alloys (Al2124-T1 and Al6061-T1) reinforced with SiC particles.
Basically, it was found that an increase in particle volume fraction and particle size increases the fatigue crack growth
resistance at near threshold and Paris regimen, with matrix strength having a smaller effect. Near final failure, the stronger
and more brittle composites are affected more by static modes of failure as the applied maximum stress intensity factor (K
max) approaches mode I plane strain fracture toughness (K
IC). 相似文献
79.
High cycle fatigue behaviour of Ti–6Al–4V alloy was studied at 623 K and 723 K. Fatigue strength decreased at elevated temperatures compared with at ambient temperature. In the short life regime, fatigue strength was lower at 723 K than at 623 K, but in the long life regime it was nearly the same at both temperatures. At elevated temperatures, cracks were generated earlier at applied stresses below the fatigue limit at ambient temperature, indicating lowered crack initiation resistance. Small cracks grew faster at elevated temperatures than at ambient temperature, which became more noticeable with increasing temperature. After allowing for the elastic modulus, small cracks still grew faster at elevated temperatures. 相似文献
80.
Effect of cold spray deposition of a titanium coating on fatigue behavior of a titanium alloy 总被引:1,自引:0,他引:1
The deposition of titanium on a titanium alloy substrate is being examined for potential use as a surface treatment for medical
prostheses. A Ti6Al4V alloy was coated with pure titanium by cold gas dynamic spraying. Coatings were deposited onto samples
with two different surface preparation methods (as-received and grit-blasted). The fatigue life of the as-received and grit-blasted
materials, both before and after coating, was measured with a rotating-bend fatigue rig. A 15% reduction in fatigue endurance
limit was observed after application of the coating to the as-received substrate, but no significant reduction was observed
on its application to the grit-blasted substrate. The reduction in fatigue endurance limit has been related to the substrate-coating
interface properties, the elastic modulus, and the residual stress states.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference, (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, 2006. 相似文献