全文获取类型
收费全文 | 15988篇 |
免费 | 1531篇 |
国内免费 | 1089篇 |
专业分类
电工技术 | 333篇 |
技术理论 | 4篇 |
综合类 | 1327篇 |
化学工业 | 909篇 |
金属工艺 | 2738篇 |
机械仪表 | 2021篇 |
建筑科学 | 2074篇 |
矿业工程 | 240篇 |
能源动力 | 392篇 |
轻工业 | 637篇 |
水利工程 | 152篇 |
石油天然气 | 498篇 |
武器工业 | 171篇 |
无线电 | 518篇 |
一般工业技术 | 4659篇 |
冶金工业 | 712篇 |
原子能技术 | 119篇 |
自动化技术 | 1104篇 |
出版年
2024年 | 51篇 |
2023年 | 257篇 |
2022年 | 394篇 |
2021年 | 536篇 |
2020年 | 660篇 |
2019年 | 584篇 |
2018年 | 525篇 |
2017年 | 601篇 |
2016年 | 774篇 |
2015年 | 858篇 |
2014年 | 1040篇 |
2013年 | 1091篇 |
2012年 | 1430篇 |
2011年 | 1020篇 |
2010年 | 822篇 |
2009年 | 895篇 |
2008年 | 721篇 |
2007年 | 798篇 |
2006年 | 677篇 |
2005年 | 585篇 |
2004年 | 529篇 |
2003年 | 442篇 |
2002年 | 383篇 |
2001年 | 355篇 |
2000年 | 356篇 |
1999年 | 313篇 |
1998年 | 250篇 |
1997年 | 267篇 |
1996年 | 262篇 |
1995年 | 181篇 |
1994年 | 162篇 |
1993年 | 137篇 |
1992年 | 119篇 |
1991年 | 90篇 |
1990年 | 90篇 |
1989年 | 72篇 |
1988年 | 63篇 |
1987年 | 28篇 |
1986年 | 20篇 |
1985年 | 37篇 |
1984年 | 38篇 |
1983年 | 37篇 |
1982年 | 35篇 |
1981年 | 3篇 |
1980年 | 10篇 |
1958年 | 2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
1.
During the service life of structural sealant glazing (SSG) facades, the load-bearing capacity of the silicone bonds needs to be guaranteed. Laboratory tests can assess the durability of SSG-systems based on mechanical characteristics of the bond after simultaneous exposure to both climatic and mechanical loads. This article studies how the material characteristics of two common structural sealants are affected by laboratory and field exposure. Dynamic mechanical analysis (DMA) confirms a reduction in the dynamic modulus of exposed silicone samples. Results from thermogravimetric analysis, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and small-angle X-ray scattering/wide-angle X-ray scattering show differences between the two sealants and indicate no/minor changes in the composition and morphology of the laboratory and field exposed sealants. Mechanical characterization methods, such as DMA, and tensile and shear testing of the structural bond, are shown to be sensitive toward the combined climatic and mechanical loadings, and are hence suitable for studying degradation mechanisms of structural sealants. 相似文献
2.
3.
4.
《Journal of the European Ceramic Society》2020,40(13):4647-4654
The in vitro lifetime assessment of dental zirconia has been the focus of researchers. This work mainly studied the cyclic fatigue lifetime in saliva and aging lifetime of three commercial zirconia dental materials: two kinds of 3 mol%-yttria stabilized zirconia ST(super-translucence) and MT(medium-translucence), in which MT contains a small amount of alumina; a 5 mol%-yttria stabilized zirconia TT(tooth-translucency). ST and MT materials have higher initial mechanical strength (flexural strength) and initial crack propagation threshold than TT materials, thus they have longer cycle fatigue lifetime, but TT has best aging resistance(no aging) in existing aging procedures. MT has a higher initial mechanical strength and better aging resistance than ST samples due to the influence of alumina at grain boundary, but has lower strength reliability. Finally the service lifetime of the three materials was evaluated, and some guidance for their use is provided. 相似文献
5.
As a symbol of sharing economy, ride-hailing services have spread to Asia, where various forms of services have been established according to the existing socio-technical regimes, including legal, policy, and environmental concerns. China, in particular, has accepted ride-hailing services by revising existing institutions. This study analyzes China’s acceptance of ride-hailing services in the socio-technical system context set up for legacy services. Simulation modeling, combined with transition theory and an agent-based model, is used to analyze the data. This study calculates consumer disutility based on mobility market share, reflecting consumer preference, and predicts the sustainability of ride-hailing services. The simulation results conclude that legalization and socio-technical context are of importance for sustainable mobility. 相似文献
6.
Muntasir Hashim Farnoosh Farhad David Smyth‐Boyle Robert Akid Xiang Zhang Philip J. Withers 《工业材料与腐蚀》2019,70(11):2009-2019
The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits. 相似文献
7.
吴敬东 《湖南工业职业技术学院学报》2015,(2):137-140
高校是培养人才的摇篮,肩负着科教兴国、人才强国两大历史性战略任务。由于社会环境的复杂化,人际关系的交错性,新时代的大学生行为状况给高校学生管理工作带来了新的挑战。针对新时期大学生行为特点,我们通过加强党建工作、强化学风建设、做好班级自主管理和深化社会服务四个方面工作进行分析,提出了全面引导、约束、规范和优化大学生的行为的建议和对策,从而有效解决新形势下普通高校学生管理工作的实际困难。 相似文献
8.
Rolling contact fatigue in bearing steels is manifested by dark-etching regions, which are attributed to deformation induced tempering. In order to quantitatively explain this phenomenon, a model is suggested for martensite tempering assisted by dislocation glide during rolling contact fatigue. In the model, dislocations transport carbon from the matrix to carbide particles, provided that the carbon is located at a certain distance range from the dislocation contributing to the tempering process. By calculating the amount of carbon in the matrix, the kinetics of carbide thickening and hardness reduction are computed. It is found that the dark-etching region kinetics can be controlled by both bearing operation conditions (temperature and deformation rate) and microstructure (type, size, and volume fraction of carbides). The model is validated against tested bearings, and its limitations are discussed. 相似文献
9.
《Ceramics International》2020,46(15):24213-24224
We report an experimental approach, designed based on the recent findings that domain switching in ferroelectric ceramics can be separated into three regimes during antiparallel electric field loading, to investigate the influence of domain switching process on the electrical fatigue behavior of ferroelectrics. Uniaxial compressive stress (−2 MPã -100 MPa) and thermal loading (20 °C–150 °C) were used to tune the domain switching process. Under the same loading condition, the bipolar electrical fatigue behavior of soft lead zirconate titanate ceramics was systematically characterized. The amplitude and frequency of the applied electric field are 2 kV/mm and 10 Hz, respectively. By analyzing the evolution of the domain switching process, combined with the measured polarization and strain response, as well as the cracks observed on the surface of the specimen, it is found that the fatigue of ferroelectric ceramics was mainly related to the domain switching process near the coercive electric field: the regime 2 defined in this paper. The underlying mechanism was further discussed by considering the interplay between the domain switching process with the main factors affecting the electrical fatigue of ferroelectrics, namely defect redistribution, charge carrier injection, and crack initiation. 相似文献
10.
Yumio Yato 《Journal of Nuclear Science and Technology》2019,56(4):311-316
When UF6 is handled in leak tight system, the amount of uranium compound formed on the surface of containers, valves, and others in UF6 handling facilities is not so significant for a short term that special attention has not been given to this problem. The present work was done to throw some more light on this problem based on the recent experiment. We discuss the possibility that the intermolecular transfer of a fluorine atom from UF6 to UF5 may participate in the formation of uranium compound. The discussion includes also the unique features contained in the experimental result, the reaction processes assumed in this problem, and the derivation of a rate equation for expressing the deposition of uranium compound. Furthermore, we propose a new method for determining nonlinear parameters included in a governing differential equation having two variables for expressing the deposition of uranium compound from experimental raw data. 相似文献