全文获取类型
收费全文 | 55230篇 |
免费 | 5609篇 |
国内免费 | 2661篇 |
专业分类
电工技术 | 3272篇 |
技术理论 | 1篇 |
综合类 | 4000篇 |
化学工业 | 11339篇 |
金属工艺 | 8468篇 |
机械仪表 | 2187篇 |
建筑科学 | 6234篇 |
矿业工程 | 1585篇 |
能源动力 | 2740篇 |
轻工业 | 4018篇 |
水利工程 | 2152篇 |
石油天然气 | 1645篇 |
武器工业 | 391篇 |
无线电 | 2782篇 |
一般工业技术 | 6806篇 |
冶金工业 | 3350篇 |
原子能技术 | 363篇 |
自动化技术 | 2167篇 |
出版年
2024年 | 351篇 |
2023年 | 1109篇 |
2022年 | 2142篇 |
2021年 | 2368篇 |
2020年 | 2317篇 |
2019年 | 1880篇 |
2018年 | 1764篇 |
2017年 | 2266篇 |
2016年 | 2237篇 |
2015年 | 2214篇 |
2014年 | 3028篇 |
2013年 | 3322篇 |
2012年 | 3679篇 |
2011年 | 4173篇 |
2010年 | 2942篇 |
2009年 | 3244篇 |
2008年 | 2716篇 |
2007年 | 3184篇 |
2006年 | 3108篇 |
2005年 | 2503篇 |
2004年 | 2092篇 |
2003年 | 1828篇 |
2002年 | 1554篇 |
2001年 | 1287篇 |
2000年 | 1060篇 |
1999年 | 936篇 |
1998年 | 765篇 |
1997年 | 651篇 |
1996年 | 483篇 |
1995年 | 463篇 |
1994年 | 408篇 |
1993年 | 279篇 |
1992年 | 229篇 |
1991年 | 189篇 |
1990年 | 142篇 |
1989年 | 120篇 |
1988年 | 78篇 |
1987年 | 63篇 |
1986年 | 44篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 32篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1964年 | 11篇 |
1961年 | 10篇 |
1959年 | 11篇 |
1957年 | 13篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
S—135钢板是水电站用高强耐磨不锈钢板,既要求强度高、韧性好,又要求耐磨、耐蚀性强,生产难度较大。除我厂外,目前国内尚无其它厂家能够生产这种钢板。该钢板在加热轧制,冷却过程中要解决很多技术难点。我们通过采用特殊的控制轧制和控制冷却工艺,很好地解决了诸多技术难点,使S—135钢板的开发研制取得了成功。为电站用高强度耐磨不锈钢生产提供了宝贵的经验,也为控制轧制及控制冷却技术在中板生产行业的应用起到了积极的推动作用。 相似文献
102.
The change in the internal energy during uniaxial tensile deformation of austenitic stainless steels EN 1.4301 (AISI 304) and EN 1.4318 (AISI 301LN) was determined by measuring the extent of γ→α'‐martensite transformation and the temperature increase of the samples. From the results the fraction of the stored energy of cold work and the free energy change related to the strain‐induced γ→α'‐martensite transformation were determined. The fraction of stored energy varied around 0.4. With the metastable steel grades the free energy change related to the γ→α'‐martensite transformation was found to vary between ‐98 MJ/m3 and ‐206 MJ/m3 depending on the austenite stability of the steel. Furthermore, the magnitude of the mechanical driving force was estimated by comparing the results with the free energy change of thermally induced transformation. 相似文献
103.
Phase-change thermal energy storage using spherical capsules: performance of a test plant 总被引:1,自引:0,他引:1
J.P Bédécarrats F Strub B Falcon J.P Dumas 《International Journal of Refrigeration》1996,19(3):187-196
The aim of this paper is the study of an industrial process of energy storage usable for air conditioning or refrigeration, investigating a test plant which is a tank with a reduced size, filled with randomly dispersed commercial nodules, placed in a refrigeration loop. The nodules are spherical capsules in which phase change materials (PCM) are encapsulated. This test plant permits the study at length of the behaviour of the tank with, in particular, the charge mode taking into account the undercooling and the discharge mode. A simulation program that considers aspects of both the surrounding heat transfer fluid and the phase-change material packed inside the nodules is developed here in the cases of the charge and the discharge processes. The simulation results are then compared with experimental observations. 相似文献
104.
用自制的旋臂式磨蚀实验仪,研究了5种高密度聚乙烯和1种顺丁橡胶改性的高密度聚乙烯,在铁尾矿和铁精矿浆体中的耐磨蚀性。耐磨蚀性最差的是HDPE2200J,耐磨蚀性较差的是HDPE6300M;HDPE5000s,6098和2480的耐磨蚀性较好;HDPE/cis-BR的耐磨蚀性最好。 相似文献
105.
In the initial part the change of microstructure for steel X20 CrMoV 121 is discussed in terms of the distribution of carbide precipitates and its effects on accelerated creep resistance and hardness are presented. In the following, experimental results of microstructure and accelerated creep resistance are presented for the steels X20CrMoV 121 and P91 annealed for up to 8760 hours at 650°C and 750°C before the testing. A similar evolution of the distribution of carbide particles of a size above 102 nm is found for both steels, while the accelerated creep resistance is diminished much stronger for the steel X20CrMoV 121. This difference is due to a greater stability of NbC than that of VC precipitates, both related to the evolution of the chemical composition of complex chromium, molybdenum and iron carbide particles. 相似文献
106.
A. Sergeev A. Semenov V. Trifonov B. Karasik G. Gol''tsman E. Gershenzon 《Journal of Superconductivity》1994,7(2):341-344
The thermal boundary resistance at the YBaCuO thin film/Al2O3 substrate interface was investigated. The transparency for thermal phonons incident on the interface as well as for phonons moving from the substrate was determined. We have measured a transient voltage response of current-biased films to continuously modulated radiation. The observed knee in the modulation frequency dependence of the response reflects the crossover from the diffusion regime to the contact resistance regime of the heat transfer across the interface. The values of transparency were independently deduced both from the phonon escape time and from the time of phonon return to the film which were identified with peculiarities in the frequency dependence. The results are much more consistent with the acoustic mismatch theory than the diffuse mismatch model.We are grateful to A. Elantev for helpful discussion. We acknowledge the financial support of the Russian Scientific Council on the HTS problem (Project No. 90462). 相似文献
107.
An experimental device able to detect the load eccentricity in helical compression springs is described. The theory underlying the resolution of measured bending strains of the apparatus into effective load eccentricity is discussed. Laboratory results are offered for heavy duty springs and compared to theoretical estimates retrieved from the literature. 相似文献
108.
介绍一种新的高阻测试方法,可满足对高达1×10^16Ω的测试要求。测试结果显示,对于1×10^13Ω重复误差优于±2%。高阻测试电路通过接口与6809微机配套使用,操作简便,读数直观,便于长时间重复测量。 相似文献
109.
110.