全文获取类型
收费全文 | 53724篇 |
免费 | 6482篇 |
国内免费 | 2479篇 |
专业分类
电工技术 | 9051篇 |
综合类 | 4046篇 |
化学工业 | 9292篇 |
金属工艺 | 7170篇 |
机械仪表 | 2733篇 |
建筑科学 | 5913篇 |
矿业工程 | 1372篇 |
能源动力 | 4720篇 |
轻工业 | 2443篇 |
水利工程 | 2172篇 |
石油天然气 | 1554篇 |
武器工业 | 482篇 |
无线电 | 2552篇 |
一般工业技术 | 5273篇 |
冶金工业 | 2004篇 |
原子能技术 | 312篇 |
自动化技术 | 1596篇 |
出版年
2024年 | 343篇 |
2023年 | 1123篇 |
2022年 | 2234篇 |
2021年 | 2416篇 |
2020年 | 2286篇 |
2019年 | 1834篇 |
2018年 | 1688篇 |
2017年 | 2303篇 |
2016年 | 2313篇 |
2015年 | 2414篇 |
2014年 | 3476篇 |
2013年 | 3263篇 |
2012年 | 4125篇 |
2011年 | 4520篇 |
2010年 | 2971篇 |
2009年 | 3289篇 |
2008年 | 2665篇 |
2007年 | 2982篇 |
2006年 | 2772篇 |
2005年 | 2264篇 |
2004年 | 1834篇 |
2003年 | 1605篇 |
2002年 | 1342篇 |
2001年 | 1175篇 |
2000年 | 976篇 |
1999年 | 865篇 |
1998年 | 665篇 |
1997年 | 590篇 |
1996年 | 425篇 |
1995年 | 426篇 |
1994年 | 350篇 |
1993年 | 250篇 |
1992年 | 199篇 |
1991年 | 165篇 |
1990年 | 108篇 |
1989年 | 101篇 |
1988年 | 67篇 |
1987年 | 52篇 |
1986年 | 27篇 |
1985年 | 25篇 |
1984年 | 45篇 |
1983年 | 20篇 |
1982年 | 23篇 |
1981年 | 9篇 |
1980年 | 18篇 |
1979年 | 7篇 |
1961年 | 2篇 |
1960年 | 3篇 |
1959年 | 6篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
火灾中考虑整体性的钢梁破坏形态研究 总被引:4,自引:0,他引:4
1990年英国broadgate火灾之后,结构整体性以及由于温度而在整体结构中产生的附加应力得到了人们的重视。处于整体结构中的梁的破坏形态与单个构件的梁的破坏形态有较大差别,当考虑梁的悬链线效应时其抗火承载力明显提高。文章采用大型通用有限元程序ANSYS,对T.C.HLiu所做试验进行了验证,表明了有限元计算悬链线效应的可靠性,同时通过计算分析,提出了处于整体结构中钢梁在火灾中破坏的5个阶段,并给出了钢结构防火的概念设计建议。 相似文献
242.
A. V. Kryukov 《Measurement Techniques》2006,49(12):1218-1223
The static characteristics of platinum resistance thermometers with different platinum purities were measured. It is shown
that in the 0–420°C range the ITS-90 method gives an error of less than 0.01°C, while in the 0–230°C range the error is less
than 0.006°C.
__________
Translated from Izmeritel’naya Tekhnika, No. 12, pp. 33–36, December, 2006. 相似文献
243.
The sliding wear and impact wear resistances of D2 steel with nitriding layer, PVD titanium nitride coating and their duplex treatment were investigated. The experimental results suggest that the duplex treatment has the best sliding and impact wear resistances under experimental conditions. And the wear resistance of PVD titanium nitride is better than that of nitriding. The impact wear resistance and wear mechanism of all three surface layers remain unchanged under impact load of 0.2 J or 1 J. All samples end with the same symptom of flaking. 相似文献
244.
245.
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
246.
247.
248.
Construction of the La Grande Complex in Eastern Canada called for complete or partial diversion of six rivers, the mean annual discharge of which varied from 60 to 1600 m3 s?1, and the transfer of water from two adjoining watersheds (1586m3 s?1) into La Grande Rivière. Three of these rivers with reduced flow, Eastmain (from 700 to 95m3 s?1), Opinaca (from 260 to 35m3 s?1), and Caniapiscau (from 1708 to 960m3 s?1) and the waterways with increased flows, Boyd-Sakami (from 1 to 811m3 s?1) and La Grande Rivière (from 1760 to 3400m3 s?1) were intensively monitored from 1978 to 1988, while the others were surveyed sporadically. Very few modifications were observed, compared to previous conditions, in banks stability, water quality, and aquatic fauna of the affected rivers: those which appeared can be explained by the water level fluctuations, the water quality of the tributaries of the residual drainage basin, and/or by the direct influence of the reservoirs. In James Bay, the areal extent of the Eastmain River and La Grand Rivière plumes varied with discharge in an exponential relation, mostly under ice cover; resources from the coastal environment had not yet undergone any major changes. Because of the very small population dwelling in the area, less than 3000 inhabitants, modifications in the hydrological regime of these rivers did cause relatively few impacts, the main being greater banks instability in specific locations, reduction of the thickness and ice cover on La Grande Rivière, enhancement of navigation constraints on Eastmain River, and higher mercury levels in fish related to operation of the reservoirs. 相似文献
249.
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
250.
从分析中心焦柱在炉缸内的受力出发,计算了1000 ̄5580m^3高炉大喷煤前后中心焦柱在炉缸铁水内的沉入深度,分析了炉缸内铁水环流的产生与炉缸内衬侵的关系,分析表明大喷煤有得利抑制铁水环流对缸内补的冲刷,提出了降低铁水环流对炉缸内衬侵蚀的途径。 相似文献