全文获取类型
收费全文 | 56524篇 |
免费 | 3383篇 |
国内免费 | 3491篇 |
专业分类
电工技术 | 2649篇 |
综合类 | 4372篇 |
化学工业 | 13123篇 |
金属工艺 | 13018篇 |
机械仪表 | 2746篇 |
建筑科学 | 2987篇 |
矿业工程 | 1461篇 |
能源动力 | 1134篇 |
轻工业 | 1983篇 |
水利工程 | 606篇 |
石油天然气 | 6044篇 |
武器工业 | 338篇 |
无线电 | 2091篇 |
一般工业技术 | 4636篇 |
冶金工业 | 3340篇 |
原子能技术 | 588篇 |
自动化技术 | 2282篇 |
出版年
2024年 | 173篇 |
2023年 | 567篇 |
2022年 | 1079篇 |
2021年 | 1389篇 |
2020年 | 1405篇 |
2019年 | 1217篇 |
2018年 | 1170篇 |
2017年 | 1725篇 |
2016年 | 1648篇 |
2015年 | 1568篇 |
2014年 | 3280篇 |
2013年 | 3040篇 |
2012年 | 3822篇 |
2011年 | 3538篇 |
2010年 | 2956篇 |
2009年 | 3354篇 |
2008年 | 2916篇 |
2007年 | 4241篇 |
2006年 | 4484篇 |
2005年 | 3391篇 |
2004年 | 2453篇 |
2003年 | 2579篇 |
2002年 | 2081篇 |
2001年 | 1723篇 |
2000年 | 1545篇 |
1999年 | 1301篇 |
1998年 | 934篇 |
1997年 | 759篇 |
1996年 | 596篇 |
1995年 | 512篇 |
1994年 | 412篇 |
1993年 | 301篇 |
1992年 | 236篇 |
1991年 | 164篇 |
1990年 | 142篇 |
1989年 | 122篇 |
1988年 | 91篇 |
1987年 | 74篇 |
1986年 | 58篇 |
1985年 | 73篇 |
1984年 | 54篇 |
1983年 | 28篇 |
1982年 | 37篇 |
1981年 | 24篇 |
1980年 | 41篇 |
1979年 | 24篇 |
1978年 | 22篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
M.G. Pujar N. Parvathavarthini Sidhartha S. Jena B.V.R. Tata R.K. Dayal H.S. Khatak 《Journal of Materials Engineering and Performance》2008,17(6):793-801
In the present work 316LN as well as 316 stainless steel (SS) coupons each of dimensions (0.025 × 0.018 × 0.006 m3) in well-polished condition were used as two nominal electrodes which were immersed in the aerated solution of 0.5 M NaCl.
Correlated current and potential electrochemical noise (EN) signals were collected at 1 Hz sampling frequency for 1 h daily
over a period of 30 days. The detrended EN data were used to calculate the noise resistance (R
N) as well as the spectral noise resistance at zero frequency (R
SNo) values and other statistical parameters. To study the nature of pits and distribution of their diameters as well as depths,
extensive observations of the pitted and the blank specimens were carried out using Confocal Laser Scanning Microscopy (CLSM).
The current and the potential records of the two alloys showed distinct differences in their corrosion behavior. It was observed
that within less than 4 h of immersion, 316SS showed signals indicative of unstable pitting and onset of stable pitting was
noticed after 48 h of exposure. However, until about 24 h, 316LN showed just the random signals and unstable pitting was observed
after 28 h. The signals clearly indicated continuous growth of the stable pits in 316SS as against the repassivation of the
unstable pits in 316LN after 7 days exposure. It was observed that R
N values showed a continuous decrease in the case of 316SS, but were quite stable in the case of 316LN over the exposure period.
Concurrent to these observations it was observed that 316SS specimen was extensively pitted. The frequency distributions of
pit diameters as well pit depths were observed to be highest at 10-20 μm and 5-10 μm, respectively. However, pits with as
large as 70-80 μm diameter and as deep as 20-25 μm too were observed. No pits were observed in case of 316LN even after 30 days
of exposure, an observation that corroborates well with the stable R
N values. Thus, in the present investigation, the long-term tests using EN technique coupled with CLSM studies conclusively
prove that many unstable pits initiated in 316SS turn into stable ones resulting in insidious localized corrosion attack whereas
the unstable pits initiated in 316LN get passivated in the simulated coastal environment. 相似文献
42.
Amanda Alliband Daniel W. Lenz Laura E. Stevenson Travis Whitmer Rex Cash Dennis Burns Sarah Hall William T.K. Stevenson 《Progress in Organic Coatings》2008
A model has been proposed to explain the failure of the original BMS10-39 epoxy paint on upper vertical surfaces in B-52 fuel tanks. The model involves interaction of the paint with DIEGME, a fuel system ice inhibitor (FSII) in jet fuel, that is distilled from the liquid fuel. In this communication, distillation experiments used to support the model are refined to better match the mass transfer of vapor from fuel in a B-52 fuel tank at close to room temperature. The interaction of these lower temperature distillates with the paint affirms the earlier model. On the basis of these experiments it is proposed that paint failure may be controlled or eliminated by reducing the level of DIEGME in the fuel. Proposed changes in military jet fuel composition are detailed. 相似文献
43.
44.
45.
正交偶极声波测井技术在碎屑岩储层评价中的应用初探 总被引:3,自引:0,他引:3
正交偶极声波测井是一种测量地层岩石声学信息,进而分析地层各向异性的测井新技术,首次在渤海海域NB35—2—8井碎屑砂泥岩地层中应用,不仅获得了明下段主要砂体储层内部的非均质性特征信息,而且还获得了地应力方向和古流向等信息。这些信息的获得,有助于储层的精细描述与评价。 相似文献
46.
Corrosion monitoring in district heating systems has traditionally been performed by using off-line methods, such as weight loss. The disadvantage is that the method is very slow, especially in low-corrosive environments, and that it only provides information about the past corrosion (accumulated over period of time). The purpose of the work is to test on-line monitoring methods in geothermal hot water in the district heating system in Reykjavik, Iceland. Geothermal water poses certain problems with regards to corrosion monitoring due to low conductivity, high pH and the presence of sulphide. These conditions make the geothermal environment low corrosive. However, a quality control is needed, especially since the sulphide causes the steel pipes to be more vulnerable towards localized corrosion. The methods used in this study were: linear polarization resistance (LPR), harmonic analysis (HA), electrochemical noise (EN) and zero resistance ammetry (ZRA). The Pitting Factor was measured with EN and showed promising results for measuring-localized corrosion on-line. A crevice corrosion cell also gave good results but had a low lifetime. However, the results of a galvanic corrosion cell (Fe/Cu) proved more difficult to interpret since they were dependent both on the dissolved oxygen and the sulphide level. 相似文献
47.
结合大同铁路分局中心医院直线加速器室工程实际,介绍了大体积防射线混凝土的特点及施工中应注意的事项,并阐述了具体的施工技术。 相似文献
48.
49.
50.