全文获取类型
收费全文 | 58801篇 |
免费 | 5086篇 |
国内免费 | 1958篇 |
专业分类
电工技术 | 1511篇 |
综合类 | 5050篇 |
化学工业 | 16676篇 |
金属工艺 | 2132篇 |
机械仪表 | 1831篇 |
建筑科学 | 8740篇 |
矿业工程 | 640篇 |
能源动力 | 586篇 |
轻工业 | 7641篇 |
水利工程 | 839篇 |
石油天然气 | 563篇 |
武器工业 | 316篇 |
无线电 | 8512篇 |
一般工业技术 | 7576篇 |
冶金工业 | 1490篇 |
原子能技术 | 279篇 |
自动化技术 | 1463篇 |
出版年
2024年 | 191篇 |
2023年 | 676篇 |
2022年 | 1314篇 |
2021年 | 1527篇 |
2020年 | 1480篇 |
2019年 | 1341篇 |
2018年 | 1327篇 |
2017年 | 1881篇 |
2016年 | 1747篇 |
2015年 | 2042篇 |
2014年 | 2940篇 |
2013年 | 3188篇 |
2012年 | 4021篇 |
2011年 | 4095篇 |
2010年 | 3260篇 |
2009年 | 3490篇 |
2008年 | 3183篇 |
2007年 | 4154篇 |
2006年 | 4063篇 |
2005年 | 3436篇 |
2004年 | 2789篇 |
2003年 | 2342篇 |
2002年 | 2121篇 |
2001年 | 1783篇 |
2000年 | 1424篇 |
1999年 | 1195篇 |
1998年 | 854篇 |
1997年 | 723篇 |
1996年 | 573篇 |
1995年 | 512篇 |
1994年 | 460篇 |
1993年 | 368篇 |
1992年 | 372篇 |
1991年 | 308篇 |
1990年 | 239篇 |
1989年 | 164篇 |
1988年 | 48篇 |
1987年 | 44篇 |
1986年 | 23篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 4篇 |
1980年 | 18篇 |
1979年 | 5篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1964年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The results of a comprehensive experimental program, aimed at providing a fundamental understanding of the behavior of shear-critical exterior reinforced concrete (RC) joints strengthened with fiber reinforced polymers (FRP) under simulated seismic load, are presented in this study. The role of various parameters on the effectiveness of FRP is examined through 2/3-scale testing of 18 exterior RC joints. Conclusions are drawn on the basis of certain load versus imposed displacement response characteristics, comprising the strength (maximum lateral load), the stiffness, and the cumulative energy dissipation capacity. The results demonstrate the important role of mechanical anchorages in limiting premature debonding, and they provide important information on the role of various parameters, including: area fraction of FRP; distribution of FRP between the beam and the column; column axial load; internal joint (steel) reinforcement; initial damage; carbon versus glass fibers; sheets versus strips; and effect of transverse beams. 相似文献
102.
对称配筋小偏心受压构件的截面设计 总被引:4,自引:1,他引:3
对小偏心受压构件在对称配筋情况下的截面配筋计算,提出用最佳一次逼近多项式简化基本公式,直接按二次方程求解ξ的近似方法,具有精度高,相对误差小,计算方便等优点,可供工程设计人员参考。 相似文献
103.
一种新型智能光纤传感器的研制与应用 总被引:5,自引:2,他引:3
光纤传感技术是一种新型的传感技术,目前已受到国内外广泛重视而得到高速发展。光纤液位变送器具有高精度、高可靠性,不受电磁干扰等优点,特别是在防爆要求非常高的油气集输领域,它的无电检测、光信号传输完全消除了不安全的因素,为易燃易爆场所提供了安全可靠的检测仪器。 相似文献
104.
防腐蚀施工工艺掌握的好坏,直接影响到工程投入生产后的使用寿命,为保证工程质量,以太钢不锈冷轧改造工程冷线防腐为例,对其常发生的质量通病进行认真分析,总结出一套行之有效的施工技术。 相似文献
105.
Interfacial hybridization kinetics of oligonucleotides immobilized onto fused silica surfaces 总被引:3,自引:0,他引:3
Jiang Zeng Amer Almadidy James Watterson Ulrich J. Krull 《Sensors and actuators. B, Chemical》2003,90(1-3):68-75
Fused silica optical fibers have been used in an intrinsic mode optical configuration as biosensors for fluorescence based detection of hybridization of nucleic acids. In this work, the kinetics of hybridization of single-stranded oligonucleotides that were covalently immobilized were studied. The probe DNA was dT20, and the target was Fluorescein-labeled non-complementary (dT20) or complementary (dA20) oligonucleotide. Chronofluorimetric monitoring of the adsorption and hybridization processes was used to investigate oligonucleotide films of different density, in different salt concentrations, at temperatures of 25 and 40 °C, with the concentration of the target DNA being 0.005–0.1 μM. Mathematical models based on first- and second-order Langmuir adsorption have been examined to describe both the adsorption and the hybridization processes. Experimental data were processed using the models, and the hybridization kinetics were calculated. Hybridization kinetics on these optical fiber DNA sensors was found to be up to three orders faster than results presented for a number of other experiments using different immobilization chemistries. 相似文献
106.
XIAKe-yu YURong-jin MENGHua-mao 《半导体光子学与技术》2004,10(2):82-85
By stretching the rod waveguide with different velocities in opposite directions, the tapered waveguide can be fabricated. In condition of taking no account of volume expansion caused by heating and under the assumptions of volume conservation,the rod waveguide can be stretched freely in the heated region without being stretched outside of the heated region. A model,which shows the relation of the transition shape and the two factors, that is the ratio of two velocity and the heated region length, is presented for the shape of the taper transition through mathematic deduction. Based on this model, a desired tapered waveguide can be fabricated. The tapered waveguide are widely used for fabricating tapered fiber couplers and sensors. In addition, the conclusion can be used for fabricating fused fiber coupler. 相似文献
107.
CHENSheng-ping LUKe-cheng LIYi-gang LIJia-fang ZHUJian-ping FENGMing LIJing 《半导体光子学与技术》2004,10(2):122-126
The effects of the variations in fiber length, fiber mirror reflectance on efficiency and output power are experimentally investigated for erbium-doped double pass backward superfluorescent fiber sources (SFSs). The influence of fiber length on mean wavelength stability (MWS) has also been demonstrated. By incorporating a short section of un-pumped erbium-doped fiber (EDF) at the output port, the pump power dependent on MWS becomes independent of pumped EDF length. This is a novel phenomenon that hasn‘t been reported up to now,and should be helpful to SFS fabrication and theory analysis. By using a fiber Michelson interferometer as spectrum slicing component,a multi-wavelength fiber source (MWFS) with ~20 channels (from 1542nm to 1559nm) is got. The MWFS has a channel spacing of ~0. 8 nm which satisfies ITUstandard. The intensity fluctuation among channels is less than 0.5dB,and the extinction ratio of all channels is above 14dB. This kind of MWFS should be useful to wavelength division multiplexing systems. 相似文献
108.
The fracture toughness of brittle thermoset resins could be improved significantly by perfectly bonded tough, short fibers through both crack trapping and bridging effects. In this paper, the crack trapping effect was studied through the analysis of the change of strain energy associated with the crack propagation across a regular array of fibers, and the bridging effect was discussed based on the Andersson–Bergkvist model. The fracture resistance increases with the fiber volume fraction, and is independent of the elastic properties of the matrix, the crack length, and the cross-sectional diameter of the fibers. 相似文献
109.
110.
聚乙烯丙纶复合防水卷材的特点及其应用 总被引:2,自引:0,他引:2
介绍了聚乙烯丙纶复合防水卷材的产品结构特点和性能特点、防水系统结构特点和配套材料、应用拼接技术以及产品应用范围。 相似文献