全文获取类型
收费全文 | 11686篇 |
免费 | 1705篇 |
国内免费 | 722篇 |
专业分类
电工技术 | 294篇 |
综合类 | 690篇 |
化学工业 | 4872篇 |
金属工艺 | 1517篇 |
机械仪表 | 611篇 |
建筑科学 | 380篇 |
矿业工程 | 137篇 |
能源动力 | 186篇 |
轻工业 | 593篇 |
水利工程 | 138篇 |
石油天然气 | 157篇 |
武器工业 | 105篇 |
无线电 | 904篇 |
一般工业技术 | 1923篇 |
冶金工业 | 457篇 |
原子能技术 | 51篇 |
自动化技术 | 1098篇 |
出版年
2024年 | 65篇 |
2023年 | 207篇 |
2022年 | 298篇 |
2021年 | 467篇 |
2020年 | 453篇 |
2019年 | 425篇 |
2018年 | 457篇 |
2017年 | 525篇 |
2016年 | 558篇 |
2015年 | 550篇 |
2014年 | 722篇 |
2013年 | 828篇 |
2012年 | 799篇 |
2011年 | 833篇 |
2010年 | 668篇 |
2009年 | 683篇 |
2008年 | 648篇 |
2007年 | 725篇 |
2006年 | 695篇 |
2005年 | 513篇 |
2004年 | 481篇 |
2003年 | 419篇 |
2002年 | 330篇 |
2001年 | 247篇 |
2000年 | 217篇 |
1999年 | 193篇 |
1998年 | 176篇 |
1997年 | 169篇 |
1996年 | 91篇 |
1995年 | 107篇 |
1994年 | 83篇 |
1993年 | 69篇 |
1992年 | 80篇 |
1991年 | 70篇 |
1990年 | 48篇 |
1989年 | 40篇 |
1988年 | 21篇 |
1987年 | 24篇 |
1986年 | 17篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 33篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
51.
Anodic aluminum oxide (AAO) membrane can be used as template for the synthesized nanostructures. In this article, we have prepared the AAO membrane by using electrooxidation of aluminum substrate in phosphoric acid, and fabricated poly(2,5‐di‐n‐butoxyphenylene) (BuO–PPP) nanofibril arrays by oxidative coupling polymerization of 1,4‐di‐n‐butoxybenzene (DBB) within the pores of the AAO template membrane. The detailed molecular structure of the polymer nanofibrils was characterized by using infrared and 1H nuclear magnetic resonance spectra, and estimated to consist of almost equal fractions of 1,4‐ and 1,3‐ linkages. We have used transmission electron microscopy, scanning electron microscopy, and atom force microscopy to confirm the morphologies and images of the AAO template membrane and the fabricated nanometer scale of BuO–PPP nanofibril arrays. The experimental results demonstrated that the pores of the AAO membrane were regular and uniform, and parallel each other, and the BuO–PPP chains in the narrowest template‐synthesized nanofibrils were oriented parallel to the porous axes of the AAO membrane and perpendicular to the surface of the aluminum substrate. The polymer chain orientation was partially responsible for the enhanced conductivity. The ultraviolet absorption spectrum of the BuO–PPP nanofibril arrays shown that the polymer contains a better extended π‐conjugation system along poly‐(p‐phenylene) backbone, which resulted in longer wavelength shift of the absorption band, the absorption maxima were located at 258 nm (E1 absorption band) and 332 nm (E2 absorption band), respectively. Photoluminescence spectrum of the BuO–PPP nanofibril arrays exhibited a blue emission. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 425–430, 2004 相似文献
52.
The phase behaviour and morphology of injection moulded specimens of polysulphone (PSF) and poly(phenylene sulphide) (PPS) blends were studied by differential scanning calorimetry (d.s.c.), dynamical mechanical thermal analysis (d.m.t.a.) and transmission electron microscopy (TEM). The blends are phase separated regardless of the blend composition as revealed by d.s.c., d.m.t.a. and TEM. Upon annealing at 160°C for 2 h, d.m.t.a. results indicate that the PPS phase remains in the amorphous state at compositions <10%. At compositions between 20 and 35%, the PPS appears to be dispersed in a mixed mode of amorphous and crystalline domains. Above 35% the PPS phase appears to become fully crystallized upon annealing of the blends. At 10% PPS, TEM results showed 35–200 nm size dispersion both in the as-moulded and in the annealed specimens. At 20% the PPS phase varied widely in size, from 35 nm to tens of micrometres but remained as an included phase. TEM also revealed a compound morphology of the included phase at a composition of 50 wt% of each component. 相似文献
53.
Mehdi Qasim Jinan Al‐Dabbagh Naser Mahmoud Ahmed V.G. Chigrinov Gurumurthy Hegde 《Journal of the Society for Information Display》2014,22(4):187-190
Indium tin oxide‐coated thin films (200 nm) are deposited on glass substrates by using R.f. sputtering technique. Here, we investigate the influence of new technique of treatment, which is called as “oil thermal annealing” on the nano‐structured indium tin oxide thin films at fixed temperature (150 °C) which improves adhesion strength, electrical conductivity and optical properties (transmittance) of the films. Oil thermal annealing is used to reduce inherent defects that may be introduced during the prepared thin film and cooling processes. Proposed technique is highly suitable for liquid crystal displays, solar cells and organic light emitting diodes, and many other display‐related applications. 相似文献
54.
Jeffrey A Galloway 《Polymer》2004,45(2):423-428
The effect of sample size on the results of solvent extraction measurements for detecting cocontinuity in polymer blends was investigated. Poly(ethylene oxide)/polystyrene (PEO/PS) blend samples of several thicknesses were analyzed by removing the PEO phase using water extraction. The experimental degree of continuity was shown to have a linear dependence on the reciprocal of sample thickness. A model is proposed to explain this dependence and to allow the bulk or true degree of continuity to be determined. Measurement of the bulk degree of continuity is useful for understanding properties of cocontinuous polymer blends such as electrical conductivity, impact strength, or tensile strength. 相似文献
55.
Compatible polymer blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) can be used as suitable model systems for investigating the relationship between the physico-chemical structure of polymers and their piezo- and pyroelectric activity. The structure of PVDF/PMMA blends can be varied over a very wide range which can lead to a strong influence on the piezo- and pyroelectric activity and the corresponding coefficients d31 and g3. The values of d31 and g3 were found to vary over nearly five decades whereas the normalized coefficients and remain largely unaffected. This emphasizes the importance of the molecular processes causing the macroscopic polarization P during the poling procedure. For a given polarization P and a given temperature T the properties of the polymer matrix, however, are far less important for the values obtained for d31 and g3. The experimental results were compared with theoretical predictions based on models which were recently developed by Tashiro et al., Broadhurst et al. and by Mopsik et al.. Considering the appropriate scope of each model a good agreement between theory and experiment is observed and general contradictions have not been found. 相似文献
56.
57.
58.
不同线密度粘胶原丝及其碳纤维的结构性能对比 总被引:1,自引:0,他引:1
用Weibull分析处理 10mm长的 4种不同线密度粘胶原丝和相应碳纤维的单丝断裂强度 ,得到原丝线密度、强度分布和碳纤维强度的对应关系。采用透射电镜 (TEM )和小角X散射 (SAXS)分析粗旦原丝 ,发现孔洞较多 ,并存在大于 70nm的大孔洞。截面和表面照片也揭示出细旦原丝截面相对规整 ,表面较光滑 ,粗旦原丝则反之。结果表明 ,原丝线密度小 ,截面形状圆整 ,缺陷少 ,所制得的碳纤维强度高。 相似文献
59.
宋冬梅 《计算技术与自动化》2021,40(2):136-139
传统边缘检测算法由于对噪声敏感,难以准确提取图像边缘,导致图像处理效果不佳.基于传统数学形态学算法中结构算子的方向性和尺寸几何的基础上进行算法改进.针对抗噪型碰撞腐蚀形态学边缘检测算子结构元素特征,采用不同大小结构元素组合来提取边缘特征,有效保证了图像细节的同时去掉较大噪声点.根据结构元素的方向性,利用同向结构元素图像的匹配来检测各边缘信息,确保不同向边缘信息的完整度.通过比较文本改进算法与传统的边缘检测算法对图像边缘检测效果表明:本文提出的改进算子在处理较大图像边缘检测时具有更快的检测速度,且图像边缘光滑,细节清晰,具备了更强的抗噪性能. 相似文献
60.
De-jun Kong Cun-dong Ye 《北京科技大学学报(英文版)》2014,(9):898-905
The surfaces of X80 pipeline steel welded joints were processed with a CO2 laser, and the effects of laser heat treatment (LHT) on H2S stress corrosion in the National Association of Corrosion Engineers (NACE) solution were analyzed by a slow strain rate test. The fracture morphologies and chemical components of corrosive products before and after LHT were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively, and the mechanism of LHT on stress corrosion cracking was discussed. Results showed that the fracture for welded joints was brittle in its original state, while it was transformed to a ductile fracture after LHT. The tendencies of hydrogen-induced corrosion were reduced, and the stress corrosion sensitivity index decreased from 35.2% to 25.3%, indicating that the stress corrosion resistance of X80 pipeline steel welded joints has been improved by LHT. 相似文献