全文获取类型
收费全文 | 21048篇 |
免费 | 913篇 |
国内免费 | 318篇 |
专业分类
电工技术 | 465篇 |
综合类 | 544篇 |
化学工业 | 3781篇 |
金属工艺 | 524篇 |
机械仪表 | 729篇 |
建筑科学 | 855篇 |
矿业工程 | 180篇 |
能源动力 | 577篇 |
轻工业 | 2083篇 |
水利工程 | 244篇 |
石油天然气 | 177篇 |
武器工业 | 27篇 |
无线电 | 2479篇 |
一般工业技术 | 2859篇 |
冶金工业 | 3711篇 |
原子能技术 | 171篇 |
自动化技术 | 2873篇 |
出版年
2023年 | 113篇 |
2022年 | 347篇 |
2021年 | 471篇 |
2020年 | 273篇 |
2019年 | 337篇 |
2018年 | 390篇 |
2017年 | 368篇 |
2016年 | 414篇 |
2015年 | 355篇 |
2014年 | 532篇 |
2013年 | 1028篇 |
2012年 | 802篇 |
2011年 | 987篇 |
2010年 | 754篇 |
2009年 | 827篇 |
2008年 | 809篇 |
2007年 | 831篇 |
2006年 | 720篇 |
2005年 | 616篇 |
2004年 | 692篇 |
2003年 | 911篇 |
2002年 | 1190篇 |
2001年 | 1029篇 |
2000年 | 601篇 |
1999年 | 537篇 |
1998年 | 1347篇 |
1997年 | 869篇 |
1996年 | 646篇 |
1995年 | 433篇 |
1994年 | 328篇 |
1993年 | 357篇 |
1992年 | 197篇 |
1991年 | 158篇 |
1990年 | 150篇 |
1989年 | 136篇 |
1988年 | 133篇 |
1987年 | 110篇 |
1986年 | 113篇 |
1985年 | 151篇 |
1984年 | 88篇 |
1983年 | 94篇 |
1982年 | 82篇 |
1981年 | 106篇 |
1980年 | 98篇 |
1979年 | 62篇 |
1978年 | 50篇 |
1977年 | 101篇 |
1976年 | 195篇 |
1975年 | 52篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
G Chessa Ricotti R Cutrì A De Bernardi M Funis S Frediani 《Canadian Metallurgical Quarterly》1995,17(3):271-273
The authors describe 5 cases, 3 boys and 2 girls, with idiopathic growth hormone deficiency in prepubertal age, treated with human growth hormone. In four of five cases the response to treatment with GH was relevant. Only in one case (F1) the response was negative. The results of this study confirm that rhGH is a safe and effective therapy in children with GHD. 相似文献
32.
Photocyclovoltammetric experiments with films of poly(3-methylthiophene) under polychromatic light irradiation show a p-type semiconductor behavior in the reduced state, with a flat band potential of 0.18 V. The photocurrent depends on film thickness and surface morphology. Films with different thickness were characterized by scanning electron microscopy, indicating a globular morphology with globule sizes changing according to the charge density used during polymer deposition. The highest photocurrent is observed for the lowest globule diameter. These films were also irradiated with monochromatic light from the electrolyte side and from the substrate side. A higher photocurrent and a photocurrent spectrum matching the absorption spectrum of the reduced form of the polymer is observed on irradiation from the electrolyte side of a 0.7 μm thick film. In contrast, for irradiation from the electrode side, the photocurrent is lower and the spectrum shows a peak at lower energy. These results were interpreted in terms of a delocalized space charge zone, different kinetics for charge transfer and mass transport across the solvent swollen polymer film and different depth of penetration of the light as a function of wavelength. 相似文献
33.
34.
35.
36.
Ⅰ线光致抗蚀剂可以同时实用电子束和光学系统曝光,在50kV加速电压下,其曝光剂量为50-100μC/cm^2,曝光后在0.7%NaOH溶液内显影1分钟。其灵敏度比PMMA快5倍,分辩率为0.5μm。采用两方法制备CaAsPHEMT:一种用Ⅰ线光致抗蚀剂,对源、漏及栅全部都采用电子束曝光,制备了0.5μm栅长的GaAs PHEMT;另一种将源、漏及栅分割成两部分,其中精细部分由电子束曝光,其余部分由光学系统曝光,用这种方法制备了0.25μm栅长的GaAs PHEMT。Ⅰ 相似文献
37.
Nicholas Biery Marc De Graef Jack Beuth Rafel Raban Andrew Elliott Tresa M. Pollock Curt Austin 《Metallurgical and Materials Transactions A》2002,33(10):3127-3136
Tensile experiments have been performed on specimens of four different investment-cast TiAl-based alloys with variations in
casting conditions. The average ductilities obtained in these experiments vary between approximately 0.8 to 2.0 pct plastic
strain to failure in tension. By using the three-parameter form of the Weibull relation, with the 0.2 pct offset yield strength
as the minimum failure strength, the resulting variability in the data can be quantified and is found to be similar for those
alloys with similar microstructural scale (grain size). Large variations in lamellar volume fraction, segregation, and phase
distribution have a minor influence on property variability, compared to changes in the scale of the grain structure caused
by either variations in cooling rate during casting or the addition of grain refiners. 相似文献
38.
采用HF HNO3溶液化学腐蚀 ,在硅片上制备减反射效果优良的多孔硅太阳电池减反射膜 ,借助原子力显微镜 (AFM)和X光电子谱 (XPS)对其表面形貌和成分进行观察 ,发现该膜与电化学阳极腐蚀得到的多孔硅具有相似性 ,其主要成分为非化学配比的硅的氧化物SiOx(X <2 )。采用带积分球的光度分光计 ,测得形成多孔硅减反射膜后 ,硅片表面反射率大大下降 ,,在波长 330~ 80 0nm范围反射率只有 1 5~ 2 9%。研究指出这种强减反射作用 ,与多孔硅具有合适的折射率及其多孔特性的光陷阱作用有关 相似文献
39.
40.
Hannes Verlinde Martine De Cock Raymond Boute 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(3):679-684
As opposed to quantitative association rule mining, fuzzy association rule mining is said to prevent the overestimation of boundary cases, as can be shown by small examples. Rule mining, however, becomes interesting in large databases, where the problem of boundary cases is less apparent and can be further suppressed by using sensible partitioning methods. A data-driven approach is used to investigate if there is a significant difference between quantitative and fuzzy association rules in large databases. The influence of the choice of a particular triangular norm in this respect is also examined. 相似文献