全文获取类型
收费全文 | 65402篇 |
免费 | 7075篇 |
国内免费 | 3871篇 |
专业分类
电工技术 | 1681篇 |
综合类 | 5101篇 |
化学工业 | 11006篇 |
金属工艺 | 8446篇 |
机械仪表 | 8705篇 |
建筑科学 | 3944篇 |
矿业工程 | 2403篇 |
能源动力 | 1669篇 |
轻工业 | 7953篇 |
水利工程 | 1692篇 |
石油天然气 | 2015篇 |
武器工业 | 657篇 |
无线电 | 4554篇 |
一般工业技术 | 9461篇 |
冶金工业 | 2388篇 |
原子能技术 | 597篇 |
自动化技术 | 4076篇 |
出版年
2024年 | 439篇 |
2023年 | 1318篇 |
2022年 | 1847篇 |
2021年 | 2226篇 |
2020年 | 2528篇 |
2019年 | 2326篇 |
2018年 | 2381篇 |
2017年 | 2769篇 |
2016年 | 2727篇 |
2015年 | 2767篇 |
2014年 | 3587篇 |
2013年 | 4538篇 |
2012年 | 4622篇 |
2011年 | 4771篇 |
2010年 | 3353篇 |
2009年 | 3435篇 |
2008年 | 3128篇 |
2007年 | 4062篇 |
2006年 | 3765篇 |
2005年 | 3059篇 |
2004年 | 2605篇 |
2003年 | 2123篇 |
2002年 | 1838篇 |
2001年 | 1580篇 |
2000年 | 1472篇 |
1999年 | 1195篇 |
1998年 | 977篇 |
1997年 | 894篇 |
1996年 | 789篇 |
1995年 | 615篇 |
1994年 | 508篇 |
1993年 | 426篇 |
1992年 | 360篇 |
1991年 | 244篇 |
1990年 | 243篇 |
1989年 | 165篇 |
1988年 | 174篇 |
1987年 | 80篇 |
1986年 | 88篇 |
1985年 | 76篇 |
1984年 | 67篇 |
1983年 | 49篇 |
1982年 | 51篇 |
1981年 | 14篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1959年 | 7篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
Daniela D'Amato Maria Rosaria Corbo Matteo Alessandro Del Nobile & Milena Sinigaglia 《International Journal of Food Science & Technology》2006,41(10):1152-1157
In enology, alcoholic fermentation is a complex process involving several mechanisms. Slow and incomplete alcoholic fermentation is a chronic problem for the wine industry and factors leading to sluggish and stuck fermentations have been extensively studied and reviewed. The most studied cause of sluggish and stuck fermentation is the nitrogen content limitation. Nevertheless, other factors, such as temperature of fermentation and sugar concentration can affect the growth of yeasts. In this study we modelled the yeast growth‐cycle in wine model system as a function of temperature, sugar and ammonium concentrations; the individual effects and the interaction of these factors were analysed by means of a quadratic response surface methodology. Cell concentrations and weight loss were monitored in the whole wine fermentation process. The results of central composite design show that lower is the availability of nitrogen, higher is the cell growth rate; moreover, initial nitrogen concentration also influences survival time of Saccharomyces cerevisiae. 相似文献
212.
硬粒子对聚合物材料表面的冲击摩擦研究 总被引:3,自引:3,他引:0
冲击摩擦为接触面切向与法向冲量之比。用聚合物材料试件与弹簧钢片组成振动测试系统 ,硬粒子以一定入射角冲击试件水平面引起系统振动 ,接触冲量通过振幅反映出来 ,记录初始振幅值而计算出一个冲击过程的冲击摩擦因数。结果表明 ,当入射角α在 2 5°-60°变化时 ,冲击摩擦因数f从 0 .5降至 0 .2左右。文章同时分析讨论了摩擦对聚合物表面接触强度的影响。 相似文献
213.
纳米二氧化钛的表面修饰与应用的研究进展 总被引:7,自引:0,他引:7
介绍了纳米二氧化钛表面修饰的两种主要方法:无机和有机表面包覆,以及进行修饰后的纳米二氧化钛的应用. 相似文献
214.
215.
The determination of the Young’s modulus and damping coefficient Q−1 by means of non-destructive vibrating techniques has been applied to bulk and coated industrial materials. Extensions of a previous analytic model of composite beam allow to determine accurately the macroscopic modulus of each component of multilayered structural materials as coated superalloys or nitride-hardened steels. Furthermore, the study of glasses and polymers has been investigated. An attempt of normalisation of the modulus versus temperature curves allows to establish master curves depending on the specific structure, from metallic glasses to polymeric glasses. Finally a comparison of dynamical modulus and Q−1 values measured between resonant (>1 kHz) and subresonant techniques (10−3 to 10 Hz) in relation to the loading frequencies applied in real conditions has been under folder. For metallic materials such as forged or rolled titanium alloys, the brittle-to-fragile transition occurs abruptly or smoothly with a shift of 300 K following the range of excitation frequencies. 相似文献
216.
The mechanical and microstructural properties of 6061+20% Al2O3p and 7005+10% Al2O3p aluminium based metal matrix composites joined by friction stir welding were analyzed in the present study. The two materials were welded into the form of sheets of 7 mm thickness after T6 treatment and were tested in tension at room temperature. The microstructure of the joints was observed by optical microscopy and the fracture surfaces were analyzed by employing a scanning electron microscope equipped with field emission gun in order to study the micromechanisms involved during the deformation. 相似文献
217.
W. Ming F. Melis R. D. van de Grampel L. van Ravenstein M. Tian R. van der Linde 《Progress in Organic Coatings》2003,48(2-4):316-321
Self-stratification strategy can be used to prepare films in which both bulk and surface properties can be optimized. By using this approach, only a very small quantity of fluorinated species is needed to generate a surface with low surface energy. When cross-linking is involved during film formation, we are dealing with a competition behavior between the diffusion of fluorinated species and the formation of cross-linked network. In this study low surface energy polymeric films were prepared on the basis of partially fluorinated polyisocyanates, in combination with hydroxyl-end-capped three-armed solventless liquid oligoesters and modified hyperbranched polyesters. At a fluorine concentration of only 0.5 wt.%, contact angles of water and hexadecane can reach 120° and 80°, respectively. A surface energy as low as 10–15 mN/m can be obtained upon the addition of less than 1 wt.% of fluorine in the films. It was shown, from real time ATR-FTIR and contact angle measurements, that the curing temperatures demonstrated significant effects on the cross-linking rate as well as on the wettability of the films. 相似文献
218.
本文通过对摩擦片厚度在线测量装置系统构成的全面分析,对其驱动电路子系统进行了理论探索和技术研究,完成了相应的电路设计、误差分析及器件选择等工作,并进行了具体的实验验证,证明该驱动电路具有良好的性能,可圆满实现摩擦片厚度在线检测和实时分析的工作任务。 相似文献
219.
220.
We have used a resonant ultrasound spectroscopy technique to measure the bulk and shear modulus of fully dense, polycrystalline MgB2 between 4 and 300 K. Both moduli show good agreement with published first principle calculations. The internal friction shows a broad maximum around 40 K. 相似文献