全文获取类型
收费全文 | 6952篇 |
免费 | 559篇 |
国内免费 | 360篇 |
专业分类
电工技术 | 311篇 |
技术理论 | 1篇 |
综合类 | 566篇 |
化学工业 | 1632篇 |
金属工艺 | 555篇 |
机械仪表 | 443篇 |
建筑科学 | 853篇 |
矿业工程 | 258篇 |
能源动力 | 126篇 |
轻工业 | 535篇 |
水利工程 | 119篇 |
石油天然气 | 701篇 |
武器工业 | 40篇 |
无线电 | 146篇 |
一般工业技术 | 822篇 |
冶金工业 | 454篇 |
原子能技术 | 38篇 |
自动化技术 | 271篇 |
出版年
2024年 | 10篇 |
2023年 | 61篇 |
2022年 | 120篇 |
2021年 | 154篇 |
2020年 | 174篇 |
2019年 | 156篇 |
2018年 | 158篇 |
2017年 | 199篇 |
2016年 | 236篇 |
2015年 | 271篇 |
2014年 | 377篇 |
2013年 | 505篇 |
2012年 | 506篇 |
2011年 | 542篇 |
2010年 | 383篇 |
2009年 | 390篇 |
2008年 | 349篇 |
2007年 | 429篇 |
2006年 | 410篇 |
2005年 | 363篇 |
2004年 | 330篇 |
2003年 | 264篇 |
2002年 | 239篇 |
2001年 | 189篇 |
2000年 | 193篇 |
1999年 | 168篇 |
1998年 | 127篇 |
1997年 | 98篇 |
1996年 | 93篇 |
1995年 | 74篇 |
1994年 | 53篇 |
1993年 | 48篇 |
1992年 | 37篇 |
1991年 | 21篇 |
1990年 | 34篇 |
1989年 | 31篇 |
1988年 | 22篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1982年 | 7篇 |
1964年 | 5篇 |
1961年 | 3篇 |
1960年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有7871条查询结果,搜索用时 15 毫秒
41.
42.
Nucleation kinetics during the growth of InxGa1−xN on a GaN substrate have been studied. The behavior of nonequilibrium between the InxGa1−xN and the GaN substrate has been analyzed, and hence, the expression derived for the stress-induced supercooling/superheating
has been numerically evaluated. The maximum amount of stress-induced supercooling is found to be 1.017 K at x=0.12. These
values are incorporated in the classical heterogeneous nucleation theory. Using the regular solution model, the interfacial
tension between the nucleus and substrate and, hence, the interfacial tension between nucleus and mother phase and thermodynamical
potential of the compounds have been calculated. The amount of driving force available for the nucleation has been determined
for different compositions and degrees of supercooling. It has been shown that the value of the interaction parameter of InN-GaN
plays a dominant role in nucleation and growth kinetics of InxGa1−xN on a GaN substrate. These values have been used to evaluate the nucleation parameters. It is shown that the nucleation barrier
for the formation of a InxGa1−xN nucleus on a GaN substrate is minimum in the range of x=0.12 to x=0.17, and it has been qualitatively proved that good quality
InxGa1−xN on GaN can be grown only in the range 0<x≤0.2. 相似文献
43.
44.
The aim of this study was to evaluate the effects of paste properties on residence time during drying in a spouted bed dryer with inert bodies. The effect of paste solids content, surface tension, and viscosity on the residence time distribution and the mean residence times were studied using factorial experimental designs. The inert bodies used were glass and polyethylene beads. The mean residence times varied from 13.6 to 16.3 and 12.2 to 17.7 min for drying on glass and polyethylene beads, respectively. The analysis of variance showed that mean residence times significantly depended on solids content and surface tension for glass beads and also on viscosity for polyethylene beads. The residence time distributions for all conditions studied fitted well to the perfect mixing cell when applying the continuous stirred vessels in series model analysis. The powder density, flowability, and particle size depended on paste properties and inert type. 相似文献
45.
46.
47.
A new curvature technique calculation for surface tension contribution in PLIC-VOF method 总被引:1,自引:0,他引:1
The volume of fluid (VOF) methods have been used for numerous numerical simulations. Among these techniques used to define
the moving interface, the piecewise linear interface reconstruction (PLIC-VOF) is one of the most accurate. A study of the
superficial tension impact on two-phase flow with free surface is presented. A new method based on direct staggered grid is
developped to include surface tension in PLIC-VOF. The new numerical curvature calculation method doesn't need smoothed colour
function and leads to less “spurious current”. This technique is applied to the calculus of surface tension force in the case
of the rise of air bubble in viscous liquid and the fall of liquid drop in the same liquid on free surface. Droplets, thin
layer and capillarity waves are observed after the free surface rupture for different Bond number. The influence of surface
tension calculus is then obvioused and when the drop hit the free surface, wavelets propagate toward the virtual boundaries
imposed. 相似文献
48.
Sodium sulfonate‐terminated dendritic poly(ester‐amine) (SPEA) was synthesized by sulfonation of acrylic double bond‐terminated dendritic poly(ester‐amine) (APEA) with sodium hydrogen sulfite (NaHSO3) in mixture of diglycol and 2‐butanone under normal pressure. The structure of SPEA was characterized by IR, 1H‐NMR, and elemental analysis. SPEA was water‐soluble. 1.0–40.0% (mass) SPEA aqueous solutions appeared as dilatant fluid. When pH value varied from 1.5 to 12.0, the viscosity of 1–5% (mass) SPEA aqueous solutions changed very small, and the electric conductivity almost kept stable within pH 3.0–10.0. The relationship between the viscosity and the concentration of SPEA water solutions was similar to that of NaCl water solutions. The surface tension of SPEA water solutions was lower than that of polyethylene glycol 2000 water solutions with the same concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
49.
This article presents the results from a study of yarn-to-yarn (YY) and yarn-to-metal (YM) frictions conducted on ring, rotor, air-jet, and open-end friction (OE friction) spun yarns at different relative speeds and input tensions. The results indicate that the behavior of frictions for YY is different than that of YM. In case of YY friction, OE friction yarn shows maximum friction followed by rotor, air-jet, and ring spun yarns; however, a reverse order is noticed for YM friction. The relative speed and input tension have significant influence on the frictional behavior of spun yarns. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
50.
基于带传动在稳定工作时的受力平衡,从理论上导出了摆架式自动张紧装置所产生的张紧力的计算公式。结果表明:只要合理选择计算安装参数,其张紧力总能满足张紧条件的要求,以对张紧装置进行设计计算;并指出该装置产生的张紧力,具有随外载荷变化而自动调节的性能,使传力零件部分卸载。 相似文献