全文获取类型
收费全文 | 6397篇 |
免费 | 679篇 |
国内免费 | 278篇 |
专业分类
电工技术 | 159篇 |
综合类 | 479篇 |
化学工业 | 2097篇 |
金属工艺 | 146篇 |
机械仪表 | 178篇 |
建筑科学 | 1328篇 |
矿业工程 | 203篇 |
能源动力 | 270篇 |
轻工业 | 269篇 |
水利工程 | 299篇 |
石油天然气 | 216篇 |
武器工业 | 47篇 |
无线电 | 439篇 |
一般工业技术 | 470篇 |
冶金工业 | 372篇 |
原子能技术 | 126篇 |
自动化技术 | 256篇 |
出版年
2024年 | 18篇 |
2023年 | 80篇 |
2022年 | 146篇 |
2021年 | 178篇 |
2020年 | 173篇 |
2019年 | 149篇 |
2018年 | 159篇 |
2017年 | 165篇 |
2016年 | 214篇 |
2015年 | 206篇 |
2014年 | 385篇 |
2013年 | 364篇 |
2012年 | 382篇 |
2011年 | 442篇 |
2010年 | 380篇 |
2009年 | 363篇 |
2008年 | 359篇 |
2007年 | 403篇 |
2006年 | 369篇 |
2005年 | 311篇 |
2004年 | 278篇 |
2003年 | 242篇 |
2002年 | 232篇 |
2001年 | 216篇 |
2000年 | 191篇 |
1999年 | 150篇 |
1998年 | 133篇 |
1997年 | 130篇 |
1996年 | 70篇 |
1995年 | 76篇 |
1994年 | 77篇 |
1993年 | 56篇 |
1992年 | 62篇 |
1991年 | 31篇 |
1990年 | 28篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 16篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1951年 | 7篇 |
排序方式: 共有7354条查询结果,搜索用时 140 毫秒
81.
三峡库区支流中水体的垂向掺混对于藻类生长的影响 总被引:2,自引:0,他引:2
三峡水库蓄水之后库区支流水华问题给当地生态环境造成了较大影响,也引起了广泛的关注和重视,然而针对这一问题尚未取得很好的解释和解决方案。本文采用EFDC模型对于2008年坝前库区干支流的三维水动力和水质进行了数值模拟,并从水体垂向掺混的角度分析支流的水华现象。模拟结果成功再现了香溪河库湾中的温度分层和异重流现象,流场、温度场的计算值和实测值吻合较好。统计结果表明:长江干支流水动力特性的差异显著,干支流垂向紊动黏性系数、垂向紊动扩散系数沿垂线分布呈现出不同的形态,且长江干流的垂向掺混强度明显高于香溪河。同时,叶绿素浓度与垂向紊动扩散系数呈显著的负相关关系,随着水体垂向紊动扩散系数的增加,叶绿素浓度逐渐降低,这一规律的发现可为采用物理方法防治三峡库区支流水华打下基础。 相似文献
82.
含白炭黑胎面胶的混炼 总被引:1,自引:0,他引:1
以白炭黑作填充剂的轮胎具有滚动阻力低等优点。但是白炭黑在橡胶中不易分散。介绍了为提高含白炭黑的胎面胶的混炼质量,加速白炭黑在轮胎中的推广应用而采取的原材料、混炼工艺和混炼设备。 相似文献
83.
A characterisation of three commonly used impellers was made in this study by measuring local mean velocities and the fluctuations of these velocities with the LDV technique. The data was used to estimate volumetric flow, velocity fluctuations and turbulent intensity in the impeller region of the tank. The impellers investigated were a high flow impeller, a pitched blade turbine and a Rushton turbine. The cylindrical vessel used was made of Perspex, had a dished bottom (DIN 28013), was equipped with four baffles and had an inner diameter of 0.45 m. It was found that the bulk velocities could be scaled with the tip-speed of the impeller (ND). The flow rate at constant impeller speed increased in the order high flow impeller — Rushton turbine — pitched blade turbine. The corresponding order for the turbulence fluctuation is: high flow impeller — pitched blade turbine — Rushton turbine. The velocity profile of the flow out from the high flow impeller was furthermore, not as smooth as could be expected. 相似文献
84.
Radial gas mixing in a fluidized bed was studied using response surface methodology (RSM), which enables effect examinations of parameters with a moderate number of experiments. All experiments were conducted in a 0.29-m ID fluidized-bed cold model. The gas dispersion process within the bed is described using the dispersed plug flow model. Pure carbon dioxide was used as the tracer gas, continuously injected into the center of the bed by a point source. The downstream radial tracer concentration profile was measured using a gas chromatograph.The radial gas dispersion coefficient, Dr, was well correlated with operating parameters and the particle and gas properties: (U−Umf)/Umf, Hs/db, φd, and Ar, with a determination coefficient R2 of 0.966. Effect test indicates that the dimensionless characteristic velocity, (U−Umf)/Umf, has the most significant influence on Dr, while the static bed height to bed diameter ratio, Hs/db, is less remarkable. The interactions of (U−Umf)/Umf with the distributor open-area ratio, φd, and with the Archimedes number, Ar, both play important roles. An evolutive response surface model was proposed to describe the radial gas mixing in the bubbling/slugging fluidization regimes. 相似文献
85.
High‐abrasion furnace black (HAF, grade N330)–filled powdered styrene butadiene rubber [P(SBR/HAF)] was prepared and the particle size distribution, mixing behavior in a laboratory mixer, and mechanical properties of P(SBR/HAF) were studied. A carbon black–rubber latex coagulation method was developed for preparing carbon black–filled free‐flowing, noncontact staining SBR powders, with particle diameter less than 0.9 mm, under the following conditions: carbon black content > 40 phr, emulsifier/carbon black ratio > 0.02, and coating resin content > 2.5 phr. Over the experimental range, the mixing torque τα of P(SBR/HAF) was not as sensitive to carbon black content and mixing temperature as that of HAF‐filled bale SBR (SBR/HAF), whereas the temperature build‐up ΔT showed little dependency on carbon black content. Compared with SBR/HAF, P(SBR/HAF) showed a 20–30% mixing energy reduction with high carbon black content (>30 phr), which confers to powdered SBR good prospects for internal mixing. Carbon black and the rubber matrix formed a macroscopic homogenization in P(SBR/HAF), and the incorporation step is not obvious in the internal mixing processing results in these special mixing behaviors of P(SBR/HAF). A novel mixing model of carbon black–filled powdered rubber, during the mixing process in an internal mixer, was proposed based on the special mixing behaviors. P(SBR/HAF) vulcanizate showed better mechanical properties than those of SBR/HAF, dependent primarily on the absence of free carbon black and a fine dispersion of filler on the rubber matrix attributed to the proper preparation conditions of noncontact staining carbon black–filled powdered SBR. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2494–2508, 2004 相似文献
86.
87.
The effects of the non-Newtonian properties on the effective deformation rate, mixing and circulation times and flow behaviour have been investigated in the transition flow regime of mixing systems. Based on the equivalent Couette flow, three models are proposed and are shown to predict similar and drastic increases of the effective deformation rate with the impeller rotational speed in the transition regime. The predictions are shown to fit very well data obtained for various non-Newtonian fluids mixed with helical ribbon agitators, and with literature data for anchor, blade turbine and flat disc agitators. The elasticity along with shear-thinning properties appear to have slight effects on the dimensionless mixing and circulation times in the transition regime, whereas their effects in the laminar regime are quite drastic, as reported by others. 相似文献
88.
89.
90.