全文获取类型
收费全文 | 321695篇 |
免费 | 32990篇 |
国内免费 | 17694篇 |
专业分类
电工技术 | 23264篇 |
技术理论 | 34篇 |
综合类 | 33744篇 |
化学工业 | 36519篇 |
金属工艺 | 17635篇 |
机械仪表 | 21581篇 |
建筑科学 | 38329篇 |
矿业工程 | 18843篇 |
能源动力 | 14048篇 |
轻工业 | 18294篇 |
水利工程 | 15091篇 |
石油天然气 | 19317篇 |
武器工业 | 6330篇 |
无线电 | 22521篇 |
一般工业技术 | 25416篇 |
冶金工业 | 15123篇 |
原子能技术 | 3088篇 |
自动化技术 | 43202篇 |
出版年
2024年 | 1670篇 |
2023年 | 4781篇 |
2022年 | 9198篇 |
2021年 | 11125篇 |
2020年 | 11126篇 |
2019年 | 8368篇 |
2018年 | 8037篇 |
2017年 | 10104篇 |
2016年 | 12183篇 |
2015年 | 13098篇 |
2014年 | 22007篇 |
2013年 | 19854篇 |
2012年 | 23979篇 |
2011年 | 26336篇 |
2010年 | 19323篇 |
2009年 | 19409篇 |
2008年 | 17959篇 |
2007年 | 21910篇 |
2006年 | 19542篇 |
2005年 | 16639篇 |
2004年 | 13918篇 |
2003年 | 11757篇 |
2002年 | 9529篇 |
2001年 | 7942篇 |
2000年 | 6581篇 |
1999年 | 5275篇 |
1998年 | 3853篇 |
1997年 | 3320篇 |
1996年 | 2782篇 |
1995年 | 2268篇 |
1994年 | 1918篇 |
1993年 | 1326篇 |
1992年 | 1083篇 |
1991年 | 804篇 |
1990年 | 681篇 |
1989年 | 609篇 |
1988年 | 361篇 |
1987年 | 254篇 |
1986年 | 231篇 |
1985年 | 222篇 |
1984年 | 168篇 |
1983年 | 149篇 |
1982年 | 96篇 |
1981年 | 99篇 |
1980年 | 109篇 |
1979年 | 62篇 |
1978年 | 26篇 |
1977年 | 29篇 |
1959年 | 48篇 |
1951年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Michael E. G. Ferguson Peter L. Spedding 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):262-278
Experimental data for air–water two-phase co-current flow in two different pipe diameters were used to test the prediction of pressure drop by a number of existing theories and correlations. Several models are shown to be useful for prediction, particularly with the stratified regimes which have proved difficult to handle in the past. The model suggested by Olujic proved to be of particular value. 相似文献
62.
Kwang Soo Lee In Soo Park & Dong Sun Lee 《International Journal of Food Science & Technology》1996,31(1):7-13
The aim of this study was to design a modified atmosphere package for a mixed vegetable salad consisting of 75 g of cut carrot, 55 g of cut cucumber, 20 g of sliced garlic and 50 g of whole green pepper. Respiration data of all the components were combined with film permeability data to predict package atmospheres and design optimal packages for experimental testing for improved shelf-life of the produce. The optimal package avoided minimum O2 and maximum CO2 tolerance limits, and chilling injury temperatures for any component. A pouch form package made of 27 mm low density polyethylene developed a modified atmosphere of 2.0–2.1% O2 and 5.5–5.7% CO2 , which was beneficial for all components and provided better quality retention than other test packages. 相似文献
63.
64.
Inverse surface design problems from light transport behavior specification usually represent extremely complex and costly processes, but their importance is well known. In particular, they are very interesting for lighting and luminaire design, in which it is usually difficult to test design decisions on a physical model in order to avoid costly mistakes. In this survey, we present the main ideas behind these kinds of problems, characterize them, and summarize existing work in the area, revealing problems that remain open and possible areas of further research. 相似文献
65.
1 Introduction A double-walled invertube is difficult to fabricate other than applying inversion process. Such kind of invertube can be used as impact energy absorbing element in transport vehicles, like aircrafts and automobiles. Reddy T Y[1] did the analysis of Internal inversion and calculated the inversion load. Reid[2] et al. examined nosing and internal inversion of cold drawn steel tube by the finite element package ABAQUS. Recently, Rosa P A[3] et al. investigated Internal invers… 相似文献
66.
Vibro-fluidized beds are widely used in drying sticky powders and agglomerated materials as milk powder. Using a vibro-fluidized laboratory scale dryer, this work is aiming at analyzing preliminarily the effect of its operational variables on the drying kinetics and characteristics of whole milk powder. The full-factorial design technique with three replications at the central point has been employed to generate data and correlations to quantify the effect of inlet air temperature, air flow rate, and vibration bed amplitude on the drying curves and the milk powder properties related to its faster reconstitution in water (as tapped density, Hausner cohesion ratio, agglomerate size distribution, and internal pore concentration). Results obtained are analyzed and discussed to identify the adequate operation condition for final drying whole milk powder in vibro-fluidized beds, assuring a high product quality. 相似文献
67.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry 相似文献
68.
暖通空调工程设计常见问题 总被引:1,自引:0,他引:1
通过对施工图审查工作进行总结,指出了暖通空调和防火防排烟设计中存在的问题及防火规范本身的一些不足。 相似文献
69.
R. Tao 《Chemical engineering science》2006,61(7):2186-2190
Molecular dynamical simulation has been carried out to investigate the structure and dynamics of a dipolar fluid under strong shear. Dipolar fluid consists of polarizable particles, which have an induced dipole moment in the applied field direction. Shear stress is perpendicular to the field direction. When shear stress is small, the flow has a flowing-chain structure. If shear stress increases to pass a critical value, flowing-chain structure changes to flowing layer structure. Each layer is parallel to the flow direction and shear direction. Within one layer, particles form strings in the flow direction. 相似文献
70.