全文获取类型
收费全文 | 23979篇 |
免费 | 1756篇 |
国内免费 | 854篇 |
专业分类
电工技术 | 540篇 |
综合类 | 1209篇 |
化学工业 | 5701篇 |
金属工艺 | 4048篇 |
机械仪表 | 918篇 |
建筑科学 | 1429篇 |
矿业工程 | 401篇 |
能源动力 | 848篇 |
轻工业 | 3607篇 |
水利工程 | 131篇 |
石油天然气 | 390篇 |
武器工业 | 112篇 |
无线电 | 519篇 |
一般工业技术 | 2120篇 |
冶金工业 | 3984篇 |
原子能技术 | 145篇 |
自动化技术 | 487篇 |
出版年
2024年 | 89篇 |
2023年 | 326篇 |
2022年 | 563篇 |
2021年 | 696篇 |
2020年 | 716篇 |
2019年 | 599篇 |
2018年 | 589篇 |
2017年 | 877篇 |
2016年 | 850篇 |
2015年 | 737篇 |
2014年 | 1377篇 |
2013年 | 2391篇 |
2012年 | 1553篇 |
2011年 | 1717篇 |
2010年 | 1170篇 |
2009年 | 1252篇 |
2008年 | 982篇 |
2007年 | 1367篇 |
2006年 | 1393篇 |
2005年 | 1152篇 |
2004年 | 974篇 |
2003年 | 821篇 |
2002年 | 793篇 |
2001年 | 707篇 |
2000年 | 554篇 |
1999年 | 470篇 |
1998年 | 372篇 |
1997年 | 348篇 |
1996年 | 261篇 |
1995年 | 202篇 |
1994年 | 134篇 |
1993年 | 140篇 |
1992年 | 100篇 |
1991年 | 55篇 |
1990年 | 52篇 |
1989年 | 69篇 |
1988年 | 36篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 19篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1978年 | 3篇 |
1975年 | 4篇 |
1959年 | 2篇 |
1956年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
The model gives the temperature and moisture distributions of the air, and of the moist sheet, as a function of time and distance in the dryer. The influence of the sheet's velocity and that of the radiant energy on the dryer performance as well as the effect of the moisture content of the entering sheet have been studied. A set of 27 experiments was carried out using the infrared dryer in order to calibrate the model. In these, the following three variables each had three operational levels: web velocity, initial web moisture and heating power. The model predictions agreed very well with the experimental data. Model predictions using arithmetic averages for the parameters, and parameters correlated with operational variables, are also presented and discussed. 相似文献
82.
83.
本文研究了单加或同时添加微量Ca和Mg对变形及铸态镍基高温合金力学性能和热塑性的影响。试验表明,适量的Mg或Ca、Mg对提高合金的持久断裂寿命、高温拉伸塑性以及改善热塑性都取得良好效果。 相似文献
84.
《Drying Technology》2007,25(11):1803-1808
Malting is a very intensive, energy-consuming process and, from the point of view of energy, green malt drying is one of the most important operations. Double-deck kiln drying, a variant of single-deck kiln drying, is the most commonly used process, but it is usually manually controlled under empirical control actions. These are the reasons why a research project was carried out based on the computer modeling of these process operations including a software tool named CIMFOOD. A knowledge-based system (KBS) allowing the entire processing-plant dynamic behavior simulation and scheduling concerning thermal energy requirements was developed. 相似文献
85.
《Drying Technology》2007,25(7):1275-1280
When using the convective drying method, the mass transfer between drying air and moisture diffusion of the material is very important. The moisture moves inside the material because of the volume change caused by the increased temperature. This movement is additionally affected by the texture of the material. According to the research dealing with colloid capillary porous texture of vegetables and fruit, the humidity migration inside the material occurs in both fluid and steam condition at the same time. This migration is stimulated by the heating and decreasing humidity along with the flow. In this research, winter varieties of apples (Jonathan, Golden Delicious, and Idared) were studied by heating of a 20 × 20 × 20 piece of apple with a thermocouple in it. On the basis of the measurements it can be stated that for the fruits with a high percentage of moisture (75-90%), when making the drying condition, the moisture gradient is influenced by the fractured cells of the cut area. It was found that the variety of apple is very important in relation to the heating and water loss gradient. According to the results, the wet volume change due to the heating highly influences the water loss. The models that describe the temperature of the material have a connection with the water loss. 相似文献
86.
Two types of conventional kiln-drying schedules (mild and harsh) based on moisture content (MC) were compared with regard to time, drying quality, and energy cost. The results were evaluated according to the classification of the European Drying Group. Proper drying periods of mild and harsh schedules were found to be 550 and 514 h, respectively. Evaluations in terms of drying quality indicated that better results were achieved with the mild schedule, especially when comparing drying defects and final MC. From an energy efficiency point of view, the harsh schedule, by saving 36 h of drying time, reduced electricity by 594 KWh and was therefore found to be $65 more profitable in this trial. 相似文献
87.
介绍了梅山2号高炉(1280m^3)引进奥钢联的改进型内燃式热风炉技术;论述了其主要结构特点和设计参数;分析了其采用附加高炉煤气为燃料的燃烧炉管束式换热器的运行情况。实践表明,在以全高炉煤气为燃料的内燃式热风炉上实现了1200℃以上的高风温。 相似文献
88.
89.
Mass transport in wood during drying can have different mechanisms at different periods of drying. Depending on the current moisture content (MC) and the structure of the wood, the driving forces for the mass transport are essentially different. Above the fiber saturation point (FSP), the lumens are partially saturated and the transport of liquid (free) water occurs as a consequence of capillary action. On the other hand, below the FSP, bound water within the cell walls is conveyed by diffusion, and water vapor in the lumens moves under influence of pressures gradient. Based on these considerations, a unified model is presented that takes into account the transport of the different moisture phases. Simulation of the drying of a Norway spruce sample at 50°C from about 135 to 7% MC is carried out using the finite element method (FEM). Comparison between the simulated average MC and the experimental observations obtained from X-ray computed tomography (CT) shows reasonable agreement. Possible simplifications in the model are briefly discussed as well as some aspects of the numerical implementation. Finally, the influence of absolute permeability on the average MC is studied. 相似文献
90.
《Drying Technology》2007,25(2):303-310
The aim of this work was to determine specifications for spray-drying manufacturing of sustained-release drug-loaded microparticles with potential application in dentistry. Chitosan was used as the microencapsulation polymer and ketoprofen as the model drug. A 1:1 chitosan/ketoprofen suspension was spray-dried under different operating conditions. The size distribution, morphology, total drug load, and release profile of the powders were characterized. In vitro release studies were performed with the powder samples entrapped in cellulose dialysis tubes. The microparticles produced had a narrow size distribution (mean diameter ranging from 2.11 to 3.27 µm), good sphericity, and a smooth surface. In vitro release studies showed a linear drug dissolution behavior. 相似文献