全文获取类型
收费全文 | 18602篇 |
免费 | 657篇 |
国内免费 | 629篇 |
专业分类
电工技术 | 199篇 |
综合类 | 666篇 |
化学工业 | 3805篇 |
金属工艺 | 2389篇 |
机械仪表 | 3185篇 |
建筑科学 | 611篇 |
矿业工程 | 417篇 |
能源动力 | 814篇 |
轻工业 | 425篇 |
水利工程 | 312篇 |
石油天然气 | 202篇 |
武器工业 | 76篇 |
无线电 | 1209篇 |
一般工业技术 | 3516篇 |
冶金工业 | 510篇 |
原子能技术 | 245篇 |
自动化技术 | 1307篇 |
出版年
2024年 | 40篇 |
2023年 | 223篇 |
2022年 | 372篇 |
2021年 | 414篇 |
2020年 | 463篇 |
2019年 | 404篇 |
2018年 | 411篇 |
2017年 | 523篇 |
2016年 | 559篇 |
2015年 | 601篇 |
2014年 | 831篇 |
2013年 | 1347篇 |
2012年 | 894篇 |
2011年 | 1407篇 |
2010年 | 946篇 |
2009年 | 1158篇 |
2008年 | 1123篇 |
2007年 | 1196篇 |
2006年 | 1049篇 |
2005年 | 832篇 |
2004年 | 800篇 |
2003年 | 698篇 |
2002年 | 622篇 |
2001年 | 432篇 |
2000年 | 373篇 |
1999年 | 359篇 |
1998年 | 313篇 |
1997年 | 290篇 |
1996年 | 252篇 |
1995年 | 198篇 |
1994年 | 143篇 |
1993年 | 139篇 |
1992年 | 84篇 |
1991年 | 84篇 |
1990年 | 66篇 |
1989年 | 55篇 |
1988年 | 51篇 |
1987年 | 32篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 23篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 1篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Shuichi Yamamoto Teruaki Morihiro Koichi Ariyoshi Turkan Aktas 《Drying Technology》2005,23(6):1319-1330
As the surface properties of the drying materials are very important not only for the drying rate but also for the quality change during drying, the effects of surface concentration on the drying behavior of liquid foods (sugar solutions) were investigated by isothermal drying experiments and by numerical calculation experiments. The isothermal drying experiments with gelled sugar solution systems (sucrose and maltodextrin) were carried out at various relative humidity (RH) values (RH = 0 to 84%). Separate experiments were carried out for determination of the desorption isotherms.
The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.
When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased. 相似文献
The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.
When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased. 相似文献
42.
A. N. Karapetyan I. A. Gribova A. P. Krasnov Yu. N. Studnev A. K. Pogosyan K. V. Oganesyan 《Journal of Friction and Wear》2007,28(6):546-550
The results of investigation of the modification of the Armenian minerals with fluorine-containing oligomers show that a modified product appears when the mineral fillers are treated with fluoroalkanes. The product preserves the structure of the fillers with a “grafted” fluoroalkane layer in which chlorine atoms locate mainly over their periphery. The composite materials based on heterochained polymers and the modified fillers possess a stronger wear resistance and a low friction coefficient. 相似文献
43.
Meng Wai Woo 《Drying Technology》2008,26(1):15-26
Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem. 相似文献
44.
Yu.V. Butenko P.R. Coxon M. Yeganeh A.C. Brieva K. Liddell V.R. Dhanak L. iller 《Diamond and Related Materials》2008,17(6):962-966
It is generally accepted that diamond is resistant to a wide spectrum of electromagnetic radiation from the ultraviolet through to the soft X-ray range, which makes it very attractive for the fabrication of diamond-based photodetectors. However the effect of photon radiation on the diamond structure has not yet been examined. In the work presented here, photoelectron spectroscopy has been used to study the graphitization of nanodiamond crystallites exposed to extreme ultraviolet radiation. Under such irradiation, the surface hydrogen groups and graphite species are found to prevent graphitization. The mechanism of radiation-induced nanodiamond graphitization is discussed. 相似文献
45.
Dong Zhang 《Korean Journal of Chemical Engineering》2008,25(5):1205-1207
Ceria-zirconia solid particles have been recognized as a key material of the automotive exhaust catalysts since they can release
and uptake oxygen owing to the rapid reversible oxidation states of cerium between Ce3+ and Ce4+. Several methods have recently been described to prepare the CeO2-ZrO2 solid particles used in the catalysts. In this paper, a new coprecipitation method is used to prepare the CeO2-ZrO2 solid particles. The Ce-Zr alcogel is dried and calcined in flowing N2 not in flowing air under atmospheric pressure. The results show that the ceria-zirconia sample calcined at 650 °C has high
surface area over 90 m2g−1, which drops to 40 m2g−1 following treatment at 900°C. 相似文献
46.
The changes in surface composition of metallic alloys caused by segregation can be very efficiently studied by low-energy ion scattering (LEIS) due to the specific surface sensitivity of this technique. Investigations of single-crystal surfaces of ordered alloys are of particular interest because they provide the possibility to investigate the interplay between segregation effects and the order-disorder phase transition when passing through the transition temperature. Exemplifying these effects for bimetallic alloys we consider in particular the CuAu-system.For the quantitative interpretation of energy and angle resolved LEIS intensity distributions we compare experimental results with those from numerical simulations using the MARLOWE code which we extended with a detailed trajectory analysis. This allows us to apply various discrimination criteria, such as number of collisions, distance of closest approach, identification of the scattering crystal layer, total path length, etc. On this basis structural effects, ion survival probabilities and the influence of thermal vibrations can be studied.We demonstrate this potential by using CuAu(1 0 0) as a special example. The scattering potential parameters were calibrated with elemental single crystals of known structures and the anisotropic Debye temperatures taken from the literature showed good agreement, neutralization was of minor importance in this case. Our procedure could be successfully used for the quantitative analysis of the composition of the first and second layer as a function of temperature. These results are in good agreement with theoretical predictions. 相似文献
47.
48.
李桂敏 《中国材料科技与设备》2007,4(4):92-93
本文介绍了一种作业效率高、省时省力新型的转炉炉底车,其特点是转盘转动灵活,炉底车上项盘径向任意方向均能平稳倾斜一定角度,以保证炉底圆周所受项力均匀可靠,满足炉底安装要求。 相似文献
49.
50.
Compared to other fields of engineering, in mechanical engineering, the Discrete Element Method (DEM) is not yet a well known
method. Nevertheless, there is a variety of simulation problems where the method has obvious advantages due to its meshless
nature. For problems where several free bodies can collide and break after having been largely deformed, the DEM is the method
of choice. Neighborhood search and collision detection between bodies as well as the separation of large solids into smaller
particles are naturally incorporated in the method. The main DEM algorithm consists of a relatively simple loop that basically
contains the three substeps contact detection, force computation and integration. However, there exists a large variety of
different algorithms to choose the substeps to compose the optimal method for a given problem. In this contribution, we describe
the dynamics of particle systems together with appropriate numerical integration schemes and give an overview over different
types of particle interactions that can be composed to adapt the method to fit to a given simulation problem. Surface triangulations
are used to model complicated, non-convex bodies in contact with particle systems. The capabilities of the method are finally
demonstrated by means of application examples.
Commemorative Contribution. 相似文献