全文获取类型
收费全文 | 90586篇 |
免费 | 10171篇 |
国内免费 | 6548篇 |
专业分类
电工技术 | 7348篇 |
技术理论 | 4篇 |
综合类 | 8673篇 |
化学工业 | 15006篇 |
金属工艺 | 5112篇 |
机械仪表 | 5680篇 |
建筑科学 | 5743篇 |
矿业工程 | 3448篇 |
能源动力 | 6727篇 |
轻工业 | 4469篇 |
水利工程 | 6336篇 |
石油天然气 | 6190篇 |
武器工业 | 1155篇 |
无线电 | 5791篇 |
一般工业技术 | 8619篇 |
冶金工业 | 5798篇 |
原子能技术 | 2282篇 |
自动化技术 | 8924篇 |
出版年
2024年 | 415篇 |
2023年 | 1304篇 |
2022年 | 2458篇 |
2021年 | 2949篇 |
2020年 | 3220篇 |
2019年 | 2752篇 |
2018年 | 2669篇 |
2017年 | 3376篇 |
2016年 | 3714篇 |
2015年 | 3787篇 |
2014年 | 5396篇 |
2013年 | 6174篇 |
2012年 | 6455篇 |
2011年 | 7098篇 |
2010年 | 5044篇 |
2009年 | 5262篇 |
2008年 | 4835篇 |
2007年 | 5796篇 |
2006年 | 5219篇 |
2005年 | 4599篇 |
2004年 | 3860篇 |
2003年 | 3418篇 |
2002年 | 2811篇 |
2001年 | 2399篇 |
2000年 | 2063篇 |
1999年 | 1717篇 |
1998年 | 1441篇 |
1997年 | 1217篇 |
1996年 | 1127篇 |
1995年 | 987篇 |
1994年 | 810篇 |
1993年 | 612篇 |
1992年 | 546篇 |
1991年 | 365篇 |
1990年 | 359篇 |
1989年 | 254篇 |
1988年 | 176篇 |
1987年 | 127篇 |
1986年 | 101篇 |
1985年 | 65篇 |
1984年 | 73篇 |
1983年 | 50篇 |
1982年 | 35篇 |
1981年 | 19篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 10篇 |
1975年 | 13篇 |
1959年 | 30篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
22.
在概括了自蔓延高温合成陶瓷内衬钢管的制备原理基础上,从降低陶瓷层孔隙率,减少陶瓷层裂纹和提高陶瓷层结合强度等方面,论述了提高自蔓延高温合成陶瓷内衬钢管性能的措施,对自蔓延高温合成陶瓷内衬钢管的应用现状及展望进行了评述。 相似文献
23.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
24.
阐述了企业人力资源投资财务评价应解决的两个重要问题:评价对象的分类和项目的财务现金流量的内容。 相似文献
25.
文章通过分析多相流模拟井的实际工作要求 ,提出了简单实用的流量自动控制模型。应用成型的计算机数据采集和控制模块及稳定可靠的流量控制部件 ,实现了各相流量的自动控制过程。该流量自动控制系统调节精度高、速度快、整体造价低 ,在实际应用中取得了良好的效果。 相似文献
26.
27.
阐述了城域光网络(MON)技术的出现背景、定义、技术方案和特点,以及与现有城域基础设施的比较,突出说明了其应用上的竞争优势。最后介绍了MON的现状和前景展望。 相似文献
28.
H. Luo 《Microsystem Technologies》2006,12(4):324-329
This paper focuses on tracking, reconstruction and motion estimation of a well-defined MEMS optical switch from a microscopic
view. For out-of-view reconstruction, a homography capable of transforming feature points and feature lines between a microscopic
image and a CAD model of the switch is implemented. The homography between two sequential microscopic images is decomposed
and factorized for motion estimation. Optical flow has also been explored to provide rough estimations of rotation centre
and angle. The paper also illustrates motion parameter optimization principles to deal with uncertainty inherent in micro
world. After non-linear optimization, estimation accuracy for rotation angle and rotation centre can reach 0.06° and pixel
level, respectively. 相似文献
29.
Lawrence K. Forbes Graeme C. Hocking Simon Wotherspoon 《Journal of Engineering Mathematics》2004,48(1):69-91
Rainwater can collect in a lens-shaped region within the rock of a tropical island, and may be separated from the underlying salt water by a sharp interface. This paper presents a nonlinear theory for determining the shape of this interface. The island is assumed to be saturated with rain, and provision is made for the outflow of rain-water through the sides of the island. The effect of a bore well on the shape of the interface is investigated, and the problem is solved using a spectral method. An integral-equation method is also presented for the case when the island has infinite width. 相似文献
30.
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