全文获取类型
收费全文 | 75417篇 |
免费 | 6290篇 |
国内免费 | 2727篇 |
专业分类
电工技术 | 6301篇 |
综合类 | 7966篇 |
化学工业 | 5195篇 |
金属工艺 | 2624篇 |
机械仪表 | 3854篇 |
建筑科学 | 13374篇 |
矿业工程 | 2396篇 |
能源动力 | 1774篇 |
轻工业 | 13841篇 |
水利工程 | 3929篇 |
石油天然气 | 3019篇 |
武器工业 | 637篇 |
无线电 | 4786篇 |
一般工业技术 | 4212篇 |
冶金工业 | 3844篇 |
原子能技术 | 455篇 |
自动化技术 | 6227篇 |
出版年
2024年 | 265篇 |
2023年 | 998篇 |
2022年 | 1746篇 |
2021年 | 2290篇 |
2020年 | 2160篇 |
2019年 | 1858篇 |
2018年 | 1654篇 |
2017年 | 2090篇 |
2016年 | 2224篇 |
2015年 | 2495篇 |
2014年 | 5171篇 |
2013年 | 4158篇 |
2012年 | 5479篇 |
2011年 | 5890篇 |
2010年 | 4549篇 |
2009年 | 4906篇 |
2008年 | 4417篇 |
2007年 | 5413篇 |
2006年 | 4837篇 |
2005年 | 3888篇 |
2004年 | 3330篇 |
2003年 | 2948篇 |
2002年 | 2528篇 |
2001年 | 1916篇 |
2000年 | 1603篇 |
1999年 | 1229篇 |
1998年 | 844篇 |
1997年 | 708篇 |
1996年 | 588篇 |
1995年 | 506篇 |
1994年 | 383篇 |
1993年 | 285篇 |
1992年 | 261篇 |
1991年 | 181篇 |
1990年 | 108篇 |
1989年 | 124篇 |
1988年 | 91篇 |
1987年 | 66篇 |
1986年 | 40篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 11篇 |
1980年 | 23篇 |
1979年 | 14篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1966年 | 4篇 |
1959年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
AbstractDifferent drying methods (spray drying (SD), vacuum drying (VD), microwave vacuum drying (MVD), and infrared vacuum drying (IFVD)) were applied in order to compare the hygroscopicity behavior of chicken powders. The hygroscopicity curves and glass transition temperature were used to evaluate the influence of ambient humidity and temperature on moisture absorption of powders. The results showed that the chicken powder dried by MVD had the lowest moisture absorption, followed by IFVD, VD, and SD. The hygroscopicity of SD chicken powders was different from other three kinds of chicken powders due to the physical properties of particles and the changes of protein secondary structure as detected by the Fourier transform-infrared spectrometer. For the three vacuum drying methods, the difference of protein secondary structure was the main reason of differences in hygroscopicity. Although MVD chicken powders were slightly inferior to SD chicken powders in taste, MVD chicken powders were the best in terms of smell and color as suggested by instrumental sensory parameter evaluations. It was found that MVD had a positive effect on reducing moisture absorption and maintaining sensory quality of chicken powders. 相似文献
12.
13.
14.
添加剂是铜电解精炼生产管理的最关键要素,合适的添加剂使用方案可以有效保障电解生产系统长期稳定。结合添加剂生产实践和其它电解厂添加剂管理优点,提出探索添加剂精细化管理,进一步保障和提升铜电解添加剂管理实效。 相似文献
15.
16.
This paper describes the design and implementation of soft sensors to estimate cement fineness. Soft sensors are mathematical models that use available data to provide real-time information on process variables when the information, for whatever reason, is not available by direct measurement. In this application, soft sensors are used to provide information on process variable normally provided by off-line laboratory tests performed at large time intervals. Cement fineness is one of the crucial parameters that define the quality of produced cement. Providing real-time information on cement fineness using soft sensors can overcome limitations and problems that originate from a lack of information between two laboratory tests. The model inputs were selected from candidate process variables using an information theoretic approach. Models based on multi-layer perceptrons were developed, and their ability to estimate cement fineness of laboratory samples was analyzed. Models that had the best performance, and capacity to adopt changes in the cement grinding circuit were selected to implement soft sensors. Soft sensors were tested using data from a continuous cement production to demonstrate their use in real-time fineness estimation. Their performance was highly satisfactory, and the sensors proved to be capable of providing valuable information on cement grinding circuit performance. After successful off-line tests, soft sensors were implemented and installed in the control room of a cement factory. Results on the site confirm results obtained by tests conducted during soft sensor development. 相似文献
17.
To realize ultimately efficient signal processing, it is necessary to replace electrical signal processing circuits with optical ones. The optical micro-resonator, which localizes light at a certain spot, is an essential component in optical signal processing. Single-crystal calcium fluoride (CaF2) is the most suitable material for a highly efficient optical micro-resonator. The CaF2 resonator can only be manufactured by ultra-precision machining processes, because its crystal anisotropy does not allow the application of chemical etching. However, the optical micro-resonator's performance depends definitely on the surface integrity.This study investigated the relationship between surface quality after ultra-precision machining and crystal anisotropy. Firstly, crack initiation was investigated on the (1 0 0), (1 1 0), and (1 1 1) planes using the micro-Vickers hardness test. Secondly, brittle-ductile transition was investigated by orthogonal cutting tests. Finally, cutting performance of cylindrical turning was evaluated, which could be a suitable method for manufacturing the CaF2 resonator. The most difficult point in cylindrical turning of CaF2 is that the crystalline plane and cutting direction vary continuously. In order to manufacture the CaF2 optical micro-resonator more efficiently, analysis was conducted on crack initiation and surface quality of all crystallographic orientations from the perspective of slip system and cleavage. 相似文献
18.
19.
本文以喷淋液滴在空气环境下运动特性为工程背景,建立单个液滴在常温、常压空气环境中的动量方程,分析液滴沉降特性、追赶特性及运动轨迹行为。计算结果表明,不同喷淋液滴初始条件下,短时间内存在重力大于曳力和重力小于曳力两种情况,但最终减速液滴均会达到受力平衡状态;液滴离开喷淋头后,垂向位移均迅速增大,液滴粒径越大、初始速度越大,垂向位移增长的速率也越大,达到相同位移的用时越短;液滴尺寸、初始速度相差越大,液滴追赶所用的时间越短,追赶位移越小,液滴尺寸、初始速度越接近,液滴追赶所用的时间越长,追赶位移越大;液滴初始速度越大、初始直径越大、喷射角度越大,横向速度消失越慢,达到的横向位移越大,喷射液滴覆盖的面积也越大。计算结果有助于优化工程实际中喷淋系统的设计与布置。 相似文献
20.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献