全文获取类型
收费全文 | 95394篇 |
免费 | 7558篇 |
国内免费 | 3260篇 |
专业分类
电工技术 | 4586篇 |
技术理论 | 26篇 |
综合类 | 7076篇 |
化学工业 | 9918篇 |
金属工艺 | 13831篇 |
机械仪表 | 6569篇 |
建筑科学 | 10376篇 |
矿业工程 | 5260篇 |
能源动力 | 2146篇 |
轻工业 | 7931篇 |
水利工程 | 1964篇 |
石油天然气 | 4943篇 |
武器工业 | 2267篇 |
无线电 | 8826篇 |
一般工业技术 | 5903篇 |
冶金工业 | 4654篇 |
原子能技术 | 370篇 |
自动化技术 | 9566篇 |
出版年
2024年 | 313篇 |
2023年 | 940篇 |
2022年 | 1951篇 |
2021年 | 2445篇 |
2020年 | 2602篇 |
2019年 | 1707篇 |
2018年 | 1596篇 |
2017年 | 2527篇 |
2016年 | 2863篇 |
2015年 | 3007篇 |
2014年 | 7319篇 |
2013年 | 5615篇 |
2012年 | 7047篇 |
2011年 | 7431篇 |
2010年 | 5703篇 |
2009年 | 5768篇 |
2008年 | 5183篇 |
2007年 | 6583篇 |
2006年 | 6165篇 |
2005年 | 5221篇 |
2004年 | 4613篇 |
2003年 | 4132篇 |
2002年 | 3399篇 |
2001年 | 2865篇 |
2000年 | 2215篇 |
1999年 | 1721篇 |
1998年 | 1194篇 |
1997年 | 922篇 |
1996年 | 797篇 |
1995年 | 624篇 |
1994年 | 456篇 |
1993年 | 303篇 |
1992年 | 247篇 |
1991年 | 183篇 |
1990年 | 152篇 |
1989年 | 123篇 |
1988年 | 78篇 |
1987年 | 48篇 |
1986年 | 42篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1963年 | 2篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
对省煤器开裂管进行了化学成分及宏、微观分析。分析结果表明,在高温高压条件下,在其焊缝溶合区出现粗大的魏氏组织,管材中的珠光体组织产生了不同程度的球化,而母材组织又存在严重的带状组织。在过热条件下熔合区极易出现裂纹,并由此快速扩展,造成省煤器管开裂。 相似文献
82.
83.
84.
针对企业集团分权化管理的缺点,设计出一套利用互联网络技术实现企业集团财务集中控制的模式,给出了模式的图示及说明。 相似文献
85.
86.
87.
88.
Z. Gruba? 《Materials Letters》2007,61(3):794-798
The initial stage of copper electrodeposition on the electrochemically activated assembly of carbon microelectrodes from an acid solution of copper sulfate was investigated using cyclic voltammetry, potentiostatic pulse technique and electrochemical impedance spectroscopy. Analysis of the experimental current transients has been carried out using a non-linear fitting procedure according to the model that takes into account spherical diffusion towards a disc-shaped microelectrode. The higher values of diffusion coefficient in comparison with those observed on planar electrodes were explained with an increased diffusion caused by the electrode geometry. Impedance spectra showed two time constants, the high-frequency related to the charge transfer process and the low-frequency corresponded to the deposit morphology. 相似文献
89.
Using process-oriented, sequencing educational technologies: Some important pedagogical issues 总被引:1,自引:0,他引:1
In recent times, sequencing technologies are becoming increasingly used, both by the university and the industry sectors. In essence, these complex systems support sequencing of, and navigation through units of content. They come in two different types: SCORM-based and workflow-based systems. Current research efforts related to sequencing technologies concentrate mostly on technical issues, while the associated pedagogical issues remain unexplored.The main objective of this paper is to describe the most important pedagogical issues that need to be taken into account when implementing any type of sequencing educational technologies (either SCORM- or workflow-based). These issues were identified during an action-learning project related to the practical implementation of a workflow-based educational system. During the reflection phase of this project, these issues were then genarised, so they could be applied to any type of sequencing technology and in any application domain (teaching discipline). The paper describes how sequencing technology can be used to enable a more flexible learning experience (especially in terms of time and flexible learning pathways) and then proceeds with the detailed analysis of the associated pedagogical issues. 相似文献
90.
G. Biallas Dr.‐Ing. C. Sick J. Schneider K.‐H. Trautmann 《Materialwissenschaft und Werkstofftechnik》2007,38(9):705-711
Biaxial fatigue of friction stir welded stiffened panels Within the framework of the European WelAir project, cruciform specimens made from stiffening FSW overlap joints were fatigued in the DLR biaxial test rig. To resemble the loading situation of pressurized fuselage structures, proportional loading without any phase shift, but with different load ratios λ between the loading components in both directions was applied.Natural crack initiation and subsequent crack growth were governed by the stiffness gradient caused by introducing the stringer. Cracks initiated and propagated at run‐in and run‐out locations in a direction perpendicular to the weld seam. The shortest fatigue life was observed for uniaxial loading in welding direction (λ = 0). An additional stress component perpendicular to the joint line (λ > 0) resulted in a higher number of cycles to failure. Similar to single stringer panels, increasing the load ratio also increased the number of cycles to failure for FSW clip‐stringer structural members, but additionally gives a different location of the fatal crack. 相似文献