全文获取类型
收费全文 | 644篇 |
免费 | 68篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 30篇 |
综合类 | 65篇 |
化学工业 | 190篇 |
金属工艺 | 14篇 |
机械仪表 | 49篇 |
建筑科学 | 36篇 |
矿业工程 | 14篇 |
能源动力 | 15篇 |
轻工业 | 58篇 |
水利工程 | 15篇 |
石油天然气 | 48篇 |
武器工业 | 4篇 |
无线电 | 50篇 |
一般工业技术 | 75篇 |
冶金工业 | 16篇 |
原子能技术 | 2篇 |
自动化技术 | 47篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 31篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 27篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 15篇 |
2015年 | 29篇 |
2014年 | 24篇 |
2013年 | 49篇 |
2012年 | 44篇 |
2011年 | 50篇 |
2010年 | 37篇 |
2009年 | 33篇 |
2008年 | 35篇 |
2007年 | 37篇 |
2006年 | 26篇 |
2005年 | 40篇 |
2004年 | 13篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 16篇 |
2000年 | 23篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1986年 | 1篇 |
排序方式: 共有728条查询结果,搜索用时 15 毫秒
1.
A poly(ethylene terephthalate) (PET)/montmorillonite clay nanocomposite was synthesized via in situ polymerization. Microscopic studies revealed that in an isothermal crystallization process, some crystallites in the nanocomposite initially were rod‐shaped and later exhibited three‐dimensional growth. The crystallites in the nanocomposite were irregularly shaped, rather than spherulitic, being interlocked together without clear boundaries, and they were much smaller than those of neat PET. With Avrami analysis, the isothermal crystallization kinetic parameters (the Avrami exponent and constant) were obtained. The rate constants for the nanocomposite demonstrated that clay could greatly increase the crystallization rate of PET. The results for the Avrami exponent were consistent with the observation of the rodlike crystallites in the PET/clay nanocomposite during the initial stage. Wide‐angle X‐ray scattering and Fourier transform infrared studies showed that, in comparison with neat PET, the crystal lattice parameters and crystallinity of the nanocomposite did not change significantly, whereas more defects may have been present in the crystalline regions of the nanocomposite because of the presence of the clay. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1381–1388, 2004 相似文献
2.
研究了文本数字水印在追溯涉密纸质文档中的重要意义,介绍了常见的文本数字水印技术,分析了Brassil经典行移编码文本数字水印技术,在算法的标记策略中引入检验编码,文本行分割划段和引入基调行三个方面进行改进,改进后算法具有更大水印信息容量,更强的鲁棒性和可控的计算量. 相似文献
3.
贫瘦煤替代瘦煤制备优质焦炭性能研究 总被引:1,自引:0,他引:1
根据瘦煤和贫瘦煤结焦机理、成焦显微结构和粒度变化特征,对贫瘦煤替代瘦煤的结焦显微结构、焦炭性能进行了研究。结果表明,瘦煤与贫瘦煤可以互相替代,并且在合理配比的情况下可改善焦炭质量;通过合理的粒度调整和配煤,在提高贫瘦煤或瘦煤比率的同时亦可得到优质焦炭。 相似文献
4.
This paper designed an embedded video monitoring system using DSP (Digital Signal Processing ) and ARM (Ad- vanced RISC Machine).This system is an important part of self-service operation of numerical control machine tools,At first the analog input signals from the CCD(Charge Coupled Device) camera are transformed into digital signals,and then output to the DSP system,where the video sequence is encoded according to the new generation image compressing standard called H.264.The code will be transmitted to the ARM system through xBus,and then be packed in the ARM system and transmitted to the client port through the gateway.Web technology,embedded technology and image compressing as well as coding technology are integrated in the system,which can be widely used in self-service operation of numerical control machine tools and intelligent robot control areas. 相似文献
5.
Yu Xiao Mengjuan Li Xiaoyi Guo Hui Zeng Xuehong Shuai Jianhua Guo Qingzhou Huang Yuefeng Chu Bo Zhou Jake Wen Jun Liu Hanwei Jiao 《International journal of molecular sciences》2022,23(21)
Brucellosis is a severe zoonotic infectious disease caused by the infection of the Brucella, which is widespread and causes considerable economic losses in underdeveloped areas. Brucella is a facultative intracellular bacteria whose main target cells for infection are macrophages, placental trophoblast cells and dendritic cells. The main clinical signs of Brucella infection in livestock are reproductive disorders and abortion. At present, the pathogenesis of placentitis or abortion caused by Brucella in livestock is not fully understood, and further research on the effect of Brucella on placental development is still necessary. This review will mainly introduce the research progress of Brucella infection of placental trophoblast cells as well as the inflammatory response caused by it, explaining the molecular regulation mechanism of Brucella leading to reproductive system disorders and abortion, and also to provide the scientific basis for revealing the pathogenesis and infection mechanism of Brucella. 相似文献
6.
通过比较多种型式板桩护岸的优缺点,结合工程实际根据当地工程地质、施工条件、工程造价等方面的要求选择高分子聚合物板桩护岸,并进行相应的渗流和抗滑稳定、桩顶位移、河道过流能力计算,结果表明河道边坡抗滑和渗流稳定在各个工况下均满足规范要求,桩顶位移在允许范围内,河道流速满足河道不冲不淤要求.高分子聚合物板桩护岸效果良好,可被... 相似文献
7.
为了有效地分析实时系统,在原计算模型的基础上,引入了时钟变量,在迁移上增加了时钟约束,扩展了异步扩展层次自动机的语义.运用基于时间扩展的ASEHA,分析了ATM系统,建立了用户和ATM的模型,并使用模型检测工具UPPAAL对模型进行验证,从无死锁、活性及可达性性质出发,验证了ATM系统的安全性.实验表明,提出的基于时间... 相似文献
8.
Energy instability strongly affects the state and the beam size of the single ion microbeam. A facility based on the Generating Voltmeter was developed to improve the energy stability of the CAS-LIBB (Chinese Academy of Sciences, key laboratory of ion beam bioengineering) single ion microbeam. This paper presents the analysis of the energy' instability of the single ion microbeam. A simplified theoretical model is set up to calculate the relationship between the energy instability and the beam spot size. By using this technique, the energy instability is adjusted to about 1%. Stable run-time is over 6 hours. The radius of the single ion beam is reduced by 10% compared to the previous olin. 相似文献
9.
文中介绍了G.726语音编解码算法的原理,详细论述了ADPCM编解码算法在DSPTMS320VC5509A上实现的硬件结构及软件算法,并给出了在实现过程中的程序优化方法. 相似文献
10.