全文获取类型
收费全文 | 29968篇 |
免费 | 1980篇 |
国内免费 | 864篇 |
专业分类
电工技术 | 745篇 |
技术理论 | 1篇 |
综合类 | 1962篇 |
化学工业 | 15314篇 |
金属工艺 | 914篇 |
机械仪表 | 484篇 |
建筑科学 | 1673篇 |
矿业工程 | 462篇 |
能源动力 | 218篇 |
轻工业 | 3822篇 |
水利工程 | 220篇 |
石油天然气 | 1449篇 |
武器工业 | 134篇 |
无线电 | 583篇 |
一般工业技术 | 3546篇 |
冶金工业 | 547篇 |
原子能技术 | 249篇 |
自动化技术 | 489篇 |
出版年
2024年 | 88篇 |
2023年 | 201篇 |
2022年 | 461篇 |
2021年 | 567篇 |
2020年 | 642篇 |
2019年 | 547篇 |
2018年 | 563篇 |
2017年 | 822篇 |
2016年 | 864篇 |
2015年 | 960篇 |
2014年 | 1426篇 |
2013年 | 1801篇 |
2012年 | 2364篇 |
2011年 | 2216篇 |
2010年 | 1660篇 |
2009年 | 1774篇 |
2008年 | 1471篇 |
2007年 | 1998篇 |
2006年 | 1989篇 |
2005年 | 1609篇 |
2004年 | 1403篇 |
2003年 | 1294篇 |
2002年 | 1067篇 |
2001年 | 922篇 |
2000年 | 823篇 |
1999年 | 741篇 |
1998年 | 587篇 |
1997年 | 400篇 |
1996年 | 327篇 |
1995年 | 293篇 |
1994年 | 231篇 |
1993年 | 179篇 |
1992年 | 161篇 |
1991年 | 92篇 |
1990年 | 66篇 |
1989年 | 57篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 11篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1972年 | 2篇 |
1968年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
《Measurement》2016
To predict fatigue life of Polyethylene Terephthalate (PET) modified asphalt mixture, various soft computing methods such as Genetic Programming (GP), Artificial Neural Network (ANN), and Fuzzy Logic-based methods have been employed. In this study, an application of Support Vector Machine Firefly Algorithm (SVM-FFA) is implemented to predict fatigue life of PET modified asphalt mixture. The inputs are PET percentages, stress levels and environmental temperatures. The performance of proposed method is validated against observed experiment data. The results of the prediction using SVM-FFA are then compared to those of applying ANN and GP approach and it is concluded that SVM-FFA leads to more accurate results when compared to observed experiment data. 相似文献
992.
993.
994.
筛选国产树脂,并与装置原进口树脂进行催化剂对比试验,结果表明:国产某型号树脂在顺酐酯化中的转化率、选择性和使用寿命方面均能满足工艺需求,部分指标优于装置原进口酯化催化剂。因此在装置酯化塔内逐步将进口树脂更换成国产树脂进行工业化试验,并不断改进和优化装置酯化塔的树脂装填方案,从而工业化应用国产树脂,降低装置生产成本,获得更好的经济效益。 相似文献
995.
阐述了杀虫剂对人体的危害及使用防护服的必要性,简要论述了防护服面料的两种整理工艺——树脂整理和压榨工艺,并对这类防护服的发展空间进行了展望。 相似文献
996.
Ramazan Solmaz 《国际能源研究杂志》2017,41(10):1452-1459
Gold‐supported Raney‐type NiZn coatings were prepared on a thin Ni film‐modified copper substrate (Cu/Ni/NiZn‐Au). The hydrogen evolution activity, time stability and corrosion behaviour of the electrode was investigated in 1 M KOH solution by electrochemical, microscopic and spectroscopic technique. It was found that Au‐modified activated coatings exhibits good hydrogen evolution activity, electrochemical and physical stability as well as corrosion resistance. The enhanced hydrogen evolution activity of the Au‐modified electrode was related to the larger available surface area and/or a possible synergistic effect between the metals. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
997.
Polymerization induced viscoelastic phase separation of porous phenolic resin from solution
下载免费PDF全文
![点击此处可从《Polymer International》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xiaolin Yi Lei Kong Xia Dong Xiaobiao Zuo Xiao Kuang Zhihai Feng Dujin Wang 《Polymer International》2016,65(9):1031-1038
The porous structure evolution of thermosetting phenolic resin controlled by polymerization induced viscoelastic phase separation from solution was investigated in this work. The ultimate morphology and the evolution of a porous texture for the resol resin/solvent system were characterized by digital camera and optical microscopy. In-situ Fourier transform infrared spectroscopy and a rheological method were used to trace the curing reaction of the resol resin/solvent system. The impacts of solvent content and curing temperature on the foaming behavior were quantitatively and systematically investigated. Based on the relationship between the morphology evolution and curing dynamics, the foaming mechanism of the polymerization induced viscoelastic phase separation was elucidated. The present work provides new insight into the foaming mechanism of thermosetting materials and may be helpful for morphological control in the preparation of lightweight porous phenolic material. © 2016 Society of Chemical Industry 相似文献
998.
For developing high performance of graphene-based nanocomposites, dispersibility of graphene sheets in matrices and interfacial interaction are challenging due to the strong tendency of agglomeration and surface inertia of graphene. Here we report an efficient way to functionalize graphene nanosheets with aniline groups on their surfaces, to attain the functionalized graphene nanosheets (FGS) by diazonium treatment following reduction of graphene oxide with hydrazine hydrate. Two kinds of nanocomposites based on diallyl bisphenol A modified bismaleimide (BMI-BA) resin which was filled with functionalized graphene and reduced graphene oxide nanosheets were prepared, and the FGS were linked with BMI resin by chemical bonds. The FGS/BMI-BA composite at a loading of 0.3 wt% revealed a 39% increase in impact strength and a slightly improvement in flexural strength, and the resulting composite remains stable at high temperature. This work provides more possibilities for incorporation of graphene into polymer matrices and an efficient method to toughening the BMI resin. 相似文献
999.
Long processing cycle makes vacuum assisted resin infusion molding (VARIM) only suitable for low and medium volumes of production, and shortening of curing time is critical to improving the processing efficiency of automotive composite parts. In this paper, unidirectional carbon fiber reinforced composite laminates were fabricated by VARIM. Three different processes (namely quick, quick-post and preheating) were employed, in which a kind of rapid curing epoxy resin is used. The preheating of mold and fiber was conducted to shorten the filling time compared with that of quick process. Quick-post process with a post cure stage was investigated to verify the composite properties fabricated by quick process. The cycle time was 16 min for preheating process, about 30% shorter than that of quick process, simultaneously, flexural strength and interlaminar shear strength (ILSS) were respectively improved by 29% and 7% compared with those of quick process. The non-uniformity of mechanical properties at different positions along resin flow direction under preheating process was found, but the processing quality of composite was good. The preheating process is confirmed to be suitable for the improvement of processing efficiency of VARIM with good mechanical properties. In addition, the composite fabricated by quick-post process has better mechanical properties, which is attributed to the alleviation of residual stress during post curing process. 相似文献
1000.
Hollow glass microsphere (HGM) filled low-density polyethylene (LDPE) composites were prepared, and the effects of density, content, and surface modification of HGM on the thermal and dielectric properties of the composites were investigated. It is found that the thermal conductivity of the composites decreases with increasing HGM content or decreasing HGM density. At the same HGM content and density, the composites filled with suitable amount of silane coupling agent (KH570) modified HGM exhibit higher thermal conductivity than unmodified-HGM filled composites. The dielectric constant at 1 MHz of the composites also decreases with increasing HGM content or decreasing HGM density, but their dielectric loss increases with increasing HGM content or increasing HGM density. By modifying the surface of HGM with suitable amount of KH570, the dielectric constant and loss at 1 MHz of the composites can be decreased at the same time. The results of microwave dielectric properties of the composites indicate that the dielectric constant decreases with increasing HGM content or decreasing HGM density, the quality factor (Q × f) decreases with increasing HGM content or increasing HGM density, but both dielectric constant and quality factor are slightly affected by the surface modification of HGM. Due to lower intrinsic thermal conductivity and dielectric constant but higher dielectric loss of HGM than LDPE, the thermal conductivity and dielectric properties of the composites can be controlled with adding HGM and varying its volume fraction. The surface modification of HGM improves the interface contact between HGM and LDPE in the composites, which is confirmed by the SEM observation, and thus the heat conduction and dielectric properties at low frequency are improved. Based on calculated thermal conductivity and dielectric constant of HGM, the experimental trends of thermal conductivity and dielectric constant at 1 MHz of the composites are analyzed by using different models, including typical models for particles-filled composites and special models developed for hollow microsphere filled composites. The results from suitable models show close correlation with the experimental values. 相似文献