全文获取类型
收费全文 | 141073篇 |
免费 | 20958篇 |
国内免费 | 3274篇 |
专业分类
电工技术 | 5496篇 |
技术理论 | 9篇 |
综合类 | 5278篇 |
化学工业 | 34790篇 |
金属工艺 | 5283篇 |
机械仪表 | 6637篇 |
建筑科学 | 9473篇 |
矿业工程 | 2159篇 |
能源动力 | 3848篇 |
轻工业 | 13667篇 |
水利工程 | 1973篇 |
石油天然气 | 4691篇 |
武器工业 | 516篇 |
无线电 | 19140篇 |
一般工业技术 | 24427篇 |
冶金工业 | 8809篇 |
原子能技术 | 1003篇 |
自动化技术 | 18106篇 |
出版年
2024年 | 272篇 |
2023年 | 1336篇 |
2022年 | 2325篇 |
2021年 | 3681篇 |
2020年 | 3858篇 |
2019年 | 5241篇 |
2018年 | 5430篇 |
2017年 | 6020篇 |
2016年 | 6340篇 |
2015年 | 6977篇 |
2014年 | 8128篇 |
2013年 | 10657篇 |
2012年 | 8526篇 |
2011年 | 8638篇 |
2010年 | 8064篇 |
2009年 | 7833篇 |
2008年 | 7140篇 |
2007年 | 6994篇 |
2006年 | 6897篇 |
2005年 | 6041篇 |
2004年 | 4724篇 |
2003年 | 4753篇 |
2002年 | 4748篇 |
2001年 | 4227篇 |
2000年 | 3917篇 |
1999年 | 3534篇 |
1998年 | 3732篇 |
1997年 | 2756篇 |
1996年 | 2375篇 |
1995年 | 1868篇 |
1994年 | 1534篇 |
1993年 | 1232篇 |
1992年 | 850篇 |
1991年 | 700篇 |
1990年 | 556篇 |
1989年 | 500篇 |
1988年 | 443篇 |
1987年 | 281篇 |
1986年 | 272篇 |
1985年 | 256篇 |
1984年 | 177篇 |
1983年 | 152篇 |
1982年 | 139篇 |
1981年 | 154篇 |
1980年 | 136篇 |
1979年 | 93篇 |
1977年 | 134篇 |
1976年 | 208篇 |
1975年 | 66篇 |
1973年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
132.
133.
Hong Wei Li Li Ya‐Li Ma Ru‐Xue Liu Shuang‐Yan Meng Li‐Tong Niu Zhe Zhang Zhi‐Wang Yang 《火与材料》2019,43(7):868-879
Through the simple precipitation of palygorskite (PGS) by zinc borate (ZB) (to make PGS@ZB) and the decoration of PGS@ZB by dodecylamine (N), a novel organic‐inorganic@inorganic hybrid flame retardant of PGS@ZB‐N was prepared and was incorporated with ethylene vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@ZB‐N were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM), and it was confirmed that the PGS@ZB‐N hybrid had been successfully prepared. The flame retardancy and burning behavior of EVA/PGS@ZB‐N/EG (EG = expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 (by the vertical burning test), and cone calorimeter test (CCT) characterizations. The prepared EVA/PGS@ZB‐N/EG composite obtained an LOI value of 41.2% with the addition of 30 wt% PGS@ZB‐N/EG. It was found that EVA/PGS@ZB‐N/EG was protected through a gas phase and condensed phase alternating synergistic effect mechanism. 相似文献
134.
Hai Huang Haichao An Haibo Ma Shenyan Chen 《International journal for numerical methods in engineering》2019,117(3):291-315
This work presents an engineering method for optimizing structures made of bars, beams, plates, or a combination of those components. Corresponding problems involve both continuous (size) and discrete (topology) variables. Using a branched multipoint approximate function, which involves such mixed variables, a series of sequential approximate problems are constructed to make the primal problem explicit. To solve the approximate problems, genetic algorithm (GA) is utilized to optimize discrete variables, and when calculating individual fitness values in GA, a second-level approximate problem only involving retained continuous variables is built to optimize continuous variables. The solution to the second-level approximate problem can be easily obtained with dual methods. Structural analyses are only needed before improving the branched approximate functions in the iteration cycles. The method aims at optimal design of discrete structures consisting of bars, beams, plates, or other components. Numerical examples are given to illustrate its effectiveness, including frame topology optimization, layout optimization of stiffeners modeled with beams or shells, concurrent layout optimization of beam and shell components, and an application in a microsatellite structure. Optimization results show that the number of structural analyses is dramatically decreased when compared with pure GA while even comparable to pure sizing optimization. 相似文献
135.
Parisa Solhi Sodeif Azadmard‐Damirchi Javad Hesari Hamed Hamishehkar 《International Journal of Dairy Technology》2020,73(1):226-233
The qualitative properties of processed cheese (PC) fortified with different levels of asparagus powder (AP) (0.5%, 1% and 1.5% wt/wt) were evaluated during storage. AP decreased the pH and lipolysis indexes and increased the phenolic content, antioxidant activity and proteolysis of the processed cheeses. AP made the structure of the cheese more elastic, increased the rigidity and decreased the spreadability compared with the control sample, which corresponded to the results obtained using dynamic oscillatory rheometry. The results showed that AP as a rich source of bioactive components could be used for the fortification of processed cheeses. 相似文献
136.
Jianmou Lu Yanli Huang Shunyan Ren 《International Journal of Control, Automation and Systems》2020,18(5):1250-1263
This paper investigates the general decay synchronization and general decay H∞ synchronization problems of multi-weighted coupled reaction-diffusion 相似文献
137.
Slim Salhi Jihen Mahfoudh Souhir Abid Leonard‐Ionut Atanase Marcel Popa Christelle Delaite 《Polymer International》2020,69(11):1161-1168
A series of random polyesteramides (PEAs) with a range of molar composition from 90/10 to 50/50 were synthesized by direct melt polycondensation of ε‐caprolactone and l ‐alanine. Their structure was fully characterized by Fourier transform IR and NMR spectroscopy. The resulting copolymers are completely amorphous with the exception of PEA‐90/10 which possesses a semicrystalline structure. These PEAs present increasing glass transition temperatures at increasing l ‐alanine contents and exhibit fairly good thermal stability with 10% mass loss temperatures reaching 315 °C. © 2020 Society of Industrial Chemistry 相似文献
138.
The in-situ fabrication of an electron-blocking layer between the Ba-containing anode and the ceria-based electrolyte is an effective approach in suppressing the internal electronic leakage in ceria-based solid oxide fuel cell (SOFC). To improve the thickness of the electron-blocking layer and to research the effect of the layer thickness on the improvement of SOFC, a Ba-containing compound (0.6NiO-0.4BaZr0.1Ce0.7Y0.2O3-δ) modified by Y stabilized zirconia (YSZ) was employed as a composite anode in this research. SEM analyses demonstrated that the thickness of the interlayer can be simply controlled by regulating the proportion of YSZ at anode. The in-situ formed interlayer in the cell with the anode modified by 20?mol% YSZ possesses a thickness of 0.9?µm which is more suitable for the cell achieving an enhanced performance. 相似文献
139.
Guankui Long Yecheng Zhou Mingtao Zhang Randy Sabatini Abdullah Rasmita Li Huang Girish Lakhwani Weibo Gao 《Advanced materials (Deerfield Beach, Fla.)》2019,31(17)
Hybrid organic–inorganic perovskites (HOIPs), in particular 3D HOIPs, have demonstrated remarkable properties, including ultralong charge‐carrier diffusion lengths, high dielectric constants, low trap densities, tunable absorption and emission wavelengths, strong spin–orbit coupling, and large Rashba splitting. These superior properties have generated intensive research interest in HOIPs for high‐performance optoelectronics and spintronics. Here, 3D hybrid organic–inorganic perovskites that implant chirality through introducing the chiral methylammonium cation are demonstrated. Based on structural optimization, phonon spectra, formation energy, and ab initio molecular dynamics simulations, it is found that the chirality of the chiral cations can be successfully transferred to the framework of 3D HOIPs, and the resulting 3D chiral HOIPs are both kinetically and thermodynamically stable. Combining chirality with the impressive optical, electrical, and spintronic properties of 3D perovskites, 3D chiral perovskites is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics. 相似文献
140.