全文获取类型
收费全文 | 10028篇 |
免费 | 2070篇 |
国内免费 | 2276篇 |
专业分类
化学 | 7656篇 |
晶体学 | 257篇 |
力学 | 626篇 |
综合类 | 223篇 |
数学 | 1303篇 |
物理学 | 4309篇 |
出版年
2024年 | 32篇 |
2023年 | 185篇 |
2022年 | 372篇 |
2021年 | 402篇 |
2020年 | 417篇 |
2019年 | 424篇 |
2018年 | 390篇 |
2017年 | 430篇 |
2016年 | 450篇 |
2015年 | 595篇 |
2014年 | 634篇 |
2013年 | 742篇 |
2012年 | 908篇 |
2011年 | 973篇 |
2010年 | 777篇 |
2009年 | 680篇 |
2008年 | 803篇 |
2007年 | 746篇 |
2006年 | 647篇 |
2005年 | 540篇 |
2004年 | 483篇 |
2003年 | 415篇 |
2002年 | 485篇 |
2001年 | 409篇 |
2000年 | 286篇 |
1999年 | 214篇 |
1998年 | 133篇 |
1997年 | 101篇 |
1996年 | 100篇 |
1995年 | 92篇 |
1994年 | 80篇 |
1993年 | 65篇 |
1992年 | 65篇 |
1991年 | 51篇 |
1990年 | 62篇 |
1989年 | 42篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 21篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1960年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
Spacelike Willmore surfaces in 4-dimensional Lorentzian space forms, a topic in Lorentzian conformal geometry which parallels the theory of Willmore surfaces in S4, are studied in this paper. We define two kinds of transforms for such a surface, which produce the so-called left/right polar surfaces and the adjoint surfaces. These new surfaces are again conformal Willmore surfaces. For them the interesting duality theorem holds. As an application spacelike Willmore 2-spheres are classified. Finally we construct a family of homogeneous spacelike Willmore tori. 相似文献
992.
A cement-based piezoelectric composite was introduced as real-time health monitoring systems to dentin. Lithium sodium potassium niobate and zinc polycarboxylate cement were mixed and made piezoelectric under different poling conditions. X-ray diffraction and scanning electron microscope confirmed the component and microstructure of the cement. The bonding force of the composites was compared to that of pure cement by analysis of variance. The optimum poling method was determined and the influencing factors of piezoelectric coefficient were discussed. 相似文献
993.
994.
995.
Enthalpy‐entropy compensation remains a mystery in chemistry and biophysics. Recent study suggested that the solvent reorganization might constitute the physical origin of the compensation, which was unfortunately not widely applicable because compensation was also observed in solid phase reactions. In this study, a general theoretical model based upon strict mathematical deduction was presented, which indicated that the redistribution of the distinguishable subspecies might be the physical origin of the enthalpy‐entropy compensation in complex systems. As examples, the enthalpy‐entropy compensations in solvation and surface adsorption were discussed. 相似文献
996.
Red Electroluminescence and Photoluminescence from Novel Binuclear Europium Complex with Squaric Acid Ligand 总被引:1,自引:0,他引:1
Wei Guo ZHU* Xiao Qiang WEI Mei Xiang ZHU Zhi Yun LU Bo LIANG Ming Gui XIE De Qiang ZHANG Yong QIU College of Chemistry Xiangtan University Xiangtan Department of Chemistry Sichuan University Chendu Department of 《中国化学快报》2001,(10)
Organic electroluminescent devices (OELDs) have attracted much attention for several years because of their potential application in large area, multi-colored flat panel displays1-5. The green organic EL display using Alq3 as emitter was commercialized in 19976. However, red-emitting OELD with excellent properties has not been well developed. In order to realize practical full-color OELDs, it is considered very important to develop red and blue emitting materials with excellent propert… 相似文献
997.
1 INTRUDUCTION During the last few years, there has been much effort paid to the synthesis of new transition-metal oxides that might be active hosts for intercalation reactions. Vanadium and molybdenum in higher oxidation states with higher reacting ability tend to form polynuclear, anionic metal-oxygen clusters with an extraordinary variety of the relevant topology and electronic structures[1~3]. The preparation of the corresponding clusters is of special interest for different aspects … 相似文献
998.
999.
IntroductionThechemistryoforganoaluminum,organogalliumandorganoindiumcomplexeshasattractedmuchat'tentionduenotonlytotheirinterestingstructuralandchemicalpropertiesbutalsotheirapplicationinsemiconductormaterialsl-5.InthecourseofourstudiesonexploringvolatileMOCVDprecursorsthathavethepropertiesoflowertoxicityandhigherstability,wehaverecentlyreportedonthesynthesisandcharacterizationofintermolecularadducts'-',novelbondingmodecomplexes",',andthecomplexesinwhichN/Omixed-donorcrownethersasligands'l'… 相似文献
1000.
一种基于梯度算子和拉普拉斯算子检测医学基因芯片荧光数字图像边缘的方法.数字图像经过图像增强等预处理以后,突出了我们感兴趣的数字图像特征,根据数字图像灰度变化的趋势,用灰度变化的一阶导数(梯度算子)检测图象中的边缘区域;用灰度变化的二阶导数确定图像边缘的中心位置.最后根据某些预定的准则把满足这些准则的象素组成一条边缘. 相似文献