全文获取类型
收费全文 | 6279篇 |
免费 | 2490篇 |
国内免费 | 1242篇 |
专业分类
化学 | 1635篇 |
晶体学 | 271篇 |
力学 | 1228篇 |
综合类 | 213篇 |
数学 | 248篇 |
物理学 | 6416篇 |
出版年
2024年 | 41篇 |
2023年 | 185篇 |
2022年 | 235篇 |
2021年 | 205篇 |
2020年 | 143篇 |
2019年 | 228篇 |
2018年 | 145篇 |
2017年 | 243篇 |
2016年 | 249篇 |
2015年 | 268篇 |
2014年 | 739篇 |
2013年 | 451篇 |
2012年 | 419篇 |
2011年 | 480篇 |
2010年 | 458篇 |
2009年 | 558篇 |
2008年 | 676篇 |
2007年 | 429篇 |
2006年 | 383篇 |
2005年 | 373篇 |
2004年 | 337篇 |
2003年 | 439篇 |
2002年 | 393篇 |
2001年 | 319篇 |
2000年 | 273篇 |
1999年 | 202篇 |
1998年 | 155篇 |
1997年 | 129篇 |
1996年 | 132篇 |
1995年 | 158篇 |
1994年 | 117篇 |
1993年 | 73篇 |
1992年 | 88篇 |
1991年 | 77篇 |
1990年 | 71篇 |
1989年 | 71篇 |
1988年 | 24篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1979年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Fei Wang Zhaolong Chen Jiawei Yang Hao Li Jingyuan Shan Feng Zhang Baolu Guan Zhongfan Liu 《物理化学学报》2022,37(10):2001024-0
Graphene has become a research focus in recent years owing to its excellent characteristics, and glass is a commonly used material with high transparency and low cost. Graphene glass combines the excellent properties of both graphene and glass; graphene glass has not only high thermal conductivity, high electrical conductivity, and good surface hydrophobicity but also exhibits superior electrothermal conversion and wide-spectrum high-light-transmittance characteristics. Therefore, the study of graphene glass films is of theoretical value and practical significance. In this study, a high-purity glass-based (JGS1 quartz glass) multilayer graphene film was developed based on an atmospheric-pressure chemical vapor deposition (APCVD) method, and its electrical characteristics, light transmittance, and electrical heating characteristics were experimentally investigated in detail. The results show that graphene glass with different surface resistance values obtained through direct growth on a high-purity quartz glass substrate using the APCVD method, not only has excellent uniformity and quality, but also has considerably flat and high transmittance across the entire visible light region and exhibits excellent heating performance and fast response time. For graphene glass with a surface resistance of 1500 Ω·sq-1, the light transmittance can reach 74%, and the saturation temperature can rise to 185 ℃ by applying a bias voltage of 40 V. In addition, when the resistance value of the graphene glass is 420 Ω·sq-1, the graphene glass reaches a high saturation temperature of 325 ℃ in 40 s, and the corresponding heating rate can exceed 18 ℃·s-1, achieving a significantly higher heating rate than other heating films at the same voltage. Compared with the polyethylene-terephthalate- (PET-) based and silicon-based graphene films obtained by the transfer, graphene glass has a higher saturation temperature, shorter thermal response time, and faster heating rate. Furthermore, graphene glass exhibits better heating cycle stability and longer-term heating stability at a constant voltage. In addition, an experiment using the graphene glass to thermally tune the wavelength of a vertical-cavity surface-emitting laser was conducted and gave good results. The position of the laser peak controlled by the graphene glass was red-shifted by 1.78 nm by applying a voltage of 20 V, and the wavelength tuning efficiency reached 0.059 nm·℃-1. Compared with PET-based and silicon-based graphene films, the actual electrical heating capacity of graphene glass increased by 195%. These experimental findings demonstrate that graphene glass transparent films with excellent electric heating characteristics can be used in various transparent electric heating fields and have relatively wide application prospects. 相似文献
72.
QUALITATIVE ANALYSIS OF DYNAMICAL BEHAVIOR FOR AN IMPERFECT INCOMPRESSIBLE NEO-HOOKEAN SPHERICAL SHELL 总被引:1,自引:0,他引:1
YUAN Xue-gang 《应用数学和力学(英文版)》2005,26(8):973-981
IntroductionIn applications, it is commonly considered that the phenomena of cavity formation,growth and run-through of adjacent cavities occur in materials as precursors to failure. Thesephenomena are mainly due to instability of materials. On the other … 相似文献
73.
碳化钨-镍-钴-钼-氧化铅系高温自润滑金属陶瓷材料的综合性能研究 总被引:2,自引:0,他引:2
为了扩大WC-Ni-Mo-PbO四组元复合材料在工程实际中的应用范围,利用中频感应热压法制备了Wc-Ni-Co-Mo-PbO系高温自润滑金属陶瓷材料,并对其物理机械性能和摩擦学性能进行了试验研究,结果表明,含镍和钴这两组元之重量比为2的Wc-Ni-Co-Mo_PbO材料的综合性能最好,即使在600℃的高温下也具有较高的机械强度和相当好的摩擦学性能,且其在高速、重载下的摩擦磨损性能也比较好,X射线衍射分析发现,这种材料在600℃时的摩擦表面形成了均匀分布的PbWO4膜,这是其在高温下具有良好自润滑性的根本原因,在烧结温度下,WC可溶解于钴相形成面心立方结构的Co3W3C、Co2W4C和Co3W6C化合物,这能增强材料中金属相与陶瓷相的结合力。在自然降温冷却过程中,从钴相中析出Co3W和元素碳,后者可与钼形成MoC,进而形成Wc-MoC固溶体,这既能细化WC晶粒,又能强化晶界,而且钴与镍形成的连续固溶体可以使金属相得以强化。这些都是提高材料的高温机械性能和摩擦学性能的直接原因。 相似文献
74.
Ming Lu Shu Bai Kun Yang Yan Sun 《中国颗粒学报》2007,5(1):180-185
Non-porous magnetic polymer microspheres with a core-shell structure were prepared by a novel micro-suspension polymerization technique. A stable iron oxide ferrofluid was used to supply the magnetic core, and the polymeric shell was made of glycidyl methacrylate (GMA monomer) and ethylene dimethacrylate (cross-linker). In the preparation, polyvinyl alcohol was used as the stabilizer, and a lauryl alcohol mixture as the dispersant. The influence of various conditions such as aqueous phase volume, GMA and initiator amounts, reaction time and stirring speed on the character of the microspheres was investigated. The magnetic microspheres were then characterized briefly. The results indicate that the microspheres with active epoxy groups had a narrow size distribution range from 1 to 10 μm with a volume-weighted mean diameter of 4.5 μm. The saturation magnetization reached 19.9 emu/g with little coercivity and remanence. 相似文献
75.
纳米二氧化硅水溶胶成膜特性研究 总被引:1,自引:0,他引:1
研究了纳米SiO2水溶胶的固液二相流成膜特性.结果表明,水溶胶中的Si02固体颗粒的粒径及质量分数对粘度的影响较小,对成膜能力和承载能力的影响较大;在薄膜润滑阶段,固体颗粒的粒径和质量分数对润滑状态的稳定性具有一定的影响,随着速度的增加,液体膜厚度逐渐增大,固体颗粒对液体润滑膜稳定性及性能的影响逐渐减弱;在弹流润滑阶段,固体颗粒的影响很小。 相似文献
76.
77.
滑带土动力学性质试验研究 总被引:3,自引:0,他引:3
为了研究地震高烈度区老滑坡的复活变形原因,本文对滑坡滑带土的动力学特性进行了系列研究。本次试验采用扰动土样,制样基本物理指标按滑带土的现场测试指标确定,在不固结不排水条件下,运用MTS810Teststar程控液压伺服土动三轴仪对单个样品逐级放大动应力的分级试验方法进行。侧向压力 (围压 )分别采用 100kPa、20 0kPa、300kPa三级,通过施加轴向振动荷载 (力 )模拟地震作用,振动波形为正弦波,频率为 1Hz,振幅随试样性质确定。研究结果表明,滑带土在动荷载作用下的动力学性质与其静荷载作用下的力学性质有着较大的差异,主要表现在滑带土的动应力与动应变关系的非线性、滞后性及变形积累特点,动弹性模量与动强度的显著降低以及动阻尼比的显著增大特性。这揭示了动力作用下的滑坡复活原因之一,同时为滑坡稳定性评价和动力作用下的变形机制模拟分析提供了基础资料,也为分析滑带土动力本构模型提供了基本内容。 相似文献
78.
79.
弹性地基梁振动特性的近似分析方法 总被引:4,自引:1,他引:4
文中介绍了用模态摄动法分析复杂情况下弹性地基梁动力特性的近似方法。这一方法中可考虑纵向钢筋以及变地基弹性系数对弹性地基梁振动特性的影响,通过算例说明了这一方法的有效性。 相似文献
80.
惯性平台台体的动态特性直接决定着惯性仪表的工作精度和可靠性,模态分析是研究机械系统动态特性的主要方法之一。在概述了实验模态分析理论的基础上,建立了某型号平台台体结构的实验模型,对其进行了实验模态分析。通过对实验结果与有限元计算结果比较,验证了有限元结果较为准确;同时针对结构存在的问题,通过灵敏度分析对结构的动力修改提出了改进意见。 相似文献