全文获取类型
收费全文 | 18155篇 |
免费 | 1045篇 |
国内免费 | 1650篇 |
专业分类
化学 | 5144篇 |
晶体学 | 75篇 |
力学 | 501篇 |
综合类 | 96篇 |
数学 | 506篇 |
物理学 | 5522篇 |
无线电 | 9006篇 |
出版年
2024年 | 45篇 |
2023年 | 206篇 |
2022年 | 392篇 |
2021年 | 614篇 |
2020年 | 563篇 |
2019年 | 270篇 |
2018年 | 255篇 |
2017年 | 627篇 |
2016年 | 722篇 |
2015年 | 635篇 |
2014年 | 1049篇 |
2013年 | 969篇 |
2012年 | 956篇 |
2011年 | 1285篇 |
2010年 | 1008篇 |
2009年 | 1158篇 |
2008年 | 1163篇 |
2007年 | 1459篇 |
2006年 | 1375篇 |
2005年 | 971篇 |
2004年 | 940篇 |
2003年 | 799篇 |
2002年 | 557篇 |
2001年 | 494篇 |
2000年 | 344篇 |
1999年 | 312篇 |
1998年 | 266篇 |
1997年 | 221篇 |
1996年 | 217篇 |
1995年 | 203篇 |
1994年 | 156篇 |
1993年 | 115篇 |
1992年 | 97篇 |
1991年 | 94篇 |
1990年 | 65篇 |
1989年 | 43篇 |
1988年 | 46篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 600 毫秒
1.
文章首先对智能化电子信息技术进行了深入的研究,而后分析了该技术在应用过程中出现的问题,最后结合该技术的相关特点给出了相应的问题解决措施,希望能够对智能化电子信息技术的发展提供帮助。 相似文献
2.
3.
4.
In this work, a continuum model is presented for size and orientation dependent thermal buckling and post-buckling of anisotropic nanoplates considering surface and bulk residual stresses. The model with von-Karman nonlinear strains and material cubic anisotropy of single crystals contains two parameters that reflect the orientation effects. Using Ritz method, closed form solutions are given for buckling temperature and post-buckling deflections. Regarding self-instability states of nanoplates and their recovering at higher temperatures, an experiment is discussed based on low pressurized membranes to verify the predictions. For simply supported nanoplates, the size effects are lowest when they are aligned in [100] direction. When the edges get clamped, the orientation dependence is ignorable and the behavior becomes symmetric about [510] axis. The surface residual stress makes drastic increase in buckling temperature of thinner nanoplates for which a minimum thickness is pointed to stay far from material softening at higher temperatures. Deflection of [100]-oriented buckled nanoplates is higher than [110] ones but this reverses at higher temperatures. The results for long nanoplates show that the buckling mode numbers are changed by orientation which is verified by FEM. 相似文献
5.
We report optical and nonlinear optical properties of CuS quantum dots and nanoparticles prepared through a nontoxic, green, one-pot synthesis method. The presence of surface states and defects in the quantum dots are evident from the luminescent behavior and enhanced nonlinear optical properties measured using the open aperture Z-scan, employing 5 ns laser pulses at 532 nm. The quantum dots exhibit large effective third order nonlinear optical coefficients with a relatively lower optical limiting threshold of 2.3 J cm−2, and the optical nonlinearity arises largely from absorption saturation and excited state absorption. Results suggest that these materials are potential candidates for designing efficient optical limiters with applications in laser safety devices. 相似文献
6.
This minireview describes the strategies for synthesis of fiuorinated surfactants potentially nonbioaccumulable.Various strategies have been focused on(Ⅰ) reducing the length of the perfluorocarbon chain,(Ⅱ) introducing hetero atoms into the fluorocarbon chain,(Ⅲ) introducing branch(herein and after branch means the fluoro-carbon chain section is not straight).In most cases,the surface tensions versus the surfactant concentrations have been assessed.These above strategies led to various highly fiuorinated(perfluorinated or not perfluorinated) surfactants whose chemical changes enabled to obtain novel alternatives to perfluorooctanoic acid(PFOA) and perfluorooctane sulphonate(PFOS). 相似文献
7.
为了提升高校实验数据处理水平,高校实验室的相关建设工作已经步入正轨,但层出不穷的信息安全问题也向高校实验室计算机网络维护工作提出了新的挑战。文章从现阶段高校实验室计算机网络的相关建设工作出发,简要论述引发网络故障的具体原因,并对其诊断技术进行探讨。 相似文献
8.
本文结合HTH电路的复杂性等特征分析与实际应用现状,研究了HTH电路的具体检测技术方法并对当前热点技术进行对比分析,探讨了HTH电路检测方法的技术发展趋势。 相似文献
9.
本文对国内外的电视技术发展现状进行了充分的研究和分析,并对超高清电视系统的相关图像技术参数进行了分析和介绍。 相似文献
10.
José Luis Olloqui-Sariego Juan José Calvente Rafael Andreu 《Current Opinion in Electrochemistry》2021
Three key challenges are stimulating intensive research in the development of productive direct electron transfer mode enzyme electrodes: proper enzyme orientation, high enzyme loading, and full retention of enzyme activity. In this review, we summarize some significant advances that have been reported in the last years on the design of mesoporous and nanostructured electrodes as enzyme scaffolds and of innovative methodologies for wiring enzymes to electrodes. Particular attention is given to investigations on physical factors that determine a favorable enzyme immobilization, to provide rational guidelines for the design of productive enzymatic electrodes. Finally, some emerging trends focused on the spatial organization of either single enzymes or enzyme cascades are also briefly addressed. 相似文献