全文获取类型
收费全文 | 291篇 |
免费 | 160篇 |
国内免费 | 594篇 |
专业分类
化学 | 69篇 |
力学 | 17篇 |
综合类 | 7篇 |
数学 | 846篇 |
物理学 | 106篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 26篇 |
2021年 | 25篇 |
2020年 | 34篇 |
2019年 | 24篇 |
2018年 | 29篇 |
2017年 | 25篇 |
2016年 | 38篇 |
2015年 | 26篇 |
2014年 | 34篇 |
2013年 | 28篇 |
2012年 | 20篇 |
2011年 | 19篇 |
2010年 | 35篇 |
2009年 | 47篇 |
2008年 | 85篇 |
2007年 | 56篇 |
2006年 | 61篇 |
2005年 | 59篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 34篇 |
2001年 | 36篇 |
2000年 | 51篇 |
1999年 | 38篇 |
1998年 | 36篇 |
1997年 | 37篇 |
1996年 | 40篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有1045条查询结果,搜索用时 15 毫秒
51.
Ag-Cu Nanoparticles Supported on N-Doped TiO\begin{document}$_2$\end{document} Nanowire Arrays for Efficient Photocatalytic CO\begin{document}$_2$\end{document} Reduction 下载免费PDF全文
Photocatalytic reduction of CO\begin{document}$_2$\end{document} into various types of fuels has attracted great interest, and serves as a potential solution to addressing current global warming and energy challenges. In this work, Ag-Cu nanoparticles are densely supported on N-doped TiO\begin{document}$_2$\end{document} nanowire through a straightforward nanofabrication approach. The range of light absorption by N-doped TiO\begin{document}$_2$\end{document} can be tuned to match the plasmonic band of Ag nanoparticles, which allows synergizing a resonant energy transfer process with the Schottky junction. Meanwhile, Cu nanoparticles can provide active sites for the reduction of CO\begin{document}$_2$\end{document} molecules. Remarkably, the performance of photocatalytic CO\begin{document}$_2$\end{document} reduction is improved to produce CH\begin{document}$_4$\end{document} at a rate of 720 \begin{document}$\mu$\end{document} mol\begin{document}$\cdot$\end{document} g\begin{document}$^{-1}$\end{document} \begin{document}$\cdot$\end{document} h\begin{document}$^{-1}$\end{document} under full-spectrum irradiation. 相似文献
52.
《Comptes Rendus Chimie》2016,19(9):1062-1070
Plant cell cultures constitute pesticide-free sources for obtaining plant secondary metabolites or plant extracts. Additionally, they do not contain any fungal contaminants, mycotoxins or heavy metals providing to the consumer potential health benefits and justifying the development of this technology at an industrial scale. Significant production levels of these secondary metabolites can be obtained through the use of elicitors, which activate plant defense mechanisms. Resveratrol, a well-known grapevine polyphenolic compound which possesses potent antioxidant and antiaging activities as well as a protective action on skin, is a good example of such plant secondary metabolites. Resveratrol and its oligomeric derivatives are used by several companies of cosmetic products but their extraction from vine stems and similar vegetal sources remains difficult. Therefore grapevine cell suspensions could represent interesting systems for the large-scale bioproduction of those compounds. Here we present an update of the methods used for the production of phytostilbenes by using grapevine cell cultures and the results obtained. 相似文献
53.
给出了一种新的二进小波1/f过程模型,从理论上证明了一类谱指数为H的近似1/f过程可通过一簇平稳随机过程产生.由于所提方法利用了1/f过程小波系数的相关性,因而有效地减少了合成1/f过程的谱误差.数值实验结果表明,新模型很好地改进了已有模型. 相似文献
54.
The notion of a fuzzy retract was introduced by Rodabaugh (1981). The notion of a fuzzy pairwise retract was introduced in 2001. Some weak forms and some strong forms of α-continuous mappings were introduced in 1988 and 1997. The authors extend some of these forms to the L-fuzzy bitopological setting and construct various α-fuzzy pairwise retracts. The concept of weakly induced spaces in the case L = [0,1] was introduced by Martin (1980). Liu and Luo (1987) generalized this notion to the case that L is an arbitrary F-lattice and introduced the notion of induced L-fts. Several results are obtained, especially, for L-valued pairwise stratification spaces. 相似文献
55.
该文对解椭圆曲线上离散对数的Pollard ρ算法和并行碰撞搜索算法分别建立了它 们的图论模型和分析了碰撞技巧,比较了两个算法,进而提出了设计迭代函数的准则并 给出一个改进的并行碰撞算法. 相似文献
56.
一般化凸空间上的变分不等式解的存在性问题 总被引:3,自引:0,他引:3
在本文,我们首先给出了KKM型定理和择一定理,然后根据上述结果讨论了一 般化凸空间上变分不等式解的存在性问题. 相似文献
57.
Lin Zhengyan 《数学年刊B辑(英文版)》1998,19(3):281-292
§1.IntroductionandResultsLet{Xn,n1}beasequenceofrandomvariableswithacommondistributionfunctionF(x)andletXn1Xn2…Xnnbetheor... 相似文献
58.
We show that a hyperbolic punctured torus bundle admits a foliation by lines which is covered by a product foliation. Thus its fundamental group acts freely on the plane.
59.
CLIFFORDMARTINGALESΦ-EQUIVALENCEBETWEENS(f)ANDf¥LONGRULIN;QIANTAO(InstituteofMathematics,AcademiaSinica,Beijing100080,China.)... 相似文献
60.
Sehie Park 《Proceedings of the American Mathematical Society》1996,124(10):3109-3114
We present a simple proof of the Leray-Schauder type theorem for approximable multimaps given recently by Ben-El-Mechaiekh and Idzik. We apply this theorem to obtain a Schaefer type theorem, the Birkhoff-Kellogg type theorems, a Penot type theorem for non-self-maps, and quasi-variational inequalities, all related to compact closed approximable maps.