全文获取类型
收费全文 | 432篇 |
免费 | 41篇 |
国内免费 | 50篇 |
专业分类
化学 | 128篇 |
晶体学 | 1篇 |
力学 | 25篇 |
综合类 | 2篇 |
数学 | 243篇 |
物理学 | 124篇 |
出版年
2023年 | 11篇 |
2022年 | 16篇 |
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 21篇 |
2016年 | 11篇 |
2015年 | 24篇 |
2014年 | 17篇 |
2013年 | 28篇 |
2012年 | 37篇 |
2011年 | 34篇 |
2010年 | 29篇 |
2009年 | 38篇 |
2008年 | 45篇 |
2007年 | 41篇 |
2006年 | 30篇 |
2005年 | 28篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 10篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
排序方式: 共有523条查询结果,搜索用时 46 毫秒
101.
化学/电化学腐蚀法快速制备超疏水金属铝 总被引:3,自引:0,他引:3
提出一种金属铝超疏水表面的快速制作方法. 先以化学腐蚀在铝表面形成微米级粗糙结构, 再通过电化学腐蚀构筑纳米结构, 在20 min内完成了超疏水表面所需粗糙结构的制备. 这种化学腐蚀/电化学腐蚀两步法比单独化学或电化学腐蚀方法在时间上缩短了1~2个数量级, 且不受铝材晶形限制, 同时电化学腐蚀所用电流密度也降低了1个数量级, 降低了对电源设备的要求, 可望大规模应用于工业生产和其它金属的超疏水表面制备. 相似文献
102.
巴戟天中一种多糖的分离与结构表征 总被引:2,自引:0,他引:2
以巴戟天的根为原料, 经热水浸提、Sevag法除蛋白、乙醇沉淀和DEAE-Sepharose CL-6B离子交换柱层析, 得到一种水溶性的巴戟天多糖(MOPI-3). 通过UV、IR、NMR、GC-MS、高碘酸氧化、Smith降解和甲基化等物理化学方法对MOPI-3的纯度、理化性质和组成结构进行表征. 结果表明, MOPI-3分子量为36061, 是一种由阿拉伯糖、半乳糖和葡萄糖组成的杂多糖, 以α-1,3-吡喃葡萄糖和α-1,4-吡喃半乳糖为主链, 平均每5个葡萄糖连接一个半乳糖, 每个重复单元具有一个支链, 支链由3个呋喃阿拉伯糖以α-1,3-键型组成, 连接在主链葡萄糖的6位碳上, MOPI-3含有乙酰基, 连接在主链半乳糖的2位碳原子上. 相似文献
103.
《力学快报》2022,12(5):100364
As a promising vibration control device, the vibro-impact nonlinear energy sink (VI-NES) gathered extensively attention in recent years. However, general optimization procedures have not been available for the design of VI-NES subjected to random excitations. To this end, this paper constitutes a research effort to address this gap. Specifically, the approximate analytical solution of the system stochastic response is obtained in conjunction with non-smooth conversion and stochastic averaging methodology. Taking advantages of this approximate solution, the variance of the system is defined and easily minimized to calculate the optimal parameters for VI-NES. In addition, the results computed by this way fairly correlate with direct numeric simulations. 相似文献
104.
105.
核磁共振(NMR)技术作为一种非植入无损伤的检测技术,已经广泛应用于化学、生物和医学等领域.本文基于哈德曼(Hadamard)编码的分子间单量子相干(iSQC)技术提出了一种新的序列,首先从理论上对该序列进行了简要的分析并阐明其原理,然后用套管模型实验和脑模型实验验证该序列在不均匀磁场下准确定域和快速获取高分辨谱的能力.实验表明,该序列在不均匀磁场下可以快速获取高分辨定域谱,同时抑制溶剂峰信号,具备一定的应用价值. 相似文献
106.
107.
《Photonics and Nanostructures》2014,12(2):199-204
Metallic bowtie antennas are used in nanophotonics applications in order to confine the electromagnetic field into volumes much smaller than that of the incident wavelength. Electrically controllable carrier concentration of graphene opens the door to the use of plasmonic nanoantenna structures with graphene so that the resonant nature of nanoantennas can be tuned. In this study, we demonstrated with the Fourier transform infrared (FTIR) spectroscopy and the Finite Difference Time Domain (FDTD) method that the intensity and resonance peak of bowtie nanoantennas on monolayer graphene can be tuned at mid-infrared (MIR) wavelength regime by applying a gate voltage, since the optical properties of graphene change by changing the carrier concentration. 相似文献
108.
Haiyan Chen 《Linear and Multilinear Algebra》2018,66(1):117-130
Let G be a connected graph. The subdivision graph of G, denoted by S(G), is the graph obtained from G by inserting a new vertex into every edge of G. The triangulation graph of G, denoted by R(G), is the graph obtained from G by adding, for each edge uv, a new vertex whose neighbours are u and v. In this paper, we first provide complete information for the eigenvalues and eigenvectors of the probability transition matrix of a random walk on S(G) (res. R(G)) in terms of those of G. Then we give an explicit formula for the expected hitting time between any two vertices of S(G) (res. R(G)) in terms of those of G. Finally, as applications, we show that, the relations between the resistance distances, the number of spanning trees and the multiplicative degree-Kirchhoff index of S(G) (res. R(G)) and G can all be deduced from our results directly. 相似文献
109.
Genzhen Yu 《Discrete Mathematics》2011,(1):38
The Aztec diamond was extensively studied in both graph theory and statistical physics. Knuth obtained a formula of the number of spanning trees of the Aztec diamond with the constrained boundary condition, which solved a conjecture posed by Stanley in 1994. In this paper, We give the formulae of the energy and the number of spanning trees of the Aztec diamond with the toroidal boundary condition. 相似文献
110.
Chen Zhangxu Fu Ming-Lai Huang Xiao-Dan Yuan Baoling Yang Jia-Cheng E. 《Research on Chemical Intermediates》2018,44(10):6369-6385
Research on Chemical Intermediates - To enhance photocatalytic activity spectra area of the TiO2 based photocatalyst, and to separate and recycle photocatalyst easily, magnetic photocatalyst was... 相似文献