全文获取类型
收费全文 | 3769篇 |
免费 | 358篇 |
国内免费 | 240篇 |
专业分类
化学 | 1002篇 |
晶体学 | 13篇 |
力学 | 527篇 |
综合类 | 16篇 |
数学 | 530篇 |
物理学 | 784篇 |
综合类 | 1495篇 |
出版年
2024年 | 8篇 |
2023年 | 26篇 |
2022年 | 53篇 |
2021年 | 76篇 |
2020年 | 103篇 |
2019年 | 58篇 |
2018年 | 75篇 |
2017年 | 89篇 |
2016年 | 97篇 |
2015年 | 86篇 |
2014年 | 123篇 |
2013年 | 261篇 |
2012年 | 153篇 |
2011年 | 163篇 |
2010年 | 144篇 |
2009年 | 150篇 |
2008年 | 188篇 |
2007年 | 204篇 |
2006年 | 191篇 |
2005年 | 162篇 |
2004年 | 178篇 |
2003年 | 165篇 |
2002年 | 152篇 |
2001年 | 150篇 |
2000年 | 150篇 |
1999年 | 131篇 |
1998年 | 127篇 |
1997年 | 114篇 |
1996年 | 109篇 |
1995年 | 85篇 |
1994年 | 101篇 |
1993年 | 85篇 |
1992年 | 75篇 |
1991年 | 58篇 |
1990年 | 48篇 |
1989年 | 45篇 |
1988年 | 35篇 |
1987年 | 31篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4367条查询结果,搜索用时 343 毫秒
1.
Dr. Joaquim Torra Dr. Felipe Viela Dr. Diego Megías Dr. Begoña Sot Prof. Cristina Flors 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(19):e202200026
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo. 相似文献
2.
利用X射线光电子能谱(XPS)测试5,10,15,20-四-(对羟基苯基)卟啉单体和5,10,15,20-四-(对羟基苯基)卟啉自组装二聚体,并通过化学模拟得到卟啉自组装二聚体分子的最优构象.结果表明:两种卟啉化合物中氧原子的类型不同;在单体卟啉中未检测到瞬态表面光电压信号,卟啉自组装二聚体表现出较好的瞬态表面光伏特性;卟啉自组装二聚体的光限幅性质优于卟啉1单体. 相似文献
3.
4.
P.A. Ramachandran 《Numerical Methods for Partial Differential Equations》2006,22(4):831-846
Time‐dependent differential equations can be solved using the concept of method of lines (MOL) together with the boundary element (BE) representation for the spatial linear part of the equation. The BE method alleviates the need for spatial discretization and casts the problem in an integral format. Hence errors associated with the numerical approximation of the spatial derivatives are totally eliminated. An element level local cubic approximation is used for the variable at each time step to facilitate the time marching and the nonlinear terms are represented in a semi‐implicit manner by a local linearization at each time step. The accuracy of the method has been illustrated on a number of test problems of engineering significance. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006 相似文献
5.
6.
Al.Th. Kermanidis D.G. Stamatelos G.N. Labeas Sp.G. Pantelakis 《Theoretical and Applied Fracture Mechanics》2006,45(2):148-158
The synergetic effect of corrosion and corrosion induced hydrogen embrittlement damage processes which occur at local scale has been found to result in a dramatic macroscopic tensile ductility loss of the 2024 aluminum alloy. In the present work, the tensile behaviour of corroded 2024 T351 specimens has been estimated on the basis of FE analysis by taking into account the local material properties in the damaged areas. A parametric study is involved to account for the effect of thickness in the results. Calculated tensile properties obtained with the analysis agree well with experimental data. 相似文献
7.
ZHANG Yongqian 《数学年刊B辑(英文版)》2005,26(3):379-392
This paper studies the asymptotic behaviour of steady supersonic flow past a piece-wise smooth corner or bend. Under the hypothese that both vertex angle and the total variation of tangent along the boundary are small, it is shown that the solution can be obtained by a modified Glimm scheme, and that the asymptotic behaviour of the solution is determined by the velocity of incoming flow and the limit of the tangent of the boundary at infinity. 相似文献
8.
Hong-Xing Zheng Dao-Yin Yu 《International Journal of Infrared and Millimeter Waves》2005,26(9):1343-1353
In this paper, a very useful numerical technique has been developed for analyzing the transient characteristics of a planar-spiral inductor on-chip. A locally conformal technique and an alternating-direction implicit scheme are applied to the finite-difference time-domain method. A formulation for solving three dimensional Maxwell’s equations is proposed. Using the proposed method, various parameters of the planar-spiral inductors have been analyzed and an equivalent circuit, which includes frequency-independent circuit elements, has been introduced. Highly computational efficiency is implemented. Numerical results show excellent agreement with the measured data over a wide frequency range. 相似文献
9.
富勒烯 (C60 /C70 )与N ,N ,N′ ,N′ 四 (对甲苯基 ) 4,4′ 二胺 1,1′ 二苯硒醚 (TPDASe)间在激光光诱导条件下 ,发生了分子间的电子转移过程 .在可见 -近红外区 ( 60 0~ 12 0 0nm) ,观测到了TPDASe阳离子自由基、富勒烯 (C60 /C70 )激发三线态和阴离子自由基 ,在苯腈溶液中 ,观测瞬态谱测定了电子从TPDASe转移到富勒烯 (C60 /C70 )激发三线态的量子转化产率(ΦTet)和电子转移常数 (Ket) . 相似文献
10.
N. Fitier 《国际流体数值方法杂志》2003,42(12):1345-1361
There is a growing interest in developing numerical tools to investigate the onset of physical instabilities observed in experiments involving viscoelastic flows, which is a difficult and challenging task as the simulations are very sensitive to numerical instabilities. Following a recent linear stability analysis carried out in order to better understand qualitatively the origin of numerical instabilities occurring in the simulation of flows viscoelastic fluids, the present paper considers a possible extension for more complex flows. This promising method could be applied to track instabilities in complex (i.e. essentially non‐parallel) flows. In addition, results related to transient growth mechanism indicate that it might be responsible for the development of numerical instabilities in the simulation of viscoelastic fluids. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献