全文获取类型
收费全文 | 15489篇 |
免费 | 2690篇 |
国内免费 | 2230篇 |
专业分类
化学 | 11428篇 |
晶体学 | 180篇 |
力学 | 908篇 |
综合类 | 156篇 |
数学 | 1954篇 |
物理学 | 5783篇 |
出版年
2024年 | 28篇 |
2023年 | 321篇 |
2022年 | 408篇 |
2021年 | 553篇 |
2020年 | 657篇 |
2019年 | 729篇 |
2018年 | 553篇 |
2017年 | 527篇 |
2016年 | 765篇 |
2015年 | 793篇 |
2014年 | 946篇 |
2013年 | 1151篇 |
2012年 | 1413篇 |
2011年 | 1454篇 |
2010年 | 1027篇 |
2009年 | 1039篇 |
2008年 | 1069篇 |
2007年 | 913篇 |
2006年 | 839篇 |
2005年 | 692篇 |
2004年 | 577篇 |
2003年 | 464篇 |
2002年 | 524篇 |
2001年 | 390篇 |
2000年 | 328篇 |
1999年 | 335篇 |
1998年 | 270篇 |
1997年 | 232篇 |
1996年 | 215篇 |
1995年 | 187篇 |
1994年 | 149篇 |
1993年 | 158篇 |
1992年 | 104篇 |
1991年 | 102篇 |
1990年 | 87篇 |
1989年 | 81篇 |
1988年 | 72篇 |
1987年 | 40篇 |
1986年 | 41篇 |
1985年 | 47篇 |
1984年 | 28篇 |
1983年 | 18篇 |
1982年 | 24篇 |
1981年 | 11篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1972年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Recently,the nested Mach–Zehnder interferometer[Phys.Rev.Lett.111,240402(2013)]was modified by adding Dove prisms in a paper[Quantum Stud.:Math.Found.2,255(2015)],and an interesting result is that,after the Dove prisms were inserted,a signal at the first mirror of the nested interferometer was obtained.But,according to the former original paper,the photons have never been present near that mirror.In this work,we interpret this result naturally by resorting to the three-path interference method.Moreover,we find that even though the photons have been somewhere,they can hide the trace of being there. 相似文献
22.
23.
Peng-Yan Gui Xiao-Hui Yan Wen-Juan Yuan Yuan-Liang Ma Xiao Ding Shuai Liu 《Natural product research》2019,33(19):2830-2836
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme. 相似文献
24.
Sun Yuan Luo Shunlong Lei Xiangyun 《International Journal of Theoretical Physics》2021,60(9):3211-3224
International Journal of Theoretical Physics - Gram matrices arise naturally in the consideration of pair-wise overlap of a family of vectors or quantum pure states, and play an important role in... 相似文献
25.
26.
27.
Yifeng Xiang Xi Tang Changjun Min Guanghao Rui Yan Kuai Fengya Lu Pei Wang Hai Ming Qiwen Zhan Xiaocong Yuan Joseph R. Lakowicz Douguo Zhang 《Annalen der Physik》2020,532(4):1900497
Near-field optical trapping can be realized with focused evanescent waves that are excited at the water–glass interface due to the total internal reflection, or with focused plasmonic waves excited on the water–gold interface. Herein, the performance of these two kinds of near-field optical trapping techniques is compared using the same optical microscope configuration. Experimental results show that only a single-micron polystyrene bead can be trapped by the focused evanescent waves, whereas many beads are simultaneously attracted to the center of the excited region by focused plasmonic waves. This difference in trapping behavior is analyzed from the electric field intensity distributions of these two kinds of focused surface waves and the difference in trapping behavior is attributed to photothermal effects due to the light absorption by the gold film. 相似文献
28.
29.
DFT mechanistic study of the H2‐assisted chain transfer copolymerization of propylene and p‐methylstyrene catalyzed by zirconocene complex 下载免费PDF全文
Cheng‐Gen Zhang Shu‐Yuan Yu Liaoyun Zhang Huayi Li Zhi‐Xiang Wang 《Journal of polymer science. Part A, Polymer chemistry》2015,53(4):576-585
DFT computations have been performed to investigate the mechanism of H2‐assisted chain transfer strategy to functionalize polypropylene via Zr‐catalyzed copolymerization of propylene and p‐methylstyrene (pMS). The study unveils the following: (i) propylene prefers 1,2‐insertion over 2,1‐insertion both kinetically and thermodynamically, explaining the observed 1,2‐insertion regioselectivity for propylene insertion. (ii) The 2,1‐inserion of pMS is kinetically less favorable but thermodynamically more favorable than 1,2‐insertion. The observation of 2,1‐insertion pMS at the end of polymer chain is due to thermodynamic control and that the barrier difference between the two insertion modes become smaller as the chain length becomes longer. (iii) The pMS insertion results in much higher barriers for subsequent either propylene or pMS insertion, which causes deactivation of the catalytic system. (iv) Small H2 can react with the deactivated [Zr]?pMS?PPn facilely, which displace functionalized pMS?PPn chain and regenerate [Zr]? H active catalyst to continue copolymerization. The effects of counterions are also discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 576–585 相似文献
30.
As a large group of cells in a central nervous system, astrocytes have a great influence on ion and energy metabolism in a nervous system. Disorders of neuronal ion and energy metabolism caused by impaired astrocytes play a key role in the pathogenesis of epilepsy. This paper reviews the existing computational models of epileptogenesis resulting from impaired astrocytes and presents several open perspectives with regard to ion and energy metabolism-induced epileptogenesis in a neuron-astrocyte-capillary coupled model. 相似文献