全文获取类型
收费全文 | 4527篇 |
免费 | 109篇 |
国内免费 | 18篇 |
专业分类
化学 | 2930篇 |
晶体学 | 65篇 |
力学 | 116篇 |
数学 | 415篇 |
物理学 | 1128篇 |
出版年
2021年 | 32篇 |
2020年 | 55篇 |
2019年 | 61篇 |
2018年 | 37篇 |
2017年 | 38篇 |
2016年 | 102篇 |
2015年 | 73篇 |
2014年 | 92篇 |
2013年 | 233篇 |
2012年 | 194篇 |
2011年 | 299篇 |
2010年 | 189篇 |
2009年 | 171篇 |
2008年 | 229篇 |
2007年 | 265篇 |
2006年 | 224篇 |
2005年 | 203篇 |
2004年 | 152篇 |
2003年 | 147篇 |
2002年 | 129篇 |
2001年 | 66篇 |
2000年 | 60篇 |
1999年 | 57篇 |
1998年 | 43篇 |
1997年 | 37篇 |
1996年 | 52篇 |
1995年 | 47篇 |
1994年 | 47篇 |
1993年 | 46篇 |
1992年 | 59篇 |
1991年 | 39篇 |
1990年 | 40篇 |
1989年 | 40篇 |
1988年 | 36篇 |
1987年 | 42篇 |
1986年 | 58篇 |
1985年 | 49篇 |
1984年 | 42篇 |
1983年 | 36篇 |
1982年 | 38篇 |
1981年 | 51篇 |
1980年 | 42篇 |
1979年 | 50篇 |
1978年 | 47篇 |
1977年 | 30篇 |
1976年 | 43篇 |
1975年 | 42篇 |
1974年 | 35篇 |
1973年 | 36篇 |
1972年 | 32篇 |
排序方式: 共有4654条查询结果,搜索用时 203 毫秒
1.
2.
Russian Physics Journal - The role of Professor V. G. Plotnikov in the development of the theoretical molecular photonics is discussed. A review is given of the principal results and the list of... 相似文献
3.
Jerry Ray Dias 《Molecular physics》2020,118(12)
Cycloparaphenylene ([r]CPP) and cyclacene ([r]CA) series are models for short carbon nanotubes. It is shown that armchair edges in model cycloparaphenylenes possess greater aromaticity and cyclic conjugation than do zigzag edges in model cyclacenes. According to Aihara’s bond resonance energy (BRE) and Bosanac and Gutman energy effect (ef) measurements, cycloparaphenylenes are twice as aromatic as cyclacenes. The general solution of all eigenvalues of all members of the cycloparaphenylene series is given. The origin of the recurrence of some eigenvalues are determined. 相似文献
4.
Seema Yadav Sriparna Ray Ajeet Singh Shaikh M. Mobin Tapta Kanchan Roy Chandrakanta Dash 《应用有机金属化学》2020,34(11):e5942
Dinuclear gold(I)-N-heterocyclic carbene complexes were developed for the hydrohydrazidation of terminal alkynes. The gold(I)-N-heterocyclic carbene complexes 2a-2b were synthesized in good yields from silver complexes synthesized in situ, which in turn were obtained from the corresponding imidazolium salts with Ag2O in dichloromethane as a solvent. The new air-stable gold(I)-NHC complexes, 2a - 2b, were characterized using NMR spectroscopy, elemental analysis, infrared, and mass spectroscopy studies. The gold(I) complex 2a was characterized using X-ray crystallography. Bis-N-heterocyclic carbene–based gold(I) complexes 2a - 2b exhibited excellent catalytic activities for hydrohydrazidation of terminal alkynes yielding acylhydrazone derivatives. The working catalytic system can be used in gram-scale synthesis. In addition, the catalytic reaction mechanism of the hydrohydrazidation of terminal alkynes by gold(I)-NHC complex was studied in detail using density functional theory. 相似文献
5.
Myriam Drouin Dr. Parvesh Wadhwani Dr. Stephan L. Grage Dr. Jochen Bürck Dr. Johannes Reichert Sébastien Tremblay Marie Sabine Mayer Christian Diel Alexander Staub Prof. Jean-François Paquin Prof. Dr. Anne S. Ulrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1511-1517
Solid-state 19F NMR is a powerful method to study the interactions of biologically active peptides with membranes. So far, in labelled peptides, the 19F-reporter group has always been installed on the side chain of an amino acid. Given the fact that monofluoroalkenes are non-hydrolyzable peptide bond mimics, we have synthesized a monofluoroalkene-based dipeptide isostere, Val-Ψ[(Z)-CF=CH]-Gly, and inserted it in the sequence of two well-studied antimicrobial peptides: PGLa and (KIGAKI)3 are representatives of an α-helix and a β-sheet. The conformations and biological activities of these labeled peptides were studied to assess the suitability of monofluoroalkenes for 19F NMR structure analysis. 相似文献
6.
Rajan Kumar Subir Kumar Ray Dr. Saikat Mukherjee Sudipta Saha Dr. Arijit Bag Prof. Dr. Pradip Kr. Ghorai Prof. Dr. Nirmalya Ghosh Prof. Dr. Raja Shunmugam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(59):13514-13522
The development of organic photoluminescent materials, which show promising roles as catalysts, sensors, organic light-emitting diodes, logic gates, etc., is a major demand and challenge for the global scientific community. In this context, a photoclick polymerization method is adopted for the growth of a unique photoluminescent three-dimensional (3D) polymer film, E, as a model system that shows emission tunability over the range 350–650 nm against the excitation range 295–425 nm. The DFT analysis of energy calculations and π-stacking supports the spectroscopic observations for the material exhibiting a broad range of emission owing to newly formed chromophoric units within the film. Full polarization spectroscopic Mueller matrix studies were employed to extract and quantify the molecular orientational order of both the ground (excitation) and excited (emission) state anisotropies through a set of newly defined parameters, namely the fluorescence diattenuation and fluorescence polarizance. The information contained in the recorded fluorescence Mueller matrix of the organic polymer material provided a useful way to control the spectral intensity of emission by using pre- and post-selection of polarization states. The observation was based on the assumption that the longer lifetime of the excited dipolar orientation is attributed to the compactness of the film. 相似文献
7.
8.
9.
10.
A new method for exact solutions of variant types of time‐fractional Korteweg‐de Vries equations in shallow water waves 下载免费PDF全文
The current article devoted on the new method for finding the exact solutions of some time‐fractional Korteweg–de Vries (KdV) type equations appearing in shallow water waves. We employ the new method here for time‐fractional equations viz. time‐fractional KdV‐Burgers and KdV‐mKdV equations for finding the exact solutions. We use here the fractional complex transform accompanied by properties of local fractional calculus for reduction of fractional partial differential equations to ordinary differential equations. The obtained results are demonstrated by graphs for the new solutions. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献