全文获取类型
收费全文 | 4517篇 |
免费 | 213篇 |
国内免费 | 106篇 |
专业分类
化学 | 3353篇 |
晶体学 | 20篇 |
力学 | 238篇 |
综合类 | 2篇 |
数学 | 528篇 |
物理学 | 695篇 |
出版年
2024年 | 4篇 |
2023年 | 24篇 |
2022年 | 96篇 |
2021年 | 134篇 |
2020年 | 179篇 |
2019年 | 217篇 |
2018年 | 255篇 |
2017年 | 204篇 |
2016年 | 358篇 |
2015年 | 229篇 |
2014年 | 300篇 |
2013年 | 560篇 |
2012年 | 378篇 |
2011年 | 346篇 |
2010年 | 273篇 |
2009年 | 217篇 |
2008年 | 247篇 |
2007年 | 174篇 |
2006年 | 123篇 |
2005年 | 93篇 |
2004年 | 105篇 |
2003年 | 65篇 |
2002年 | 54篇 |
2001年 | 21篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 3篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1937年 | 2篇 |
1927年 | 3篇 |
排序方式: 共有4836条查询结果,搜索用时 15 毫秒
151.
A novel approach using Monte Carlo method applied to simulation of low‐density polyethylene (LDPE) polymerization in tubular reactor showing topological characteristics, and the comprehensive kinetic mechanism has been taken into consideration. The results show the precise details of the structure of a chain in the three levels of the backbone, the main branches, and branches on branch. The chain types include dead polymer, dead polymer with unsaturated end, and live polymer with primary radical, secondary radical, and tertiary radical. In this work, the branches on branch were identified in terms of number, length, and position of the branch. Sixty percent of branches on branch are 1 to 5 carbons long, and the longest branch on branch is about 50 carbons. Thus, this study provides a tool for more accurately mapping the polymer chains architecture, superior to determine the number, and position of long‐ and short‐chain branches in past researches. Finally, this approach will advance the prediction of microstructure‐related properties of polymer one step further. 相似文献
152.
Morsy H. A. Mohammed S. M. Abdel Hamid A. M. Moustafa A. H. El-Sayed H. A. 《Russian Journal of Organic Chemistry》2020,56(1):143-147
Russian Journal of Organic Chemistry - A facile synthesis of a new series of 1,2,3-triazolyl nucleosides via one-pot click reaction is described. Acetylenic nicotinonitriles synthesized previously... 相似文献
153.
Pouretedal Hamid Reza Damiri Sajjad Sharifi Alireza 《Journal of Thermal Analysis and Calorimetry》2020,139(1):545-553
Journal of Thermal Analysis and Calorimetry - The polymorphs of HMX explosive show the different sensitivities to heat, friction, impact, shock, electrostatic charge, etc. Knowledge and... 相似文献
154.
Tahmasbi Milad Siavashi Majid Abbasi Hamid Reza Akhlaghi Mohammad 《Journal of Thermal Analysis and Calorimetry》2020,141(5):1829-1846
Journal of Thermal Analysis and Calorimetry - Mixed convection inside a square cavity with internal rotating heater and cooler is analyzed numerically by simultaneous application of porous media... 相似文献
155.
Tofighi-Niaki Ebrahim Asgharifard-Sharabiani Pouya Ahmadian Hamid 《Nonlinear dynamics》2018,94(4):2937-2956
Nonlinear Dynamics - Rub–impact phenomenon occurring in hydrodynamic journal bearings is one of the main malfunctions in rotating machines and causes undesirable dynamic behavior. In order to... 相似文献
156.
157.
158.
Majid Abdellahi Aliakbar Najfinezhad Saeed Saber-Samanadari Amirsalar Khandan Hamid Ghayour 《Chinese Journal of Physics (Taipei)》2018,56(1):331-339
In the present study, hard ferromagnetic (M-type strontium hexaferrite) SrFe12O19 was co-doped by Zn and Zr for magnetic hyperthermia applications. As a result of the high concentration of single domain SrFe12O19 nanoparticles (suspended in the ferrofluid), they found a large hydrodynamic diameter, which caused a long-time Brownian relaxation under the AC magnetic field. On the other hand, increasing the Zn-Zr content (low concentration of SrFe12O19) led to a drop in anisotropy, which coincided with a short-time N´eel relaxation. All of the substituted samples with a multi-disperse state in ferrofluid exhibited an almost equal amount of the N´eel and Brownian effects. Consequently, the magnetic saturation (Ms) was considered as the dominant factor in the specific absorption rate (SAR) of the substituted samples. Transformation to the mono-disperse state was followed by the decrease of the Brownian relaxation time and hence the increase of the SAR. The interesting point in mono-disperse state was the heat generation of pure SrFe12O19 under the AC magnetic field as a result of the decrement of the Brownian relaxation time. 相似文献
159.
In the Randall-Sundrum braneworld scenario via the Goldberger-Wise mechanism, the effective mass of 4D radion, where the bulk scalar field is coupled to 5D gravity, has been investigated in two different case of the self-coupling constants, infinite and finite cases. It is shown that in the finite case, the modulus parameter should be greater than the finite coupling constants. 相似文献
160.
In this study, dendrimer‐encapsulated Cu(Π) nanoparticles immobilized on superparamagnetic Fe3O4@SiO2 nanoparticles were prepared via a multistep‐synthesis. Then, the synthesized composite was fully characterized by various techniques such as fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), dynamic light scattering (DLS), UV‐vis spectroscopy, energy dispersive X‐ray analysis (EDX), thermogravimetric analysis (TGA) and vibration sample magnetometer (VSM). From the information gained by FE‐SEM and TEM studies it can be inferred that the particles are mostly spherical in shape and have an average size of 50 nm. Also, the amount of Cu is determined to be 0.51 mmol/g in the catalyst by inductively coupled plasma (ICP) analyzer. This magnetic nano‐compound has been successfully applied as a highly efficient, magnetically recoverable and stable catalyst for N‐arylation of nitrogen heterocycles with aryl halides (I, Br) and arylboronic acids without using external ligands or additives. The catalyst was also employed in a one‐pot, three‐component reaction for the efficient and green synthesis of 5‐substituted 1H‐tetrazoles using various aldehydes, hydroxylamine hydrochloride and sodium azide in water. The magnetic catalyst can be easily separated by an external magnet bar and is recycled seven times without significant loss of its activity. 相似文献