全文获取类型
收费全文 | 134505篇 |
免费 | 20198篇 |
国内免费 | 13611篇 |
专业分类
化学 | 70813篇 |
晶体学 | 1223篇 |
力学 | 6833篇 |
综合类 | 533篇 |
数学 | 11954篇 |
物理学 | 40314篇 |
无线电 | 36644篇 |
出版年
2024年 | 320篇 |
2023年 | 3217篇 |
2022年 | 3409篇 |
2021年 | 5022篇 |
2020年 | 5157篇 |
2019年 | 4818篇 |
2018年 | 4034篇 |
2017年 | 3978篇 |
2016年 | 5851篇 |
2015年 | 5957篇 |
2014年 | 7307篇 |
2013年 | 9367篇 |
2012年 | 11306篇 |
2011年 | 11707篇 |
2010年 | 8199篇 |
2009年 | 8141篇 |
2008年 | 8607篇 |
2007年 | 7797篇 |
2006年 | 7305篇 |
2005年 | 6367篇 |
2004年 | 4409篇 |
2003年 | 3705篇 |
2002年 | 3310篇 |
2001年 | 2761篇 |
2000年 | 2603篇 |
1999年 | 3028篇 |
1998年 | 2665篇 |
1997年 | 2324篇 |
1996年 | 2581篇 |
1995年 | 2038篇 |
1994年 | 1933篇 |
1993年 | 1555篇 |
1992年 | 1448篇 |
1991年 | 1278篇 |
1990年 | 993篇 |
1989年 | 694篇 |
1988年 | 559篇 |
1987年 | 442篇 |
1986年 | 428篇 |
1985年 | 371篇 |
1984年 | 276篇 |
1983年 | 197篇 |
1982年 | 165篇 |
1981年 | 114篇 |
1980年 | 88篇 |
1979年 | 52篇 |
1978年 | 40篇 |
1976年 | 41篇 |
1975年 | 37篇 |
1974年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
111.
Alessandro Morando Paola Trebeschi Tao Wang 《Journal of Differential Equations》2019,266(9):5397-5430
We show the short-time existence and nonlinear stability of vortex sheets for the nonisentropic compressible Euler equations in two spatial dimensions, based on the weakly linear stability result of Morando and Trebeschi (2008) [20]. The missing normal derivatives are compensated through the equations of the linearized vorticity and entropy when deriving higher-order energy estimates. The proof of the resolution for this nonlinear problem follows from certain a priori tame estimates on the effective linear problem in the usual Sobolev spaces and a suitable Nash–Moser iteration scheme. 相似文献
112.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
113.
114.
115.
He Haidong Yang Haifeng Zhou Longpeng Chen Tianchi 《Journal of Russian Laser Research》2015,36(3):292-299
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting. 相似文献
116.
117.
Floquet engineering appears as a new protocol for designing topological states of matter,and features anomalous edge modes pinned at quasi-energy π/T with vanished topological index.We propose how to predict the anomalous edge modes via the bulk Hamiltonian in frequency space,and use Zak phase to quantitatively index the topological properties.The above methods are clarified by the example of time periodic Kitaev chain with chemical potential of harmonic driving and pulse driving,and topological phase transitions are manifested at different driving frequencies. 相似文献
118.
In this paper,we investigate the non-autonomous Hamilton-Jacobi equation ■ where H is 1-periodic with respect to t and M is a compact Riemannian manifold without boundary.We obtain the viscosity solution denoted by T_(t_0)~tφ(x) and show T_(t_0)~tφ(x) converges uniformly to a time-periodic viscosity solution u~*(x,t) of ?_tu+H(t,x,?_xu,u)=0. 相似文献
119.
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
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
120.
Zhang Kailun Wu Hongjuan Wang Tian Yao Meng Xie Jixing Jiao Yunhong 《Journal of Thermal Analysis and Calorimetry》2021,145(6):3067-3075
Journal of Thermal Analysis and Calorimetry - A phosphazene-based flame retardant (PBFA) was synthesized by hexachlorocyclotriphosphazene and N-aminoethylpiperazine. To improve the flame retardancy... 相似文献