全文获取类型
收费全文 | 83948篇 |
免费 | 430篇 |
国内免费 | 404篇 |
专业分类
化学 | 27930篇 |
晶体学 | 826篇 |
力学 | 6889篇 |
数学 | 33217篇 |
物理学 | 15920篇 |
出版年
2020年 | 65篇 |
2018年 | 10452篇 |
2017年 | 10280篇 |
2016年 | 6130篇 |
2015年 | 908篇 |
2014年 | 368篇 |
2013年 | 516篇 |
2012年 | 3943篇 |
2011年 | 10656篇 |
2010年 | 5741篇 |
2009年 | 6145篇 |
2008年 | 6740篇 |
2007年 | 8930篇 |
2006年 | 387篇 |
2005年 | 1490篇 |
2004年 | 1676篇 |
2003年 | 2092篇 |
2002年 | 1164篇 |
2001年 | 317篇 |
2000年 | 398篇 |
1999年 | 227篇 |
1998年 | 253篇 |
1997年 | 236篇 |
1996年 | 283篇 |
1995年 | 201篇 |
1994年 | 162篇 |
1993年 | 183篇 |
1992年 | 151篇 |
1991年 | 138篇 |
1990年 | 121篇 |
1989年 | 144篇 |
1988年 | 155篇 |
1987年 | 138篇 |
1986年 | 153篇 |
1985年 | 174篇 |
1984年 | 176篇 |
1983年 | 126篇 |
1982年 | 172篇 |
1981年 | 165篇 |
1980年 | 161篇 |
1979年 | 175篇 |
1978年 | 150篇 |
1977年 | 134篇 |
1976年 | 119篇 |
1975年 | 135篇 |
1974年 | 100篇 |
1973年 | 120篇 |
1972年 | 77篇 |
1971年 | 76篇 |
1970年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Solvent Influence on Cellulose 1,4‐β‐Glycosidic Bond Cleavage: A Molecular Dynamics and Metadynamics Study 下载免费PDF全文
Claudia Loerbroks Eliot Boulanger Prof. Dr. Walter Thiel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5477-5487
We explore the influence of two solvents, namely water and the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate (EmimAc), on the conformations of two cellulose models (cellobiose and a chain of 40 glucose units) and the solvent impact on glycosidic bond cleavage by acid hydrolysis by using molecular dynamics and metadynamics simulations. We investigate the rotation around the glycosidic bond and ring puckering, as well as the anomeric effect and hydrogen bonds, in order to gauge the effect on the hydrolysis mechanism. We find that EmimAc eases hydrolysis through stronger solvent–cellulose interactions, which break structural and electronic barriers to hydrolysis. Our results indicate that hydrolysis in cellulose chains should start from the ends and not in the centre of the chain, which is less accessible to solvent. 相似文献
2.
3.
4.
5.
S. V. Panin I. V. Vlasov V. P. Sergeev B. B. Ovechkin P. O. Marushchak Sunder Ramasubbu P. S. Lyubutin V. V. Titkov 《Physical Mesomechanics》2015,18(3):261-272
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method. 相似文献
6.
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
7.
8.
9.
10.