全文获取类型
收费全文 | 349043篇 |
免费 | 4928篇 |
国内免费 | 1179篇 |
专业分类
化学 | 186721篇 |
晶体学 | 5295篇 |
力学 | 14645篇 |
综合类 | 10篇 |
数学 | 41599篇 |
物理学 | 106880篇 |
出版年
2021年 | 2314篇 |
2020年 | 2791篇 |
2019年 | 2814篇 |
2018年 | 3345篇 |
2017年 | 3407篇 |
2016年 | 5990篇 |
2015年 | 4234篇 |
2014年 | 6041篇 |
2013年 | 16187篇 |
2012年 | 12394篇 |
2011年 | 15156篇 |
2010年 | 10018篇 |
2009年 | 10023篇 |
2008年 | 14193篇 |
2007年 | 14095篇 |
2006年 | 13295篇 |
2005年 | 12179篇 |
2004年 | 10973篇 |
2003年 | 9652篇 |
2002年 | 9432篇 |
2001年 | 10700篇 |
2000年 | 8200篇 |
1999年 | 6279篇 |
1998年 | 5052篇 |
1997年 | 4951篇 |
1996年 | 4897篇 |
1995年 | 4464篇 |
1994年 | 4373篇 |
1993年 | 4256篇 |
1992年 | 4704篇 |
1991年 | 4546篇 |
1990年 | 4279篇 |
1989年 | 4147篇 |
1988年 | 4163篇 |
1987年 | 4071篇 |
1986年 | 3875篇 |
1985年 | 5448篇 |
1984年 | 5526篇 |
1983年 | 4646篇 |
1982年 | 4903篇 |
1981年 | 4641篇 |
1980年 | 4563篇 |
1979年 | 4613篇 |
1978年 | 4770篇 |
1977年 | 4646篇 |
1976年 | 4621篇 |
1975年 | 4470篇 |
1974年 | 4384篇 |
1973年 | 4617篇 |
1972年 | 2828篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
13.
Algebra and Logic - Unary functions definable in o-stable ordered groups of nonvaluational type are studied. Such functions are proved to be piecewise monotone and continuous. 相似文献
14.
Nonlinear Dynamics - In this article, the authors simulate and study dark and bright soliton solutions of 1D and 2D regularized long wave (RLW) models. The RLW model occurred in various fields such... 相似文献
15.
16.
17.
Sun Guo-Hua Dong Qian Bezerra V. B. Dong Shi-Hai 《Journal of mathematical chemistry》2022,60(4):605-612
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,... 相似文献
18.
Journal of Applied and Industrial Mathematics - We study the problem of optimal location of the ambulance fleet at the base stations. The objective is to minimize the average waiting time for... 相似文献
19.
A liquid dewetting method for the determination of the viscoelastic properties of ultrathin polymer films has been extended to study thickness effects on the properties of ultrathin polycarbonate (PC) films. PC films with film thicknesses ranging from 4 to 299 nm were placed on glycerol at temperatures from below the macroscopic glass transition temperature (Tg) to above it with the dewetting responses being monitored. It is found that the isothermal creep results for films of the same thickness, but dewetted at different temperatures can be superposed into one master curve, which is consistent with the fact of PC being a thermorheologically simple material. Furthermore, the results show that the Tg of PC thin films is thickness dependent, but the dependence is weaker than the results for freely standing films and similar to literature data for PC films supported on rigid substrates. It was also found that the rubbery plateau region for the PC films stiffens dramatically, but still less than what has been observed for freely standing polycarbonate films. The rubbery stiffening is discussed in terms of a recently reported model that relates macroscopic segmental dynamics with the stiffening. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1559–1566 相似文献
20.
In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography. 相似文献