全文获取类型
收费全文 | 468170篇 |
免费 | 5756篇 |
国内免费 | 1489篇 |
专业分类
化学 | 255694篇 |
晶体学 | 6870篇 |
力学 | 19416篇 |
综合类 | 14篇 |
数学 | 55834篇 |
物理学 | 137587篇 |
出版年
2021年 | 4152篇 |
2020年 | 4696篇 |
2019年 | 5045篇 |
2018年 | 6217篇 |
2017年 | 6098篇 |
2016年 | 9687篇 |
2015年 | 6254篇 |
2014年 | 9407篇 |
2013年 | 21699篇 |
2012年 | 17523篇 |
2011年 | 21394篇 |
2010年 | 14688篇 |
2009年 | 14403篇 |
2008年 | 19585篇 |
2007年 | 19360篇 |
2006年 | 18060篇 |
2005年 | 16279篇 |
2004年 | 14989篇 |
2003年 | 13109篇 |
2002年 | 12874篇 |
2001年 | 13885篇 |
2000年 | 10543篇 |
1999年 | 8306篇 |
1998年 | 6926篇 |
1997年 | 6706篇 |
1996年 | 6509篇 |
1995年 | 5771篇 |
1994年 | 5759篇 |
1993年 | 5530篇 |
1992年 | 6131篇 |
1991年 | 6203篇 |
1990年 | 5900篇 |
1989年 | 5691篇 |
1988年 | 5696篇 |
1987年 | 5605篇 |
1986年 | 5284篇 |
1985年 | 6918篇 |
1984年 | 7013篇 |
1983年 | 5586篇 |
1982年 | 5713篇 |
1981年 | 5635篇 |
1980年 | 5246篇 |
1979年 | 5592篇 |
1978年 | 5727篇 |
1977年 | 5602篇 |
1976年 | 5537篇 |
1975年 | 5110篇 |
1974年 | 5051篇 |
1973年 | 5001篇 |
1972年 | 3546篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
C. Vaca‐Garcia G. Gozzelino W. G. Glasser M. E. Borredon 《Journal of Polymer Science.Polymer Physics》2003,41(3):281-288
The main transitions of cellulose fatty esters with different degrees of substitution (DSs) were investigated with dynamic mechanical thermal analysis. Two distinct main relaxations were observed in partially substituted cellulose esters (PSCEs). They were attributed to the glass‐transition temperature and to the chain local motion of the aliphatic substituents. The temperatures of both transitions decreased when DS or the number of carbon atoms (n) of the acyl substituent increased. Conversely, all the transitions of fully substituted cellulose esters occurred within a narrow temperature range, and they did not vary significantly with n. This phenomenon was explained by the formation of a crystalline phase of the fatty substituents. The presence of few residual OH groups in PSCEs was responsible for a large increase in the storage bending modulus, and it eliminated the effect of n on damping. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 281–288, 2003 相似文献
112.
In this paper, we find the approximate solution of a second order nonlinear partial differential equation on a simple connected region inR 2. We transfer this problem to a new problem of second order nonlinear partial differential equation on a rectangle. Then, we transformed the later one to an equivalent optimization problem. Then we consider the optimization problem as a distributed parameter system with artificial controls. Finally, by using the theory of measure, we obtain the approximate solution of the original problem. In this paper also the global error inL 1 is controlled. 相似文献
113.
S. M. Saprikin 《Journal of Mathematical Sciences》2004,120(5):1752-1765
An arbitrary operator-valued function from the generalized Shur class is realized as the transfer function of a minimal optimal and minimal *-optimal dissipative scattering system with the Pontryagin state space. These results generalize Arov's results for the case of the Hilbert state space. Bibliography: 11 titles. 相似文献
114.
115.
116.
The projection approach is applied to construct and investigate an operator-difference scheme for fluid dynamics in Lagrangean variables which has first-order local approximation in the axisymmetric case near the symmetry axis. The scheme also has operator properties that make it suitable for rederiving and substantiating previous results, methods, and algorithms. 相似文献
117.
Glezer A.M. Blinova E.N. Pozdnyakov V.A. Shelyakov A.V. 《Journal of nanoparticle research》2003,5(5-6):551-560
Journal of Nanoparticle Research - It was shown that the thermoelastic martensite transformation B2 ? B19 inside nanoparticles surrounded by amorphous matrix in Ni–Ti–Cu alloys as... 相似文献
118.
S. M. Finashin 《Journal of Mathematical Sciences》2004,119(1):124-127
A formula of type indicated in the title is presented and discussed. Bibliography: 7 titles. 相似文献
119.
Russian Journal of General Chemistry - 相似文献
120.
Maria G. Semenova Larisa E. Belyakova Anna S. Antipova Yu. N. Polikarpov Lida Klouda Anna Markovic Michael M. Il'in 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):47-54
We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na+), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed. 相似文献