全文获取类型
收费全文 | 14459篇 |
免费 | 648篇 |
国内免费 | 5篇 |
专业分类
化学 | 10694篇 |
晶体学 | 86篇 |
力学 | 264篇 |
数学 | 1988篇 |
物理学 | 2080篇 |
出版年
2023年 | 118篇 |
2022年 | 71篇 |
2021年 | 122篇 |
2020年 | 209篇 |
2019年 | 228篇 |
2018年 | 210篇 |
2017年 | 219篇 |
2016年 | 493篇 |
2015年 | 458篇 |
2014年 | 492篇 |
2013年 | 932篇 |
2012年 | 1129篇 |
2011年 | 1213篇 |
2010年 | 655篇 |
2009年 | 496篇 |
2008年 | 1061篇 |
2007年 | 1038篇 |
2006年 | 937篇 |
2005年 | 893篇 |
2004年 | 726篇 |
2003年 | 598篇 |
2002年 | 517篇 |
2001年 | 190篇 |
2000年 | 176篇 |
1999年 | 112篇 |
1998年 | 86篇 |
1997年 | 85篇 |
1996年 | 129篇 |
1995年 | 81篇 |
1994年 | 65篇 |
1993年 | 87篇 |
1992年 | 72篇 |
1991年 | 55篇 |
1990年 | 51篇 |
1989年 | 42篇 |
1988年 | 45篇 |
1987年 | 42篇 |
1986年 | 62篇 |
1985年 | 89篇 |
1984年 | 73篇 |
1983年 | 43篇 |
1982年 | 69篇 |
1981年 | 68篇 |
1980年 | 71篇 |
1979年 | 53篇 |
1978年 | 54篇 |
1977年 | 41篇 |
1976年 | 49篇 |
1975年 | 28篇 |
1974年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
Brandão Pedro Francisco Ramos Rui Miguel Rodrigues José António 《Analytical and bioanalytical chemistry》2018,410(26):6873-6880
Analytical and Bioanalytical Chemistry - Formaldehyde is often applied in the industrial production of different products, such as textiles, insulation materials, or cosmetics, due to its... 相似文献
14.
In this Note we give a necessary and sufficient condition for the spectral controllability from one simple node of a general network of strings that undergoes transversal vibrations in a sufficiently large time. This condition asserts that no eigenfunction vanishes identically on the string that contains the controlled node. The proof combines the Beurling–Malliavin's theorem and an asymptotic formula for the eigenvalues of the network. The optimal control time may be characterized as twice the sum of the lengths of all the strings of the network. To cite this article: R. Dáger, E. Zuazua, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 545–550. 相似文献
15.
16.
Abstract. We propose a general approach to deal with nonlinear, nonconvex variational problems based on a reformulation of the problem
resulting in an optimization problem with linear cost functional and convex constraints. As a first step we explicitly explore
these ideas to some one-dimensional variational problems and obtain specific conclusions of an analytical and numerical nature. 相似文献
17.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
18.
Monika Goikoetxea María J. Barandiaran José M. Asua 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5838-5846
The mechanisms involved in the formation of n‐butanol during the synthesis of butyl acrylate containing latices were investigated. The experimental results showed that neither the hydrolysis of butyl acrylate nor of the ester bond in the butyl acrylate segments of the polymer played a major role in the formation of n‐butanol, which was mainly generated from the polymer backbone, by transfer reactions to polymer chain followed by cyclization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5838–5846, 2007 相似文献
19.
Thermodynamic fluctuations in systems that are in nonequilibrium steady states are always spatially long ranged, in contrast to fluctuations in thermodynamic equilibrium. In the present paper we consider a fluid subjected to a stationary temperature gradient. Two different physical mechanisms have been identified by which the temperature gradient causes long-ranged fluctuations. One cause is the presence of couplings between fluctuating fields. Secondly, spatial variation of the strength of random forces, resulting from the local version of the fluctuation-dissipation theorem, has also been shown to generate long-ranged fluctuations. We evaluate the contributions to the long-ranged temperature fluctuations due to both mechanisms. While the inhomogeneously correlated Langevin noise does lead to long-ranged fluctuations, in practice, they turn out to be negligible as compared to nonequilibrium temperature fluctuations resulting from the coupling between temperature and velocity fluctuations. 相似文献
20.
José Francisco Rodrigues 《Monatshefte für Mathematik》2004,29(2):157-177
This paper presents further developments in the study of strong solutions and their coincidence sets to the obstacle problem for linear transport operators. Under natural mild assumptions, the strong convergence of the solutions and the characteristic functions of their coincidence sets is obtained in the passage of second order to first order problems. An application to a steady-state chemotaxis problem is given. The extension to the two obstacles problem of first order is also presented, having in view an application to a porous media model in presence of saturation arising in petroleum engineering. 相似文献