全文获取类型
收费全文 | 8833篇 |
免费 | 460篇 |
国内免费 | 121篇 |
专业分类
化学 | 6508篇 |
晶体学 | 79篇 |
力学 | 200篇 |
综合类 | 15篇 |
数学 | 1035篇 |
物理学 | 1577篇 |
出版年
2023年 | 86篇 |
2022年 | 75篇 |
2021年 | 131篇 |
2020年 | 202篇 |
2019年 | 178篇 |
2018年 | 190篇 |
2017年 | 169篇 |
2016年 | 390篇 |
2015年 | 317篇 |
2014年 | 314篇 |
2013年 | 628篇 |
2012年 | 629篇 |
2011年 | 702篇 |
2010年 | 337篇 |
2009年 | 311篇 |
2008年 | 602篇 |
2007年 | 595篇 |
2006年 | 493篇 |
2005年 | 451篇 |
2004年 | 330篇 |
2003年 | 310篇 |
2002年 | 295篇 |
2001年 | 194篇 |
2000年 | 193篇 |
1999年 | 124篇 |
1998年 | 86篇 |
1997年 | 84篇 |
1996年 | 109篇 |
1995年 | 72篇 |
1994年 | 73篇 |
1993年 | 91篇 |
1992年 | 72篇 |
1991年 | 44篇 |
1990年 | 35篇 |
1989年 | 35篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 27篇 |
1985年 | 60篇 |
1984年 | 58篇 |
1983年 | 37篇 |
1982年 | 35篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 11篇 |
1978年 | 22篇 |
1977年 | 18篇 |
1976年 | 11篇 |
1975年 | 16篇 |
1974年 | 16篇 |
排序方式: 共有9414条查询结果,搜索用时 15 毫秒
11.
12.
We study a site analogue of directed percolation. Random trajectories are generated and their critical behavior is studied. The critical behavior corresponds to that of simple percolation in some of the parameter space, but elsewhere the exponents reveal new universality classes. As a byproduct, we use the model to make an improved estimate of the percolation hull exponents and to calculate the site percolation probability for the square lattice. 相似文献
13.
14.
15.
Behavior of cellulose in NaOH/Urea aqueous solution characterized by light scattering and viscometry
Cellulose was dissolved in 6 wt % NaOH/4 wt % urea aqueous solution, which was proven by a 13C NMR spectrum to be a direct solvent of cellulose rather than a derivative aqueous solution system. Dilute solution behavior of cellulose in a NaOH/urea aqueous solution system was examined by laser light scattering and viscometry. The Mark–Houwink equation for cellulose in 6 wt % NaOH/4 wt % urea aqueous solution at 25 °C was [η] = 2.45 × 10?2 weight‐average molecular weight (Mw)0.815 (mL g?1) in the Mw region from 3.2 × 104 to 12.9 × 104. The persistence length (q), molar mass per unit contour length (ML), and characteristic ratio (C∞) of cellulose in the dilute solution were 6.0 nm, 350 nm?1, and 20.9, respectively, which agreed with the Yamakawa–Fujii theory of the wormlike chain. The results indicated that the cellulose molecules exist as semiflexible chains in the aqueous solution and were more extended than in cadoxen. This work provided a novel, simple, and nonpollution solvent system that can be used to investigate the dilute solution properties and molecular weight of cellulose. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 347–353, 2004 相似文献
16.
Francesc Carreras M. Dolors Llongueras Antonio Magaña 《Annals of Operations Research》2005,137(1):67-89
A partnership in a cooperative game is a coalition that possesses an internal structure and, simultaneously, behaves as an
individual member. Forming partnerships leads to a modification of the original game which differs from the quotient game
that arises when one or more coalitions are actually formed.
In this paper, the Shapley value is used to discuss the convenience to form either coalitions or partnerships. To this end,
the difference between the additive Shapley value of the partnership in the partnership game and the Shapley alliance value
of the coalition, and also between the corresponding value of the internal and external players, are analysed. Simple games
are especially considered.
Research partially supported by Grant BFM 2003-01314 of the Science and Technology Spanish Ministry and the European Regional
Development Fund. 相似文献
17.
Ricardo Mañé 《Bulletin of the Brazilian Mathematical Society》1997,28(2):141-153
The objective of this note is to present some results, to be proved in a forthcoming paper, about certain special solutions of the Euler-Lagrange equations on closed manifolds. Our main results extend to time dependent periodic Lagrangians with minor modifications.We have chosen the autonomous case because this formally simpler framework allows to reach more easily the core of our concepts and results. Moreover the autonomous case exhibits certain special features involving the energy as a first integral that deserve special attention. They are closely related to the link found by Carneiro [C] between the energy and Mather's action function [Ma].Reprinted by permission of Addison Wesley Longman Ltd. 相似文献
18.
19.
20.
René Meziat Diego Patiño Pablo Pedregal 《Computational Optimization and Applications》2007,38(1):147-171
We propose an alternative method for computing effectively the solution of non-linear, fixed-terminal-time, optimal control
problems when they are given in Lagrange, Bolza or Mayer forms. This method works well when the nonlinearities in the control
variable can be expressed as polynomials. The essential of this proposal is the transformation of a non-linear, non-convex
optimal control problem into an equivalent optimal control problem with linear and convex structure. The method is based on
global optimization of polynomials by the method of moments. With this method we can determine either the existence or lacking
of minimizers. In addition, we can calculate generalized solutions when the original problem lacks of minimizers. We also
present the numerical schemes to solve several examples arising in science and technology. 相似文献