全文获取类型
收费全文 | 492922篇 |
免费 | 6724篇 |
国内免费 | 1692篇 |
专业分类
化学 | 262185篇 |
晶体学 | 7011篇 |
力学 | 21223篇 |
综合类 | 16篇 |
数学 | 60518篇 |
物理学 | 150385篇 |
出版年
2021年 | 3369篇 |
2020年 | 3938篇 |
2019年 | 4026篇 |
2018年 | 4776篇 |
2017年 | 4600篇 |
2016年 | 7890篇 |
2015年 | 5652篇 |
2014年 | 8041篇 |
2013年 | 22469篇 |
2012年 | 17420篇 |
2011年 | 21235篇 |
2010年 | 13841篇 |
2009年 | 13651篇 |
2008年 | 19354篇 |
2007年 | 19625篇 |
2006年 | 18904篇 |
2005年 | 17020篇 |
2004年 | 15505篇 |
2003年 | 13630篇 |
2002年 | 13256篇 |
2001年 | 14802篇 |
2000年 | 11496篇 |
1999年 | 9034篇 |
1998年 | 7308篇 |
1997年 | 7192篇 |
1996年 | 7113篇 |
1995年 | 6531篇 |
1994年 | 6236篇 |
1993年 | 6040篇 |
1992年 | 6766篇 |
1991年 | 6450篇 |
1990年 | 6193篇 |
1989年 | 5864篇 |
1988年 | 6095篇 |
1987年 | 5870篇 |
1986年 | 5528篇 |
1985年 | 7826篇 |
1984年 | 8029篇 |
1983年 | 6551篇 |
1982年 | 7072篇 |
1981年 | 7042篇 |
1980年 | 6729篇 |
1979年 | 6852篇 |
1978年 | 7003篇 |
1977年 | 7001篇 |
1976年 | 6975篇 |
1975年 | 6633篇 |
1974年 | 6513篇 |
1973年 | 6679篇 |
1972年 | 4032篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
961.
962.
In this paper, we present a unified treatment and analysis of a dynamic traffic network model with elastic demands formulated and studied as a projected dynamical system. We propose a travel route choice adjustment process that satisfies the projected dynamical system. Under certain conditions, stability and asymptotical stability of the equilibrium patterns are then derived. Finally, two discrete-time algorithms, the Euler method and the Heun method, are proposed for the computation of the solutions, and convergence results established. The convergence results depend crucially on stability analysis. The performance of the algorithms is then illustrated on several transportation networks. 相似文献
963.
E. D. Nursultanov 《Mathematical Notes》1998,63(2):205-214
In this paper we prove theorems on multiplicators of Fourier series inL
p, where the conditions depend on a parameterp. An example illustrating the importance of these conditions is constructed.
Translated fromMatematicheskie Zametki, Vol. 63, No. 2, pp. 235–247, February, 1998. 相似文献
964.
The characterisation of iron-containing species in Chinkombe ilmenite and its reduction products was undertaken using Mössbauer Spectroscopic techniques. The ore was reduced by graphite in an inert atmosphere. The effects of such variables as quantity of reductant, temperature and preoxidation were investigated. The ore was completely reduced to alpha-iron and titanium dioxide with 20% carbon for a period of one hour at 1373 K. Chemical mechanisms are proposed for the reduction and oxidation of Chinkombe ilmenite. In the processing of ilmenite to obtain synthetic rutile, the ultimate desire is to separate the Fe phase from the TiO2. Mössbauer Spectroscopy has unambiguously confirmed the desired transformation of the iron phase according to thermodynamic predictions. The information gained would be used to choose the conditions of the reduction process. The alpha-iron could be separated physically or chemically from the completely reduced product mass to obtain synthetic titanium dioxide suitable for the paint industry. 相似文献
965.
966.
967.
L.-H. Tang P. Smilauer D.D. Vvedensky 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):409-412
Two types of mechanisms are proposed for mound coarsening during unstable epitaxial growth: stochastic, due to deposition
noise, and deterministic, due to mass currents driven by surface energy differences. Both yield the relation H=(RWL)2 between the typical mound height W, mound size L, and the film thickness H. An analysis of simulations and experimental data shows that the parameter R saturates to a value which discriminates sharply between stochastic () and deterministic () coarsening. We derive a scaling relation between the coarsening exponent 1/z and the mound-height exponent which, for a saturated mound slope, yields .
Received: 11 November 1997 / Revised in final form: 28 November 1997 /
Accepted: 28 November 1997 相似文献
968.
969.
The plane contact problem of steady thermoelasticity taking heat generation into account 总被引:2,自引:0,他引:2
The plane steady contact problem of thermoelasticity when there is heat generation from friction, which arises when an infinite cylindrical punch moves over the surface of an elastic half-space along its generatrix, is considered. It is assumed that heat exchange between the free boundary of the half-space and the surrounding medium obeys Newton's law, while the condition for ideal thermal contact exists in the region in which the solids interact. The problem is reduced to a system of three integral equations in the heat fluxes and temperature. The effect of the thermal and mechanical properties of the cylinder and the half-space on the main contact characteristics is investigated numerically. 相似文献
970.
G. J. Groenewald M. A. Petersen Y. Zucker 《Integral Equations and Operator Theory》1997,28(4):466-491
For an arbitrary rational matrix function, not necessarily analytic at infinity, the existence of a right canonical Wiener-Hopf factorization is characterized in terms of a left canonical Wiener-Hopf factorization. Formulas for the factors in a right factorization are given in terms of the formulas for the factors in a given left factorization. All formulas are based on a special representation of a rational matrix function involving a quintet of matrices. 相似文献