全文获取类型
收费全文 | 11177篇 |
免费 | 954篇 |
国内免费 | 797篇 |
专业分类
化学 | 1445篇 |
晶体学 | 148篇 |
力学 | 748篇 |
综合类 | 143篇 |
数学 | 8694篇 |
物理学 | 1750篇 |
出版年
2024年 | 20篇 |
2023年 | 98篇 |
2022年 | 128篇 |
2021年 | 146篇 |
2020年 | 268篇 |
2019年 | 287篇 |
2018年 | 298篇 |
2017年 | 311篇 |
2016年 | 348篇 |
2015年 | 252篇 |
2014年 | 473篇 |
2013年 | 1035篇 |
2012年 | 419篇 |
2011年 | 588篇 |
2010年 | 611篇 |
2009年 | 697篇 |
2008年 | 783篇 |
2007年 | 759篇 |
2006年 | 628篇 |
2005年 | 567篇 |
2004年 | 521篇 |
2003年 | 490篇 |
2002年 | 463篇 |
2001年 | 354篇 |
2000年 | 299篇 |
1999年 | 285篇 |
1998年 | 237篇 |
1997年 | 216篇 |
1996年 | 186篇 |
1995年 | 133篇 |
1994年 | 115篇 |
1993年 | 93篇 |
1992年 | 88篇 |
1991年 | 60篇 |
1990年 | 51篇 |
1989年 | 41篇 |
1988年 | 45篇 |
1987年 | 27篇 |
1986年 | 46篇 |
1985年 | 52篇 |
1984年 | 60篇 |
1983年 | 41篇 |
1982年 | 55篇 |
1981年 | 43篇 |
1980年 | 40篇 |
1979年 | 51篇 |
1978年 | 33篇 |
1977年 | 21篇 |
1976年 | 22篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Marko Nedeljkov 《Mathematical Methods in the Applied Sciences》2004,27(8):931-955
This work gives a condition for existence of singular and delta shock wave solutions to Riemann problem for 2×2 systems of conservation laws. For a fixed left‐hand side value of Riemann data, the condition obtained in the paper describes a set of possible right‐hand side values. The procedure is similar to the standard one of finding the Hugoniot locus. Fluxes of the considered systems are globally Lipschitz with respect to one of the dependent variables. The association in a Colombeau‐type algebra is used as a solution concept. Copyright © 2004 John Wiley &Sons, Ltd. 相似文献
52.
Bogdan Ka
mierczak Kazimierz Piechr 《Mathematical Methods in the Applied Sciences》2004,27(11):1317-1345
In this paper we study travelling wave solutions to a system of four non‐linear partial differential equations, which arise in a tissue interaction model for skin morphogenesis. Under the ‘small‐stress’ assumption we prove the existence and uniqueness (up to a translation) of solutions with the dermis and epidermis cell densities being positive, which are a perturbation of a uniform epidermal cell density. We discuss the problem of the minimal wave‐speed. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
53.
In this paper, a generalized anti–maximum principle for the second order differential operator with potentials is proved. As an application, we will give a monotone iterative scheme for periodic solutions of nonlinear second order equations. Such a scheme involves the Lp norms of the growth, 1 ≤ p ≤ ∞, while the usual one is just the case p = ∞. 相似文献
54.
n阶矩阵A称为完全正的,如果A有分解:A=BBT,其中B为元素非负矩阵,B的最小可能列数称为A的分解指数.本文考察低阶双非负矩阵在整数环上的完全正分解及其分解指数. 相似文献
55.
56.
映象方程多解问题的某些研究 总被引:1,自引:0,他引:1
本文用fp-同伦方法,在一定的技巧和变换的配合下,在紧性条件支持下,研究了赋范线性空间中一类集值映象方程的多解问题。还给出所得理论结果的一个应用。 相似文献
57.
In the present article, we aim at treating the existence of fundamental solutions of linear partial differential operators with constant coefficients from the viewpoint of setting up explicit formulae yielding fundamental solutions. 相似文献
58.
Many biological and medical studies have as a response of interest the time to occurrence of some event, such as the occurrence of a particular symptom or disease, remission, relapse, death due to some specific disease, or simply death. In this paper we study the problem of assessing the effect of potential risk factors on the outcome event of interest through a parametric or semi-parametric frailty model where the lifetimes have a reason to be considered dependent. This dependence may arise because of multiple endpoints within the same individual or because, when studying a single endpoint, there are natural groupings between study subjects. The objective of this paper is to extend both parametric and semi-parametric approaches to regression analysis in which the lifetimes of individuals in a group are effected by the same random frailty which follows a positive stable distribution. Some comparisons of the properties of this frailty distribution with other frailty distributions are made and an example which assesses the effect of a treatment in a litter-matched tumorigenesis study is presented. 相似文献
59.
本文以fp 同伦方法为工具,借助于一些适当的变换,研究有序的(B)空间中的集值映象方程的多正解问题;在文中的有关工作中,还使用了集值映象的拟导数的某些性质. 相似文献
60.
Liquid-liquid phase equilibria of aqueous two-phase systems containing salts and polyethylene glycol 总被引:2,自引:0,他引:2
Liquid-liquid phase equilibria of the ternary systems: (a) polyethylene glycol - ammonium sulfate- water and (b) polyethylene glycol - sodium carbonate -water have been determined experimentally at 15°, 25°, 35° and 45°C and for two different molecular weights of the polymer (Avg. M.W. 1000 and 2000). Details of the glass cell and of the equilibration and analytical procedures used are described. Equilibrium data along with phase diagrams are presented. Finally the effect of temperature and of the molecular weight of the polymer are also discussed. 相似文献