全文获取类型
收费全文 | 44950篇 |
免费 | 6298篇 |
国内免费 | 3105篇 |
专业分类
化学 | 11577篇 |
晶体学 | 112篇 |
力学 | 6226篇 |
综合类 | 581篇 |
数学 | 20531篇 |
物理学 | 15326篇 |
出版年
2024年 | 99篇 |
2023年 | 453篇 |
2022年 | 819篇 |
2021年 | 914篇 |
2020年 | 1485篇 |
2019年 | 1348篇 |
2018年 | 1292篇 |
2017年 | 1284篇 |
2016年 | 1558篇 |
2015年 | 1325篇 |
2014年 | 2151篇 |
2013年 | 3938篇 |
2012年 | 2399篇 |
2011年 | 2762篇 |
2010年 | 2432篇 |
2009年 | 2690篇 |
2008年 | 2810篇 |
2007年 | 2886篇 |
2006年 | 2486篇 |
2005年 | 2456篇 |
2004年 | 2109篇 |
2003年 | 1977篇 |
2002年 | 1726篇 |
2001年 | 1375篇 |
2000年 | 1295篇 |
1999年 | 1203篇 |
1998年 | 1108篇 |
1997年 | 910篇 |
1996年 | 733篇 |
1995年 | 648篇 |
1994年 | 503篇 |
1993年 | 438篇 |
1992年 | 388篇 |
1991年 | 374篇 |
1990年 | 295篇 |
1989年 | 201篇 |
1988年 | 193篇 |
1987年 | 178篇 |
1986年 | 153篇 |
1985年 | 150篇 |
1984年 | 133篇 |
1983年 | 64篇 |
1982年 | 118篇 |
1981年 | 103篇 |
1980年 | 76篇 |
1979年 | 78篇 |
1978年 | 48篇 |
1977年 | 39篇 |
1976年 | 34篇 |
1973年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
方程w"-w+f(t,w)=O的Dirichlet边值问题的正解存在性与多解性 总被引:1,自引:0,他引:1
姚庆六 《应用泛函分析学报》2002,4(1):4-9
考察了下列常微分方程的Dirichlet边值问题的正解[w″(t)-w(t) f(t,w(t))=0,0≤t≤1 w(0)=w(1)=0建立了n正解的存在性,其中n是一个任意的自然数。 相似文献
73.
Alexander Krasnosel'skii Dmitrii Rachinskii 《NoDEA : Nonlinear Differential Equations and Applications》2002,9(1):93-115
We consider autonomous systems with a nonlinear part depending on a parameter and study Hopf bifurcations at infinity. The
nonlinear part consists of the nonlinear functional term and the Prandtl--Ishlinskii hysteresis term. The linear part of the
system has a special form such that the close-loop system can be considered as a hysteresis perturbation of a quasilinear
Hamiltonian system. The Hamiltonian system has a continuum of arbitrarily large cycles for each value of the parameter. We
present sufficient conditions for the existence of bifurcation points for the non-Hamiltonian system with hysteresis. These
bifurcation points are determined by simple characteristics of the hysteresis nonlinearity. 相似文献
74.
According to an induced-matter approach, Liu and Wesson obtained the rest mass of a typical particle from the reduction of a 5D Klein–Gordon equation to a 4D one. Introducing an extra-dimension momentum operator identified with the rest mass eigenvalue operator, we consider a way to generalize the 4D Dirac equation to 5D. An analogous normal Dirac equation is gained when the generalization reduces to 4D. We find the rest mass of a particle in curved space varies with spacetime coordinates and check this for the case of exact solitonic and cosmological solution of the 5D vacuum gravitational field equations. 相似文献
75.
76.
Summary Considered here are model equations for weakly nonlinear and dispersive long waves, which feature general forms of dispersion and pure power nonlinearity. Two variants of such equations are introduced, one of Korteweg-de Vries type and one of regularized long-wave type. It is proven that solutions of the pure initial-value problem for these two types of model equations are the same, to within the order of accuracy attributable to either, on the long time scale during which nonlinear and dispersive effects may accumulate to make an order-one relative difference to the wave profiles.This research was supported in part by the National Science Foundation. A considerable portion of the project was completed while the first author was resident at the Institute for Mathematics and Its Applications, University of Minnesota. 相似文献
77.
Koumei Tanaka 《Mathematical Methods in the Applied Sciences》2006,29(12):1451-1466
We consider a compressible viscous fluid with the velocity at infinity equal to a strictly non‐zero constant vector in ?3. Under the assumptions on the smallness of the external force and velocity at infinity, Novotny–Padula (Math. Ann. 1997; 308 :439– 489) proved the existence and uniqueness of steady flow in the class of functions possessing some pointwise decay. In this paper, we study stability of the steady flow with respect to the initial disturbance. We proved that if H3‐norm of the initial disturbance is small enough, then the solution to the non‐stationary problem exists uniquely and globally in time, which satisfies a uniform estimate on prescribed velocity at infinity and converges to the steady flow in Lq‐norm for any number q? 2. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
78.
79.
用能量法求多自由度振动系统的角频率 总被引:2,自引:1,他引:1
利用简谐振动能量方程,通过分析振幅矢量的关系,用能量法求多自由度振动系统的角频率或简正振动频率。 相似文献
80.
通过改变带细玻璃管的烧瓶中水的温度导致水位变化来粗略演示水的收缩情况.为较准确测定水最大密度时的温度,将2个温度计放在水下较浅处和较深处,分别测量当温度经由4℃升高时和由4℃降低时两温度计的示数,进而验证水的反常热膨胀特性. 相似文献