全文获取类型
收费全文 | 7760篇 |
免费 | 729篇 |
国内免费 | 644篇 |
专业分类
化学 | 615篇 |
晶体学 | 24篇 |
力学 | 356篇 |
综合类 | 151篇 |
数学 | 5972篇 |
物理学 | 734篇 |
无线电 | 1281篇 |
出版年
2024年 | 17篇 |
2023年 | 60篇 |
2022年 | 124篇 |
2021年 | 169篇 |
2020年 | 164篇 |
2019年 | 174篇 |
2018年 | 167篇 |
2017年 | 252篇 |
2016年 | 266篇 |
2015年 | 199篇 |
2014年 | 417篇 |
2013年 | 586篇 |
2012年 | 423篇 |
2011年 | 491篇 |
2010年 | 404篇 |
2009年 | 487篇 |
2008年 | 514篇 |
2007年 | 550篇 |
2006年 | 471篇 |
2005年 | 398篇 |
2004年 | 374篇 |
2003年 | 330篇 |
2002年 | 307篇 |
2001年 | 258篇 |
2000年 | 238篇 |
1999年 | 179篇 |
1998年 | 192篇 |
1997年 | 172篇 |
1996年 | 145篇 |
1995年 | 92篇 |
1994年 | 87篇 |
1993年 | 48篇 |
1992年 | 41篇 |
1991年 | 42篇 |
1990年 | 39篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 31篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 22篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 3篇 |
1969年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有9133条查询结果,搜索用时 15 毫秒
991.
In this paper, we will show the existence of partially regular solutions to the initial-boundary value problem for Landau-Lifshitz equations with nonpositive anisotropy constants in three or four space dimensions. The partial regularity is proved up to the boundary both for the Dirichlet problem and for the Neumann problem. In addition, for the Neumann case, a generalized stability condition which ensures the partial regularity is given. For equations with positive or negative anisotropy coefficients, we will give two results of existence and uniqueness for the solutions corresponding to ground states. 相似文献
992.
By using fixed-point theorems, some new results for multiplicity of positive solutions for some second order m-point boundary value problems are obtained.The associated Green's function of these problems are also given. 相似文献
993.
Peter Somora 《Mathematica Slovaca》2008,58(4):439-454
A second order nonlinear differential equation with homogeneous Dirichlet boundary conditions is considered. An explicit expression
for the root functions for an autonomous nonlinear boundary value problem is obtained using the results of the paper [SOMORA,
P.: The lower bound of the number of solutions for the second order nonlinear boundary value problem via the root functions method, Math. Slovaca 57 (2007), 141–156]. Other assumptions are supposed to prove the monotonicity of root functions and to get the exact number
of solutions. The existence of infinitely many solutions of the boundary value problem with strong nonlinearity is obtained
by the root function method as well.
The paper was supported by the Grant VEGA No. 2/7140/27, Bratislava. 相似文献
994.
利用夏普里值来识别导致顾客不满意的质量属性.因为夏普里值差异很小的质量属性具有高度的相关性,所以可以把具有相同或者类似的夏普里值的质量属性划分为同类属性,从而能够识别导致顾客不满意的质量属性.算例进一步验证该方法的可行性和正确性. 相似文献
995.
996.
This paper considers the problems of determining center or focus and isochronous centers for the planar quasi-analytic systems.
Two recursive formulas to determine the focal values and period constants are given. The convergence of first integral near
the center is proved. Using the general results to quasi-quadratic systems, the problem of the isochronous center of the origin
is completely solved.
This research is partially supported by the National Natural Science Foundation of China (10671179 and 10771196) and the Natural
Science Foundation of Yunnan Province (2005A0092M) 相似文献
997.
利用变分原理和Z2不变群指标研究了二阶常微分方程边值问题{u″(t)-u(t) f(t,u(t))=0,0<t<1,u′(0)=0,α1u(1) u′(1)=0,(其中α1>-1/2).得出了这类方程存在无穷个解的充分条件. 相似文献
998.
999.
We consider the construction of methods based on trigonometric polynomials for the initial value problems whose solutions are known to be periodic. It is assumed that the frequency w can be estimated in advance. The resulting methods depend on a parameter ν = hw, where h is the step size, and reduce to classical multistep methods if ν → 0. Gautschi [4] developed Adams and Störmer type methods. In our paper we construct Nyström's and Milne-Simpson's type methods. Numerical experiments show that these methods are not sensitive to changes in w, but require the Jacobian matrix to have purely imaginary eigenvalues. 相似文献
1000.
R Saunders 《Applied Mathematical Modelling》1985,9(5):385-386
A proposed iterative method for solving nonlinear differential two-point boundary value problems is generalized and shown to be equivalent to using the standard method of adjoints on a linearized form of the nonlinear boundary-value problem. 相似文献