全文获取类型
收费全文 | 73154篇 |
免费 | 5796篇 |
国内免费 | 6641篇 |
专业分类
化学 | 26142篇 |
晶体学 | 286篇 |
力学 | 7396篇 |
综合类 | 1292篇 |
数学 | 28697篇 |
物理学 | 21778篇 |
出版年
2023年 | 577篇 |
2022年 | 952篇 |
2021年 | 1243篇 |
2020年 | 1425篇 |
2019年 | 1658篇 |
2018年 | 1395篇 |
2017年 | 1666篇 |
2016年 | 1862篇 |
2015年 | 1688篇 |
2014年 | 2452篇 |
2013年 | 4726篇 |
2012年 | 2844篇 |
2011年 | 3236篇 |
2010年 | 2806篇 |
2009年 | 3989篇 |
2008年 | 4452篇 |
2007年 | 4648篇 |
2006年 | 4349篇 |
2005年 | 3734篇 |
2004年 | 3426篇 |
2003年 | 3470篇 |
2002年 | 3205篇 |
2001年 | 2707篇 |
2000年 | 2622篇 |
1999年 | 2382篇 |
1998年 | 2215篇 |
1997年 | 1814篇 |
1996年 | 1622篇 |
1995年 | 1471篇 |
1994年 | 1357篇 |
1993年 | 1161篇 |
1992年 | 1118篇 |
1991年 | 878篇 |
1990年 | 739篇 |
1989年 | 633篇 |
1988年 | 572篇 |
1987年 | 450篇 |
1986年 | 388篇 |
1985年 | 457篇 |
1984年 | 447篇 |
1983年 | 224篇 |
1982年 | 361篇 |
1981年 | 416篇 |
1980年 | 313篇 |
1979年 | 312篇 |
1978年 | 228篇 |
1977年 | 218篇 |
1976年 | 162篇 |
1974年 | 112篇 |
1973年 | 109篇 |
排序方式: 共有10000条查询结果,搜索用时 578 毫秒
131.
采用溶解-反应量热法在具有恒温环境的溶解-反应热量计内,测定了[Gd(Gly)4(Im)(H2O)](ClO4)3和[Y(Gly)4(Im)(H2O)](ClO4)3两种稀土甘氨酸咪唑配合物的标准生成焓分别为(-3 461.46 ±0.22) kJ·mol-1 和(-3 926.6±0.90) kJ·mol-1. 相似文献
132.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
133.
INTERSECTION OF PRIME SUBMODULES AND DIMENSION OF MODULES 总被引:1,自引:0,他引:1
A.Azizi 《数学物理学报(B辑英文版)》2005,25(3):385-394
The aim of this paper is to study the conditions by which a P-prime submodule can be expressed as a finite intersection or union of P-prime submodules. Also corresponding to dimension and rank of modules, some equivalent conditions for a ring to be a Dedekind domain are given. 相似文献
134.
Jeannette H. C. Woerner 《商业与工业应用随机模型》2005,21(1):27-44
In the framework of stochastic volatility models we examine estimators for the integrated volatility based on the pth power variation (i.e. the sum of pth absolute powers of the log‐returns). We derive consistency and distributional results for the estimators given high‐frequency data, especially taking into account what kind of process we may add to our model without affecting the estimate of the integrated volatility. This may on the one hand be interpreted as a possible flexibility in modelling, for example adding jumps or even leaving the framework of semimartingales by adding a fractional Brownian motion, or on the other hand as robustness against model misspecification. We will discuss possible choices of p under different model assumptions and irregularly spaced data. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
135.
Deborah M. Greaves 《国际流体数值方法杂志》2006,50(6):693-711
An adaptive hierarchical grid‐based method for predicting complex free surface flows is used to simulate collapse of a water column. Adapting quadtree grids are combined with a high‐resolution interface‐capturing approach and pressure‐based coupling of the Navier–Stokes equations. The Navier–Stokes flow solution scheme is verified for simulation of flow in a lid‐driven cavity at Re=1000. Two approaches to the coupling of the Navier–Stokes equations are investigated as are alternative face velocity and hanging node interpolations. Collapse of a water column as well as collapse of a water column and its subsequent interaction with an obstacle are simulated. The calculations are made on uniform and adapting quadtree grids, and the accuracy of the quadtree calculations is shown to be the same as those made on the equivalent uniform grids. Results are in excellent agreement with experimental and other numerical data. A sharp interface is maintained at the free surface. The new adapting quadtree‐based method achieves a considerable saving in the size of the computational grid and CPU time in comparison with calculations made on equivalent uniform grids. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
136.
A localH-theorem is derived for a recently proposed extension of Enskog kinetic theory to a dense model fluid composed of particles with interactions extending beyond a hard core.On leave from: Katedra Fizyki, Uniwersytetu Szczecinskiego, 70-451 Szczecin, Poland. 相似文献
137.
系统研究了具有急性和慢性两个阶段的MSIS流行病模型.由两节构成,第1节建立和研究了具有急慢性阶段的MSIS流行病模型;第2节在第1节的基础上建立和研究了具有慢性病病程的MSIS流行病模型.第1节的模型是四个常微分方程构成的方程组.第2节的模型既含有常微分方程,又含有偏微分方程.运用微分方程和积分方程中的理论和方法,得到了这两个模型再生数R0的表达式.证明了当R0<1时,无病平衡态是全局渐近稳定性,给出了各模型地方病平衡态的存在性和稳定性条件. 相似文献
138.
We study the structure of invertible substitutions on three-letter alphabet. We show that there exists a finite set
of invertible substitutions such that any invertible substitution can be written as Iwσ1σ2σk, where Iw is the inner automorphism associated with w, and
for 1jk. As a consequence, M is the matrix of an invertible substitution if and only if it is a finite product of non-negative elementary matrices. 相似文献
139.
We obtain expressions for the energy spectrum widths of Rayleigh waves corresponding to their deformational coupling to Fermi and Boltzmann electrons in a two-dimensional layer near the surface of a semibounded solid. We evaluate the nonequilibrium energy of Rayleigh waves that depends on these widths and is caused by the same coupling to the corresponding hot electrons. We show that this energy is independent of the degeneracy degree of the electrons and is given by the mean energy of free Rayleigh waves heated up to temperature of the electrons. We find conditions under which the thermodynamics is determined by this nonequilibrium energy of Rayleigh waves in films of a certain thickness with Fermi electrons near the surface and by the equilibrium energy of bulk phonons in thicker samples. All the results are obtained using the Keldysh diagram technique applied to the case of semibounded media. 相似文献
140.
We establish a relation between stable distributions in probability theory and the fractional integral. Moreover, it turns out that the parameter of the stable distribution coincides with the exponent of the fractional integral. It follows from an analysis of the obtained results that equations with the fractional time derivative describe the evolution of some physical system whose time degree of freedom becomes stochastic, i.e., presents a sum of random time intervals subject to a stable probability distribution. We discuss relations between the fractal Cantor set (Cantor strips) and the fractional integral. We show that the possibility to use this relation as an approximation of the fractional integral is rather limited. 相似文献