首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   79031篇
  免费   6062篇
  国内免费   7332篇
化学   28364篇
晶体学   314篇
力学   7283篇
综合类   1435篇
数学   31194篇
物理学   23835篇
  2024年   108篇
  2023年   686篇
  2022年   1316篇
  2021年   1491篇
  2020年   1604篇
  2019年   1909篇
  2018年   1539篇
  2017年   1851篇
  2016年   2132篇
  2015年   1863篇
  2014年   2807篇
  2013年   5327篇
  2012年   3081篇
  2011年   3661篇
  2010年   3171篇
  2009年   4346篇
  2008年   4785篇
  2007年   5040篇
  2006年   4654篇
  2005年   3987篇
  2004年   3662篇
  2003年   3684篇
  2002年   3369篇
  2001年   2824篇
  2000年   2754篇
  1999年   2463篇
  1998年   2302篇
  1997年   1880篇
  1996年   1686篇
  1995年   1526篇
  1994年   1374篇
  1993年   1194篇
  1992年   1140篇
  1991年   897篇
  1990年   721篇
  1989年   641篇
  1988年   572篇
  1987年   450篇
  1986年   391篇
  1985年   457篇
  1984年   441篇
  1983年   221篇
  1982年   351篇
  1981年   415篇
  1980年   314篇
  1979年   302篇
  1978年   230篇
  1977年   219篇
  1976年   159篇
  1974年   111篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
61.
Fillmore在[1]中得到一个定理:设A,T是Banach空间X上的线性变换,A有界,若Lat(A) Lat(T)且AT=TA,则T是A的多项式.在本文里,以此作为引理,讨论了Banach空间上可逆线性变换A在什么情况下,A-1可表示为A的多项式.本文最主要的结论是定理3.4:设X是Banach空间,A是X上的有界线性变换,且可逆,则A-1是A的多项式当且仅当A-1是A的局部多项式.  相似文献   
62.
We study the probabilistic consequences of the choice of the basic number field in the quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p‐adic representations.  相似文献   
63.
基于气固两相流体动力学理论,建立气体纳米颗粒团聚物两相流动双流体模型.模型中采用了Jung & Gidaspow (2002)测量的固相应力模量和王垚等(2001)提出的聚团曳力系数计算模型.对纳米颗粒团聚物的流化过程进行了数值模拟,得到纳米颗粒团聚物的流化特性.模拟得出的床层膨胀比与文献中实验的结果较为接近.  相似文献   
64.
Summary We obtain preservation inequalities for Lipschitz constants of higher order in simultaneous approximation processes by Bernstein type operators. From such inequalities we derive the preservation of the corresponding Lipschitz spaces.  相似文献   
65.
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   
66.
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   
67.
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   
68.
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   
69.
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   
70.
In the ever fusion experiments in SWIP, pellet forming process was carried out through adjusting relative devices by staff member in site, which will make every pellet-forming process slight distinction and will result in pellet difference in shape, size and intensity. In the intervals of HL-2A discharges, staff member have to go site to accomplish the pellet-forming process, this wastes human power and increase the potential danger. So it is necessary to develop a remote control system to perform the pellet-forming process. The control system needs have the features of real-time, reliability and be easy to operate and maintain.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号