全文获取类型
收费全文 | 75507篇 |
免费 | 5504篇 |
国内免费 | 7135篇 |
专业分类
化学 | 29836篇 |
晶体学 | 352篇 |
力学 | 6747篇 |
综合类 | 1297篇 |
数学 | 26901篇 |
物理学 | 23013篇 |
出版年
2023年 | 616篇 |
2022年 | 1341篇 |
2021年 | 1446篇 |
2020年 | 1508篇 |
2019年 | 1749篇 |
2018年 | 1392篇 |
2017年 | 1660篇 |
2016年 | 1907篇 |
2015年 | 1767篇 |
2014年 | 2505篇 |
2013年 | 4708篇 |
2012年 | 2978篇 |
2011年 | 3312篇 |
2010年 | 2944篇 |
2009年 | 4434篇 |
2008年 | 4831篇 |
2007年 | 4908篇 |
2006年 | 4628篇 |
2005年 | 3771篇 |
2004年 | 3455篇 |
2003年 | 3511篇 |
2002年 | 3274篇 |
2001年 | 2703篇 |
2000年 | 2631篇 |
1999年 | 2356篇 |
1998年 | 2234篇 |
1997年 | 1813篇 |
1996年 | 1613篇 |
1995年 | 1448篇 |
1994年 | 1343篇 |
1993年 | 1134篇 |
1992年 | 1099篇 |
1991年 | 853篇 |
1990年 | 715篇 |
1989年 | 616篇 |
1988年 | 555篇 |
1987年 | 441篇 |
1986年 | 376篇 |
1985年 | 438篇 |
1984年 | 442篇 |
1983年 | 216篇 |
1982年 | 357篇 |
1981年 | 407篇 |
1980年 | 306篇 |
1979年 | 295篇 |
1978年 | 224篇 |
1977年 | 209篇 |
1976年 | 157篇 |
1974年 | 110篇 |
1973年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
L. T. Ashchepkov 《Computational Mathematics and Mathematical Physics》2006,46(7):1168-1175
A general nonlinear programming problem with interval functions is considered. Two reductions of this problem to the deterministic nonlinear programming problem are proposed, and illustrative examples are discussed. 相似文献
32.
A. D. Matveev 《Journal of Applied Mechanics and Technical Physics》2003,44(5):721-726
Modified three-dimensional formulations of bending problems of homogeneous elastic plates and beams are considered. Modification of the known three-dimensional formulations reduces to using additional constraints imposed on displacement functions. An advantage of the formulations proposed is that complex fixing conditions of plates and beams can be taken into account. 相似文献
33.
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
34.
A. Khrennikov 《Annalen der Physik》2003,12(10):575-585
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
35.
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
36.
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
37.
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
38.
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
39.
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
40.
N. A. Lockerbie 《General Relativity and Gravitation》2004,36(3):593-600
By using a novel free-flying, rotating, optical bench aboard the International Space Station (ISS) as the basis for a measurement of differential acceleration between two gravitating bodies, in principle the Newtonian inverse-square law and the constant of gravitation, G, can be determined at the parts in 106 level. 相似文献