全文获取类型
收费全文 | 7567篇 |
免费 | 551篇 |
国内免费 | 681篇 |
专业分类
化学 | 1587篇 |
晶体学 | 8篇 |
力学 | 502篇 |
综合类 | 161篇 |
数学 | 5218篇 |
物理学 | 1323篇 |
出版年
2024年 | 10篇 |
2023年 | 76篇 |
2022年 | 139篇 |
2021年 | 133篇 |
2020年 | 149篇 |
2019年 | 200篇 |
2018年 | 138篇 |
2017年 | 268篇 |
2016年 | 301篇 |
2015年 | 200篇 |
2014年 | 331篇 |
2013年 | 553篇 |
2012年 | 442篇 |
2011年 | 385篇 |
2010年 | 375篇 |
2009年 | 448篇 |
2008年 | 461篇 |
2007年 | 546篇 |
2006年 | 405篇 |
2005年 | 369篇 |
2004年 | 292篇 |
2003年 | 305篇 |
2002年 | 317篇 |
2001年 | 215篇 |
2000年 | 239篇 |
1999年 | 203篇 |
1998年 | 192篇 |
1997年 | 165篇 |
1996年 | 133篇 |
1995年 | 114篇 |
1994年 | 96篇 |
1993年 | 70篇 |
1992年 | 57篇 |
1991年 | 61篇 |
1990年 | 37篇 |
1989年 | 28篇 |
1988年 | 28篇 |
1987年 | 35篇 |
1986年 | 26篇 |
1985年 | 44篇 |
1984年 | 35篇 |
1983年 | 15篇 |
1982年 | 28篇 |
1981年 | 25篇 |
1980年 | 29篇 |
1979年 | 31篇 |
1978年 | 16篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1974年 | 8篇 |
排序方式: 共有8799条查询结果,搜索用时 15 毫秒
11.
Artūras Dubickas 《Proceedings Mathematical Sciences》2005,115(4):391-397
Suppose that α > 1 is an algebraic number and ξ > 0 is a real number. We prove that the sequence of fractional partsξα
n
, n = 1, 2, 3, …, has infinitely many limit points except when α is a PV-number and ξ ∈ ℚ(α). For ξ = 1 and α being a rational
non-integer number, this result was proved by Vijayaraghavan. 相似文献
12.
A least‐squares meshfree method based on the first‐order velocity–pressure–vorticity formulation for two‐dimensional incompressible Navier–Stokes problem is presented. The convective term is linearized by successive substitution or Newton's method. The discretization of all governing equations is implemented by the least‐squares method. Equal‐order moving least‐squares approximation is employed with Gauss quadrature in the background cells. The boundary conditions are enforced by the penalty method. The matrix‐free element‐by‐element Jacobi preconditioned conjugate method is applied to solve the discretized linear systems. Cavity flow for steady Navier–Stokes problem and the flow over a square obstacle for time‐dependent Navier–Stokes problem are investigated for the presented least‐squares meshfree method. The effects of inaccurate integration on the accuracy of the solution are investigated. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
13.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
14.
A new grid‐free upwind relaxation scheme for simulating inviscid compressible flows is presented in this paper. The non‐linear conservation equations are converted to linear convection equations with non‐linear source terms by using a relaxation system and its interpretation as a discrete Boltzmann equation. A splitting method is used to separate the convection and relaxation parts. Least squares upwinding is used for discretizing the convection equations, thus developing a grid‐free scheme which can operate on any arbitrary distribution of points. The scheme is grid free in the sense that it works on any arbitrary distribution of points and it does not require any topological information like elements, faces, edges, etc. This method is tested on some standard test cases. To explore the power of the grid‐free scheme, solution‐based adaptation of points is done and the results are presented, which demonstrate the efficiency of the new grid‐free scheme. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
15.
Yao Ping HOU 《数学学报(英文版)》2005,21(4):955-960
A signed graph is a graph with a sign attached to each edge. This paper extends some fundamental concepts of the Laplacian matrices from graphs to signed graphs. In particular, the relationships between the least Laplacian eigenvalue and the unbalancedness of a signed graph are investigated. 相似文献
16.
Krzysztof Pawaowski 《K-Theory》1998,13(1):41-55
The paper presents a procedure for constructing smooth actions of finite perfect groups on spheres with fixed point sets having certain prescribed properties (Theorem A); in particular, having any prescribed configuration of Chern and Pontryagin numbers (Corollary C). The main ingredients used are equivariant thickening and equivariant surgery. 相似文献
17.
A Fixed Point Theorem for Multi-valued Composite Increasing OperatorsLiFengyou(李凤友)(DepartmentofMathematics,Tianjin'NormalUni... 相似文献
18.
S. Moss de Oliveira P. M. C. de Oliveira F. C. de Sá Barreto 《Journal of statistical physics》1995,78(5-6):1619-1627
Using the finite-size scaling renormalization group, we obtain the two-dimensional flow diagram of the Blume-Capel model forS=1 andS=3/2. In the first case our results are similar to those of mean-field theory, which predicts the existence of first- and second-order transitions with a tricritical point. In the second case, however, our results are different. While we obtain in theS=1 case a phase diagram presenting a multicritical point, the mean-field approach predicts only a second-order transition and a critical endpoint. 相似文献
19.
Hidetoshi Shimodaira 《Annals of the Institute of Statistical Mathematics》1997,49(3):395-410
The asymptotic error probability of Linhart's model selection test isevaluated, and compared with the nominal significance level. We examine thecase where the expected discrepancies of the candidate models from the truemodel are asymptotically equal. The local alternatives method is employed inthe limiting operation of the asymptotic evaluation. Although the errorprobability under the null hypothesis is actually shown to be equal to orless than the level for most situations, intolerable violations of the errorcontrol are observed for nested models: It is often erroneously concludedthat the smaller model is significantly better than the larger model. Toprevent this violation, a modification of Linhart's test statistic isproposed. The effectiveness of the proposed test is confirmed throughtheoretical analysis and numerical simulations. 相似文献
20.
Browder-Petryshyn 型的严格伪压缩映射的粘滞迭代逼近方法 总被引:1,自引:0,他引:1
主要研究Browder-Petryshyn型的严格伪压缩映射的粘滞迭代逼近过程,证明了Browder-Petryshyn型的严格伪压缩映射的不动点集F(T)是闭凸集.在q-一致光滑且一致凸的Banach空间中,对于严格伪压缩映射T,利用徐洪坤在2004年引进的粘滞迭代得到的序列弱收敛于T的某个不动点.同时证明了Hilbert空间中Browder-Petryshyn型的严格伪压缩映射的相应迭代序列强收敛到T的某个不动点,其结果推广与改进了徐洪坤2004年的相应结果. 相似文献