全文获取类型
收费全文 | 8527篇 |
免费 | 434篇 |
国内免费 | 466篇 |
专业分类
化学 | 1761篇 |
晶体学 | 81篇 |
力学 | 789篇 |
综合类 | 68篇 |
数学 | 3976篇 |
物理学 | 2752篇 |
出版年
2023年 | 45篇 |
2022年 | 106篇 |
2021年 | 100篇 |
2020年 | 110篇 |
2019年 | 164篇 |
2018年 | 140篇 |
2017年 | 159篇 |
2016年 | 156篇 |
2015年 | 158篇 |
2014年 | 211篇 |
2013年 | 495篇 |
2012年 | 240篇 |
2011年 | 345篇 |
2010年 | 363篇 |
2009年 | 857篇 |
2008年 | 861篇 |
2007年 | 710篇 |
2006年 | 701篇 |
2005年 | 462篇 |
2004年 | 378篇 |
2003年 | 381篇 |
2002年 | 386篇 |
2001年 | 253篇 |
2000年 | 206篇 |
1999年 | 215篇 |
1998年 | 219篇 |
1997年 | 147篇 |
1996年 | 103篇 |
1995年 | 79篇 |
1994年 | 88篇 |
1993年 | 51篇 |
1992年 | 47篇 |
1991年 | 46篇 |
1990年 | 34篇 |
1989年 | 29篇 |
1988年 | 33篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 32篇 |
1984年 | 36篇 |
1983年 | 18篇 |
1982年 | 32篇 |
1981年 | 33篇 |
1980年 | 27篇 |
1979年 | 19篇 |
1978年 | 21篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1975年 | 13篇 |
1974年 | 11篇 |
排序方式: 共有9427条查询结果,搜索用时 0 毫秒
81.
This paper presents a method to estimate reflected and transmitted wave amplitude spectra in a bounded domain such as a wave tank, when available data signals must be shortened due to interferences and wall effects. This paper extends the well known Goda and Suzuki two-probe method to three probes. The paper also suggests solutions to compute reliable transmission and reflection coefficients in spite of problems linked to higher harmonics and to the interference between different wave trains propagating in the tank. To cite this article: G. Duclos, A.H. Clément, C. R. Mecanique 331 (2003). 相似文献
82.
Ioan Tomescu 《Journal of Graph Theory》2003,43(3):210-222
In the set of graphs of order n and chromatic number k the following partial order relation is defined. One says that a graph G is less than a graph H if ci(G) ≤ ci(H) holds for every i, k ≤ i ≤ n and at least one inequality is strict, where ci(G) denotes the number of i‐color partitions of G. In this paper the first ? n/2 ? levels of the diagram of the partially ordered set of connected 3‐chromatic graphs of order n are described. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 210–222, 2003 相似文献
83.
N[a,b]类中边界Nevanlinna-Pick插值(I) 总被引:1,自引:1,他引:0
用所谓的Hankel向量方法求解N[a,b]函数类中带边界插值数据的Nevanlina-Pick插值(BNP(N[a,b]))问题,并建立BNP(N[a,b])问题与[a,b]上的某种带约束条件的Hausdorff矩量问题之间等价的可解条件以及解之间明确的一一对应关系.这使得当BNP(N[a,b])问题有多解时,能通过带约束条件的矩量问题的可解性准则和解获得BNP(N[a,b])问题的可解性准则和解的参数化描述,而在唯一解的情况下,通过BNP(N[a,b])问题解的存在唯一性准则和唯一解来获得带约束条件的 相似文献
84.
Shi Rong LI 《数学学报(英文版)》2005,21(4):797-802
For a finite group G, let T(G) denote a set of primes such that a prime p belongs to T(G) if and only if p is a divisor of the index of some maximal subgroup of G. It is proved that if G satisfies any one of the following conditions: (1) G has a p-complement for each p∈T(G); (2)│T(G)│= 2: (3) the normalizer of a Sylow p-subgroup of G has prime power index for each odd prime p∈T(G); then G either is solvable or G/Sol(G)≌PSL(2, 7) where Sol(G) is the largest solvable normal subgroup of G. 相似文献
85.
The goal of this paper is to compute the shape Hessian for a generalized Oseen problem with nonhomogeneous Dirichlet boundary
condition by the velocity method. The incompressibility will be treated by penalty approach. The structure of the shape gradient
and shape Hessian with respect to the shape of the variable domain for a given cost functional are established by an application
of the Lagrangian method with function space embedding technique.
This work was supported by the National Natural Science Fund of China (No. 10371096) for ZM Gao and YC Ma. 相似文献
86.
设M^n是De Sitter空间S1^n+1中具有常数平均曲率且第二基本形式长度的平方为常数的完备类空超曲面,若S≤2(n-1)^1/2,则M^n是等参超曲面。 相似文献
87.
高斯光束照射下的圆盘夫琅禾费衍射 总被引:9,自引:3,他引:6
推导了高斯光束照射圆孔或圆盘的衍射场普遍表达式,计算了半波带数接近于零的情况下上述衍射场的数据,进而分析了圆盘衍射场在艾里斑中增加一个暗环的原因。 相似文献
88.
Curtis Bennett Kathy J. Dempsey Bruce E. Sagan 《Journal of Algebraic Combinatorics》1994,3(3):261-283
We construct a family of partially ordered sets (posets) that are q-analogs of the set partition lattice. They are different from the q-analogs proposed by Dowling [5]. One of the important features of these posets is that their Whitney numbers of the first and second kind are just the q-Stirling numbers of the first and second kind, respectively. One member of this family [4] can be constructed using an interpretation of Milne [9] for S[n, k] as sequences of lines in a vector space over the Galois field F
q. Another member is constructed so as to mirror the partial order in the subspace lattice. 相似文献
89.
Simultaneous imaging of laser-induced fluorescence of toluene and 3-pentanone was used to determine the local absolute oxygen
and residual gas concentrations present within an engine. The technique utilizes the different sensitivities of the laser-excited
molecules to quenching by molecular oxygen as a means to determine quantitative images of in-cylinder oxygen concentrations.
The difference in the amount of oxygen available between two operating conditions was investigated. Results are in agreement
with measurements in the exhaust gas.
Received: 4 June 2002 / Published online: 8 August 2002 相似文献
90.
J.Y. Wang 《Applied Surface Science》2006,252(15):5347-5350
A general theoretical analysis of the effect of film thickness on equilibrium and kinetic surface segregation in binary alloy thin films is presented. In this analysis, a constrained condition that represents the finite size of thin film system has been introduced to the modified Darken model, which has been used to describe both equilibrium and kinetic surface segregation in bulk materials. Simulation of surface segregation for alloy thin films can be carried out for all composition ranges and all film thicknesses if only knowing the surface segregation parameters for bulk materials. Simulations of equilibrium and kinetic surface segregation in Cu(1 1 1)Ag binary alloy thin film are presented. 相似文献