全文获取类型
收费全文 | 36641篇 |
免费 | 5126篇 |
国内免费 | 5013篇 |
专业分类
化学 | 27635篇 |
晶体学 | 495篇 |
力学 | 1851篇 |
综合类 | 438篇 |
数学 | 4403篇 |
物理学 | 11958篇 |
出版年
2024年 | 72篇 |
2023年 | 559篇 |
2022年 | 914篇 |
2021年 | 1072篇 |
2020年 | 1212篇 |
2019年 | 1268篇 |
2018年 | 1053篇 |
2017年 | 1023篇 |
2016年 | 1607篇 |
2015年 | 1616篇 |
2014年 | 1969篇 |
2013年 | 2703篇 |
2012年 | 3099篇 |
2011年 | 3217篇 |
2010年 | 2356篇 |
2009年 | 2186篇 |
2008年 | 2628篇 |
2007年 | 2338篇 |
2006年 | 2112篇 |
2005年 | 1722篇 |
2004年 | 1586篇 |
2003年 | 1377篇 |
2002年 | 1525篇 |
2001年 | 1183篇 |
2000年 | 923篇 |
1999年 | 889篇 |
1998年 | 589篇 |
1997年 | 511篇 |
1996年 | 497篇 |
1995年 | 431篇 |
1994年 | 378篇 |
1993年 | 366篇 |
1992年 | 317篇 |
1991年 | 271篇 |
1990年 | 224篇 |
1989年 | 193篇 |
1988年 | 124篇 |
1987年 | 117篇 |
1986年 | 95篇 |
1985年 | 98篇 |
1984年 | 57篇 |
1983年 | 37篇 |
1982年 | 32篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1978年 | 21篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1959年 | 14篇 |
1957年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献
72.
73.
Existence, Multiplicity and Infinite Solvability of Positive Solutions for One-Dimensional p-Laplacian 总被引:5,自引:0,他引:5
Qing Liu YAO 《数学学报(英文版)》2005,21(4):691-698
The existence, multiplicity and infinite solvability of positive solutions are established for some two-point boundary value problems of one-dimensional p-Laplacian. In this paper, by multiplicity we mean the existence of m solutions, where m is an arbitrary natural number. 相似文献
74.
75.
S. H. Park J. H. Chang M. Yang H. S. Ahn S. N. Yi K. Goto M. W. Cho T. Yao J. S. Song 《Current Applied Physics》2004,4(6):607-610
Photoluminescence (PL) linewidth broadening of CdxZn1 − xSe/ZnSe triple quantum wells, grown on GaAs substrates by molecular beam epitaxy (MBE), has been investigated. Various quantum well (QW) samples have been prepared with different QW thickness and composition (Cd-composition). Measured and calculated PL linewidth are compared. Both composition and thickness fluctuations are considered for the calculation with the parameters such as the volume of exciton, nominal thickness and composition of QWs. Surface roughness measured by atomic force microscopy (AFM) is used to estimate the interface roughness. Results show that when Cd-composition increases additional linewidth broadening due to Zn/Cd interdiffusion is enhanced. 相似文献
76.
MATLAB/SIMULINK在电力系统仿真中的应用 总被引:2,自引:0,他引:2
介绍了Matlab/Simulink仿真工具在电力系统仿真中的应用方法. 相似文献
77.
78.
A new stochastic method of reconstructing porous media 总被引:1,自引:0,他引:1
We present a new stochastic method of reconstructing porous medium from limited morphological information obtained from two-dimensional
micro- images of real porous medium. The method is similar to simulated annealing method in the capability of reconstructing
both isotropic and anisotropic structures of multi-phase but differs from the latter in that voxels for exchange are not selected
completely randomly as their neighborhood will also be checked and this new method is much simpler to implement and program.
We applied it to reconstruct real sandstone utilizing morphological information contained in porosity, two-point probability
function and linear-path function. Good agreement of those references verifies our developed method’s powerful capability.
The existing isolated regions of both pore phase and matrix phase do quite minor harm to their good connectivity. The lattice
Boltzmann method (LBM) is used to compute the permeability of the reconstructed system and the results show its good isotropy
and conductivity. However, due to the disadvantage of this method that the connectivity of the reconstructed system’s pore
space will decrease when porosity becomes small, we suggest the porosity of the system to be reconstructed be no less than
0.2 to ensure its connectivity and conductivity. 相似文献
79.
Shen-shui Lü 《高分子科学》2006,(5):441-447
Two kinds of water-soluble metallophthalocyanines, binuclear cobalt phthalocyanine (Co2Pc2) and binuclear ferric phthalocyanine (Fe2Pc2), were synthesized through phenylanhydride-urea route and characterized by elemental analysis and FT-IR spectra. Binuclear metallophthalocyanine derivatives (Mt2Pc2) were immobilized on silk fibers and modified viscose fibers to construct bioactive fibers of mimic enzyme. Mt2Pc2 was used as the active center of bioactive fibers, viscose and silk fibers as the microenvironments. The catalytic oxidation ability of bioactive fibers on the malodors of methanthiol and hydrogen sulfide was investigated at room temperature. The experimental results indicated that the catalytic activity of such bioactive fibers was closely correlative to the types ofbioactive fibers and substrates. 相似文献
80.
矩阵方程AXB=D的最小二乘Hermite解及其加权最佳逼近 总被引:1,自引:0,他引:1
本中,我们讨论了矩阵方程AXB=D的最小二乘Hermite解,通过运用广义奇异值分解(GSVD),获得了解的通式。此外,对于给定矩阵F,也得到了它的加权最佳逼近表达式。 相似文献