全文获取类型
收费全文 | 8697篇 |
免费 | 1504篇 |
国内免费 | 977篇 |
专业分类
化学 | 6389篇 |
晶体学 | 76篇 |
力学 | 511篇 |
综合类 | 45篇 |
数学 | 1054篇 |
物理学 | 3103篇 |
出版年
2024年 | 26篇 |
2023年 | 208篇 |
2022年 | 360篇 |
2021年 | 362篇 |
2020年 | 469篇 |
2019年 | 394篇 |
2018年 | 352篇 |
2017年 | 285篇 |
2016年 | 415篇 |
2015年 | 433篇 |
2014年 | 539篇 |
2013年 | 640篇 |
2012年 | 774篇 |
2011年 | 822篇 |
2010年 | 549篇 |
2009年 | 490篇 |
2008年 | 484篇 |
2007年 | 452篇 |
2006年 | 467篇 |
2005年 | 355篇 |
2004年 | 276篇 |
2003年 | 227篇 |
2002年 | 278篇 |
2001年 | 160篇 |
2000年 | 173篇 |
1999年 | 179篇 |
1998年 | 129篇 |
1997年 | 127篇 |
1996年 | 139篇 |
1995年 | 108篇 |
1994年 | 97篇 |
1993年 | 64篇 |
1992年 | 66篇 |
1991年 | 57篇 |
1990年 | 46篇 |
1989年 | 42篇 |
1988年 | 38篇 |
1987年 | 18篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1957年 | 3篇 |
1935年 | 1篇 |
1931年 | 1篇 |
1930年 | 3篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
The adsorption of human serum albumin onto hydroxyapatite-modified silver electrodes has been in situ investigated by utilizing the piezoelectric quartz crystal impedance technique. The changes of equivalent circuit parameters were used to interpret the adsorption process. A kinetic model of two consecutive steps was derived to describe the process and compared with a first-order kinetic model by using residual analysis. The experimental data of frequency shift fitted to the model and kinetics parameters, k1, k2, psi1, psi2 and qr, were obtained. All fitted results were in reasonable agreement with the corresponding experimental results. Two adsorption constants (7.19 kJ mol(-1) and 22.89 kJ mol(-1)) were calculated according to the Arrhenius formula. 相似文献
3.
4.
5.
研究了三包层WⅠ和WⅡ型单模光纤的波导色散特性。结果发现在相同条件下,三包层WⅠ和WⅡ型单模光纤零色散点的调节范围比传统的双包层W型单模光纤明显增大。详细分析了几何参量P、Q和光学参量R1、R2对单模传输时的波导色散特性和低次模截止频率的影响。所得的研究结果为获得更为理想的色散补偿、色散平坦光纤及设计新型无源光器件提供了重要的依据。计算波导色散的方法可推广到多包层光纤。 相似文献
6.
A graph G is 3‐domination critical if its domination number γ is 3 and the addition of any edge decreases γ by 1. Let G be a 3‐connected 3‐domination critical graph of order n. In this paper, we show that there is a path of length at least n?2 between any two distinct vertices in G and the lower bound is sharp. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 76–85, 2002 相似文献
7.
We study a GI/M/c type queueing system with vacations in which all servers take vacations together when the system becomes empty. These servers keep taking synchronous vacations until they find waiting customers in the system at a vacation completion instant.The vacation time is a phase-type (PH) distributed random variable. Using embedded Markov chain modeling and the matrix geometric solution methods, we obtain explicit expressions for the stationary probability distributions of the queue length at arrivals and the waiting time. To compare the vacation model with the classical GI/M/c queue without vacations, we prove conditional stochastic decomposition properties for the queue length and the waiting time when all servers are busy. Our model is a generalization of several previous studies. 相似文献
8.
A fourth‐order compact finite difference scheme on the nine‐point 2D stencil is formulated for solving the steady‐state Navier–Stokes/Boussinesq equations for two‐dimensional, incompressible fluid flow and heat transfer using the stream function–vorticity formulation. The main feature of the new fourth‐order compact scheme is that it allows point‐successive overrelaxation (SOR) or point‐successive underrelaxation iteration for all Rayleigh numbers Ra of physical interest and all Prandtl numbers Pr attempted. Numerical solutions are obtained for the model problem of natural convection in a square cavity with benchmark solutions and compared with some of the accurate results available in the literature. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
Yanqing Tian Xiaohe Xu Yingying Zhao Xinyi Tang Fengyu Su Xiaoguang Zhao Enle Zhou 《Liquid crystals》1995,19(3):295-300
The synthesis of three new series of chiral Schiff's bases containing benzilideneaniline and 2-hydroxybenzilideneaniline moieties as mesogenic cores is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements were used to study the phase transition temperatures and behaviour. The results reveal that most of these materials show chiral smectic mesomorphism. 相似文献
10.
光照与彩陶俑表面色变关系的实验研究 总被引:1,自引:0,他引:1
本文以秦彩俑表面色彩为研究对象,通过光照实验与色彩变化的色度测量,分析了光照引起彩俑颜料色变的规律,为秦彩俑这一大型重点文物的色彩保护提供了科学理论依据. 相似文献