全文获取类型
收费全文 | 5795篇 |
免费 | 776篇 |
国内免费 | 620篇 |
专业分类
化学 | 1932篇 |
晶体学 | 84篇 |
力学 | 818篇 |
综合类 | 99篇 |
数学 | 1482篇 |
物理学 | 2776篇 |
出版年
2024年 | 13篇 |
2023年 | 53篇 |
2022年 | 88篇 |
2021年 | 131篇 |
2020年 | 108篇 |
2019年 | 118篇 |
2018年 | 107篇 |
2017年 | 161篇 |
2016年 | 230篇 |
2015年 | 169篇 |
2014年 | 297篇 |
2013年 | 420篇 |
2012年 | 333篇 |
2011年 | 415篇 |
2010年 | 357篇 |
2009年 | 383篇 |
2008年 | 394篇 |
2007年 | 437篇 |
2006年 | 344篇 |
2005年 | 341篇 |
2004年 | 269篇 |
2003年 | 255篇 |
2002年 | 247篇 |
2001年 | 181篇 |
2000年 | 181篇 |
1999年 | 149篇 |
1998年 | 125篇 |
1997年 | 124篇 |
1996年 | 89篇 |
1995年 | 91篇 |
1994年 | 88篇 |
1993年 | 81篇 |
1992年 | 59篇 |
1991年 | 53篇 |
1990年 | 40篇 |
1989年 | 36篇 |
1988年 | 26篇 |
1987年 | 18篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 27篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1974年 | 4篇 |
排序方式: 共有7191条查询结果,搜索用时 312 毫秒
81.
Experts were interviewed to identify criteria for evaluation of vocal performance. A scale was then constructed and inter- and intrajudge reliability assessed. Experts listened to 19 different performances, plus 6 presented a second time. Interjudge reliability for one judge was modest, but increased dramatically as the size of the judge panel increased. The most reliable items were overall score and intonation accuracy. Diction was less reliable than other items. Intrajudge reliability was higher for overall score than for any other item. A factor analysis on the test items yielded factors labelled intrinsic quality, execution, and diction. Another factor analysis, using the experts as variables, revealed two underlying evaluative dimensions. It was found that 13 experts were primarily influenced by execution, and that 8 were mainly affected by intrinsic quality. Interjudge and intrajudge reliabilities of these two groups differed. 相似文献
82.
本文提出一种简单实用的MTBF(Mean time between failures-平均无故障工作时间)分配方法.这种方法适合于工程系统设计的对分系统的结构(可靠性模型)有了初步的了解,并能估算出各分系统故障率的情况.同时对于需要进行可靠性分配,又苦于对可靠性理论知识缺乏深入了解的人员也非常适用. 相似文献
83.
This paper introduces a definition of reliability based on a process range. Thus, process failure is defined when the range of a process first reaches a given and unacceptable level. The Mean Time To Failure (MTTF) which is denned as the mean of the first time for a range to attain a given amplitude is then calculated for an asymmetric random walk process. The probability distribution of the range is then given and the process reliability over long periods of system operations are then calculated. Applications such as the control of wings movements, stock price and exchange rates volatility (defined in terms of reliability) are also used to motivate the usefulness of range processes in reliability studies. Finally, we point out that there is necessarily a relationship between the range reliability and the propensity of a series to become chaotic. 相似文献
84.
Francesca Aicardi 《Functional Analysis and Other Mathematics》2006,1(2):93-109
We give a recursive method for building X
p
(a,b) for each prime p. Arnold’s triangle is composed of positive integers: for a>1 and 0<b<a, X
p
(a,b) is the degree of the highest power of p dividing the difference of the binomial coefficients C
pa
pb
−C
a
b
.
相似文献
85.
In the present work, ferrites with compositions of (Ni0.27Zn0.64Cux)Fe1.98O4 (x=0.1, 0.2) were prepared by conventional ceramic methods. The relationship between the microstructure and the temperature dependence of relative initial permeability was investigated. It was found that intergranular pores in the ferrites generate large demagnetizing fields, reducing the temperature dependence of the effective anisotropy field Heff, and decreasing the temperature dependence of the relative initial permeability accordingly. However, intragranular pores pin the movement of domain walls. Compared with the permeability induced by domain wall motion, the permeability that resulted from the spin rotation is more sensitive to temperature. As a result, the relative initial permeability of ferrites becomes more sensitive to temperature with increasing micropores within grains. 相似文献
86.
This article will combine the finite element method, the interpolated coefftcient finite element method, the eigenfunction expansion method, and the search-extension method to obtain the multiple solutions for semilinear elliptic equations. This strategy not only grently reduces the expensive computation, but also is successfully implemented to obtain multiple solutions for a class of semilinear elliptic boundary value problems with non-odd nonlinearity on some convex or nonconvex domains. Numerical solutions illustrated by their graphics for visualization will show the efficiency of the approach. 相似文献
87.
Seppo Hassi Manfred Mö ller Henk de Snoo 《Proceedings of the American Mathematical Society》2006,134(10):2885-2893
The class of Nevanlinna functions consists of functions which are holomorphic off the real axis, which are symmetric with respect to the real axis, and whose imaginary part is nonnegative in the upper halfplane. The Kac subclass of Nevanlinna functions is defined by an integrability condition on the imaginary part. In this note a further subclass of these Kac functions is introduced. It involves an integrability condition on the modulus of the Nevanlinna functions (instead of the imaginary part). The characteristic properties of this class are investigated. The definition of the new class is motivated by the fact that the Titchmarsh-Weyl coefficients of various classes of Sturm-Liouville problems (under mild conditions on the coefficients) actually belong to this class.
88.
89.
分布耦合系数对线性啁啾光栅色散的影响 总被引:7,自引:1,他引:6
本文从光栅反向耦合波方程出发,经相位共轭变换用Runge-Kuta-Gil方法对其数值求解。针对线性啁啾光栅耦合系数变化服从不同的分布,分析了各种分布对光栅反射谱特性和色散特性的影响。 相似文献
90.