全文获取类型
收费全文 | 10947篇 |
免费 | 1455篇 |
国内免费 | 934篇 |
专业分类
化学 | 3001篇 |
晶体学 | 69篇 |
力学 | 778篇 |
综合类 | 242篇 |
数学 | 4591篇 |
物理学 | 4655篇 |
出版年
2023年 | 74篇 |
2022年 | 234篇 |
2021年 | 286篇 |
2020年 | 238篇 |
2019年 | 213篇 |
2018年 | 230篇 |
2017年 | 310篇 |
2016年 | 342篇 |
2015年 | 282篇 |
2014年 | 560篇 |
2013年 | 776篇 |
2012年 | 577篇 |
2011年 | 660篇 |
2010年 | 561篇 |
2009年 | 672篇 |
2008年 | 772篇 |
2007年 | 740篇 |
2006年 | 636篇 |
2005年 | 605篇 |
2004年 | 489篇 |
2003年 | 470篇 |
2002年 | 454篇 |
2001年 | 325篇 |
2000年 | 334篇 |
1999年 | 316篇 |
1998年 | 310篇 |
1997年 | 238篇 |
1996年 | 202篇 |
1995年 | 182篇 |
1994年 | 185篇 |
1993年 | 118篇 |
1992年 | 116篇 |
1991年 | 90篇 |
1990年 | 71篇 |
1989年 | 80篇 |
1988年 | 72篇 |
1987年 | 65篇 |
1986年 | 47篇 |
1985年 | 73篇 |
1984年 | 47篇 |
1983年 | 34篇 |
1982年 | 47篇 |
1981年 | 23篇 |
1980年 | 22篇 |
1979年 | 28篇 |
1978年 | 33篇 |
1977年 | 19篇 |
1976年 | 20篇 |
1975年 | 10篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
The symplectic, optical, and photon-number tomographic symbols of binomial states of the radiation field are studied. Explicit relations for all tomograms of the binomial states are obtained. Two measures for nonclassical properties of these states are discussed. 相似文献
162.
The paper is devoted to the research of large deviation probabilities in the approximation by compound Poisson law. 相似文献
163.
The existing model for multivariate skew normal data does not cohere with the joint distribution of a random sample from a
univariate skew normal distribution. This incoherence causes awkward interpretation for data analysis in practice, especially
in the development of the sampling distribution theory. In this paper, we propose a refined model that is coherent with the
joint distribution of the univariate skew normal random sample, for multivariate skew normal data. The proposed model extends
and strengthens the multivariate skew model described in Azzalini (1985,Scandinavian Journal of Statistics,12, 171–178). We present a stochastic representation for the newly proposed model, and discuss a bivariate setting, which confirms
that the newly proposed model is more plausible than the one given by Azzalini and Dalla Valle (1996,Biometrika,83, 715–726). 相似文献
164.
165.
For the purpose of testing the spherical uniformity based on i.i.d. directional data (unit vectors) zi, i=1,…,n, Anderson and Stephens (Biometrika 59 (1972) 613–621) proposed testing procedures based on the statistics Smax=maxu S(u) and Smin=minu S(u), where u is a unit vector and nS(u) is the sum of squares of u′zi's. In this paper, we also consider another test statistic Srange=Smax−Smin. We provide formulas for the P-values of Smax, Smin, Srange by approximating tail probabilities of the limiting null distributions by means of the tube method, an integral-geometric approach for evaluating tail probability of the maximum of a Gaussian random field. Monte Carlo simulations for examining the accuracy of the approximation and for the power comparison of the statistics are given. 相似文献
166.
基于厄米-双曲余弦高斯光束通过无光阑限制薄透镜聚焦的解析传输公式,研究了厄米-双曲余弦高斯光束聚焦区域的光强分布,并对光束的焦移进行了分析,讨论了偏心参数对光强主极大位置的影响。结果表明:TEM11模厄米-双曲余弦高斯光束的相对焦移(绝对值)随偏心参数和菲涅尔数的减小而增大,菲涅尔数较大时相对焦移趋于零。TEM22模光束在偏心参数小于0.54时,轴外与轴上光强极大值的比值大于1,此时光强主极大在轴外,偏心参数大于0.54时则相反;在偏心参数等于0.54时比值为1,此时光束有两个主极大,偏心参数愈大光强愈集中于轴上。使用LW法和GH法得到的TEM22模光束的相对焦移(绝对值)随偏心参数和菲涅尔数的变化规律与TEM11模光束一致,但相同参数下使用这两种方法得出的具体结果不同。 相似文献
167.
168.
Joanna Tarasińska 《Applications of Mathematics》2003,48(1):67-72
Two estimates of the regression coefficient in bivariate normal distribution are considered: the usual one based on a sample and a new one making use of additional observations of one of the variables. They are compared with respect to variance. The same is done for two regression lines. The conclusion is that the additional observations are worth using only when the sample is very small. 相似文献
169.
170.
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