全文获取类型
收费全文 | 2155篇 |
免费 | 104篇 |
国内免费 | 106篇 |
专业分类
化学 | 723篇 |
力学 | 132篇 |
综合类 | 14篇 |
数学 | 1009篇 |
物理学 | 487篇 |
出版年
2024年 | 4篇 |
2023年 | 19篇 |
2022年 | 41篇 |
2021年 | 57篇 |
2020年 | 42篇 |
2019年 | 60篇 |
2018年 | 43篇 |
2017年 | 76篇 |
2016年 | 95篇 |
2015年 | 80篇 |
2014年 | 111篇 |
2013年 | 163篇 |
2012年 | 138篇 |
2011年 | 118篇 |
2010年 | 88篇 |
2009年 | 151篇 |
2008年 | 134篇 |
2007年 | 167篇 |
2006年 | 102篇 |
2005年 | 84篇 |
2004年 | 76篇 |
2003年 | 68篇 |
2002年 | 66篇 |
2001年 | 40篇 |
2000年 | 39篇 |
1999年 | 43篇 |
1998年 | 45篇 |
1997年 | 26篇 |
1996年 | 34篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有2365条查询结果,搜索用时 875 毫秒
131.
132.
In a recent work, S. Cooper (J. Number Theory 103:135–162, [1988]) conjectured a formula for r
2k+1(p
2), the number of ways p
2 can be expressed as a sum of 2k+1 squares. Inspired by this conjecture, we obtain an explicit formula for r
2k+1(n
2),n≥1.
Dedicated to Srinivasa Ramanujan. 相似文献
133.
134.
E. Übi 《Central European Journal of Mathematics》2008,6(1):171-178
The strictly convex quadratic programming problem is transformed to the least distance problem — finding the solution of minimum
norm to the system of linear inequalities. This problem is equivalent to the linear least squares problem on the positive
orthant. It is solved using orthogonal transformations, which are memorized as products. Like in the revised simplex method,
an auxiliary matrix is used for computations. Compared to the modified-simplex type methods, the presented dual algorithm
QPLS requires less storage and solves ill-conditioned problems more precisely. The algorithm is illustrated by some difficult
problems.
相似文献
135.
The distribution theory is developed for a generalized least squares estimator of the growth curve model. A special case of the estimator is the maximum likelihood estimator which is weighted by the sample covariance matrix. The distribution of two conditional forms of the estimator are derived and from these its density is obtained. Two general pivots and their distributions are derived from the conditional forms and special cases of these are investigated. The results obtained are linked to carlier work. 相似文献
136.
137.
138.
《Analytica chimica acta》2002,452(2):311-319
The characterisation of adsorption or impregnation processes using conventional or supercritical fluid technologies becomes an increasing part of the research on drug formulations. The complexity of the relationships between these adsorption processes and the experimental variables potentially influencing them, however, makes these studies more problematic. In this paper, a chemometric approach based on nonlinear partial least squares (NL-PLS) modelling is applied to characterise the effect of the experimental variables on the supercritical impregnation process. Various adsorbent materials such as silica gel, zeolite and amberlite were investigated using the following model compounds as adsorbates: benzoic, salicylic and acetylsalicylic acids. 相似文献
139.
Xue-mei Hu Zhi-zhong Wang Feng Liu 《应用数学学报(英文版)》2008,24(1):99-116
This paper studies estimation and serial correlation test of a semiparametric varying-coefficient partially linear EV model of the form Y = X^Tβ +Z^Tα(T) +ε,ξ = X + η with the identifying condition E[(ε,η^T)^T] =0, Cov[(ε,η^T)^T] = σ^2Ip+1. The estimators of interested regression parameters /3 , and the model error variance σ2, as well as the nonparametric components α(T), are constructed. Under some regular conditions, we show that the estimators of the unknown vector β and the unknown parameter σ2 are strongly consistent and asymptotically normal and that the estimator of α(T) achieves the optimal strong convergence rate of the usual nonparametric regression. Based on these estimators and asymptotic properties, we propose the VN,p test statistic and empirical log-likelihood ratio statistic for testing serial correlation in the model. The proposed statistics are shown to have asymptotic normal or chi-square distributions under the null hypothesis of no serial correlation. Some simulation studies are conducted to illustrate the finite sample performance of the proposed tests. 相似文献
140.
首先给出了Jam es-S te in估计优于岭估计的充分条件,随后在P itm an准则下给出了Jam es-S te in估计优于最小二乘估计的简短证明. 相似文献